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A simplified process flowsheet for recovering unburned uranium from uranium-aluminum reactor fuel elements at Idaho Chemical Process Plant, Idaho Falls

Private Nuclear Fuel Reprocessing? Industry eyes reprocessing of nuclear fuel as a r e a of possible profit, competitive nuclear power

AVE PROCESSING NUCLEAR FUELS to re­move fission products is done only at government facilities at present, but private industry may be allowed to participate eventually—perhaps in a few months. It seems doubtful, however, that there will be a stampede of com­panies rushing into this portion of the nuclear industry.

In a nuclear reactor, fission products build up and poison, or physically damage, fuel elements, usually long before the expensive fissionable ma­terial is used up. So fuel must be re­moved and reprocessed into usable form. This phase of nuclear reactor operation offers the chemical industry one of its best possibilities of partici­pating in nuclear power. All nuclear power plants now under construction will return fuel elements to AEC plants for reprocessing.

At the Nuclear Congress in Cleve­land last month, general opinion of companies most likely to be con­cerned with private fuel processing was that private industry will eventu­ally get into the business, but it will not be too soon. "We have to get in, it's the main part of the business," said one spokesman, "but there are not enough private nuclear power plants under construction, or even pro­

posed, to make a plant economical today."

Not only will a large number of nu­clear power plants be needed before a private reprocessing plant becomes eco­nomical, but they will have to be fairly close to each other to lower transportation costs. Most thinking is in terms of one reprocessing plant for 10 power plants.

• Technology Difficult. Problems in large scale chemical processing of radioactive materials are enormous, but they have already been solved in AEC plants—on a scale larger than that likely to be used by private industry.

Radiochemical separation plants are similar to other chemical plants. Proc­essing equipment for materials of low enrichment is small compared to that of a heavy chemical plant, and smaller still for highly enriched materials, says W. G. Stockdale of Oak Ridge National Lab. Chemical makeup equipment is standard. Control equipment and in­strumentation is complex, but con­structed of standard commercial units.

It is the radioactivity of the feed that makes radiochemical plants unique. Vessel spacing, geometry, batch size, and concentration must be such that there is no possibility of a self-sustain­ing neutron chain reaction starting, and

personnel must be protected from beta and gamma radiation.

Costs of radiochemical plants are therefore higher than conventional fa­cilities. Piping and equipment are complex, and careful attention must be given to all connections to avoid leak­age. Much piping and equipment is duplicated to allow processing to con­tinue during decontamination and main­tenance. Elaborate ventilation systems are required. Lead pigs and carts or conveyors must be used to take con­trol samples to the lab.

Besides a more expensive processing area, a radiochemical plant needs rather fancy auxiliary facilities. Fuel elements are usually allowed to decay radioactively for a few months under water before being fed to process. Laboratory units are expensive—$35 to $75 per square foot. Disposal of radio­active plant waste is another big head­ache, and increases plant costs still more.

Some reprocessing plants are op­erated remotely; others are "limited access" plants in which individual units are shielded, and it is possible to de­contaminate them for a certain amount · of maintenance work.

The Idaho Chemical Processing Plant, located at the Nuclear Reactor Testing Station near Idaho Falls is a limited access plant, according to Κ. Κ. Kennedy and D . G. Reid of Phillips Petroleum. Fuels initially used in the Materials Testing Reactor, are among the simplest treated. They consist of uranium (U2 3 5 enriched) alloyed with pure aluminum, and clad in a pure aluminum jacket.

Fuel elements (including jackets) are dissolved in nitric acid; the solution is neutralized and extracted with methyl isobutyl ketone in columns packed with stainless steel raschig rings.

Concrete walls from two- to five-feet thick divide the below-grade-level proc­essing building into several cells. Mov­ing parts require maintenance and are avoided whenever possible. When es­sential, provision is made for lubrica­tion, gear box flushing, and impending failure detection from remote locations.

Special long handled tools and radia­tion shields permit handling of filter cartridges. Air sparging is used in place of mechanical agitation, and liquids move by gravity flow, steam jet syphons, or special diaphragm pumps.

• Improvements Expected. Chem­ical reprocessing is an area where con­siderable process improvement with consequent cost reduction may be ex­pected says John R. Dunning of Colum­bia University, who was chairman of the congress. Not only can completely new procedures be developed, but in­dividual steps of existing processes can

1 1 6 C & E N J A N . 9, 1956

be improved. For instance, pilot plant studies by A. F . Boeglin and his asso­ciates at Phillips Petroleum, Idaho Falls, show it is possible to use a con­tinuous instead of a batch dissolving process for uranium-aluminum fuel elements.

Fuel slugs are fed into the top of a cylindrical stainless steel column. Ni­tric acid (containing mercuric nitrate catalyst) solution is fed in at the bot­tom, flows upward past the slugs and out the overflow pipe at the top, carry­ing material dissolved from the slugs with it. At constant feed rates the metal level seeks an equilibrium value, giving a steady dissolving rate and uniform product composition.

• Which Process? Even if all re­actors used the "conventional" alumi­num-clad uranium fuel elements, there would be a number of processes avail­able. Development of a whole series of different type reactors makes the situation even more confusing.

Solvent extraction is not the only technique for separating fissionable ma­terial in solid elements. Precipitation, ion-exchange, fractional distillation, and pyrometallurgical methods have been tried.

The difficulty in fabricating fuel ele­ments to the exact mechanical specifica­tions required for nuclear reactors has been one of the reasons for developing homogenous reactors using liquid fuels and moderators. Foster Wheeler is ready to design and build a 100,000 kw. aqueous homogenous power breeder reactor for private industry. It could be completed in 1960 or 1961.

In this reactor, core solution contain­ing uranyl sulfate and heavy water,

would be purified continuously in a chemical processing unit at t he site. Fission of TJ235 would be the initial source of heat, but U2 3 3 from the tho-rium-232 in the breeder blanket mate­rial would be added eventually. Solu­tion from the breeder blanket would be processed periodically at an AEC installation.

Precipitation and electrolytic proc­essing have also been subject to some research as a means of purifying liquid metal fuels.

Molten silver will extract most of the plutonium, rare earths, and zirconium fission products from molten uranium, A. F. Voigt of the Ames Laboratory at Iowa State reports. Like other pyro­metallurgical techniques the method has the advantage of small volumes of material for handling.

• Company interests. Attitudes of companies towards private reprocess­ing plants differ. Many, like Carbide, at Oak Ridge, and Vitro Corp., at Hanford, already run AEC reprocess­ing facilities for the government. Car­bide is not committing itself, but has undoubtedly considered the question. Vitro is interested, but like most com­panies cannot see entering the private reprocessing field immediately.

Sylvania, which fabricates fuel mate­rial into reactor elements, has an­nounced that it hopes to establish a complete out-of-pile service. It would not only reprocess fuel elements chemi­cally, but fabricate the recovered ma­terial into fuel elements, clad and ready for the reactor again. Another fuel element fabricator, Babcock & Wilcox, is not anxious to get into chemical re­processing, but will if it is necessary.

Many others, like National Lead, have at tended government meetings on the subject, but are probably more interested in their existing profitable lines of activity than they are in getting into reprocessing. National Lead pro­duces a number of metals and other materials used in construction in atomic energy installations.

The tremendous existing capacity of government-owned reprocessing plants for weapon materials has slowed down many companies. Another difficulty is the fact that even the small potential business forseen might not b e uniform, so it would be difficult to keep a plant operating continuously. Then there is the problem posed by the wide variety of fuel elements. American companies have prided themselves on building re­actors of different designs. Uranium, plutonium, thorium, and their alloys and compounds, can be combined with an almost infinité diversity of cladding materials. This is good in some re­spects, but it makes reprocessing diffi­cult.

There may be changes that will make reprocessing more attractive. One is that the Government might conceiv­ably think it desirable to have private plants, and let contracts for private re­processing of some of its own fuel. Another is the possibility tha t a plant would b e designed to operate in con­junction with some other plant such as a raw materials plant, and not suffer too much from irregular or small volume operation. These opinions were put forth as only the barest possibilities, and most companies believe the t ime for private reprocessing plants is still a long way off.

Operating aisle of remote analytical facility (left) with its controls, manipulators, and viewing windows for heavily shielded dry boxes lining the walls, is used for making chemical analyses of intensely radioactive solu­tions processed from spent reactor fuel. Control apparatus (center) of the plant as viewed from the operating corridor. Pipes and vessels used in recovery of uranium are cleared

of radioactive contents (right) before repairs can be made to them. Here an operator regulates the flow of decon­taminating solution through a process vessel. Once the pipes and vessels are cleaned, maintenance employees can enter the cells to work on equipment with hand tools. Radioactive process equipment he is cleaning is shielded with thick walls of concrete

J A N . 9, 1956 C & E N 1 1 7