PEBBLE BED REACTOR PROGRAM. Progress Report for June 1, 1958-May 31, 1959
6 5 3 3 5 3 5 4 6 , tcloaded, pebble bed reactor operating on the thorium-uranium fuel cycle and having a conversion ratio of 0.563 is described. From a study of the neutron balance of this system it was apparent that the conversion ratio could be improved, and in fact breeding might be attained, by designing as continuously loaded core where fresh fuel was added and spent fuel removed at a ratt such that reactivity would just be maintained. A study was made of such a system from which a reactor was evolved having a breeding ratio of unity with a fuel residence time of 169.5 days at the 125 Mwe PBR operating conditions. Simultaneously, spherical uranium-graphite fuel elements were procured; tested mechanically, for fission product leakage andd irradiated. From the results of this work it has been demonstrated that fuel elements having satisfactory structural characteristics can be built. They do not after any degradation of structural properties after irradiation to 1 1/2 atom burnup of fissile material. They show promise of retention of fission products such that direct maintenance of the primary loop, under controlled conditions, is possible. Fuel Element Technology. The three basic types of uncoated PBR fuel elemerts (impregnated, admixtured, and lumped) were irradiated to a burnup equivalent to 18% of the fissile atoms in a referencc PBR fuel element at a temperature of about 1300 deg F. Both the impregnated and the admixtured element gained in compressive strength, showed essentially no impairment of impact strength, and no damage to the surfaces. The lumped element showed a definite impairment of its physical properties. The leakage rate of several volatile fission product isoapes from a siliconized silicon carbide coated PBR fuel element was initially found to be of the order of 10/sup -7/ of the isotope production rate while under high level irradiation at 1350 deg F. However, this leakage rate increased several orders of magitude after continued irradiation indicating a coating violation the nature of which remains a be determined. Reactor Physics. Three fuel cycles have been investigated. The continuously-fueled reactor concept provides a method of achieving a breeder reactor with a high fuel burnup and thus a reasonable fuel cost. If breeding were not relifetime and a corresponding reduction in fuel cost. The batch-fueled reactor can be designed to breed on a Th232 and U-233 fuel cycle at the expense of core lifetime. The reactor considered which is near the optimum with respect a breeding ratio, had a core lifetime of only 39 days based on a uniform burnup calculation. When nonuniform burnup of the fuel is considered the lifetime will be reduced further. Batch-fueled reactors utilizing U-235 and U-235 can be designed to operate with enrichments varying from about 3 to 35% depending on the core diameter and lifetime required. Initial breeding ratios as high as 0.9 can be realized, although they should be subordinated to the core lifetime in order to minimize fuel cost. A further reduction in fuel cost could be made by using the continuously fueled concept, although the mechandical design problems involved should be given due consideration. Thermal and Hydraulic Analysis. The previous analysis of the batchloaded reactor has been revised. Means of reducing fuel element temperatures are considered. Analysis of a continuously loaded reactor is included. System Activity and Clean-up. Extensive studies are described which were made in and effort a predict quantitatively the fission product leakage rate to the coolant system. Experimental Programs. Experiments using lead shot were performed to study the void distribution in packedsphere beds. The shot was poured into a cylinder, and an epoxy resin was poured in filling the interconnected
- Research Organization:
- Sanderson and Porter, New York
- DOE Contract Number:
- AT(30-1)-2207
- NSA Number:
- NSA-13-018737
- OSTI ID:
- 4256713
- Report Number(s):
- NYO-2373
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-59
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BREEDING- BURNUP- ECONOMICS- EFFICIENCY- FUELS- PEBBLE BED- PELLETS- PLANNING- POWER PLANTS- REACTIVITY- REACTOR CORE- REACTOR FUELING- REACTORS- SPHERES- THORIUM- THORIUM 233- URANIUM- URANIUM 233- URANIUM 235- URANIUM 238- VOLUME
BREEDING- BURNUP- FUEL ELEMENTS- GRAPHITE- HIGH TEMPERATURE- IMPACT SHOCK- IRRADIATION- MECHANICAL PROPERTIES- PEBBLE BED- PELLETS- PLANNING- POWER PLANTS- RADIATION EFFECTS- REACTORS- SPHERES- SURFACES- TESTING- THORIUM- URANIUM
BREEDING- CONTAMINATION- COOLANTS- FISSION PRODUCTS- LEAKAGE- PEBBLE BED- PELLETS- PLANNING- POWER PLANTS- REACTORS- SPHERES- THORIUM- U