nuclear waste management

Health Effects of Radiation&

Nuclear Waste Management

Biplab Das

Scientific Officer & Safety Coordinator

Kalpakkam Reprocessing Plant

BARC, Kalpakkam1

NATURALSOURCES OF RADIATION

• COSMIC RAYS

• EARTH’S CRUST

• AIR

• HUMAN BODY2

Natural Radiation : Terrestrial sources

Radon, Thoron

Th, U - a few grams per 1,000,Kg of ground material

K-40 : 30 Bq per gram of potassium

3

Radon and Thoron

Man

aval

akku

rich

i

&K

eral

a co

ast

Stable Daughter

210Tl

214Bi

218Rn222Rn

238U

234Th

234Pa

238U

230Th

226Ra

218Po

214Pb

218At214Po

210Pb

210Bi

210Po

206Pb

Natural uranium as ore in soilUnstable parent

Gas

Gamma emitters

Alpha emitters

208Tl

212Bi

220Rn

232Th228Pa

228Th

224Ra

216Po

212Pb

212Po

208Pb

Gas

Gamma emitters

228Ra

Stable Daughter

Thorium as ore in soilUnstable parent

Alpha emitters

86Rn2224

List of Natural occurring and artificially produced Radionuclides

238U – 4.5 x 109 y

232Th – 1.4 x 1010 y

40K – 1.3 x 109 y

14C – 5700 y

99mTc – 6 h131I – 8 d60Co – 5.26 y137Cs – 30 y239Pu – 24000 y233U – 6.2 x 105 y

Natural Artificial

Produced in nuclear reactors & using accelerators

Present in earth crust and produced in the atmosphere by cosmic radiation

5

Technologically Enhanced Sources (Man-Made)

Diagnostic X-rays, radiopharmaceuticals

Nuclear Weapons Tests fallout

Industrial Activities, Research

Consumer Products

Miscellaneous:

Air Travel, Transportation of Radioactive Material

6

Air 51%

Radon & Thoron

Cosmic 10%

Food 12%

Terrestrial 14%

Natural 87%

2.5 mSv/y

Manmade 13%

Misc. 0.3%

Fallout 0

.4%

Occupational 0

.2%

Nuclear 0.1%

Medical 12%

7

high energyhigh energyionizing radiationionizing radiation

Alpha particlesBeta particlesX -rays Gamma raysNeutrons

low energylow energynon-ionizingnon-ionizing

Radio wavesMicro wavesLight Heat

8

• RADIATION

• RADIO ACTIVITY

• RADIOACTIVE MATERIAL

9

Unstable atoms attain stability by throwing out the excess nucleons in the form of Radiation as Particles or Electromagnetic waves.

Material with radioactive atoms are called Radioactive Material.

Beta radiation

RadioactivityRadioactivity

The process of spontaneous emission radiation by unstable nucleus is called Radioactivity.

Tritium (unstable) Helium (stable)

10

Beta radiation

Tritium(unstable)

Helium (stable)

Example :

11

ActivitySpontaneous decay of nucleus of an atom

Usually by emission of Particles ( Alpha and Beta )

And by electromagnetic Radiation ( X, Gamma ray )

12

Alpha Particles

• Heavy and Charged particles• Cause more ionisation• Loose energy faster• Less penetration power

13

Beta Particles

• Smaller mass • Chararged particles• Cause ionisation• Less penetration power

14

Gamma Rays

• More Penetrating waves• Also cause ionisation

15

Penetrating power of Radiation

Alpha

Beta

Gamma and X-rays

Paper Plastic Lead Concrete

Neutronn

Use of right shielding materials reduces radiation exposure 16

Fission• If neutron absorption occurs

in certain nuclei, fission can be induced.– 235U, 239Pu and 233U can all

undergo fission by the absorption of a thermal neutron

– 238U can fission from the absorption of a fast neutron.

17

18

Nuclear Fission

Consider a neutron bombarding a 235U nucleus:

19

Units of Radioactivity

• Becquerel (Bq) - the SI unit of radioactivity. Defined as one radioactive transformation per second.

• Curie (Ci) - the traditional unit of radioactivity. Now defined as below:

• 1 curie (Ci) = 3.7 x 10 10 becquerel (Bq)20

Units of Exposure

• Roentgen: 1 Roentgen = 2.58x10 -4 C/kg

• Absorbed Dose:1 Gy = 1 J/kg = 100 Rad

• REM = Rad x W.F21

Types of radiation exposures

External exposure

Internal exposure

source

sourceInhalation

Ingestion

Injection

Skin Absorption22

• Measures for control of exposures

External exposures – TLD

Internal exposures – PPE, ventilation and isolation

Management control

Training of personnel

Adequate supervision and radiation protection surveillance

23

ZONING

• Red Zone• Amber Zone• Green Zone• White Zone

24

Radiation and Contamination• Two frequently confused quantities

• Radiation arises as a flux of energy in the form of EM waves or a stream of particles that gives rise to a field. Energy absorbed per unit mass is the dose of radiation

• Contamination is the presence of radioactive material in the wrong place. It gives rise to a human internal hazard and to the presence of a radiation field (an external hazard).

• Contamination control is an essential radiation protection activity.

25

WHAT IS radioactive CONTAMINATION?

• Presence of radioactive material in undesired place.

• Radioactive material either in powder or liquid form can be present inside a glove box but not in the operating /working area

26

Control of airborne contamination

• Result in internal exposure, skin contamination

• Design measure : Layout , Ventilation

• On-job protection: PPEs, Respirators etc

27

Control of Surface contamination: area/equipment

• Result in airborne contamination, personnel contamination and internal exposure

• Detection method : Swipe sample on the floor, scan with monitor for fixed contamination

28

Control of Personnel Contamination

• Skin exposure or internal exposure

• Gloves, gumboots, plastic suit, Hoods

• Detection method: swipe samples and scan with monitor, nasal swaps etc.

29

Swipe Samples

• Swipe samples indicate the amount of transferable contamination

• Swipe a piece of absorbent sheet on the floor or equipment

• Estimate the activity in the swipe paper

• Measure the area covered

• Expressed in terms of Bq /100 cm2

30

CONTROL OF INTERNAL EXPOSURE

• RUBBER STATION

• VENTILLATION

• USING PPE

31

PROTECTIVE CLOTHING

Protective clothing serves two functions:

• Protects the individual from body

contamination.

• Prevents the spread of contamination

32

EVLAUATION OF RADIATION STATUS

• AREA MONITORING- area gamma monitors

• AIR MONITORING- air monitors, air sampler

• CONTAMINATION MONITORING- swipe samples

33

Evaluation of personnel exposure

• EXTERNAL-- TLD– DRD etc.

• INTERNAL– WHOLE BODY COUNTING,

BIO- ASSAY( URINE, BLOOD)

DOSELIMIT:INTERNAL+EXTERNAL= 20 mSv

DOSE RECORDS MAINTAINED34

Biological Effects of Radiation

1. Somatic Effects

2. Hereditary Effects

35

Stochastic Effects

1. Probabilistic Occurrence of effect

2. No threshold dose

3. Low probability

4. Long latent Periods

5. Result of acute and chronic exposure

6. Important from protection point

36

Deterministic Effects

1. Severity of dose is considered

2. Threshold present

37

Deterministic Effects

– Occurs above threshold dose– Severity increases with dose

– Tend to occur at

– whole-body doses > 100 rem.

Examples:– Alopecia (hair loss)– Cataracts– Erythema (skin reddening)– Radiation Sickness– Temporary Sterility

38Dose

Effects

“Dose-ResponseCurves”

Stochastic Effects

• Occurs by chance• Probability increases with dose

• effects are documented only at doses > 10 rem.

39

• Carcinogenesis• Mutagenesis• Teratogenesis

Dose

Effect

“Dose-ResponseCurves”

?

While moderate doses cause well-documented effects, one cannot measure significantly effects at the doses where real doses or regulated doses occur

Effect

Dose 40

Type of Exposure

1. Acute Exposure: Dose received in a short time

2. Chronic Exposure:Dose received over longer time periods

41

Energy Deposition

• Radiation interacts by either ionizing or exciting the atoms or molecules in the body (water)

• Energy is deposited and absorbed as a result of these interactions

• Absorbed Dose is defined as the energy absorbed per unit mass of material (tissue in this case)

42

• Produce free radicals.

• Break chemical bonds.

• Produce new chemical bonds and cross-linkage between macromolecules.

• Damage molecules that regulate vital cell processes (e.g. DNA, RNA, proteins).

How does radiation injure people?

43

Direct Action

• Radiation interacts directly with a molecule through excitation or ionization

• The molecule dissociates

• The effect depends on which molecule was affected

Indirect Action

• The body is composed primarily of water and most direct action will be on water

• This results in hydrolysis of water

End Result:

• Disruption cell membrane integrity, cellular chemistry and DNA replication.

44

Biological Damage

• Damage can occur at various biological levels– Sub-cellular– Cellular (cell death)– Organ (malfunction)– Organism (cancer, death)

45

Cellular Radio-sensitivity

46

Cells that divide more rapidly are more sensitive to the effects of radiation ...

… essentially because the resulting effect is seen more rapidly.

Most Sensitive: Blood-forming organsReproductive organsEyes, Skin, Bone and teeth, Muscles

Least sensitive: Nervous system

Factors Influencing Biological Effect

• Total absorbed energy (dose)

• Dose rate– Acute (seconds, minutes)– Chronic (days, years)

• Type of radiation

• Source of radiation– External– Internal

• Age at exposure47

Quality Factors

Radiation Quality Factor (Q)

Alpha particles 20

Beta particles 1

Gamma rays 148

Different Ionization densities

X-ray,γ-Ray, neutron-- not many ionizations

α- particles -- Very high density

β- particles -- High density at end

X-ray passes straightthrough cell

No change to cell

Cells are undamaged by the dose

What will happen when radiation interacts with tissues?

49

X-ray causes achemical reaction incell, but no damage

done or damagerepaired by cell

No change to cell

*

Cells are damaged, repair the damage and operate normally

50

DNA damaged in a“fatal” way”

Cell killed

*

Cells die as a result of the damage

51

OBJECTIVE

Keeping radiation exposure As Low As Reasonably Achievable (ALARA) and

within the prescribed limits;

Taking actions to prevent accidental exposures,

Mitigating the consequences of any accident that might occur in nuclear

and radiological installations.

52

PRINCPLE OF RADIATION PROTECTION

• JUSTIFICATION

• OPTIMISATION

• EQIVALENT DOSE LIMITS

53

Short-term effects usually occur when there’s a large amount of

exposure to radiation.

Short-Term Effects of Radiation

54

Long-Term Effects of Radiation

These effects take longer to become apparent and can be caused by much lower levels of radiation.

Uranium miners tended to get lung cancer due to breathing in gases which emitted alpha particles.

People who painted the dials of clocks with luminous paint developed one cancer from using their lips to make points on the brushes.First example of radiation induced leukaemia (blood cancer)

One of the most important long-term effects of radiation is that of cancer in various parts of the body.

55

Exposure to ionising radiation does not necessarily cause cancer

The mechanisms for cancer occurring are poorly understood at the moment. One theory is that the ionising radiation affects the DNA material within us – our genetic make-up. Our DNA contains genetic instructions which control the operation and reproduction of the cells. If ionisations caused by ionising radiations alter these instructions in the DNA, there is a chance that cancer will develop.

Genetic damage can be caused to cells by radiation, including cells which are involved in reproduction.

56

ACUTE RADIATION DOSE

An acute radiation dose more than 10 rad or greater, to the whole body delivered during a short period of time.

Blood-Forming Organ • Dose threshold : >100 rad• Affected organs/cells : bone marrow, the spleen

and lymphatic tissue. Symptoms: Internal bleeding, fatigue, bacterial

infections, and fever.

57

Gastrointestinal Tract Syndrome : >1000 Rad • Affected organs/cells: Linings of stomach & intestines. • Symptoms: nausea, vomiting, diarrhea, dehydration,

electrolytic imbalance

Central nervous system syndrome • Dose threshold: >5000 Rad • Affected cells: Nerve Cells.• Symptoms: loss of coordination, confusion, coma,

convulsions, shock, and the symptoms of the blood forming organ

58

Chronic dose

A chronic dose is a relatively small amount of radiation received over a long period of time.

• The body is better equipped to tolerate a chronic dose than an acute dose. The body has time to repair damage because a smaller percentage of the cells need repair at any given time. The body also has time to replace dead or non-functioning cells with new, healthy cells.

• This is the type of dose received as occupational exposure.

59

• Reproductive System: Doses of about 6 Gy are required to permanently sterilize males (sterility occurs after several months)

• Lens of Eye: At doses 2-6 Gy, damage to the lens, significant to cause eventual cataract formation.

• Skin: Dose of 6-8 Sievert — effects occur 1-2 days after exposure: Effects: Erythema.

• Cataract Dose of 50 Sievert, Superficial Cataract

• Lungs: Relatively radio resistantDoses at 7-8 Sievert, 60

Prompt Effects

• Examples• Blood count changes----above 10 rem• Vomiting (threshold)---100 rem• Mortality (threshold)---150 rem• LD50/60* (with minimal supportive care)--320 – 360

rem• LD50/60---(with supportive medical treatment)--480 – 540 rem• 100% mortality --(with best available treatment) -800 rem 

61

Seen immediately after large doses of radiation delivered over short periods of time

Delayed Effect- Cataract

• Cataracts are induced when a dose exceeding approximately 200-300 Rem is delivered to the lens of the eye. 

• Radiation-induced cataracts may take many months to years to appear.

• Radiation-induced cancers may take 10 - 15 years or more to appear.

62

That may appear months or years after a radiation exposure. Ex-cataract and cancer

RADIOACTIVE WASTE MANAGEMENT

Radioactive Waste

Radioactive wastes are waste containing radioactive chemical elements that do not

have a practical purpose.

Objective of Radioactive Waste Management

To protect radiation workers, general public and their environment from potential hazards arising from waste

SOURCES OF RADIOACTIVE WASTES

• Natural radioactive material• Artificial radioactive elements by neutron

activation ( Co-60 )• Fission products and alpha wastes from

nuclear fission

Rad.Waste from Nuclear Fuel Cycle

– Mining and Milling,

– Fuel Fabrication,

– Nuclear Power Generation

– Reprocessing & Waste Management

• Fission products: Cs137, I131, Sr90

• Activation products: Ar41, Co60, H3

• Solid and Liquid Waste from decontamination of equipment, spaces and materials, contaminated equipment etc.

Rad. Waste from Industries, Medical facilities and Research

Sealed Spent Sources, Contaminated filter papers. Plastics, Glassware, Syringes, Carcasses etc.

Co60, C14, P32, Sr90, Au198, Ir192, Cs137

Basic Philosophies of Waste Management

Delay and decay Delay and decay

Dilute and disperseDilute and disperse

Concentrate & containConcentrate & contain

CATEGORIES OF RADIOACTIVE WASTE

LIQ U ID W AST E

N on-trea tab le T rea tab le

SO LID W AST E G ASEO U S W AST E

W A S T E S F R O M N U C LE A R IN D U S T R Y

LIQUID WASTES – SEGREGATION, COLLECTION & TRANSPORT

TypeCategory&Sp. activity

(mCi /l)Source Collection Disposal

Potentially Active

I (<10-6)Personal washes & showers

PipelinesDilution and

discharge

Low LevelII (<10-3) & III (<10-1)

Sumps, Labs &

decontamination

Spl. Pipelines/ tankers

Treatment, dilution and discharge

Intermediate Level

IV (<104)Research Activities

Spl. Containers/tankers

Treatment, dilution and discharge

High Level V (>104)Reprocessing of spent fuel

Spl. containers/tankers

after coolingImmobilisation

TREATMENT OF LOW AND INTERMEDIATE LEVEL LIQUID WASTES

• Solid Phase Separation

• Chemical Precipitation( Using Chemicals to precipitate Cs and Sr)

• Ion-exchange ( Polishing treatment prior to Disposal Cs 137)

• Evaporation (After proper conditioning passed thro evaporator and the vapor is condensed)

CLASSIFICATION OF SOLID WASTE

CATEGORYSURFACE DOSE

[D] (mR/h)REMARKS

I D < 200 No shielding required

II 200 < D < 2000 Some shielding

III D > 2000 Shielding required

IVAlpha

Contaminated (Bq/m3)

Specially treated

TREATMENT OF SOLID WASTES

Types of waste and Immobilisation Matrix

Sludges Spent ion-exchange resins Evaporator bottoms

Cement Bitumen Plastics Glass or Synrock

Types of waste

Immobilisation Matrix

Near Surface Disposal FacilitiesDisposal Criteria

• The solid waste, packed suitably are disposed in the Near Surface Disposal Facilities.

• These NSDF are of three types:– Brick Walled Trenches – 20 mR/hr.– RCC Trenches 20 mR/hr to 50 R/hr.– Tile Holes > 50 R/hr.

• The facilities are engineered to provide multiple barriers between the waste and the environment.

• The higher the surface dose, the more the number of barriers.

• NSDFs are designed to hold the waste for up to 300 years - activity would see 10 half lives or decay to 1/210 of its original value.

CLASSIFICATION OF GASEOUS WASTES

CATEGORYSPECIFIC ACTIVITY

[A] (Bq/ml)

I A <3.7 X 10-6

II 3.7x10-6 < A < 3.7x10-2

III A > 10-2

MANAGEMENT OF GASEOUS WASTES

• Particulate Removal- High Efficiency Filter

• Gaseous Waste Removal- Charcoal Filter & Molecular Sieve

• Gaseous Wastes from Nuclear Power Plants – Particulate Filter System (such as HEPA)– Iodine Adsorption System– Noble Gas Delay System

• Gaseous Wastes from Fuel Reprocessing Plants – 85Kr by cryogenic distillation and adsorption– 129I by caustic scrubbing

SURVEILLANCE

• REGULAR AREA / AIR MONITORING

• PERIODIC BORE WELL WATER ANALYSIS

• PERIODIC SOIL ANALYSIS

• PERIODIC VEGETATION SAMPLES

• ENVIRONMENTAL SURVEY AROUND NUCLEAR FACILITY

Ion-exchange method

Ion-exchange is one of the methods used to remove the radionuclides from the liquid waste.

e.g. If NaCl has to be removed from a liquid

R-H+ + NaCl R-Na+ + HCl (Cation exchange)R+OH- + HCl R+Cl- + H2O (Anion exchange)

Regeneration of the bed….

2 R-Na+ + H2So4 2 R-H+ + Na2SO4

R+Cl- + NaoH R+OH- + NaCl

Solidified high level waste equivalent to power consumed by an average Indian family in 25 years, if all the power is from nuclear power station.