Industrial Applications and Chemisty Section
Areas of Activities
in
Radioisotopes and Radiation Technology
INTRODUCTION
A vast variety of nuclear techniques are available for industrial, environmental, medical and research applications. Radiation and isotopic technology such as gamma irradiation, electron beam or ion beam as well as nucleonic gauges, radiotracers and sealed sources, non destructive testing and nuclear analytical techniques are used for process control, material modifications, to reduce harmful industrial emissions and to reprocess waste streams. Sterilisation of medical products and wastewater treatment is another area for application of radiation. Non-destructive evaluation of welds, castings, assembled machinery and ceramics help to make industrial processes safer and more cost effective. For natural resource exploration radiotracers, sealed sources and nucleonic gauges are used in the oil industry, in mineral processing and waste water treatment plants. The application of these nuclear techniques has considerable economic and environmental impact as they are introduced in developing countries.
In virtually all Member States, even if they do not pursue an active nuclear programme, one or the other nuclear technique is applied for the benefit of the private and/or the public sector. Support has been given in acquiring the technical conditions, in training qualified personnel and in increasing the quality output of their application. Due to rapid development of new techniques and new applications a permanent knowledge transfer from the developers to the end users is necessary. Research in the area of nuclear applications has been fostered and supported for the benefit of economical growth and sustainability.
1. RADIOISOTPES
Radioisotopes make important contributions in several sectors of economic significance including medicine, food processing, industry, agriculture, structural safety and research. They are generally produced in research reactors or cyclotrons. More than 150 different radioisotopes in different forms are in use for various applications.
It has been observed that the consumption of isotopes in a country depends on the level of its economic development and industrialization, the more advanced, more the consumption. However, the pattern of use is similar in all countries. The medical field accounts for majority of the applications, followed by industry and research. The potential for expansion of radioisotope applications and reaching the benefits to developing and underdeveloped regions of the world is enormous.
1.1 Current Status of Radioisotopes Production
1.1.1 Radioisotopes for medicine
Radioisotopes in medicine are used either in liquid form called radiopharmaceuticals for diagnosis and therapy or as a solid sealed source for therapy, mainly for cancer. Radioisotopes also find extensive applications in in vitro diagnosis, the most important being in immunoassays.
Radiopharmaceuticals are used mainly for diagnostic imaging studies, however, therapeutic applications are showing a substantial growth in the last few years. The radioisotope , 99m Tc is used more than 70% of the diagnostic imaging studies for assessing the dynamic functions of the various organs in the body as well as for the localization of infections. About 20% of medical applications use radioisotopes such as 201 Tl, 111 In, 67 Ga, 123 I, 81m Kr, 131 I and 133 Xe. The use of the cyclotron produced long-lived isotope, 201 Tl for cardiac studies is also widespread.
The use of radioisotopes for Positron Emission Tomography (PET) studies is showing a faster growth rate. 18 F-fluoro deoxy glucose ( 18 FDG) accounts for more than 90% of PET imaging with a remaining 10% being accounted by 11 C, 13 N and 15 O based radiopharmaceuticals. Interest in setting up medical cyclotrons and PET facilities is growing in many developing countries in the recent years.
Radiopharmaceuticals based on 131 I have the primary role in the treatment of hyperthyroidism and thyroid cancer. The treatment certain other cancers, arthritis and palliation of bone pain due to secondary cancer using radioisotopes is showing a substantial growth. 131 I, 32 P, 153 Sm, 90 Y and 186 Re are the major isotopes used in therapy. The annual turnover in this area is more than 30 million US Dollars and is growing at the rate of 10% per annum.
Radioactive sealed sources are widely used for teletherapy and brachytherapy of cancer. About 1500 teletherapy machines using the radioisotope 60 Co are estimated to be in use, the worldwide. The main radioisotopes used in brachytherapy are 192 Ir, 137 Cs, 125 I, 198 Au, 106 Ru and 103 Pd. About 3000 brachytherapy centres are estimated to be in operation across the globe. High dose rate sources using 192 Ir are becoming increasingly popular. These use high specific activity 192 Ir sources, which are encapsulated by precision technology using advanced laser welding machines. The implantation of tiny sources of 125 I for ocular and prostate cancer is also being tried. The treatment of prostate cancer using 103 Pd has become very successful. The production of these sources requires remote fabrication including encapsulation by remote welding procedures.
1.1.2 Radioisotopes for industry
Radioisotopes are used for nucleonic control systems, radiation processing, non-destructive testing (NDT) and in radiotracer studies. Sealed sources of 137 Cs, 60 Co, 241 Am, 85 Kr, 147 Pm, 90 Sr/ 90 Y, 204 Tl, 252 Cf, 63 Ni, 55 Fe, 109 Cd, 57 Co and 241 Am-Be neutron source are used in nucleonic control systems. 60 Co in the form of high intensity sources is the main isotope used for radiation processing. 192Ir sources are used in more than 90% of the gamma radiography devices. 169 Yb and 75 Se sources are other radioisotopes used in NDT. A large number of isotopes in various chemical forms are used as tracers in industry. Further details of industrial applications are given in another chapter.
1.2 Future Trends
Radioisotopes will continue to play an important role in national development. With many techniques having an important bearing on either industrial activity or health care, the sustainability of radioisotope supply or “isotope security” continues to be a major cause of concern in view of the decrease in the number of operating research reactors worldwide and difficulties in transporting radioisotopes worldwide due to security concerns related to terrorism. Robust and reliable programme for the supply of essential radioisotopes for different applications even in countries not having reactors or accelerators is essential.
The radionuclides in demand in regular medical diagnosis would continue to be 99m Tc, 131 I, 201 Tl, 111 In, 123 I and 18 F. A substantial part of the use of 201 Tl for cardiac studies is likely to be carried out with 99m Tc radiopharmaceuticals due to cost advantage and ready availability. The use of 99m Tc generators, the technology of which is well standardised is expected to increase significantly due to the establishment of increased number of nuclear medicine centres in both developing and developed countries. Cold kits for the formulation of 99m Tc radiopharmaceuticals for different imaging studies would be in regular and expanded use than now. New 99m Tc radiopharmaceuticals based on peptides and other bio-molecules will be added.
The use of 18 FDG will increase due to well refined chemistry starting from the production of the radioisotope through the preparation of the radiopharmaceuticals and its final quality assurance before the product is delivered for the end use. With ready availability of 18F in several centres, further research and development of 18 F labelled molecules for various applications is expected to increase. Long-lived PET tracers i.e. 124 I and 76 Br are under development for studying slow processes such as monitoring gene therapy. 123 I production via 123 Xe gas target would become more widespread and economical. It could emerge as another widely used diagnostic isotope. 68 Ge- 68 Ga generators are likely to see increase in demand for use in PET where cyclotrons are not available.
Due to increased regulatory concerns and Good Manufacturing Practices' requirements, centralised production and distribution of 99m Tc radiopharmaceuticals and 18 FDG are expected to be the evolving practice from the predominantly hospital based production in vogue now. Even through 99 Mo production would continue to be dominated by 2 or 3 large producers, widespread use of 99m Tc coupled with logistics of supplies and reluctance of airlines to carry radioactive material could generate need for many small scale producers of fission 99 Mo serving regional needs.
There will be considerable interest in therapy using radiopharmaceuticals and the range of isotopes and their products in regular use is expected to expand significantly. Refined technologies for both 90 Y and 188 Re generators would be available. Due to the similarity in the chemistry of 99m Tc and 188 Re, research in the development of new radiopharmaceuticals based on peptides and other target specific biomolecules labelled with them for diagnosis followed by therapy is being pursued vigorously. The availability of 188 Re in sufficient quantities will be a major problem due to the limited availability of high flux reactors for its production.
The use of 90 Y radiopharmaceuticals has shown considerable increase for the treatment of cancer. The use of 90 Y is advantageous as the parent radionuclide, 90 Sr is available in large quantities as nuclear waste in fuel reprocessing programs. The sale of 90 Y has shown substantial growth in the United States of America necessitating the need for privatising the production of 90 Y by the Department of Energy. The recovery of 90 Sr followed by large scale centralized separation of 90 Y or preparation of ready to use radionuclide generators could become a major radiochemistry program in other countries which have fuel reprocessing facilities. Several 90 Y based radiopharmaceuticals for cancer therapy and treatment of arthritis are in the clinical trial stage at present and their widespread applications in the near future is envisaged.
Use of many beta particle emitting isotopes including 177 Lu, 166 Ho, 153 Sm, 165 Dy and 186 Re for therapy could increase by taking advantage of local reactor production. 177 Lu offers particular advantage as this isotope can be prepared in very high specific activity and in large quantities even in reactors having moderate flux available in many developing countries. Several new radiopharmaceuticals are under investigation and clinical trials using 177 Lu. The near future could see large scale deployment of 177 Lu in cancer therapy. 124 I and 103 Pd from cyclotrons would also be increasingly used for therapy. 125 I and 103 Pd seed production technology for brachytherapy applications would be in demand in many countries.
2. RADIATION TECHNOLOGY FOR CLEAN AND SAFE INDUSTRY
2.1. Radiation processing
Beside of economical impacts radiation and radioisotope applications have tremendous impacts on different aspects of social and industrial development :
- human health ( radiation sterilization of medical products, blood and transplanting grafts irradiation)
-environment protection (electron beam flue gas and wastewater treatment, gamma rays sludge hygenisation)
-clean and safe industry (radiotracer leakages testing and Non Destructive Testing of installations, pipes, tanks)
-quality system enhancement (nuclear analytical techniques, NDT)
-process optimisation (radiotracers and Nucleonic Control Systems)
-raw materials exploration and exploitation (on-line processing, borehole logging )
-homeland security (cargo inspections, governmental mail irradiation).
The radiation and radioisotope applications have a high contribution to the economy. The economical scale of industrial applications of radiation and isotopes in USA and Japan based on studies done in few years back is given in the Table 1.
The number of industrial gamma irradiators, working on the service basis or installed on-line all over the world exceeds 160, out of them 65 units are operational in developing countries. More than 20% of these gamma irradiators have activities over 1 MCi of 60 Co.
The total number of electron beam accelerators installed exceeds 13,000, among them the number of units applied for radiation processing being close to 1,200. New environmental applications demand development of high power, reliable accelerators. The most powerful radiation processing facility, applying electron accelerators over 1 MW total power, has been constructed for power plant emitted flue gases purification in Poland.
Application of X-rays for radiation processing based on X-ray tubes is quite popular in the case of blood irradiation. Commercial irradiators are offered on the market. The concept of electron beam to X ray conversion is a new technological approach for constructing powerful X ray machines. R&D is under way in some pilot units. However, a breakthrough in the technology is expected after implementation of the high energy unit (up to 700 kW), which is already tested in Belgium.
Chemical or material engineering mostly applies high temperature and/or high pressure processes for material synthesis/modification and quite often a catalyst is required to speed up the reaction. Radiation is the unique source of energy, which can initiate chemical reactions at any temperature, including ambient, under any pressure, in any phase (gas, liquid or solid), without use of catalysts.
Polymers are quite often irradiated, either for modification or as component of radiation sterilized medical products. Therefore, changes in their structure may be beneficial or undesirable. These facts are the reason why R&D concerning these materials is broad and most developments are foreseen in this area.
The application of radiation for modification of synthetic materials, mostly curing and crosslinking is a well-established technology. Better understanding of processes such as crosslinking and scission in polymers is achieved. New, unexpected discoveries are possible. Moreover, since radiation technology is, like all other, product-oriented, developments in other fields (polymer tubing for household) increase the demand for irradiation services.
Radiation as a tool for producing sensors or membranes is still a not fully exhausted area of application. A good example for such a successfully implemented solution is hydrogel wound dressing.
The other field of possible applications is the processing of natural polymers. Cellulose materials for the pharmaceutical and cosmetics industry have already been implemented. Some chitosan derivatives are manufactured as well. New sorbents for various applications were developed.
Radiation sterilization is a well established technique. Multi technique services (radiation, heat) emerged recently. The new application of this technique is decontamination of the official mail against the biological contaminants like anthrax.
Some radiation processes are very promising applications for environment conservation. The plant for liquid sludge hygienization, furnished in 60Co gamma source, is in operation in India since 1991.
The pilot plant for dye factory wastewater treatment equipped in an electron accelerator has been constructed in South Korea, and an industrial project aiming treatment of 10,000 cubic meters of effluent per day is in progress.
The electron beam flue gas treatment plants are operating in the coal-fired plants in China and Poland (in both cases purification of flue gases from 100 MWe blocks). The high efficiency of SOx and NOx removal was achieved and by-product is a high quality fertilizer. The other possible application of the technology is Volatile Organic Compound and Polycyclic Hydrocarbour treatment, e.g. in municipal waste incinerator plants flue gas purification units. The advantage of this technology over conventional ones was demonstrated clearly, both from technical and economical points of view. Further, its implementation depends on development in construction of reliable, high power accelerator with short maintenance time requirements.
Conservation of archaeological artefacts and art objects by radiation (gamma rays or electron beam) appears to have perspective. On going studies on application of radiation for consolidation revealed that wood objects, lacquer, textiles, paper, objects made of stone and gypsum can be considered for conservation purposes. Regarding radiation treatment of cellulose materials, although the disinfection's effect of radiation is well known and proven, extensive research is needed to develop pre-treatment methods to lower the radiation dose.
2.2. Radiotracers and sealed source applications
Radioisotopes (T-3, Br- 82, Tc-99m, La-140, Na-24, I-131) are applied as radiotracers in industry and environment. Oil fields and refineries, chemical and metallurgical industries and wastewater purification installations are the end users benefiting from radioisotope techniques.
Radioisotope techniques (radiotracers, gamma scanning, tomography and single particle tracking) are extensively used to identify and quantify multiphase reactors (phase hold-up distributions, velocity and mixing patterns). Multiphase reactor technology is the basis of petroleum refining, synthesis gas conversion to fuels and chemicals, bulk commodity chemicals production, manufacture of specially chemicals and polymers, and conversion of undesired products into recyclable materials. While progress has been made in understanding fundamental reaction mechanisms and in computing from first principles the effect of mass transfer on the reaction rate locally, the description of the reactor scale flow pattern and mixing is in general primitive and rests on the assumption of ideal flow patterns. Radioisotope techniques help optimising multiphase reactors saving hundreds of million of US dollars annually in world scale.
2.3. NDT inspection
Big industrial and hydrological catastrophes were connected with material and engineering defects in such structures like industrial installations, pipes, tanks, air crafts, tankers, dams, tunnels and bridges. Non Destructive Testing (NDT), Gamma or X- ray radiographies are most commonly used techniques to inspect industrial installations for safe use and preventing purposes.
Cargo inspection using radiation for checking unknown packages and truck is the only technique may ensure homeland security in many regions of the world. Gamma and X ray digital radioscopy and tomography systems are in operation in many countries for full track border inspection. 60 Co sources and powerful X ray machines coupled with array of detectors and computer data logger are installed in borders to see inside tracks and other vessels. Vehicles are passing through source-detection system in remote way.
3. NUCLEAR ANALYTICAL TECHNIQUES
Nuclear analytical techniques play an important role in certification of element content in a variety of materials. Particularly in international trade of e.g. food items legal limits have to be observed and analytical results should be based on mutual recognition. This recognition is obtained if laboratories work according to internationally accepted quality standards such as the ISO 17025. National accreditation following the installation of a concise quality system assures nuclear analytical laboratories' superior performance compared to conventional analysis.
New trends in nuclear applications can be seen in the development of robust, automated and portable instruments, which can be used under laboratory as well as under field conditions. Flexible XRF instruments have been used for non-destructive analysis of art objects. Portable neutron sources of variable strength are developed for field applications of prompt gamma neutron activation analysis enabling fast and non-destructive element screening of e.g. unknown packages suspect to illicit trafficking of nuclear materials. There are different nuclear analytical techniques applied for package inspection depending of the size and content of the packages. Dual energy X-ray absorption (DEXA) analysers are most familiar in their use as on-line security devices screening baggage at airports.
Long lived radionuclides and stable isotopes are increasingly used to study metabolic effects of essential and toxic elements in plants, animals and the human body. Monte Carlo simulations of neutrons and gamma rays enable the design of new irradiation and counting devises optimised for a particular application.
Finally nuclear techniques serve in preserving of human cultural heritage. Neutron Activation Analysis is very sensitive multielemental analysis, which allows identification of art objects. Coins and other metallic artefacts, stones, pottery and ceramics have all been subjected to trace-element fingerprinting to distinguish original from fake ones. The neutron activation analysis has been successfully demonstrated to add valuable information to the interpretation of archaeological problems.
