Radiations in Plutonium Facilities - STD-1128-98master0169

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

In reality, most instruments and personnel dosimeters used at DOE facilities are still

calibrated in terms of dose equivalent. For example, consider the case in which personnel

neutron dosimeters are calibrated on acrylic plastic phantoms at a specified distance from a

calibrated neutron source. For DOELAP testing, the dose equivalent at this point has been

calculated in accordance with NBS Special Publication 633, Procedures for Calibration of

Neutron Personnel Dosimeters (Schwartz and Eisenhauer, 1982). These calculations are

based on the Grundl-Eisenhauer energy spectrum and the conversion coefficients from

NCRP Report 38 (NCRP, 1971), which are for the "old" values of dose equivalent from the

cylindrical phantom calculations.

In most instances, the present methods based on dose equivalent over-estimate effective dose

equivalent. In cases where personnel are approaching dose limits, it may be prudent to more

accurately evaluate effective dose equivalent using special calibrations. Depending on the

irradiation geometry and energy, effective dose equivalent may be as much as a factor of

two less than dose equivalent.

6.2

RADIATIONS IN PLUTONIUM FACILITIES

As outlined in Section 2.0 of this report, plutonium emits a wide variety of radiations, including

alpha and beta particles, as well as more penetrating X-rays and gamma rays. Because of the short

half-life of 241Pu, the radioactive decay progeny are also important sources of radiation. This

section outlines methods to calculate the dose equivalents from radiations emitted by plutonium and

its progeny. Examples of measured dose rates are also included.

6.2.1 Alpha and Beta Doses

Plutonium is primarily an alpha-emitter and is of great concern if inhaled, ingested or

injected into the body. However, the skin is an effective barrier to alpha particles, and

external contamination is only a problem if there is a wound or break in the skin.

Plutonium-241 is a beta-emitter that produces low-energy beta particles with a maximum

energy of 0.022 MeV. Both alpha and beta particles are completely shielded by thin rubber

gloves or other protective devices. The dose rate through a rubber glove originates primarily

from the X-rays and low-energy photons generated from plutonium and 241Am, the decay

progeny of 241Pu.

6-5