Dry Powder and Metal

DOE-HDBK-3010-94

6.0 Inadvertent Nuclear Criticality; Material Release in Criticality Excursions

evaluation of the most recent experiments on irradiated field heating and may not reflect

response for lesser conditions.

6.3.3 Dry Powder and Metal

As discussed in the previous subsection, the products generated from a nuclear excursion are

assumed to be enclosed in the matrix of the solid and the fractions listed in Table 6-10

(Release Fractions for Various Chemical Classes From Heated Spent Fuel) are assumed to be

made airborne from the response of the solids to the thermal energy generated by the

excursion. At the reference yield (1E+17 fissions), very little if any melting of the solid

would be anticipated. It is still assumed that 10% (0.1 fraction) of the metal melts/softens due

to the heat generated, thus allowing noncondensible gases and volatile radionuclides

(radioiodine) in that fraction to be released. For powders or fines in solutions, the surface

area to volume ratio of individual particles is sufficiently large that all noncondensible gases

and radioiodines will escape.

The 10% value is supported by a simple precedent within DOE for such calculations. If it is

postulated that the all the fission products in the gaseous state under heated conditions in a

shallow layer (1 mm deep) on the surface of the metal or ceramic oxide exposed to air are

released. The Damage Ratio would be:

DRc3 = [As X 1-mm]/Volf

(6-7)

where: DRc3 =

Damage Ratio for Bare, Dry Solids during a nuclear

excursion.

Area of fissionable material exposed to air, mm2

As =

Volume of fissionable material, mm3

Volf =

For 3 kg of plutonium metal considered to be in the shape of an ideal cube, this equation

would indicate ~ 10% of the overall metal is softened/damaged. The same ARFs assigned for

moderated, reflected solids are assigned to dry solid criticalities (see Table 6-10).

6.3.4 Large Storage Arrays

This configuration was intended to apply only to fuel storage arrays with moderation. The

same ARFs assigned for moderated, reflected solids (see Table 6-10) are assigned to these

fuel arrays without assuming physical damage to the fuel array material. Therefore, only the

fission product noble gases and iodine generated are considered released.

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