Neutron Dose Equivalents - STD-1128-98master0176

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

= the weight fraction of the ith isotope of plutonium

= the time since chemical separation of the plutonium, days.

This equation is only valid for a year or so after chemical separation, when the

ingrowth of 241Am can be represented linearly.

A similar equation has been derived for lead-loaded rubber gloves using the

calculations from the computer code PUSHLD. The 80-mil lead-loaded glove is

nominally 1.9-mm (0.076-in.) thick in the palm and forearm and contains the

equivalent of about 1 mm of lead. The surface dose rate, DPbGl, is given by the

following equation:

DpbGl(t) = 2.83 f238 e-0.00789t + 0.104 f239 + 0.0315 f240

(6.3)

+ 6.35 x 10-5 f242 + f241 (158.5 e-0.0016t - 152.5 e-0.0457t)

where DpbGl(t)

= surface dose rate as a function of time, rad/h

= weight fraction of the ith plutonium isotope

= time since chemical separation of the plutonium, years.

This equation includes the radiations from plutonium, as well as the 237U and 241Am

progeny from the decay of 241Pu. The expression is valid for times between 50

days and 100 years after the chemical separation of the plutonium. The formula

predicts dose rates from 0% to +20% of those calculated by the computer code

PUSHLD.

6.2.3 Neutron Dose Equivalents

Neutron dose equivalents are significant in any process or decommissioning efforts

involving kilogram quantities of plutonium or gram quantities of 238Pu. Neutrons originate

from three sources:

-- Spontaneous fission of even isotopes of plutonium

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