Table 6-5. Theoretical Criticality Accident Fission Yields

DOE-HDBK-3010-94

6.0 Inadvertent Nuclear Criticality; Total Fission Yield

Table 6-5. Theoretical Criticality Accident Fission Yields

(McLauglin, 1991)

System

Initial Burst Yield (fissions)

Total Yield (fissions)

Solutions under 100 gal (0.46 m3)

1 x 1017

3 x 1018

Solutions over 100 gal (0.46 m3)

1 x 1018

3 x 1019

Liquid/powder(a)

3 x 1020

Liquid/metal pieces(b)

3 x 1018

1 x 1019

3 x 1019

Solid uranium

1 x 1018

Solid plutonium

Large storage arrays(c)

1 x 1019

None

below prompt critical

Large storage arrays(c)

3 x 1022

above prompt critical

(a)

A system where agitation of a powder layer could result in progressively higher reactivity insertion.

(b)

A system of small pieces of fissile metal.

(c)

Large storage arrays in which many pieces of fissile material are present and could conceivably come together.

criticality behavior. As a potential precedent, however, they will be discussed in the

individual criticality categories of (1) solutions, (2) moderated, reflected solids, (3) dry

solids, and (4) large arrays.

6.2.3.1

Solutions

The eight excursions that have occurred in processing plants (non-experimental facilities) are

listed in Table 6-6 reproduced from Paxton (1980). Total fission yield ranges from

~ 1E+15 to 4E+19 fissions. All 9 events involve solution systems. Five involved

inadvertent transfer to non-safe vessels or systems. Two involve extraction/concentration

into a solvent layer with the aqueous phase providing reflection. The last event was

attributed to equipment/procedural failures. The highest value (4E+19 fission) resulted from

the siphoning of a large volume (~ 800 liter) containing 34.5 kg of 235U (approximately 70

time the minimum critical mass) from a safe to unsafe geometry with neutrons reflected by

concrete below the cylinder.

Woodcock lists two levels of solution excursion, >100 gallon and <100 gallons, with an

order of magnitude difference in both initial and total fission yields. The U.S. NRC

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