Reprocessing Spent N-Fuel: Neither Safe nor Economical

Reprocessing Spent N-Fuel: Neither Safe nor Economical

Praful Bidwai

The Times of India, November 7, 1983

2017/09/29: This is the first digitized version of an article written by Praful Bidwai in 1983

Recently a Bombay-based weekly paper carried a front-page report which claimed that about six kg of plutonium was “missing” from the Power Reactor Fuel Reprocessing Plant (PREFRE) at Tarapur. The unaccounted-for fissile material, the report stressed, had not been pilfered or diverted to military uses.

The “loss,” if it is a fact, represents a discrepancy between the designed rate of recovery of plutonium and the actual yield obtained at PREFRE which has been reprocessing spent fuel from the Rajasthan atomic power station since December. The “missing” six kg is not missing, it is present somewhere in the plant’s vessels, pipes and cells, from where it cannot, however, be simply recovered.

The Department of Atomic Energy (DAE) has not yet confirmed or denied the report. In the absence of hard evidence from other sources, it must be assumed that the plutonium (representing, depending on its purity, up to half the quantity needed to put together a bomb) has neither been pilfered nor diverted. It has been claimed by the inefficiency of the PREFRE and the plant’s failure to recover it from the 20 tonnes of spent fuel reportedly reprocessed so far.

If this is indeed the case, it means not only that PREFRE has functioned at less than a third of its rated capacity, but also that the process employed in the plant is defective. Equally important, the plant has already become contaminated with fissile plutonium—a factor that is certain to cause many more problems in future and further reduce PREFRE’s efficiency.

This is not unique to PREFRE. The DAE’s earlier experience with reprocessing was also marked by design deficiencies, operational bottlenecks, contamination and breakdowns. The department built a 30 tonnes-a-year plutonium reprocessing facility at Trombay in 1964. The plant, geared to reprocess spent fuel from a Canadian-Indian research reactor, was designed and commissioned hastily. In fact, it was not even cleared by the DAE’s safety committee.

Problem-ridden Plant

The Trombay plant was badly contaminated within months. The reprocessors had to resort to manual cleaning operations which involved the risk of exposing workers to radiation and plutonium poisoning. So numerous and difficult were the problems posed by its operation that the plant had to be closed down in just ten years after a record of fitful and inefficient working. The plutonium plant was for long the most dangerously contaminated site in Trombay and had eventually to be scrapped (“extended” in the DAE’s words, for another, larger plant is now being built at Trombay.)

This unhappy experience was the basis on which the 100 tonnes-a-year PREFRE was designed and built at Tarapur. For the most part, PREFRE is simply a scaled-up version of the problem-ridden Trombay design and has inherited most of the latter’s defects and shortcomings. Both use the same basic process. According to DAE engineers, very little of the Trombay experience was fed into the Tarapur design to modify it. The commissioning of PREFRE, delayed by about five years, also points to the magnitude of problems posed by its design and operating procedures. Meanwhile, the cost of the project has more than trebled to Rs. 32 crores.

Massive cost overruns and long delays are, of course, entirely characteristic of the DAE. Also the DAE’s performance in reprocessing has also been probably worse than that of most other countries. The rates of recovery that it accepts as normal are much (30 to 50 per cent) lower than those recorded elsewhere, while fissile material losses tend to be over 20 per cent. However, the basic technological problems it faces in reprocessing are in no way unique to it.

The reprocessing of fuel from commercial (as opposed to military or “research”) reactors appears to be both technologically unviable and economically unfeasible. This has been argued for long by engineers critical of the nuclear industry in the West. But now irrefutable evidence that should clinch the issue is provided by a U.S.-based Indian, Dr. Arjun Makhijani, a paper recently published by the Health and Energy Learning Project of Washington, D.C.

Several Difficulties

The facts he reveals are astounding. Of the five reprocessing plants (in as many countries), with any length of operating experience, four were shut down within just a few years of working, owing to major technical, economic and environmental difficulties. The fifth, at La Hague in France has been operating since 1970 at about ten per cent of its rated capacity. It has on the average had one serious accident every four months between January 1980 and June last year [1982].

The average life of these reprocessing plants has only been six years. Their capacity utilization has varied between 10 and 35 per cent—only a fraction of the 80 per cent level generally assumed in economic calculations. The plant that has recorded the highest (35 per cent) level of capacity use (West Valley in the U.S.) was shut down in 1972. The world’s second largest plant at Tokai Mura in Japan (capacity 210 tonnes a year) started working in 1981 after several years of trial runs. “It has already had several breakdowns, accidents and severe worker exposures to radioactivity.”

The fate of the other major plants has been worse. The infamous one at Windscale in the U.K., for instance, was closed down in 1973 after four years of operation when a serious accident caused extensive radioactivity contamination. A total of 31 workers at Windscale received lung dose radiation exposures exceeding 15 rems (a unit of radiation). One of them absorbed a dose as high as 1,023 rems and another ten received between 36 and 155 rems. The French plant at La Hague has had accidents including a fire in radioactive waste tanks and their near blow-up consequent upon a power failure.

Major breakdowns, accidents, radioactivity leaks and intractable maintenance problems are indeed routine in reprocessing plants throughout the world. They occur with much greater ferocity and frequency than in nuclear power stations, which are themselves scarcely free of major operating problems.

The key to the understanding of these problems lies in three factors: the chemistry of reprocessing, the problems of transporting, handling and treating radioactive wastes; and the difficulties associated with operating a plant which contains hot, hyperactive spent fuel with huge quantities of plutonium. Plutonium, named after the Roman god of Hell, is among the most toxic substances known to humanity.

Reprocessing seems deceptively simple, in theory. Spent fuel from power reactors, containing more than 200 different isotopes, is brought into reprocessing plants in casks. The casks are opened and the fuel rods removed under water.

In the common PUREX process used at PREFRE, the rods are chopped up into small segments along with their zircalloy cladding and reacted with hot nitric acid. Most of the radioactive isotopes in the rods dissolve while the zircalloy does not. The uranium and plutonium present in the fuel solution are separated from other chemicals by another solvent, tributyl phosphate, and are later separated from each other. Finally the plutonium is concentrated and solidified, while the rest of the radioactive waste is vitrified and buried or stored.

The whole problem is that the chemistry of reprocessing is only imperfectly understood. There are great difficulties with the dissolver itself: three plants had to be shut down due to these. Several unexplained chemical reactions, sedimentation and corrosion, that can cause big leaks, and blockages occur with unpredictable frequency in various other parts of the plant. There have been major problems with the rod-chopping shears, pumps, ventilation systems, cranes, storage tanks and evaporators. The result is, to take one instance, leaks: as much as 1,000 to 1,500 litres of radioactive liquids spilt at La Hague in 1981; plutonium leaked from a pipe to the floor last year, and up to 10 kg of plutonium was probably spilt in 1980. Because they are unpredictable and governed by factors that are not understood, breakdowns and accidents related to reprocessing chemistry cannot be controlled.

Contamination Risk

The other basic problem is in the transportation and handling of fuel and the storage of radioactive wastes. All these steps render fissile material mobile or expand and reduce its volume—thus increasing the probability of contamination and radioactivity spreading by contact. Once plutonium contamination occurs, nothing can be done that will not expose workers and compromise on safety.

It seems likely that all these problems will remain insoluble. For the nuclear industry appears to be giving up on reprocessing primarily because of its exceedingly high cost. This is crucial. According to Dr. Makhijani, reprocessing adds between 25 per cent and 150 per cent to the costs of power generation. Going by the actual historical experience, it costs between $1.7 million and $12 million to reprocess one tonne of spent fuel—altogether too expensive for the nuclear power industry. This knocks the bottom of its argument (now reduced to a mere hope) that reprocessing would reduce the cost of the nuclear fuel cycle and help it become competitive with power from other sources.

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