brochure - three mile island - 30 years on - web

7/29/2019 Brochure - Three Mile Island - 30 Years on - Web

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30 years on

STUDIECENTRUM VOOR KERNENERGIE

CENTRE DETUDE DE LENERGIE NUCLEAIRE

THREE

MILEISLAND


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A SCKCEN compilation

Written by Ellen Van Roey with the support ofFrank Joppen, Frank Hardeman, Anne Verledensand Inge van Aert.

Graphic design by Ilse Beirens

Contact

Ellen Van RoeySCKCEN

Communication AssistantTel. + 32 14 33 21 49Fax + 32 14 33 25 [email protected]

SCKCENBoeretang 200BE-2400 MOL

[email protected]

Publisher

Eric van Walle

Copyright 2009 - Ellen Van Roey - SCKCEN

This is a copyright protected publication (2009).No part of this publication may be reproduced and/ormade public without the express written consent of SCKCEN.

Photo front: the Three Mile Island nuclear power plant near Harrisburg, Pennsylvania, USA


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79Photo: the Three Mile Island nuclear power plant near Harrisburg, Pennsylvania, USA

THREE

MILEISLAND


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Three Mile Island 1979

30 years on


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CONTENTS

1. Introduction...................................................................................................................... p. 4

2. The operation of a pressurized water reactor..................................................................p. 5

Nuclear ssionThe pressurized water reactor

3. The Three Mile Island accident.......................................................................................p. 8A succession of technical defects and operator errorsGeneral emergencyCooling restoredChaotic communication

4. Causes of the accident..................................................................................................... p. 11 Technical defects and confusing equipmentOperator errors

Inadequate trainingInstitutional failuresRobust design

5. Further developments..................................................................................................... p. 14A day of calmThe hydrogen bubbleAnxiety and evacuationFear of an explosionThe end of the crisisCold shutdown

6. Consequences.................................................................................................................. p. 18 Environmental effectsHealth effectsClosure of the other Three Mile Island reactor

7. The clean-up.................................................................................................................... p. 21 Decontamination and dismantlingCurrent situation

8. Impact.............................................................................................................................. p. 23 Effect on policy in the USAInvestigations, reports and recommendations

Improved safety and controlMore extensive trainingDetailed emergency planningThe development of nuclear energy

Effect on public opinion in the USAInternational impact

National reactionsThe reinforced role of the International Atomic Energy Agency

9. Conclusion....................................................................................................................... p. 29

10. More information.......................................................................................................... p. 30


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1. Introduction

On Wednesday 28 March 1979 a serious accident occurred at theThree Mile Island nuclear power plant. What began as a minordefect of the water pumps in the cooling circuit ended up with thepartial meltdown of the reactor core. The accident originated froma succession of small technical failures, unclear designed equipmentand operator errors. The safety procedures and the training ofthe operators appeared inadequate to get the emergency undercontrol.

The nuclear power plant of Three Mile Island (TMI) is locatednear Harrisburg, Pennsylvania in the United States. It owes itsname to the place where it was built: a 5 km (3 mile) long, narrowisland in the Susquehanna River. On the nuclear site there weretwo pressurized water reactors for generating electricity. The rstunit, in operation since 1974, still produces electricity. The secondwas brand new and had been in operation since 28 March 1978.

Exactly a year later a series of fateful events put an abrupt end tothat.

In the tense days after the accident scientists and engineersscrambled to prevent a total meltdown of the core. In the meantimeofcials such as the Governor of Pennsylvania and President

Jimmy Carter tried to calm the local residents. Communicationproblems between several of the parties involved led to conictingand incorrect information being circulated. The confusion anduncertainty exacerbated the prevailing public anxiety. Over200 000 people ed into emergency bunkers or to neighbouringstates.

The Three Mile Island accident was the rst and most severe nuclear accident in the history ofAmerican commercial nuclear energy. It was also the rst to attract genuine media attention bothnationally and internationally. Fortunately there were no deaths or injuries, despite the seriousness ofthe accident. Furthermore, the discharge of radioactive substances outside the nuclear site was minimaland there were no directly demonstrable consequences for public health or the environment. However,this event had a negative impact on public opinion on nuclear energy that cannot be underestimated.The awareness that such a severe accident was possible revived the debate on nuclear safety and hada great effect on policy in the USA. With technical modications, more efcient training, extensiveregulation and strict control, nuclear power plants performed better and better in terms of safety andreliability. The nuclear sector underwent permanent fundamental changes and thus a strong safetyculture gradually developed.

Figure above: map of the United States with Harrisburg in the state of PennsylvaniaPhoto below: the Three Mile Island nuclear power plant near Harrisburg, Pennsylvania, USA


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2. The operation of a pressurized water reactor

The Three Mile Island nuclear power plant consisted of twopressurized water reactors: Unit 1 and Unit 2. In order tounderstand exactly what went wrong in Unit 2 on 28 March 1979,a basic knowledge of the components and operation of this type ofreactor is needed.

Nuclear ssion

Every substance consists of millions of small building blocks knownas atoms. The gure top right represents an atom. An atom has anucleus of protons and neutrons (here the blue and red balls). Theirnumber differs from one substance to another and determines theproperties and mass of the atom. The protons and neutrons are

bound together by the strong nuclear force and it takes a lot ofenergy to pull them apart. Other particles, namely electrons orbit

around the nucleus.

In a nuclear reactor energy is generated by nuclear ssion. Innuclear ssion a heavy atom such as uranium splits apart afterabsorbing a neutron (see gure bottom right). The nuclear fuelin a reactor consists of such heavy atoms. When the nucleus splits,a great deal of energy is released because the atomic particles inthe newly formed smaller atoms are more strongly bound togetherthan in the original atom. The higher binding energy is released inthe form of ionising radiation and heat. From this heat a nuclearpower plant produces electricity. The nuclear ssion and radiationmake the nuclear fuel highly radioactive so that without shielding

it is dangerous to people and the environment.

Nuclear ssion generates besides the two new atoms two or three free neutrons. These y around andare able to split other atoms again. Such a chain reaction of nuclear ssions occurs in the particles ofssile material in the reactor core. This is known as the ssion process.

Figure above: an atom with a nucleus of neutrons and protons and electrons orbiting around itFigure below: a ssion reaction


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The pressurized water reactor

There are various types of nuclear reactors. The pressurized waterreactor (PWR) is the most commonly found type in power plantsthroughout the world. A pressurized water reactor uses water asa coolant to remove the heat generated by the ssion process. Inorder to prevent it boiling, the water is under high pressure. It alsoacts as a moderator to keep the ssion process under control. Waterslows down the free neutrons that are released in nuclear ssion.This makes them more easily absorbed by another particle of ssilematerial, causing a new nuclear ssion.

The reactor core consists of fuel rods. These are long metal tubeslled with nuclear fuel, generally uranium. The fuel rods aregrouped into bundles or assemblies. Grids keep them an equaldistance from one another. The assemblies are located in a steelreactor vessel. From the top of the vessel there hang control rodsfor starting, stopping and adjusting the reactor. They keep the

chain reaction of nuclear ssions under control. When the controlrods drop between the nuclear fuel, they absorb the free neutronsthat cause new ssions. This stops the ssion process and the heatproduced in the reactor core progressively falls. However, thession process creates radioactive by-products that still give off heatafter the chain reaction has stopped.

Most pressurized water reactors have three main separate water/steam circuits that are responsible forcooling: the primary circuit, the secondary circuit and the condenser circuit (see gure page 7).

The primary nuclear circuit runs through the reactor core. There the water comes into contactwith the radioactive nuclear fuel and consequently is also radioactive. Pumps circulate the waterin order to remove the heat arising from ssion. The temperature in the reactor core is well abovethe boiling point and uctuates between 275 C and 315 C. To prevent the primary water boiling,it is maintained at high pressure (155 bar) because when steam forms, the cooling of the core is in

jeopardy. The pressurizer ensures that the pressure in the system is correct. This water reservoir ispart of the primary circuit.

The secondary non-nuclear circuit is responsible for cooling the primary circuit. Because the twocircuits consist of separate pipes, the secondary water is not radioactive. Pumps propel this waterto the heat exchanger or steam generator. By means of a system of tubes the primary cooling watertransfers heat to the secondary cooling water, which consequently boils. The steam generated drivesa turbine, which is connected to an alternator that generates electricity. When the steam has passedthrough the turbine, it is converted back into water inside the condenser. Pumps propel it back tothe steam generator and so the process repeats itself.

The condenser circuit provides the condenser with water to cool the steam in the secondary circuit.The water then ows from the condenser to the cooling tower where its heat is released in to the air.

Photo above: a pellet of uranium fuelPhoto below: a reactor vessel with control rods


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A. Primary circuitB. Secondary circuitC. Condenser circuit

1. Reactor building2. Reactor core3. Reactor vessel4. Control rods5. Pressurizer6. Relief valve

7. Block valve8. Drain tank9. Steam generator

10. Pumps11. Steam12. Turbine13. Alternator14. Transformer15. Condenser

16. Water17. Cooling tower

In the Three Mile Island nuclear power plant there was a defect of the pumps of the secondary circuitof Unit 2. This cut off the water supply to the steam generator and the cooling of the primary circuit

became at risk. Because of a succession of technical defects and operator errors the core becameseriously overheated.

Figure: diagram of a pressurized water reactor (PWR)


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3. The Three Mile Island accident

A succession of technical defectsand operator errors

At 4 a.m. on Wednesday 28 March 1979 the reactorof Unit 2 was running at 97 % power. At that timea minor defect occurred in the secondary non-nuclear circuit. The most important water pumpstopped because of a technical failure. The exactcause is unknown. That night staff had cleanedparts of that cooling circuit. Water probably gotinto an air line during cleaning and the pumpfailed as a result. The supply of secondary coolingwater to the steam generator stopped and so thetemperature of the water in the primary nuclearcircuit rose. This meant that the heat of the reactor

core could no longer be removed.

After eight seconds the control rods automaticallydropped into the reactor core. The ssion processstopped and heat production fell. However,residual heat from the radioactive by-productsstill had to be removed. However, the pumps ofthe secondary circuit were no longer working.The emergency pumps for cooling the primarycircuit started automatically but nobody noticedthat the valves of the emergency circuit wereclosed, so the water could not get through to the

steam generator. An operator only discovered thisafter eight minutes and opened the valves at once.With hindsight, this incident does not appearimportant. Analysis showed that the extra waterwould have had little or no effect on the course ofthe accident.

In the meantime the primary cooling water wasbecoming steadily hotter and expanding. Thusthe water level in the pressurizer rose with aconsequential increase in pressure. To reducethe pressure a relief valve above the pressurizeropened automatically. After ten seconds the

pressure had fallen sufciently, but the valvedid not close again automatically as designed.Because of a design fault this was not displayedon the operating panel in the control room. Theoperators did not realise that a great deal of thewater in the primary circuit was running away toa drain tank through that valve. Furthermore,

because of the heat steam bubbles developed inthe pipes. Because too little cooling water wasreaching the reactor core, the latter graduallyoverheated.

As a reaction to the loss of water, two pumpsautomatically forced replacement water into theprimary circuit. The level in the pressurizer rose,

but water and steam were escaping through theopen valve. To prevent extra water running intothe pressurizer, the operators reduced the watersupply by stopping a pump. They did not realisethat this was making the situation even worse.More steam was generated and more waterwas running out of the cooling circuit than was

being supplied. This is called a loss-of-coolantaccident or LOCA. In the rst hundred minutes

of the accident 120 000 litres of water were lost,approximately a third of the total capacity.

Because the pumps of the primary circuit had tocope with a mixture of water and steam, they beganto vibrate. In order to stop them being damaged,the operators switched the pumps off. This cut offthe water supply to the core completely. Graduallythe core became partly uncovered so that itheated up even more. In the core there were over36 000 fuel rods lled with uranium. Because ofthe tremendous heat the zirconium cladding of

the rods split and they began to melt. The reactorvessel did remain intact but through the damagedcladding radioactive particles were released intothe cooling water. Some of these escaped into thereactor building via the open valve.

Approximately half of the nuclear fuelmelted during the rst hours of the accident.

Approximately two thirds of the 3.6 metre highcore was above the water and the temperatureincreased to 5 000 C. Experts regard the meltingof the nuclear fuel, also known as nuclearmeltdown, as the most dangerous possible

accident in a reactor. In the worst case scenario thecore melts its way through the reactor vessel andruns over the oor like a kind of lava. A chemicalreaction then takes place with the concrete of theoor and the walls of the reactor building. Finallyholes appear and huge quantities of radioactivematerial are liberated, which will contaminate theoutside environment for centuries. FortunatelyThree Mile Island was spared this catastrophe.The operators succeeded in restoring coolingthereby limiting the damage.


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General emergency

Three quarters of an hour after the accident began, the dutysuperintendant arrived at Three Mile Island, but he could notimmediately contain the crisis. Somewhat later a number of siteengineers and managers from the operating company MetropolitanEdison (Met Ed) arrived. At 6.22 a.m. they discovered that the reliefvalve at the top of the pressurizer was still open. An operator closedthe backup block valve, thus stopping the loss of water. The pumpsof the primary circuit were turned on again. However, steam andgas formed in the core hampered the ow of water and made thepumps vibrate too much. They had to be turned off again.

The melting of the fuel rods caused radioactive particles to bereleased into the reactor building via the cooling water. In theauxiliary building and control room the radiation level also rose sothat more and more alarms went off. Around 7 a.m., three hoursafter the accident began, it was apparent that the situation was very

serious. There was a threat of an uncontrolled discharge of harmfulsubstances with possible severe consequences for the health of localresidents and for the environment. The management of Met Edproclaimed a general emergency and warned the authorities. Allnon-essential staff were ordered to leave Three Mile Island.

The Nuclear Regulatory Commission (NRC), the regulator andcontroller of the nuclear sector in the USA, immediately sent ininspectors. Other institutions such as the Environmental Protection

Agency also mobilised staff to assist. The authorities were concernedchiey about the emission of a small quantity of radioactive gases.Radiation technicians turned out to measure the radiation level on

the island and in its surroundings. A helicopter took air samples.The results were below the threshold values for taking emergencyaction. However, the authorities were worried about the possible risks to the population. They dideverything they could to get the reactor under control and to cool down the core. At that time, nobodyrealised that the core had partly melted.

Cooling restored

Over the course of the morning operators tried to force more water into the primary circuit to condensethe steam. It was not until 10.30 a.m. that the core was again fully submerged. After midday theyattempted to reduce the pressure in order to be able to top up the cooling circuit with emergencywater. In the late afternoon they started to supply water under high pressure so as to compress thesteam bubbles and make them splatter. From then on the temperature in the reactor core fell steadily.

At 18.50 the steam had condensed sufciently that it was possible to turn one of the primary pumpson again without it vibrating. Finally the core was once again adequately cooled and the situationstabilised.

Photo above: staff in the reactor control roomPhoto below: a helicopter takes air samples above the reactor


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Chaotic communication

During the rst hours of the accident nobodyknew exactly what was happening. Spokespersonsfor Metropolitan Edison Company (Met Ed)played down the situation. In doing so they

broke the rst rule of crisis communication:overestimate a crisis in the bad sense, becauseafterwards It wasnt as bad as we thoughtsounds better than It is worse than expected.The operator, Met Ed, assured that everythingwas under control and that safety arrangementswere working properly. In the course of the dayit became apparent that this was not the case andthey had to admit publicly that the situation wasvery serious. The companys management alsoconceded that radioactive steam had escaped andthat increased radiation levels had been measured

in the environs. However, PR ofcers at Met Edsheadquarters denied this until after midday.

The faulty communications and conictinginformation harmed the companystrustworthiness so far as the media, the authoritiesand the public were concerned. In the days afterthe accident, relations with the media deterioratedfurther. Questions about the condition of thereactor and the release of radioactive gasesand contaminated water were met with vagueanswers and peppered with incomprehensibletechnical jargon. Many journalists and membersof the public suspected that Met Ed was keepinginformation back or even telling outright lies. Thecomment of one of the managers I dont knowwhy we need to tell you each and every thing thatwe do specically eliminated the last scrap ofcredibility that the company still had.

The Federal Government feared that the generaluncertainty combined with the contradictionsin the media would fan public anxiety.

Accordingly one of the directors of the NuclearRegulatory Commission (NRC) was appointedas spokesman and coordinator of the emergencyoperations. From Friday 30 March he was to

brief the authorities and reporters regularly incomprehensible language. The man came acrossas calm, honest and believable and he succeededin setting peoples minds somewhat more at rest.

The China-syndrome

Less than two weeks before the accident the lm The China Syndrome premired in theUSA. By chance the lm was about a nuclear power plant where a serious accident almost

happened because the operators overestimated the quantity of cooling water in the core. Thetitle The China Syndrome refers to the theory that the core gets so dreadfully overheatedthat the mass of molten nuclear fuel burns through the reactor vessel and the oor and makesits way to the other side of the world to China. As fate would have it, a safety expert in thelm says literally that such a nuclear meltdown could render an area the size of Pennsylvaniapermanently uninhabitable.

Right after premire representatives of the nuclear industry defended their sector. Theymaintained that the lm was an irresponsible ploy by the left-wing anti-nuclear movementto arouse public anxiety about nuclear energy. But even the critics would never have dared

believe that 12 days later reality would overtake ction. The Three Mile Island accident did,however, prove that the reactor vessel and building were proof against the extreme conditionsof a meltdown. There is also scientic and technical proof that it is impossible for the China

syndrome to occur in reality. Despite this the idea lived on in the collective consciousness.


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4. Causes of the accident

Various investigations concluded that the accident began with thefailure of the equipment. A pump in the secondary circuit fell out

but the crucial mechanical defect was the relief valve at the topof the pressurizer remaining open. Because of operator errors aminor incident almost turned into an outright disaster. However,the operators were not the only people at fault. Investigatorsplaced part of the responsibility on the management of the nuclearpower plant and the Nuclear Regulatory Commission (NRC), theregulator and controller of the sector.

Technical defects and confusing equipment

Because a pump in the secondary circuit failed, the water in theprimary circuit was no longer adequately cooled. The heat causedthis water to expand and the pressure in the circuit rose. Becauseof a design fault, the relief valve at the top of the pressurizer did

not close when the pressure had fallen sufciently. The operatorsassumed that the valve had closed again since the equipmentshowed that a close signal had been sent. However, this could not

be checked since the control panel gave no indication of the actualposition of the valve.

The reactors control panel exhibited yet more failings. It was outof date and tremendously large with hundreds of indicators andgauges. Some were in places where the operators could not seethem. Others were hidden behind maintenance tags. In the rstminutes of the accident, over a hundred alarms went off and allkinds of warning lights ashed. In this chaos of signals there was no

system for suppressing the less important ones so that the operatorscould concentrate on the most crucial. Neither was there a meterfor the water level in the reactor core. The equipment provided only confusing information and theoperators did not realise that more and more water was being lost. One of them stated later: I wouldhave liked to have thrown away the alarm panel. It wasnt giving us any useful information.

Photo above: the operators give evidence before the government commission investigating the accidentPhoto below: the control panel of the reactor with maintenance tags


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Operator errors

In the rst minutes after the reactor shutdown,nobody noticed that the valves of the emergencywater circuit were not open. A few days beforethey had been closed for a test and people hadforgotten to open them again. A light on thecontrol panel was indeed on, indicating that thevalves were closed, but there was a maintenancetag hanging in front of it. Only after eight minutesdid an operator discover that the light was on andstart the emergency water supply.

For over two hours nobody in the control roomrealised that they were dealing with a LOCA, aloss-of-coolant accident, although there wereindications that more and more cooling water was

being lost.

The high temperature in the drainpipe of thepressurizer should have alerted the operators.The pipe was hotter when water was owingthrough it, and this was only possible if thevalve was open. However, they explainedthat the temperature was always high becausethe valve leaked slightly. Nevertheless, theyshould have noted the extreme temperatureas abnormal.

The vibration of the pumps suggested thatsteam was being generated in the pipes andcooling water was evaporating. Despite this,

nobody realised that the water in the primarycircuit was boiling.The operators ignored these signs or wereunable to judge their importance correctly in theabundance of alarms.

Despite their incorrect interpretations, the blamecannot be heaped entirely on the heads of theoperators. Those who were present stated thatthe accident was a combination of events that theyhad never experienced before, neither duringthe operation of the reactor or during trainingsimulations. The operators were inadequately

trained for emergencies and were unable torespond correctly to the unexpected problems.The confusing and antiquated control panel gavethem little help. Furthermore, they did not haveproperly worked out safety procedures rather,these were confusing and could lead to incorrectaction.

Inadequate training

To become a reactor operator in the USA, youdid not need any minimum training. You weretrained on the job without a set syllabus orclear requirements. Even the basic principles ofnuclear energy did not get a look in. In principlethe operators simply learned to press buttons.

According to the training procedure, on a reactorshutdown they had to prevent the pressurizerlling up since control over pressure would then

be lost and the pipes of the cooling circuit couldburst. Operators also learned that the level in thepressurizer was the only indicator of the quantityof water in the entire primary circuit. Because thelevel rose, they assumed that there was enoughwater in the core and that it was adequatelycooled. However, they did not realise that water

and steam were escaping via the open valve at thetop of the pressurizer.


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Institutional failures

When the accident was analysed, it appeared that the operatorMetropolitan Edison Company (Met Ed) had inadequate expertiseand staff to run and maintain the nuclear power plant properly.There was a quality plan but its implementation was substandard.There were not enough inspectors for the control of materials andequipment. The review and application of procedures exhibiteddefects. Safety problems were insufciently reported, analysed andresolved. These shortcomings jeopardised the safe operation of thenuclear power plant.

The management of Met Ed and, by extension, the entire nuclearsector did not worry very much about nuclear safety. The NuclearRegulatory Commission (NRC), too, paid too little attention to itwhen granting licenses and during inspections. The regulationswere indeed very extensive but complex and not very coherent.Sometimes operators and even inspectors could no longer see

the wood for the trees. Apart from that, safety consists of morethan following the rules. The importance of the human factor wasforgotten. Safety has to be an attitude, a systematic concern in theminds of the people who operate the plants and manage nuclearpower plants. Furthermore, clear procedures, good training andspecic attention to the interaction between man and machine arevital.

Despite its important task as watchdog of the nuclear sector, theNRC did not function as it should. Its management was heavilyfragmented and bureaucratic and the various divisions and regionalofces did not communicate adequately with one another. There

was a lack of advice and feedback to operating companies aboutincidents and safety problems. Lessons from previous accidentsgenerally did not result in concrete instructions to improve safety.

A year and a half before these events there was an identical incident with the valve at the top of thepressurizer in another similar reactor. That time it stayed open for twenty minutes. An investigatorreported: if the reactor had been operating at full power, it is quite possible, perhaps probable, thatcore uncovery and possible fuel damage would have occurred. An engineer wrote a memorandumand alerted colleagues: we must warn operators that they must not only keep an eye on the pressurizersince that can be misleading. Along with other advice, his cry of distress became lost in the bureaucraticmachine. The warnings reached the top levels of the NRC and the industry too late. The rest is history

Robust design

Despite the defects and errors, it cannot be denied that the consequences of the accident remainedlimited thanks to the robustness of the reactor and the reactor building. The core suffered seriousdamage and a portion of the fuel rods actually melted. However, the reactor vessel remained intactand only small quantities of radioactive substances were released into the immediate environs of thepower plant.

Photo above: the President and Vice-President of Metropolitan Edison CompanyPhoto below: the headquarters of the Nuclear Regulatory Commission in Rockville, Maryland


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5. Further developments

A day of calm

Thursday 29 March seemed to be a day ofcalm and a change for the better. The NuclearRegulatory Commission (NRC) calmed the public

by claiming that the danger had passed. In themeantime experts tried to estimate the damage tothe reactor. It was not yet completely stabilised andattempts to cool the core further had little effect.The radiation level in the auxiliary building alsoremained high. This building contained a watertank with make-up and let-down piping for theprimary nuclear circuit. Radioactive gas leakedinto the auxiliary building via these pipes andthen escaped into the atmosphere through thevent stack. However, offsite measurements never

exceeded the alarm threshold. The AmericanFood Agency took samples of food, milk and waterto check for radioactive contamination. All resultsremained well below the health limits.

The hydrogen bubble

From Friday 30 March onwards, experts wereworried about a possible gas explosion in thereactor core. During the accident the core waspartly above water. Because of the heat, a chemicalreaction occurred between the zirconium cladding

of the fuel rods and the water vapour. This formedhydrogen, a part of which was released into thereactor building. When the operators were tryingto restore cooling at around 14:00, they heard athud. No one realised that this was an explosionof the hydrogen generated. They thought it was aventilation valve closing and the sudden increasein pressure was ignored. However, part of the gasremained in the reactor vessel.

Only two days later on Friday did experts realisethat the sound and the increase in pressure werecaused by a hydrogen explosion. The gas bubble

remaining in the reactor caused great concern.Specialists and the authorities feared that this

bubble too could explode, tearing the reactorbuilding apart and causing it to collapse. Thenlarge quantities of radioactive substances would

be released with disastrous consequences forpublic health and the environment. In order toavert a catastrophe, scientists tinkered with waysof eliminating the gas bubble. Initially the publicwas not informed of this new potential danger.

Anxiety and evacuation

On Friday 30 March a panic to evacuate held swayin the vicinity of Three Mile Island. That morningan operations supervisor decided to transferthe radioactive gases from the water tank in theauxiliary building to the waste gas decay tank. Heconsidered this necessary to reduce the pressurein the primary circuit and ensure the ow ofwater. During the transfer, gases leaked into theauxiliary building and part of them escaped tothe outside via the vent stack. In order to checkon the emission, a helicopter took air samples.Because of the high concentration of radioactiveparticles above the reactor unit, the result was12 millisieverts. If measured on the ground

in nearby Harrisburg, this value was the limitfor evacuation of the population. However,where there is a release into the atmosphere,the radioactive particles are spread out by thewind and reach the ground at much lowerconcentrations.

A series of misunderstandings about themeasurement arose because of communicationproblems within and between various institutions.Some ofcials assumed that the high dose wasmeasured off the nuclear site. Furthermore,

they believed that another hydrogen explosionin the reactor was possible. They gave the localauthorities the order to evacuate everyone withina radius of 8 km. Shortly afterwards it emergedthat the measurement was recorded immediatelyabove the plant. The NRC withdrew its order butin the meantime the re departments had beenwarned and the news was on local radio. Somewhatlater the Governor stated in a radio message thatit was a false alarm and that no mass evacuationwas necessary. Evacuation in an atmosphere offear and panic is not without risk because peoplemay die or be injured in the chaos.


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Nonetheless, the uncertainty and confusion about the conditionof the reactor persisted. In the afternoon the Governor decidedin consultation with the NRC to evacuate the most vulnerablemembers of the public within a radius of 8 km as a precaution. Allpregnant women and children under two were recommended toleave the area. Local residents within a radius of 16 km were advised

to stay indoors. Schools closed for some days. On the evening ofFriday 30 March, Three Mile Island was the main item on thenews throughout the USA. The words of a well-known newsreaderwe are faced with the remote but very real possibility of a nuclearmeltdown drew the attention of the world to Pennsylvania. Inthe days that followed, some 200 000 people voluntarily left theirhomes, driven by uncertainty and lack of unequivocal informationfrom the media and authorities.

Radioactive iodine

The Department of Health also considered evacuating local residents and feared a releaseof radioactive iodine. This substance is easily absorbed by the thyroid gland. They thereforewent looking for non-radioactive iodine. Early intake of non-radioactive iodine saturates thethyroid and it cannot then absorb any more harmful radioactive iodine. A chemical companywas prepared to deliver a quarter of a million bottles. The rst load arrived in Harrisburg onSunday 1 April. The authorities did not start preventive distribution in order to avoid publicconcern. During and after the accident the level of radioactive iodine always stayed far below thealarm threshold. The bottles were never distributed.

The Department of Health was also worried about radioactive iodine in milk. If the cattle inthe meadow eat contaminated grass, the radioactive substances can get into their milk. For twoweeks the population were advised not to drink milk from local cattle. The samples subsequently

showed that there was no contamination.

Figure above: map of the Three Mile Island area showing evacuation zonesPhoto below: the stock of non-radioactive iodine at a storage place in Harrisburg


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Fear of an explosion

Throughout the weekend scientists tried to determine if and whenthe hydrogen in the reactor might explode. An explosion is onlypossible if there is sufcient oxygen present so they attempted towork out how much oxygen had been formed in the core. Varioussources conrmed that oxygen was indeed being released byradiolysis. In radiolysis water molecules (H

2O) are broken down

into hydrogen (H) and oxygen (O) by the radiation. However,opinions were divided on the quantity of oxygen and the speedwith which this was increasing. However, all estimates indicated itwould take at least another few days before the gas could explode.

Until Saturday 31 March the public was not aware of the hydrogengas problem. That afternoon NRC staff admitted in an interviewthat there was a risk of explosion. The news spread like wildre.People ran down the streets in panic, wanting to know whether theyshould evacuate. To calm peoples nerves, the Governor and the

NRCs spokesman held a joint press conference that evening. Theystated that it was again a false alarm since there was no immediaterisk of explosion. However, many members of the public wereworried by the conicting reports. Even within the NRC itself therewas disagreement about the potential risk.

The end of the crisis

The crisis ended on Sunday 1 April when experts established that the infamous gas bubble could notexplode because no excess oxygen was being formed in the core, since hydrogen (H) reabsorbs theoxygen (O) released by radiolysis, thus forming new water molecules (H

2O). In the meantime the

hydrogen was largely eliminated by regularly opening the valve above the pressurizer. However, theNRC did not share the good news with the public and never admitted to its incorrect calculations.They did make vague statements about estimates being too conservative. Afterwards the anxiety ofthe local residents appeared unfounded, but they were never told this clearly.

President Jimmy Carters visit that Sunday nally allayed the publics fears. Before the eyes of thecameras, he, together with his wife and the Governor, were given a tour of the nuclear site including

the control room of the reactor. The pictures had the desired effect on the public: If its safe enoughon Three Mile Island for the President and Governor, it must also be safe for the public.

But that did not bring the accident to a close. The danger to public safety and health had not completelygone away. A small gas bubble remained in the core and the reactor was seriously damaged and theauxiliary building still contained radioactive gases. Periodic emissions of low concentrations persistedfor days. On Monday 9 April, twelve days after the accident, the Governor ofcially stated that allevacuees could return home. The schools reopened.

Figure above: impression of water moleculesPhoto below: President Jimmy Carter in the control room of the reactor


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Cold shutdown

After a tense month the operators achievednatural circulation of the cooling water on27 April. The unit was now in cold shutdown.This meant that the temperature of the waterhad fallen below boiling point. The pumps nolonger had to force the water through the pipesmechanically. Henceforth the core was cooled bythe natural circulation of the water.

The cold shutdown was only the beginning of theend. There were still radioactive gases and over3 million litres of radioactively contaminatedwater left in the reactor building and auxiliary

building. The walls and oors of the buildingswere also heavily contaminated. Now the clean-upand decontamination of the unit could begin. Thework took around fourteen years and cost almost1 billion dollars.


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6. Consequences

Despite the seriousness of the accident and the damage to thereactor, there were no deaths or injuries. Furthermore, the releaseof radioactive substances outside the Three Mile Island nuclear sitewas minimal. Extensive surveys and studies by various institutions

concluded that the direct consequences for public health and theenvironment were negligible.

Environmental effects

In the initial stage of the accident radioactive cooling water leakedpast the valve at the top of the pressurizer. It ended up in a draintank in the basement of the reactor building. The tank burst andthe oor was ooded. Some of the water was automatically pumpedto a waste tank in the auxiliary building. After twenty minutesthe operators noticed this and stopped the transfer. Because thewater was very hot, radioactive steam was nevertheless released.

Radioactive gas also leaked into the auxiliary building via the otherstorage tank connected to the primary circuit. Part of this escapedup the vent stack to the outside. In the weeks after the accidentthere were still regular atmospheric emissions. Radiation expertsconstructed mathematical models to determine how much wasreleased and where the contamination ended up.

Just after the accident the reservoirs for the efuent from toilets,showers, etc. almost overowed. Normally this water is barelyradioactive if at all, but because of the accident it had become slightlycontaminated. Metropolitan Edison Company dumped around1.5 million litres of this water in the Susquehanna River. The

radiation level remained well below the emission limits. In additionover 4 million litres of radioactive cooling water ended up in the basement of the reactor buildingand in the storage tanks of the auxiliary building. After the clean-up of the unit, this was processed,stored and nally evaporated safely along with the waste water produced during decontamination anddismantling. In total this involved some 10 million litres.

In order to investigate the consequences of the release of radioactive gases and contaminated water,investigators collected thousands of air, water, milk, plant, soil and food samples. Some showed veryslightly elevated levels of radioactive substances that were attributable to the emissions during and afterthe accident.

Photo above: view of the cooling towers of the nuclear power plant seen from Goldsboro, PennsylvaniaPhoto below: radiation experts determine the quantity and location of the emissions in the area


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Before the accident the industry and the NuclearRegulatory Commission (NRC) regardedradiation protection as a matter of secondaryimportance. There was also little expertise on thehealth effects of ionising radiation. Nuclear power

plants were not required to keep les on employeeexposure. During the accident repair teams withinadequate protective clothing entered highlyradioactive parts of the unit. This happenedwithout the knowledge of those responsible forradiation protection. The staff who recorded theradiation in and around the auxiliary buildingsustained a dose of 8 millisieverts (mSv). This isroughly equivalent to a CT scan. Over the period28 to 30 March, 3 people received a dose of30 to 40 millisieverts. This was more than the thenmaximum quarterly dose of 30 millisieverts. Todaythe limit for an employee in the Belgian nuclear

sector is 20 millisieverts per twelve consecutivemonths.

According to calculations, the most heavilyexposed people at the nuclear site sustained a

maximum of 1 millisievert. This is approximatelyone third of the annual natural backgroundradiation in the USA. People within a radius of16 km received an average dose of0.08 millisieverts. This is equivalent to a chestX-ray and is less than 3 percent of the annualamount of natural background radiation in theUSA. In Belgium the dose of natural plus articialradiation averages 4.6 millisieverts per year (seediagram bottom left).

On basis of the measurements it was concluded thatthe concentrations emitted were so low that therewould be no directly demonstrable consequencesfor public health. More than ten epidemiologicalstudies carried out since 1981 conrm this. For18 years the Pennsylvania Department of Healthmonitored more than 30 000 people who livedwithin a radius of 8 km of Three Mile Island. Theregister was closed in 1997 without any proof ofunusual developments in public health.

Units

Becquerel (symbol Bq) is the unit of radioactivity and indicates how many nuclei of aradioactive material decay per second. Every type of atom with an equal number of protonshas different versions with a different number of neutrons. These are the isotopes of anelement. If an isotope has too many or too few neutrons, it is unstable. After a certain timethe nucleus will split or give off surplus energy so as to arrive at a stable state. We say thatthe nucleus decays and is radioactive. In the decay process ionising radiation is given off,which can be dangerous in large doses. Such an unstable isotope is called a radioisotope orradionuclide.

Gray (symbol Gy) is the unit of absorbed dose. It is the quantity of radiant energy transferredin a substance (1 Gray is 1 Joule/kg). The gray is used as a unit for very high doses of radiationthat have short-term effects such as acute radiation sickness.

Sievert (symbol Sv) is the unit of equivalent or weighted radiation dose. It is the absorbeddose multiplied by weighting factors for the type of radiation and the sensitivity of the partof the body irradiated. The sievert is used in relation to long-term health effects of ionisingradiation such as cancer and physical deformities.

Health effects


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Studies of the population in the widersurroundings up to 30 km conrm this trend. According to two studies in the early 80s

there was no increase in neonatal and infantmortality in the years after the accident. Astudy from 1988 supports this conclusion.

Two other studies from the early 80s found nosignicant difference in mortality from cancerin the years after the accident. A second studyfrom 1990 conrmed this result. By the end of the 80s it was apparent that theaccident had not affected the general mortalitygures or life expectancy. In the early 90s another national studyon mortality rates of municipalities in theneighbourhood of nuclear installations foundno increased mortality from cancer.

And now, decades later, these results still stand.The radiation released during and after theaccident has not had any perceptible effect onthe development of cancer, mortality rates or lifeexpectancy in the neighbourhood of Three MileIsland.

Doctors did nd evidence of psychological stresswhich in some cases persisted for ve years. It alsoappears that the people with stress perceived theirhealth as less good than it actually was accordingto their medical records. The provost of the

Capitol Campus of Pennsylvania State Universityexplained the mental pressure as follows: Neverbefore have people been asked to live with suchambiguity. The TMI accident - an accident wecannot see or taste or smell . . . is an accidentthat is invisible. I think the fact that it is invisiblecreates a sense of uncertainty and fright on thepart of people that may well go beyond the realityof the accident itself.

Closure of the other reactor at ThreeMile Island

In 1979 the Three Mile Island nuclear powerplant was jointly owned by the PennsylvaniaElectric Company, Jersey Central Power & LightCompany and Metropolitan Edison Company(Met Ed). The last of these was responsible forthe day-to-day management and operation ofthe plant, which consisted of two pressurizedwater reactors: Unit 1 and Unit 2. Both unitswere constructed by the construction company,Babcock & Wilcox.

When the accident in Unit 2 happened, Unit 1was not in operation because the nuclear fuelwas due for replacement. Since both reactorswere of a similar design, doubts arose about the

safety of Unit 1. Accordingly, the reactor was notimmediately put back into service. Other Babcock& Wilcox reactors also had to cease operations. TheNuclear Regulatory Commission (NRC) requiredthat all lessons from the accident be put into effect

before restarting. General Public Utilities (GPU),Met Eds parent company, modied the plantand updated training and procedures. Becauseof the accident, the regulation and managementof nuclear power plants in the USA changeddramatically. Unit 1 had to satisfy new rules andtechnical requirements. Because of legal and

regulatory complications, the reactor was idle forsix years.

Many people were severely disillusioned by thedecision of the NRC to restart Unit 1 despitethe many protests and the fact that the peopleof Pennsylvania had voted against the proposal.When the reactor restarted in October 1985 GPUpromised that they would operate the unit safelyand efciently and would become a world leader.The company kept its promise. The plant hasan impressive reputation for safety. It is highlyimprobable that a similar accident could happen

in Unit 1. The reactor performs admirably andactually exceeds safety and reliability standards.The key factor in this success was the applicationof the lessons from the accident in Unit 2.


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7. The clean-up

The clean-up of the damaged nuclear unit on Three MileIsland lasted for approximately fourteen years and costalmost 1 billion dollars. The operation represented atremendous technical and radiological challenge since thesafety of staff and local residents could not be endangeredduring decontamination and dismantling. The removal ofnuclear fuel from the core demanded years of preparationand was a tricky undertaking. Furthermore, the surface ofthe installation had to be decontaminated and a solution wassought for the radioactively contaminated water.

Decontamination and dismantlingThe clean-up work began in August 1979 with the rst loadsof low level radioactive waste being shipped to Richland inWashington. In early July 1980 GPU ventilated the reactor

building in preparation for the rst manned entry on 23July. In the process krypton and other radioactive gases werereleased for a period of eleven days. The local populationprotested against the emissions and in November the DistrictCourt of Appeals ruled that they were illegal. For thisviolation, the parent company General Public Utilities (GPU)was ned $40,000 by the Nuclear Regulatory Commission(NRC).

In November 1980 the advisory panel for the dismantlingof the reactor met for the rst time. Ofcials, scientists andmembers of the public were represented. In July 1981 the

Governor of Pennsylvania presented a billion dollar clean-upplan. Its implementation and the division of costs requiredthe collaboration of the industry and federal and local authorities. GPU and the engineering companyBechtel Northern Corporation were given the task of dismantling and decontaminating the unit. TheNRC supervised the entire operation.

Over a thousand staff contributed to the work being carried out safely and successfully. They usedhigh-pressure pumps to decontaminate the oors, walls and pipes of the reactor building. The top-most layer of contaminated concrete was removed using mechanical chisels and scrubbers. Robotswere employed for camera inspections, for taking samples of oors and walls, to measure radiation, todecontaminate walls and equipment and to remove debris.

Photo above: staff cleaning the auxiliary building of the reactorPhoto below: the rst manned entry into the reactor building in 1980


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In 1979 the processing of the 4 million litres of high level and intermediate radioactive water that wasleft in the basement of the reactor building and in the storage tanks began. The decontamination wasdone using special lters that absorb radioactive material. The contaminated water was put back intostorage and later evaporated together with the radioactive wastewater produced during the clean-upwork. In total this represented some 10 million litres. The task started in early 1991 and lasted for ayear and a half.

Current situation

In 1991 the National Society of Professional Engineers recognised the clean-up programme as one ofthe most sophisticated technical accomplishments in the USA in the 90s. The clean-up ofcially cameto an end in December 1993 when the Nuclear Regulatory Commission (NRC) approved the licensefor monitored storage, a state in which Unit 2 has been ever since. The long-term supervision of theinstallation and its surroundings will remain in effect until everything is dismantled. The ventilationand rainwater systems are subject to continual inspection. The basic equipment needed to guaranteesafety is maintained. Regular reports keep the NRC, the State of Pennsylvania and the public informedof the state of affairs. When, in the future, Unit 1 is also closed down, the industrial owners willdismantle both installations together.

The damage to the reactor core

In the months and years after the accident the damage tothe reactor core was the subject of debate and speculation. In

July 1982 a camera took the rst pictures of the partly melted

core. Only then did it become apparent that the extent of themeltdown was much greater than expected. The removal of thenuclear fuel and parts from the reactor vessel formed the heartof the clean-up operation. The material was highly radioactiveand so the work was done completely under water because itabsorbs the radiation and thus provides protection.

The dismantling of the core began in October 1985 afteralmost six years of preparation. In order to remove the debrisfrom the reactor vessel and put it in containers, the staff stoodon a platform and used tools twelve metres long. They worespecial clothing and gas masks to protect themselves against

the radioactively contaminated water and the radiation. Theradiation levels were comparable with those when replacing thenuclear fuel in a working reactor.

Between 1985 and 1990 GPU removed around 100 tons ofuranium fuel and around 50 tons of damaged parts from thereactor vessel. 342 containers of high level radioactive wastewere transferred to the Idaho National Laboratory for long-term storage. However, some parts of the reactor vessel werenot accessible and in the end 1 percent of the nuclear fuel anddebris was left behind.

Photo above: staff on the platform above the reactor vesselPhoto below: lter system for decontaminating radioactive water


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8. Impact

The Three Mile Island accident marked a turningpoint for the nuclear sector in the USA. Variousinvestigative commissions analysed the causesand made numerous technical and legislativerecommendations. The Nuclear RegulatoryCommission (NRC) made the regulations andsupervision stricter. Since then, the operationand management of nuclear power plants have

been subject to close inspection. The eventsshowed that the human factor can be decisive inkeeping incidents in check. The sector reformedthe training of operators and supervisors and setup a national academy for nuclear training. Inaddition, more attention was paid to radiationprotection. Despite the incisive measures andimprovements, the accident had a severe negative

impact on the public opinion on nuclear energy.

Effect on policy in the USA

Investigations, reports andrecommendations

The authorities and the nuclear sector reactedquickly and energetically after the accident. Theyveried the causes and took action to preventthe possibility of such an event happening again.The industry set up a centre to analyse the

facts. The federal authorities and the NuclearRegulatory Commission (NRC) each put togetheran investigative commission. On the basis of thendings, the NRC imposed a ne of $155 000 onthe operator Metropolitan Edison Company.

In October 1979 the government commissionpublished a report with importantrecommendations for fundamental changes in themanagement, operation and control of nuclearpower plants: The nuclear sector must drastically change its

attitude to safety and regulation. The industry must itself set standards andoversee them. Every nuclear power plant must systematicallycollect, check and analyse its experiences. Every company must have a specialistdepartment responsible for its nuclearoperations. The industry must set up recognised traininginstitutions for training operators andsupervisors.

The industry, the NRC and the FederalGovernment commended the report andsupported the recommendations. The nuclearsector underwent a genuine transformation.

Improved safety and control

On the basis of the analyses of the accident, theNuclear Regulatory Commission (NRC) expandedthe regulations. It formed a separate departmentto deal with this, and there were more safetyinspections, which were followed up better. TheNRC started to publish periodic reports on theperformance and management of nuclear powerplants. It also expanded its international activitiesto exchange knowledge about nuclear safety with

other countries.

The industry established its own watchdog - theInstitute of Nuclear Power Operations (INPO).INPO promotes the highest standards of safetyand reliability in the operation of nuclear powerplants. The Institute lays down guidelines,criteria and objectives and regularly evaluatesthe performance and management of all nuclearelectricity producers. On the basis of reports andgood practices, INPO gives advice and assistanceon optimising the operation of installations. The

Institute was so successful that it provided themodel for the formation of the World Association ofNuclear Operators (WANO). WANO determinesthe performance standards for all nuclear powerplants throughout the world.

The nuclear power plants in the USA drew upaction plans to improve safety. Technical changeswere made and procedures were reviewed. Inorder to optimise control room ergonomics, extraequipment was installed, taking account of theinteraction between man and machine. For bettercontrol of the installation, the operator panel was

designed to be clearer, including a distinctionbetween important and less important signals.Thanks to the extended regulation and strictsupervision by the NRC and INPO, the nuclearpower plants performed better and better. Year byyear they operated more safely, more efcientlyand more reliably, so that there have been fewerand fewer incidents and accidents since the mid-80s. Employee exposure to radiation also fell toone sixth of its value in 1985 and is well below thenational limits.


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More extensive training

The accident showed that the human factorcan be critical in guaranteeing safety. Propertraining of operators and supervisors is of crucialimportance. That is why training has beencompletely modernised. Henceforth the emphasislay on maintaining the cooling capacity of thereactor, irrespective of the cause of a problem.During the accident the operators were using aprocedure manual and applied what seemed mostappropriate to them. This method of working wasreplaced by a series of yes/no questions in orderto ensure in the rst place that the reactor coreremained under water. Only then should theoperators identify the specic defect. This is asymptom-based approach to reacting to events.

A large part of the training currently takes placein sophisticated simulators. In a mock-up controlroom, operators learn to operate a virtual reactorand control emergencies. But the redesignedtraining goes much further than pressing buttons.Staff acquire a basic knowledge of the theoreticaland practical aspects of the operation of a nuclearinstallation. In addition to this, attention is paidto effective communication and collaborating withteam members.

In 1985 the Institute of Nuclear Power Operations

(INPO) established the National Academy forNuclear Training. The Academy sets uniformtraining standards on for the entire industryin order to guarantee professionalism andexcellence. It is also responsible for approving thetraining programmes of individual nuclear powerplants. The Nuclear Regulatory Commission(NRC) also supervises all aspects of training fornuclear staff via regulations and inspections.

Since the accident the industry has investedthousands of man-hours and hundreds of millionsof dollars in education and training. This has

resulted in a denite improvement in the safetyand reliability of nuclear power plants.

Detailed emergency planning

Both on a nuclear site as in its immediateenvirons, emergency planning or readiness foremergencies is of great importance. The accidentproved that the emergency plan for Three MileIsland was weak and undeveloped. Uncertaintyabout the necessary actions prevailed bothamong the management of the power plantand the authorities. Should the local population

be evacuated or advised to shelter indoors? Itwas apparent from the confusion that a clearframework for protective measures for localresidents and the environment was needed. Thelack of a stockpile of non-radioactive iodine wasalso a deciency.

In the aftermath of the accident, the American

Congress demanded stricter rules for nuclearemergency plans. The Nuclear RegulatoryCommission (NRC) revised the requirements forthe protection of people and the environment,amended the regulations and dened emergencyplanning zones in the proximity of nuclear powerplants. The new regulations are intended to limitthe consequences of accidents and minimiseexposure to radiation. If an accident shouldhappen, the nuclear power plant staff evaluatethe situation and make recommendations to theauthorities. The latter are responsible for decisions

on protective measures and communicating theseto the public.

By 1981 all nuclear power plants were required todraw up a detailed emergency plan. Local and stateauthorities also had to develop a disaster plan withguidelines for evacuation and other preventiveactions. The Federal Emergency Management

Agency (FEMA) and the NRC are responsible forthe supervision of nuclear emergency planning.Every nuclear power plant is required to test itsemergency plan jointly with FEMA, the NRC,local authorities, the re department and other

emergency workers at least once every two years.In addition, small-scale exercises are organisedregularly. The emergency plans are still beingcontinuously improved on the basis of evaluationsof exercises and actual incidents.


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Development of nuclear energy

There was no prohibition on new nuclear power plants in theUSA. Many reactors under construction or being commissionedwere subject to expensive reviews and modications. In 1979 theconstruction plans for 129 reactors were approved. Eventually only53 of them were completed. Fifty-one orders with the producer ofThree Mile Islands reactors, Babcock & Wilcox, were cancelled.Between 1979 and 2009 no additional nuclear power plants were

built due to the regulations becoming much stricter. To meet thesestringent requirements the construction of installations requiredmore time and huge investments. Furthermore, the opposition oflocal residents was growing. At the start of 2009 around a hundrednuclear reactors accounted for 20 percent of electricity supplied inthe USA. It is to be expected that most operators will want to renewtheir licenses to allow a total of sixty years operation. At the start of2009, 48 applications had already been approved.

According to International Atomic Energy Agency (IAEA) statistics,the accident also marked a turning point in the global developmentof nuclear energy. From 1963 to 1979, the number of reactorsunder construction throughout the world rose practically everyyear. From 1980 to 1998 the number fell again every year. Sincethe beginning of this century there has been renewed interest innuclear energy in the ght against CO2 emissions and climatechange.

Effect on the public opinion in the USA

Most Americans saw nuclear energy as the wonder of their age: the

ultimate answer to the growing demand for energy. The authoritiesand the nuclear industry portrayed the new technology as a cheap,clean and safe source of electricity. Also the population in the neighbourhood of Three Mile Island waspro-nuclear. Civilians did not doubt the safety and trusted the industry and the authorities. The sectorkept quiet about problems in nuclear power plants. Nor was the public informed of previous nuclearincidents.

However, the Three Mile Island accident occurred in the open and crisis communication as such hadnot yet been invented. Because of unclear and conicting statements and confusion over protectivemeasures, Metropolitan Edison Company, the Nuclear Regulatory Commission (NRC) and theauthorities all came over as incompetent and misleading. The entire nuclear sector lost a great deal ofits credibility. It appears from research that no systematic attempt was made to suppress information.The conclusion was that the parties concerned had communicated feebly and confusingly about the

facts and the risks. Furthermore, it was extremely difcult for the media to understand this complexsubject. All this led to civilians not being well informed and feeling misled. Public dissatisfaction withand distrust of the sector grew. From now on people demanded more information about nuclearactivities.

Immediately after the accident there were numerous demonstrations against nuclear energy in theUSA. In Washington around 120 000 people took to the streets. Before then many people regardedthe antinuclear activists as extremists, but from 1979 on the public at large recognised the real risks ofthe technology. In the early 80s national opinion polls showed that the accident had a negative impacton public opinion and support for nuclear energy. Before the accident, an average of 55 percent of Americans supported the construction of new

nuclear power plants. After the accident this fell to 47 percent.

The accident also boosted the NIMBY syndrome. (NIMBY stands for Not In My Back Yard.This means that many people want to make use of services, but dont want any bother from them.)

Figure above: global evolution of new reactorsPhoto below: protests against restarting the other reactor at Three Mile Island


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Ever since 1975 the number of opponents ofbuilding nuclear power plants in the immediateenvirons had been rising steadily from 32 to41 percent in 1978. After the accident thisproportion increased to 60 percent. Despite this opposition, over 70 percent ofthe population supported the completion ofthe nuclear power plants under construction.Only 20 percent wanted permanent closure ofall nuclear power plants.

These events did not just have an effect on publicopinion on nuclear energy. During the 70s therewere around 15 percent more proponents ofnuclear energy than of coal-red power stations.

After the accident the tables were turned andthere were more champions of coal-red powerstations than of nuclear ones.

Since 1979 public concern about nuclear energyin the USA has not changed much. At 49 percent in 2009, almost half of Americans

are still for the construction of new nuclearpower plants. The number of declared opponents has fallenfrom 45 percent immediately after the accidentto 32 percent in 2009. Three quarters of the public see the disposal ofradioactive waste as a problem. Half are worried about releases of radioactivematerial and public health.

International Impact

In the immediate aftermath of the accident atThree Mile Island there were worldwide protestsagainst nuclear energy. In Western Europe,

Japan and Australia tens of thousands of peopletook to the streets. Despite the demonstrationsthe accident had little effect on public opinionin Europe. Here the disaster at the Chernobylnuclear power plant in 1986 had a strong negativeimpact. Conversely, Chernobyl had little effect on

public opinion in the USA. The distance from theaccident explains the different reactions.

National reactions

Because of the accident, various countries withnuclear installations acquired a greater concernfor safety. They sent experts to Three Mile Islandto study the causes. Their ndings led to revisionsof national safety programmes. However, becausethe accident was due to technical defects andoperator errors, no major design changes wereneeded in Western reactors. The emphasis waschiey on improving the control equipment andmaking training more professional.

The impact of the accident on general energypolicy remained very limited in most Europeancountries. France did not depart from the nuclear route

it had taken. It ensured that its installations

were safe and tted with automatic control andcooling systems that are completely differentfrom those at Three Mile Island. Japan also refused to change its policy, butpromised to enhance safety measures andimprove systems where necessary. Germany did make minor concessions to theantinuclear movement. It scrapped plans for anuclear fuel recycling plant. The Netherlands deferred a programme forthe storage of nuclear waste. In Spain the socialist and communist partiesdemanded suspension of all new nuclear plans. In Belgium the mayor of Huy ordered theclosure of the pressurized water reactor inTihange out of concern about safety problems.The decision was quashed by a ministerialorder.

In December 1979 the Governor of Pennsylvaniaand some of his staff paid a visit to the SovietUnion. In order to share their experiences, theymet top ofcials and scientic leaders in the eldsof nuclear energy and emergency planning. Tothe great concern of the Americans, the Russians

stated that they regarded nuclear safety as a solvedproblem. They thought that the events at ThreeMile Island, or as they called it Five KilometreIsland, were over-dramatised. Soviet reactorswould shortly be so safe that they could be built inRed Square. Unfortunately history proved themwrong when in 1986 a reactor at the Chernobylnuclear power plant exploded.


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The reinforced role of the International Atomic EnergyAgency

Together with the disaster at Chernobyl the Three Mile Islandaccident led to worldwide awareness of the risks of nuclear energy.They acted as the spur for national governments to reinforce the

role of the International Atomic Energy Agency (IAEA) in nuclearsafety. The Agency was formed in 1957 as an intergovernmentalforum for the promotion of nuclear research and safety and theexchange of technological knowledge. In 1983 the IAEA started itsIncident Reporting System. This requires the national governmentsof the member states to report nuclear incidents and accidentsto the IAEA. Cooperation with this system is in the interest of allmembers since, in order to learn the maximum from one another,members have to exchange as much information as possible.

Since the 80s the IAEA has played a central role in the jointdetermination of standards that form the basis of an international

nuclear safety culture. The Agency has also started voluntaryprogrammes to assist nuclear power plants in evaluating andoptimising safety performance. In 1994 the member states ratieda new convention on nuclear safety. For the rst time it laid downinternationally accepted obligations on such things as the design,construction and emergency planning of nuclear power plants. Atthe beginning of 2009 the IAEA counted 146 member states whichhave given their assent to the agreed arrangements.

Photo above: the Chernobyl nuclear power plant in UkraineFigure below: the ag of the International Atomic Energy Agency (IAEA)

The Federal Agency for Nuclear Control (FANC)

In Belgium the Federal Agency for Nuclear Control (FANC) is responsible for the supervision ofthe nuclear sector. The Agency ensures that staff, the public and the environment are protected

from the dangers of ionising radiation. It imposes laws and regulations on the subject andguarantees compliance with them by means of checks and inspections. On an international level,the FANC operates within the European Union and the International Atomic Energy Agency(IAEA). In 2007 Bel V was formed as a subsidiary. Bel V is answerable to the FANC and dealswith all regulatory activities related to nuclear safety and radiation protection.

FANC manages the automatic Telerad measurement network, which continuously records theradiation on Belgian territory. It also checks radioactive contamination of the environment,drinking water and food. The Agency is closely involved in the organisation of the nuclearemergency plan, especially in the evaluation of the consequences of an accident and crisiscommunication with the public and media. In addition to this, FANC stimulates and coordinatesresearch and development relating to radiation protection and nuclear safety and disseminates

information on these subjects.


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9. Conclusion

The accident at the Three Mile Island nuclearpower plant was the most serious in the historyof American commercial nuclear energy. It beganas a minor technical defect, but because of humanand organisational failures it almost ended up as afull-blown disaster. Operators made crucial errors,partly attributable to unclear safety proceduresand inadequate training. They were unable toappraise the emergency correctly and deal withit. The management of the power plant and theNuclear Regulatory Commission (NRC) werealso responsible because of a lax attitude towardsnuclear safety.The events led to the realisation that a severenuclear disaster was quite possible and that the

human factor plays a crucial role in guaranteeingsafety. This understanding resulted in atransformation of the nuclear sector in the USA.Nuclear power plants underwent technicalreviews and modications. Control roomergonomics were optimised by better matchingthe operator equipment with the interaction

between man and machine. More attentionwas paid to reporting, feedback and advice onincidents and to radiation protection. In addition,staff training was modernised and emergencyplanning enhanced. Thanks to strict regulation

and stringent inspections nuclear power plantsin the USA have performed better and better interms of safety and reliability since the 80s.

Despite the seriousness of the accident and thepartial melting of the reactor core, the emission ofradioactive substances remained limited and therewere no directly demonstrable consequencesfor public health or the environment. But theaccident did have a severe negative effect onpublic opinion. In the collective memory nuclearpower plants were henceforth associated withdanger. Great efforts by the industry could not

restore public condence. In the USA supportfor nuclear energy fell and members of the publicnow demanded more information about nuclearactivities.

In Europe the disaster at the Chernobyl nuclearpower plant in 1986 resulted in a comparablechange in public opinion. Both accidents ledto a worldwide realisation about the risks ofnuclear energy. They had a far-reaching effecton the nuclear sector and acted as the spur tofundamental changes. Scientic research andtechnical safety arrangements were expanded.The human factor attracted more attention andpolicy on supervision and control was adjusted.Nuclear safety has grown to become a matterof international importance. The International

Atomic Energy Agency played a central partas a policy instrument for intergovernmentalagreements. In this way there developed over theyears an international nuclear safety culture.

Because of the accident at Chernobyl theEuropean Union laid down contamination levelsfor agricultural products in the event of radioactiveemissions. Belgium drew up a nuclear emergencyplan and set up the Telerad measurementnetwork to perform continuous checks on theradiation on its own territory. Later the Federal

Agency for Nuclear Control (FANC) was formedin order to centralise the fragmented powers overradiation protection and nuclear safety.


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10. More information

Websites

www.sckcen.be: Website of the Belgian Nuclear Research Centre with all kinds of information and

documentation on nuclear topics.

www.threemileislandinfo.com: Website of the still operational Unit 1 at Three Mile Island withinformation about that unit and about the accident in Unit 2.

www.threemileisland.org: Website of Dickinson College, a university in the Three Mile Island area,with extensive information about the accident and its consequences.

www.nrc.gov: Website of the Nuclear Regulatory Commission (NRC) with a fact sheet about theaccident and its consequences and extensive information about the nuclear industry in the USA.

www.ans.org: Website of the American Nuclear Society (ANS) with thematic documents about the

accident and information and news about the nuclear industry in the USA.

www.euronuclear.org: Website of the European Nuclear Society (ENS) with information and newsabout the nuclear industry in Europe.

www.world-nuclear.org: Website of the World Nuclear Association (WNA) with information aboutthe accident and the consequences and all kinds of information about the nuclear industry throughoutthe world.

www.iaea.org: Website of the International Atomic Energy Agency (IAEA) with information about theAgencys activities.

www.fanc.be:Website of the Federal Agency for Nuclear Control (FANC) with information aboutthe FANCs activities and the regulations, cases, brochures and publications concerning radiation

protection and nuclear safety.

Documentation

The Presidents Commission -Report of the Presidents Commission on the accident at three mile Island - theneed for change: the legacy of TMI- Washington, DC, USA: The Presidents commission, 1979. - 179 p.

Alvin M. Weinberg - Continuing the nuclear dialogue - Illinois, USA: American Nuclear Society, 1985. -204 p.

Mosey, D - Reactor accidents - Nuclear safety and the role of institutional failure - Sutton, UK: Nuclearengineering international, 1990. - 180 p.

Kemeny J.G. Het ongeluk op Three Mile Island - Terugblik op Harrisburg In: Natuur en Techniek,48:5(1980), p. 360-377

Brian K. Grimes, Steve L. Ramos, Bernard H. Weiss - Emergency Planning and Preparedness Since ThreeMile Island - In: Progress in Nuclear Energy, 10:3(1982), p. 363-386

Barbara D. Melber - The Impact of TMI Upon the Public Acceptance of Nuclear Power - In: Progress inNuclear Energy, 10:3(1982), p. 387-398

Llory, M -Laccident de la centrale nuclaire de Three Mile Island - Vingt ans aprs : nouvelles perspectives pour

la scurit, nouvelles inquitudes - Paris, France: LHarmattan, 1999. - 366 p.


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30 years on

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MILEISLAND

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