SPECIFICATIONS FOR FUEL ASSEMBLIES FOR CORE I OF THE EXPERIMENTAL GAS- COOLED REACTOR

Specifications for the fuel assemblies Experimental Gas Cooled Reactor (EGCR) Core-I were developed for use in procuring the first core loading. A fuel assembly for the EGCR consists of a cluster of seven cylindrical fuel elements spaced and supported within a graphite sleeve. Each fuel element consists of a stainless-steel tube containing a column of hollow UO/sub 2/ pellets and having a spacer brazed at the midsection to control the spacing between fuel elements in a cluster. A master specification for the fuel assembly, a supplementary specification for each of the components, and a specification on record keeping daring manufacture are included. (auth

GRAPHITE-STAINLESS STEEL COMPATIBILITY STUDIES

S>The compatibility of type 304L stainless steel in intimate contact with graphite is being studied as a function of temperature and contact pressure. This study is an outgrowth of materials compatibility problems in present and advanced gas-cooled reactors, where structural members in direct contact with graphite provide the possibility of both carburization and self-welding. Initial studies were concerned with surface reactions in the absence of gaseous contaminants under a vacuum of 10/sup -6/ mm Hg at 540 to 705 deg C. Stainless steel specimens are pretreated to provide three surface conditions: H/sub 2/- fired, preoxidized, and Cu-plated. Surface contact pressures ranged from 0 to 10,000 psi. Test results are presented which establish the lower temperature limit for significant diffusion between graphite and stainless steel at approximately 60O deg C. Above this temperature, diffusion between untreated or H2-fired stainless steel surfaces was found to effect complete bonding of the two materials at contact pressures as low as 500 psi. Bonding was effectively prevented by the presence of either an oxide film or a Cu plate at temperatures up to 700 deg C. Where bonding occurred, diffusion rates measured for C in stainless steel were comparable with those reported for stainless steel ln C- saturated Na. However, phases produced in surface reactions between graphite and stainless steel were of higher order than those reported for the Na carrier. Lack of carburization in control specimens not in contact with graphite indicated the role of the gas phase to be unimportant at impurity pressures of 10/sup -6/ mm Hg. (auth

Irradiation performance of advanced fuels for HTGR's

From international conference on nuclear fuel performance; London, UK (15 Oct 1973). Fuel for large HTGR power stations in the United States consists of coated particles of ThO/sub 2/ as fertile material mixed with smaller coated particles containing fissile material, either /sup 233/U from recycle of bred fuel or /sup 233/U as makeup fuel. Recycle fuel particles containing /sup 233/U mixed with thorium in sol-- gel oxide microspheres have been prepared and experiments in progress will test a fuel compositon consisting of Th/U = 4 to full exposure and burnup. The use of weak-acid ion exchange resin particles as precursors for either type of fissile fuel kernel offers several advantages.in processing and properties. Pilot-scale preparation and testing of resin-base fuels demonstrated that their performance is adequate and indicate that such fuels may be capable of operating at temperatures well above 1300 deg C. Such high-performance fuels are desirable for process heat and direct-cycle applications. (auth