Evaluation and Results - s3007cn10081

DOE-STD-3007-93

Calculations for this evaluation were taken directly from the Safety Analysis Report for

the TRUPACT-II4 and are reported in this section for completeness. The calculations were

performed to establish limits for the shipment of radioactive waste in casks covered by this

evaluation.

A summary of materials and compositions used for this analysis is given in Appendix A.

Typical ANISN input listings are given in Appendix B.

Calculations to determine the minimum mass of Pu-239 required to obtain k-effective

values of 0.95 and 1.0 were performed with the one-dimensional Sn discrete-ordinates transport

theory code, ANISN. The model consisted of a sphere of Pu-239, polyethylene, and water

surrounded by a 30-cm-thick (12-in.-thick) polyethylene-water reflector. A 60 vol.%

polyethylene - 40 vol.% water composition was used in the centrally located fuel sphere and in the

external reflector. This composition was used as an upper bound on mechanically compacted

polyethylene [Note: Information such as this should be referenced; however, a reference is not

available in this instance] and, for relatively small quantities of plutonium, conservatively

represents transuranic waste. Displacement by plutonium was conservatively neglected (the

actual effect of this assumption is insignificant). The radius of the fuel sphere was determined

from the mass of plutonium in the sphere and the desired H/Pu ratio, both of which were varied

parametrically. All plutonium was represented as Pu-239.

A quadrature order of 8 and a relative convergence criterion of 0.0001 was used in all

calculations. One hundred mesh intervals were used in both the fuel sphere and in the reflector

region. The width of each mesh interval is, therefore, 0.30 cm in the reflector and less than 0.20

cm in the fuel. The 16-energy-group Hansen-Roach cross section data have a Legendre scattering

expansion order of 1.

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