Nuclear techniques for peaceful development

Radioisotopes and radiation technologyin industryA report on some lesser known,but widely applied, industrial applications

by Jacques Guizerix, Vitomir Markovic, and Peter Airey

Industrial radiation processing is based on the use ofradiation as a source of energy to induce specificchemical, physical, and biological changes. On the otherhand, applications of isotopes in industry, either assealed sources or as tracers, rely on the measurementsof physical signals which monitor properties of interest.

Examples of applications abound: For example,thousands of nucleonic gauges are used in the paper andsteel industry to optimize product quality and productionefficiency by monitoring continuously the paper weightper unit area, or the thickness of steel. Many tens ofthousands of level gauges often permit measurements indifficult conditions, e.g. in corrosive media, or toprovide simple, reliable, and cheap solutions thatcompete favourably with those involving non-radioactive equipment. Non-destructive testing isdeveloped worldwide, and gammagraphy is a classicalcomponent, in use with other, non-nuclear methods, ofall modern laboratories specialized in this area.

Many of these applications, which involve sealedsources of low to high activities — say, a few millicuriesup to several curies — are well known to the generalpublic* This article offers an overview of radiationprocessing and tracer applications which are perhapslesser known, although widely applied for the benefit ofindustry.

Industrial applications of radiation

In industrial applications, radiation effects areproduced at rates comparable to manufacturing output ofother industrial techniques. Therefore, both the energy— to ensure proper penetration through products — andpower — to ensure adequate throughput — play impor-tant roles. Other important factors for industrial applica-tions are reliability of operation (usually not less than90% of utilization), process control, efficiency, andsafety.

Mr Guizerix is head of the Industrial Applications and ChemistrySection of the Division of Physical and Chemical Sciences, of whichMr Markovic is a staff member. Mr Airey is a member of theAgency's Division of Technical Assistance and Co-operation.* The curie is a unit of the rate of isotope decay. One curie is equiva-lent to 37 X10 disintegrations per second or 37 gigabecquerels(37GBq).

Several types of radiation sources satisfy all theserequirements. It can be safely stated that today's radia-tion source technology and engineering can matchalmost any industrial requirement. The principal sourcesof radiation are the radioactive isotope cobalt-60 forgamma radiation, and electron beam (EB) acceleratorsfor high-energy electrons, from 0.15 to 10 mega-electron volts (MeV).

Gamma radiation sources and technology.Cobalt-60 has dominated this market almost exclusively.This situation is likely to persist, since another isotopeonce considered an alternative, namely caesium-137, isnot available in quantities needed for industrial through-puts. Although one such commercial irradiator hasrecently been installed in the USA, it is unlikely thatmany more will be commissioned in the next decade.

Gamma radiation from cobalt-60 penetrates deeplythrough irradiated materials and is very convenient forthe treatment of bulky and packaged products. Its mainapplication is for industrial sterilization of single-usemedical products and, to a lesser extent, for the steriliza-tion of Pharmaceuticals, spices, and other products.

About 140 industrial facilities are in commercial useworldwide (about 40 countries) for radiation steriliza-tion. Total installed activity is about 3.1018 becquerels(Bq), or 80 megacuries (MCi). A typical industrial facil-ity loaded with 3.7xlO16Bq (1 MCi) has a capacityequivalent to about 15 kilowatts (kW) of radiationpower. It can sterilize (at 2 Mrad) about 25 000 to30 000 cubic metres of materials per year. Facilitieswith total installed activity up to 2.2 x 1017Bq (6 MCi or90 kW) are in operation.

Other applications include food irradiation (severalcommercial installations and a number of smaller,demonstration units); disinfection of sewage sludge (onecommercial irradiator in the Federal Republic of Ger-many) and several pilot facilities; and some other small-scale or special applications to, for instance, wood-polymer composites, polymerization, radiation graftingfor battery separators, biomedical applications, and thevulcanization of rubber latex.

EB radiation sources and technology. Industrialapplications of electron beams started in the 1950s withcrosslinking of polyethylene film (to produce heat

20 IAEA BULLETIN, 2/1987

Nuclear techniques for peaceful development

shrinkable film for packaging) and wire insulation. It hassteadily expanded. At present, several hundred EBaccelerators are used for different commercial applica-tions. Two distinct classes of accelerators and applica-tions have been developed:• Low energy EB accelerator. In an energy range of0.15 to 0.5 MeV, they have fully shielded product hand-ling areas and radiation shielding is an integral part ofthe accelerator. They are relatively small in volume,with small space requirement, and can be easily and con-veniently installed in any working area or in existingproduction lines. The useful range of electrons in thisenergy range is very small (less than 1 mm) and applica-tions are limited to irradiation of the surface layers.Typical applications are crosslinking of thin plastic film;crosslinking of thin wire insulation; curing of coatingson paper, wood, plastics, metal, etc.; curing of siliconrelease coatings on paper and film; curing of offset inks;and curing of laminating adhe.sives.

The radiation curing technology replaces the ultravio-let (UV) technology whenever pigmented coatings areused or very high production speeds are required. Inmany applications, such as the curing of laminatingadhesive between wood panels and foil/paper withsimultaneous curing of the protective top-coat, the use ofradiation cannot be replaced by any other method. Highpower EB machines, 300-500 kW, are available with anenergy range up to 0.3 MeV. Production capacities ofthe order of 1000 metres per minute (at 10 kilograyabsorbed dose) are easily attainable with commercialaccelerators. These machines have also been success-fully tested for treatment of flue gases for environmentalconservation. (See the article on this subject in thisedition on page 25.)

• EB accelerators in the energy range of 0.5 to10 MeV. These are commercially available with powerratings up to about 200 kW. Thick concrete shielding(1.5 to 2 metres) surrounds radiation areas. Thesemachines are now used by many major industries,including plastics, automotive, rubber goods,petrochemical, and wire and cable. The main applica-tions include radiation crosslinking of plastics (wire andcable insulation, heat shrinkable materials, hot waterpolyethylene pipes, foam, etc.); radiation vulcanizationof rubber; and modification of bulk polymers (controlleddegradation).

Most accelerators used for these applications are inthe energy range of 0.5 to 4 MeV. A few are used forfood irradiation (disinfestation of grain in the USSR anddecontamination of animal feed in Israel). Attempts touse accelerators for decontamination of sewage sludgehave not been very successful up to now, but no definiteconclusions have yet been reached. The machines in theenergy range of 600-800 kV appear to have great poten-tial for use in environmental applications, namely forprocessing of combustion flue gases.

Several linear electron accelerators (LINAC) areused commercially for sterilization of medical products(in the UK, USA, France, Denmark, and Poland).

Projected annual demand for cobalt-60for different industrial applications

I 30

20

Medical sterilization s

Waste decontamination

1980 1985 1990

The trend tor cobalt-60 demand in medical sterilizationcan be expected to follow or even surpass the prediction (aswas the case in the period 1983-85). The development of foodpreservation and waste decontamination is subject to severalexternal factors. Actual data for 1987 are probably below thepredicted values.

However, due principally to high cost and low powerlevels, they have not found as widespread use as low-energy direct current (DC) machines. The steady growthof EB applications is well illustrated by the situation inJapan, as shown below.

100

90

80

| 7 0

5 60

| s oo

I 40

I 30

20

10

0

Electron accelerators installed in Japan

I I Others

7771 Tire rubber

E2S3 Curing

IIHII Shrmicabletubesandsheets

£2221 Polyolefin foams

I I Wire and cable insulation

ES3

'.*.i .v.i >vJ fc>*3 t.'r'i. f^A tyJ fcy2 L'.'l f.;.-l ty.i Lvj Lv*. L̂ *t ivJ 1*V'

1969 70 71 72 73 IK 75 76 77 78 79 80 81 82 83 81. 85Year

Application

Electron accelerator

Number Total power (kW)

Number of

companies

Wire and cableinsulation

Polyolefin foams

Shrinkable tubes

and sheets

Pre-vulcanization of

tire rubber

30

10

7

1600

338

480

410

13

IAEA BULLETIN, 2/1987 21

Nuclear techniques for peaceful development

Radiation processing in developing countries

The transfer of radiation technology to developingcountries is taking place with a varying degree ofsuccess, depending on the technology, country, existinginfrastructure, and many other external factors. Radia-tion sterilization is by far at the most advanced stage ofdevelopment at the commercial level. About 20 coun-tries now operate some 25 commercial cobalt-60 gammafacilities for sterilization of medical products.

The other areas of industrial applications are gener-ally not well developed, with very few commercialinstallations in industrial use.

The Agency is continuing to provide active support inthe promotion and transfer of radiation technologythrough various activities. One of the most effectivemeans is through regional projects. An example is theproject in Asia and the Pacific of the United NationsDevelopment Programme (UNDP) and the IAEA underthe Regional Co-operative Agreement (RCA). About140 people have been trained in different subjects of

Nature of information from tracers

W////////////////////////////////////////////A

proving the reality of" Y e s - N o " type connecting links

between 2 populations

W////////////M

establishing a quantitativeAnalog type relation between

2 populations

Questions

connection?

connection?where?

connection?where?how much?

how much?

how much?when?

how much?when?

connection?where?how much?when?

Signal

0 1

J 10

0

0

llll,

\

Timedepen-dency

no

no

no

no

f(t)

f(t)

h(t)

f(t x y)

Examples

• leaks detection

• autoradiography

• autoradiography+ densitometry

Dilution method

• weighting mercuryin electrolytic cells

• flow rate measurement

System analysis

• mass flux function

• transit time distribution

• mapping pollutantdispersion

radiation technology during the past 5 years. In 1986alone, a series of eight national executive managementseminars on radiation sterilization and radiation curingwere held. More seminars and training courses areplanned for the period 1987-91. As a result, severalindustrial projects have been identified and initiated inthe region.

Industrial tracer applications

In solving problems of material transport, engineersare frequently faced with the requirement for absolute"bulk flow" measurements. As this information isnormally not available directly, they add an accuratelyknown auxiliary flow of a substance that can bemeasured, a "tracer". But first, however, it is neces-sary to establish a relation between tracer flow informa-tion and the desired bulk flow.

Tracer information is interpreted through a signalwhich can be electrical, e.g. the output of a detectingdevice, or the variation in the darkness of a nuclearemulsion, as in autoradiography. (See accompanyingdiagramme for the type of information tracers provide.)

As an example, consider the problem of leak detec-tion in a heat exchanger, which consists of the flow ofliquids in two circuits. A simple question may be posed:"Is there a connection between the two flows?" Theresponse is yes or no, and the existence of a leak isproved when a tracer injected in the first circuit isdetected in the second circuit.

More sophisticated tracer applications benefit fromsystems analysis, which is a method based on the exploi-tation of the response of a system to a stimulus appliedat the entrance to this system. One imagines a constantflow of water in a mixer in a chemical plant. The con-centration of a given species varies at the entrance to thissystem. A pulse of tracer of this species is injected at thesystem's entrance and the concentration is measured atthe exit. This function defines the transit time distribu-tion (TTD) of this material and constitutes the best"sample of mass transfer" that can be obtained. It canbe used to calculate the variation of concentration at theexit of the system, knowing the variation of concentra-tion at the entrance.

The TTD of a system can best be obtained throughthe tracer technique. It is easy to understand the impor-tance of this function, which permits the incorporationof residence times and dispersion in analysing problems.One may choose to exploit these phenomena in industry,e.g. in mixers, or to minimize them, e.g. when manykinds of oil are transported, in series, in a pipeline.

Radioactive tracer techniques present advantages:First, their concentration can be measured with detectorslocated outside pipes or vessels. Second, measurementon samples taken from a flow are simple and indepen-dent of the matrix of samples. Third, a radioactive traceris unique for labelling specific elements or chemicalspecies. For example, sulfur in hot corrosion studies ofsteel alloys may be labelled with sulphur-32 and

22 IAEA BULLETIN, 2/1987

Electron beam processor for radiation curing applica-tions. (Credit: Energy Sciences, Inc.)

revealed at the grain boundaries by autoradiography.The information obtained from the radioactive tracer,for a given cost, is normally much more extensive thanwith non-radioactive tracers.

Radioactive tracer applications are regulated by theappropriate national authorities. The very low concen-trations and the short half-lives of commonly usedtracers normally make it possible to use levels muchlower than the maximum stipulated in the regulations.

Status of industrial tracer applications

As illustrated by a guidebook now in preparation atthe IAEA, tracers are of benefit to most industries. (Seebox.) The book is being prepared by 20 authors fromeleven countries: Czechoslovakia, Finland, France,Federal Republic of Germany, German DemocraticRepublic, India, Israel, Netherlands, Poland, UnitedKingdom, and United States of America. Othercountries are also making significant tracer applications.The guidebook's scope shows that practically all indus-tries benefit from tracer applications — 68% of thecontent of this guidebook deals with chemical engineer-ing, and the remainder is mainly devoted to metallurgy,mineral exploration, and environmental and sanitaryengineering.

Tracer applications take place in laboratories, e.g. forkinetic and chemical reaction mechanism studies, aswell as in plants for trouble shooting investigations (leakdetection, pipe blockage); for the determination ofcircuit characteristics (flow rates, dead volume, branch-ing ratio, bypassing); and for process optimization andprocess control. They are used in laboratories forresearch work, or by governmental or private institu-tions providing services on a commercial basis.Commercial organizations include the Physics andRadioisotope Services, ICI, in the United Kingdom; theFrench Atomic Energy Commission; a private companyin India making only mercury inventories; and anotherone in Finland specialized in flow-rate measurements.The success of such enterprises, subject to the laws of

supply and demand, is the best proof of the economicbenefits induced by tracer applications.

In developing countries, the development of indus-trial tracer applications is very heterogeneous. Somecountries are at the stage of the most advanced countriesin this field, e.g. Chile, India, and Poland, and othersare still submitted, as are some industrialized countries,to the law which states that a "time constant" of15 to 20 years is always necessary for the application ofa new technology. Some additional delays arise foreconomic reasons and also due to the lack of informa-tion. Nevertheless, much has been achieved. (See thetable on the next page for applications in Asia and thePacific.)

Guide to radioisotope tracers in industry

The IAEA currently is preparing a comprehensiveguidebook on applications of radioisotope tracers inindustry, covering subjects from tracer methodology tocase studies in specific industries. Major headings andsections include:• The concept of tracers• General tracer technology• Tracer methodology (tracer and system analysis;basic flow modelling; tracer information in modellinglarger systems; tracer information in solving complexproblems; processes with variable flows and volumes)• Generalized applications (use of flow models; value ofparameters; flow rate; mass balances; characteristicsand use of solid tracers; mixing efficiency; trouble shoot-ing; diffusion, permeation; particle size distribution;corrosion and surface phenomena; the use of isotopes inmechanistic and kinetic studies; two-phase flows;process control; kinetic parameters)• Case studies (chemical industry; paper and cellulosepulp industry; petroleum industry; cement industry;metallurgical industry; energy industry; electronicsindustry; mechanical industry; environmental and sani-tary engineering; mineral industry)• Current trends in development and applications.

Further information on the guidebook may be obtained fromthe IAEA's Section on Industrial Applications and Chemistry.

IAEA BULLETIN, 2/1987 23

Nuclear techniques for peaceful development

Some industrial applications of radioisotopes in Asia and the Pacific

Industry Application Isotope Country Comment

Petroleum

Petroleum

Petroleum

Petroleum

Natural gas

Petrochemical

Mechanicalengineering

MechanicalengineeringMechanicalengineeringPower generation

Power generation

Power generation

Iron and steel

Iron and steel

Iron and steel

Iron and steel

Coastalengineering

Coastalengineering

Coastalengineering

Chemical

Chemical

Chemical

ChemicalWater resourcesengineeringWater resourcesengineering

Water resourcesengineering

Water resourcesengineering

Electronics

Electronics

water intake profiles in water barium-131 Chinainjection wells (microspheres)

leak testing in 140-kilometre bromine-82 IndiaViramgam-Koyali crude oil pipeline

leak testing

leaks in underground wells

neutron activation(thin layer activation)

krypton-85(implantation)

bromine-82,tritiated water

sodium-24

calcium-45

calcium-45

sulphur-35(sodium sulphate)

India

India

China

Philippines

India

Rep. of Korea

China

China

China

Sri Lanka

anlimony-124 China(triphenyl antimony)iodine-131-iodobenzene

distribution of corrosion tritiated water Chinaretarding agent in pipeline

location of pipeline blockages cobalt-60 India

wear measurement studies oninternal combustion engines

oil consumption measurements

highest working temperature andtemperature distribution of moving partsdynamics of the migrationof reinjected water (geolhermal)measurement of turbine efficiency

carry-over test for steamgenerator at nuclear power planteffect of ladle lining onsteel quality

effect of calcium on nozzle clog duringcasting of aluminium killed steelhot corrosion behaviour of some alloys(nickel-based iron alloys; nickel-basedniobium containing alloys)

determination of wear of refractory Indialinings in blast furnace; investigation ofsources of refractory inclusions; determina-tion of slag carry-over in molten metaloff-shore sand and sediment studies forharbour development, navigation channelssilt movement to develop dredgingstrategies and assist withdesign of navigation channelsand drift studies

mercury inventory in electrolytic cells

mercury inventory in electrolytic cells

determination of a range of processparameters and plant operatingcharacteristics

mixing characteristics of urea reactor

mapping seepage contours in the faceof Pedu Damlocation of mayor seepage areas inKihung Reservoirflow-rate measurements in sewer lines

discharge measurements in riversand irrigation canals

leakage in semiconductors krypton-85 China

leakage in semiconductors krypton-85 Thailand

iridium-192(glass)

scandium-46,gold-198(sand)

cobalt-60(glass)

mercury-197

mercury-197

carbon-14 dioxide

gold-198tritiated watersodium-24

technetium-99m

Indonesia

India

Rep. of Korea

India

China

India

Rep. of Korea

Malaysia

Rep. of Korea

Philippines

Malaysia

3095 wells tested to mid-1985; estimated10 000 by 1990

5 curies/kilometre; following 24-hourpressurization and flushing, leak waslocated to within 1 metre

5 field tests since 1968

3-metre curie source to locate blockages innaphthaline from Trombay refineries toNOCIL complex, New Bombayextensive programme involving wear inpiston rings, bearings, fuel injection equip-ment, valves

effect of rated load and speed, brake,horsepower studied

volume flow by tracer dilution withother measurements to give ± 1 % accuracyat hydrostation near Bombay

inclusion of ladle lining erosionproducts in steel studied; estimated 1.3 mil-lion Yuan saved on lining materialestimated savings of 52 000 Yuanannually

five major steel plants used radioactivetracers: Jamshedpur (TISCO); Rourkela;Ourgapur; Bhilai; Bokaro (SAIL)

extensive applications

examples include studies at Chochin andMarmugao harbours

studies undertaken at Mukho Port,Sam Cheong Port, and Young II Bayoffered as a commercial service

examples include residence time distribu-tion; dilusion; flow rate at Century Rayon

Chung Ju fertilizer plant

major seepage areas and transit linesidentified

work undertaken on the Langat, Semenyih,and-Lui rivers for the Department of Irriga-tion and Drainage and on canals for theKemulen Agriculture Development Authority(KADA), Kelantan

The table surveys some industrial applications of radioisotopes in developing Member Slates of the IAEA participating in (he regional co-operative programme in Asia and the Pacific

(Regional Co-operative Agreement). The survey is not exhaustive and excludes Australia and Japan, Iwo donor countries of the programme. Excluded applications include "closed

source" uses, such as radiography, nuclear gauging, and borehole logging, for example.

24 IAEA BULLETIN, 2/1987