Solutions - h3010v10249

DOE-HDBK-3010-94

6.0 Inadvertent Nuclear Criticality; Total Fission Yield

not include particulate fission product generation, and are thus less precise than computer

codes. However, the quantity of particulate fission products are normally small, their

potential release fractions are likewise small, and, unlike noble gases and iodine, they are

subject to facility filtration. Accordingly, not accounting for them is typically an adequate

approximation. It is noted again that site personnel should perform whatever background

work they believe is warranted to verify that unusual or unique circumstances do not exist at

their facilities.

The anticipated quantities and radionuclides generated by solution criticalities with total

fission yields of 1E+19 fissions involving three fissionable material compositions are:

235

Table 6-7 - spent nuclear fuel (<5%

U Enrichment) (NRC, April 1977)

Table 6-8 - unirradiated 400 g enriched uranium/l (enrichment level not

specified but assumed to be <5% as in Reg. Guide 3.34) (NRC, April 1979);

and,

Table 6-9 - plutonium (of unspecified isotopic composition) (NRC, July 1979).

Distinct ARFs are assigned for different types of radionuclide fission products and, if

necessary, base fissionable materials.

6.3.1

S olu tion s

The NRC Regulatory Guides define the airborne release of the noble gases and radioiodine

generated in a solution from the facility. In almost all cases, the amount of energy generated

by the excursion is not sufficient to disable the engineered gaseous effluent treatment devices

on the facility exhaust, but no DOE non-reactor facility is known to have gaseous effluent

treatment device to attenuate the noble gases. All the noble gases generated in a liquid are

assumed to be released to the atmosphere, generally through the facility effluent treatment

system. Additionally, the NRC assumes that all the radioiodine generated is released to the

liquid and a fraction of 0.25 is not captured by the liquid. If iodine removal devices (e.g.

impregnated activated charcoal, silver-substituted zeolite, silver-salt coated ceramic pieces)

are not present in the gaseous effluent system, the LPF is assumed to be 1.0. The RF for a

vapor is assumed to be 1.0.

As previously noted, the heat generated by the excursion results in heating of the liquid and

the combination of density changes/microvoids rapidly terminates the reaction. Some of the

liquid is assumed lost by evaporation. The system again becomes critical with sufficient

cooling but the yield level is lower due to density changes not reversed. The reaction is

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