There are only a few codes specifically designed for plutonium dose
calculations in the ORNL code center(1); they include the following:
-- PUSHLD - Calculation of Gamma Radiation Dose Rates from
Three- Dimensional Plutonium Sources and Shield Geometries at
Various Distances, HEDL-TME 73-89, Hanford Engineering
Development Laboratory (Strode, 1974).
and Gamma-Ray Shielding Code System for Plutonium, BNWL-
1855, Pacific Northwest Laboratory (Zimmerman, 1975).
-- PURSE - A Plutonium Radiation Source Code, PNCT 852-78-13,
Japan Power Reactor and Nuclear Fuel Development Corp., Tokai-
The PUSHLD computer code has the advantage that the calculated
results were experimentally verified to make certain that the low-energy
build-up factors were correct. There are undoubtedly several other codes
that could give accurate dose rates from plutonium, particularly if a
radioactive decay code is used to calculate the amount of progeny as a
function of time. For example, the Los Alamos code MCNP (Briesmeier,
1986) would provide accurate neutron and photon doses if the decay
progeny were included in the calculations. Unfortunately, all of these
codes were developed years ago to operate on mainframe computers, and
simple "user-friendly" versions are not available for personal computers.
There are some empirical equations that can be used to calculate dose
rate through simple shields, such as Neoprene, when plutonium is
directly handled in a glove box. Because of the dominance of low-energy
X-rays, the surface dose rates from plutonium sources can be quite high.
Roesch and Faust have derived a formula for predicting the surface dose
rate from plutonium through a 100-mg/cm2 shield:
Ds(rad/h) = 171 f238 + 0.51 f239 + 2.4 f240 + 8.7 f241
+ 0.15 f242 (0.074 f241)t
= the surface dose rate of plutonium metal or oxide, rad/h
(1) RISC, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6362, Telephone (423) 574-6176.