US EPA

1433627 

Journal Article 

ORNL Studies of Fission Product Release under LWR Severe Accident Conditions 

Osborne, MF; Lorenz, RA 

1992 

0 

Nuclear Safety
ISSN: 0029-5604 

NIOSH/00220087 

33 

3 

344-365 

Studies of fission products release conducted at the Oak Ridge National Laboratory (ORNL) for severe accident conditions in light water reactors (LWRs) were considered. The fuel specimens in the vertical irradiated (VI) and horizontal irradiated (HI) test series were highly irradiated Zircaloy clad uranium-oxide (UO2) fuel. The specimens and cladding were heated to 1675 to 2700 degrees-K in both steam and hydrogen atmospheres within induction furnaces developed specially for the test. Fibrous ceramic insulation provided an isothermal test region. The ORIGEN2 computer program was used to calculate the inventories of fission products in the fuel. Direct measurement of the inventories of long lived gamma emitting species was also conducted before and after the test. Results showed that in the HI tests, volatile fission products (krypton, iodine, and cesium varied from 3% at 1675 degrees to about 60% at 2275 degrees. Although temperature was the dominant test parameter influencing fission product release, atmosphere and time were also significant. The most volatile fission products were the rare gases and alkali metals. The less volatile species were divided into three broad groups, the semivolatiles (tellurium and antimony), the low volatiles (strontium, barium, and europium), and the refractories. Data for krypton and cesium releases were used to develop the ORNL diffusion release model that reliably predicted the release of volatile fission products. Chemical forms and behavior, as well as mass transport and deposition were addressed. The authors conclude that the ORNL diffusion release model is simple and reliable to use for the prediction of fission product release. 

DCN-224203; Nuclear reactor accidents; Radiation contamination; Environmental contamination; Fission reactors; Mathematical models; Radioisotopes; Nuclear fission