Industrial irradiation

In industrial irradiation processes, either UV photons with energies between 2.2 and 7.0 eV or accelerated electrons with energies between 100 and 300 eV are used. Fast electrons transfer their energy to the molecules of the reactive substance (liquid or solid) during a series of electrostatic interactions with the outer sphere electrons of the neighboring molecules. This... 

Millions of radioactive sources exist around the world, usually distributed not only at nuclear power plants, but also medical radiotherapy facihties and industrial irradiators. Unfortunately, the radioactive materials housed in these places are often not under adequate control and are therefore susceptible to theft by terrorists.34 The appalling events of September 11, 2001, spawned a major international initiative to strengthen security for such materials and facihties worldwide. Highly toxic radionuchdes (plutonium radionuclides, 210Po or 137Cs) at trace level are increasingly being used as modern weapons to kill undesirable persons. 

Several industrial irradiation facilities can now provide both X-ray and electron beam processing for a variety of applications. There are three such facilities in Japan. One of these is equipped with a 5.0 MeV, 150 kW Cockcroft Walton accelerator [14], Another one has a 5.0 MeV, 200 kW Dynamitron accelerator [15], and the third facility has a Rhodotron... 

M.R. CLELAND AND G.M. PAGEAU, Comparisons of X ray and Gamma Ray Sources for Industrial Irradiation Processes, Nuclear Instruments and Methods in Physics Research B24/25, pp. 967-972, 1987. 

Although the controlling factor in industrial irradiation is the conveyor speed, it is usual to supplement this by inclusion of dosimeters in the irradiator. The dosimeters are there as a confirmatory monitor that all factors remain under control. Routine dosimeters are not used as a control or a feedback system. 

The sources of ionizing radiation used for research or industrial irradiation purposes can be divided into two groups sources containing radionuclides, such as Co, Cs, or the Sr— pair, and machine sources of radiation, such as X-ray equipment or electron accelerators. Without going into details, this chapter will briefly mention those characteristics of some of the radioactive nuclides and accelerators, which are important from the point of view of using them for irradiation purposes. 

Phosphorous. The presence of trace amounts of phosphorus in metals and semiconductors is known to affect material properties. The produced in the (n,y) reaction is a pure emitter and has to be separated and rigorously purified. Paul (1998,2000) developed a method for P determination in steels and other high-temperature refractory alloys of interest to the aircraft industry. Irradiated samples were dissolved passed through cation-exchange columns to remove Co, Ni, and Cr followed by repeated precipitations of magnesium ammonium phosphate and ammonium phosphomolybdate. One of the major advantages of this technique is the determination of the chemical yield by gravimetry. Phosphorus was determined by INAA in matrices other than metals, e.g., polymers. In this case, the beta spectrum was corrected for interferences and self-absorption (St-Pierre and Kennedy 1998). A modified version of this procedure has been used to certify implanted phosphorus in silicon (Paul et al. 2003). 

Industrial irradiation There are 160 gamma-irradiation facilities and over 600 electron-beam facilities in operation in the world. Most facilities are for the sterilization of medical and pharmaceutical products, the preservation of foodstuffs, polymer synthesis and modification, and the eradication of insect infestation. Dose rates in the irradiation chamber would be of the order of 1 Gy s Therefore, there is a need for sophisticated engineered safety systems, and during normal usage the exposure of workers should be very low. The average annual effective dose of 57,200 monitored workers in 15 countries is 0.10 mSv. 

Large Facilities. Research indicates (NRC, 1988, 1990) that nuclear power plants or facilities storing large amounts of nuclear waste from reprocessed nuclear fuel pose the only risk of early deaths off-site resulting from a radioactive release. Other facilities containing large amounts of radioactive material, such as industrial irradiators, can result in serious injuries or deaths on-site. 

The oxidative degradation of isotactic PP in the presence of air (as well as the postradiation oxidation) takes place frequently in industrial irradiation processes. The estimation of peroxy radicals, formed as a direct product of radiolytic oxidation reactions between oxygen and carbon-centred free radicals, is very useful in understanding the oxidation process. The application of electron spin resonance (ESR) is a practical method to follow the quantitative effect of this process [2],... 

The heart of a cobalt-60 industrial irradiator is a radiation room with concrete walls more than two metres (6feet) thick to contain the gamma radiation. 

CPD s construction of industrial irradiators helped establish it as an international leader in the field. In order to build on this reputation, it sponsored a series of meetings of experts on industrial irradiators from around the world. In 1967, it built its biggest irradiator to date near Stuttgart for Firma Willy Rusch, a West German manufacturer of plastic, rubber, and latex medical supplies. With a 1.5-million-curie cobalt-60 source that could sterilize 1.2 tons of medical products a day, it was the largest such facility... 

Although CPD s R D expenditures had been high, they were not necessarily excessive. It was, after all, involved in a high-tech field that required educated staff, extensive safety precautions, and expensive processing equipment. Besides, the fact that CPD spent twice what most Canadian companies did on R D could be interpreted to mean that Canadian industry spent too little, rather than CPD too much. The problem was not the amount of money that CPD put into R D, but the negligible return on its investment. A decade and a half of active R D had resulted in just two modest successes - the Gammacell and industrial irradiators. 

The process worked, and it solved many serious problems, but there was little demand for it. In fact, there was serious public resistance to the idea. Along with irradiated wood flooring, it demonstrated how product development that is driven by technological innovation more than market demand can be a sinkhole for investment. CPD s new product successes, such as Gammacells and industrial irradiators, were in the medical field, where it had a better handle on customers needs. In this area a disposition to accept technical innovation on the basis of experimental proof prevailed over the general public s apprehensions about nuclear technology. 

Frank Fraser (left) and Ron Harrod inspect a J6500 industrial irradiator that has been pre-assembled far testing at the Kanata equipment production facility (March 1973). 

The withdrawal from heavy water was offset by unspectacular but steady growth in industrial irradiation. By 1970, CPD had sold thirty-one plants - an average of about five per year since 1964. It was able to bypass competitors primarily by providing better customer service. Its main competitor, H.S. Marsh Ltd., tended to tell customers what it could give them, while CPD assessed customers needs and built plants to fit... 

In July 1978, AECL reorganized its operations into four companies - the Research Company (Chalk River) the Chemical Company (heavy water) the Engineering Company (for CANDU) and the Radiochemical Company, or RCC (formerly CPD). Acceptance of the new name for CPD was slow, however, and it did not come into general internal use until well into the 1980s. (To avoid confusion, CPD continues to be used in this chapter.) In the new CPD, sales of BTUs did not dominate as they once had industrial irradiation was building slowly, and molybdenum-99 was generating sohd sales. 

The production of cohalt-60 sources for industrial irradiators begins with slugs of cobalt-59. The slugs are placed into capsules, then three capsules are bundled together and placed in a control rod in a CANDU reactor. After at least 18 months of irradiation, the capsules are removed and shipped to the cohalt-60 facility at Kanata where they are loaded into pencils for shipment to irradiator customers worldwide. 

In contrast to the heyday of CPD, most of RCC s revenues came from industrial irradiation or isotopes rather than medical equipment. In 1981 RCC sold no fewer than forty-two units of its new research irradiator, the Gammacell 1000. It was used primarily in hospitals to inactivate white blood cells in blood for transplant operations or for patients with weakened immune systems. Gammacells were also used in studies of radiation effects on materials, for hardening electronic components, and in biological experiments. 

By the early 1980s, RCC was selling half a dozen or more industrial irradiators a year to customers around the world. It guaranteed its cobalt-60 pencils for fifteen years when its own technicians installed them in its irradiators. Since cobalt-60 decayed at a rate of about 12 per cent a year, RCC could depend on a steady business replacing old sources. A standard sales technique was to invite customers to visit RCC s plant in Kanata. A tour of the equipment-production and cobalt-60 hicilities inevitably left them impressed by the division s technological capabilities. 

The performance of the isotopes business rivalled that of the industrial irradiation division. In 1980-81 the isotopes group had almost twice as many orders as it had had the previous year, most of them on the strength of rising demand for molybdenum-99. It was still too early to judge the success of its diversification into cyclotron-produced isotopes and radiopharmaceuticals, but preliminary results in these areas looked very promising. 

By this time, three years had passed since privatization had first been intimated, and Nordion personnel were still uncertain about their future. The delay proved to be a good thing for the government, however, for the passage of time was increasing Nordions value. From 1980 to 1989, revenues for the industrial-irradiation division increased from 14 million to 68 million, or an average of 19 per cent per annum, while revenues from the isotope division rose from 13 million to 45 million, an average of 16 per cent per annum. Revenue in 1989 was 113 million. 

Its development was echoed in the invention of Gammacells and industrial irradiators, both practical commercial applications of the latest discoveries in nuclear science. The practice was still evident in the 1980s as MDS Nordion moved into making radiopharmaceudcals as an outgrowth of its bulk isotopes business. 

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