Total Fission Yield

DOE-HDBK-3010-94

6.0 Inadvertent Nuclear Criticality; Total Fission Yield

6.2

T O T A L F I SS I ON Y I EL D

The potential releases from criticality events are directly related to the total fission yield of

the event. This section provides historical and analytical information relating to fission

yields to assess bounding values.

6.2.1

H istorical E xcu rsion s

To provide some perspective on the types of situation that have resulted in excursions in the

past, lists compiled by various authors, of the excursions that have actually taken place are

presented. Several incidents are listed in multiple tables due to the diverse nature of sources

used.

Stratton (September 1967) reviewed information on 34 excursions that occurred between

1945 and 1965. Ten involved water solutions of 235U or 239Pu systems, 9 involved metal

assemblies in air, and 9 involved inhomogeneous light- and heavy-water-moderated metal

systems. Olsen et al. (July 1974) reviewed Stratton's excursion data and experimental data

from the French study Consequences Radiologiques d'un Accident de Criticite (CRAC). The

excursions are listed by system type in Table 6-1. The total fission yield of the

12 excursions listed involving aqueous solutions ranges from 1E+15 to 4E+19 fissions. All

but one are bounded by a total fission yield of 1.3E+18 fissions. The 11 excursions listed

for excursions involving metal systems (including some reflection) range from ~ 3E+15 to

3.8E+17 fissions. All but one are bounded by a yield of 1.5E+17 total fissions. Only

3 excursions are listed for moderated foil and powder systems with total fission yield listed

for only 2 excursions (~ 6E+15 & 3E+16 total fissions). Excursions in reactor and reactor

experiments are reproduced in Table 6-2, (Nyer, Bright and McWhorter, 1965) and Tables

6-3 and 6-4 (Table I - Inhomogeneous Water-Moderated and Miscellaneous Systems,

Stratton, Sept 1967). These values are considered at least partially representative of

excursions that may occur in an array. The total fission yields range from 3E+16 to

1.2E+20 for the 9 inhomogeneous water-moderated excursions listed in Stratton and

3.3E+17 to 4.7E+18 for the reactor excursion experiments covered in Nyer, Bright and

McWhorter (1965). A value of 1E+20 (rounding the coefficient to a single digit) bounds the

reported values.

6.2.2

A n alytical M od els for S olu tion C riticalities

Two empirical models to estimate the total fission generated in excursions involving solutions

have been developed (Tuck August 1974, Olsen et al., July 1974). Tuck's (August 1974)

empirical relationships were developed from data for experimental studies on solution

criticalities in Kinetic Experiments on Water Boilers and the French study CRAC.

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