The distribution sphere model

Conference · Sun Aug 01 00:00:00 EDT 1993

OSTI ID:10185591

Myers, B F; Montgomery, F C; Morris, R N

The equivalent sphere model, which is widely used in calculating the release of fission gases from nuclear fuel, is idealized. The model is based on the diffusion of fission products in and their escape from a homogeneous sphere of fuel; the fission products are generated at a constant rate and undergo radiodecay. The fuel is assumed to be a set of spherical particles with a common radius. The value of the radius is such that the surface-to-volume ratio, S/V, of the set of spherical particles is the same as the S/V of the fuel mass of interest. The release rate depends on the dimensionless quantity {lambda}a{sup 2}/D where {lambda} is the radiodecay constant, a, the equivalent sphere radius and D, the diffusion coefficient. In the limit {lambda}t {much_gt} 1, the steady-state fractional release for isotopes with half-lives less than about 5 d is given by the familiar relation R/B = 3{radical}D/{lambda}a{sup 2} (1). For the spherical particles, S/V = 3/a. However, in important cases, the assumption of a single value of a is inappropriate. Examples of configurations for which multiple values of a are appropriate include powders, hydrolyzed fuel kernels, normally configured HTR fuel particles and perhaps, fuel kernels alone. In the latter case, one can imagine a distribution of values of a whose mean yields the value appropriate for agreement of Eq. (1) with measurement.

• Research Organization: Oak Ridge National Lab., TN (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 10185591
• Report Number(s): CONF-9306234-1; ON: DE93018722
• Resource Relation: Conference: International Atomic Energy Agency (IAEA) coordinated research program (CRP2),Vienna (Austria),23-25 Jun 1993; Other Information: PBD: [1993]
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
HTR REACTOR
NUCLEAR FUELS
MATHEMATICAL MODELS
FISSION PRODUCTS
SPHERES
ANALYTICAL SOLUTION
KRYPTON 87
KRYPTON 85
METASTABLE STATES
IRRADIATION
URANIUM CARBIDES
REACTOR PHYSICS
220600
220100
RESEARCH
TEST
TRAINING
PRODUCTION
IRRADIATION
MATERIALS TESTING REACTORS
THEORY AND CALCULATION