Criticality Accident Dosimetry - doe-std-1128-98

DOE-STD-1128-98

Extremity doses are typically determined by TLD finger rings, which are usually

worn with the TLD chip facing the radiation source on the palm side of the hand.

In glove-box and in D&D operations, the photon dose is usually significantly

higher than any neutron dose. However, neutron dosimeters are sometimes worn

to estimate extremity doses. Two types of neutron extremity dosimeters have

been used: nuclear track dosimeters worn in special finger rings and specially

calibrated TLD-albedo dosimeters worn on the wrist or forearm. DOE STD-

1095-95 (DOE 1995h) is currently applicable to personnel dosimeters for whole

body irradiation. However, it contains guidance for the development of

correction factors for neutron doses that may be applicable for developing

correction factors for neutron extremity dosimeters.

There is some question about the correct quality factor to apply to extremity

neutron dosimeters. Existing quality factors are defined in terms of linear energy

transfer (LET), so a numerical value for quality factor can be readily derived by

calculation or measurement of the neutron energy spectra. However, the

relationship between quality factor and LET was derived from biological

experiments on cancer induction, especially leukemia in blood-forming organs.

There are no blood-forming organs in the extremities, so there is no biological

basis for large values of quality factors for extremity exposures. However,

regulatory agencies typically apply quality factors derived for whole-body

exposures to the extremities, thus for compliance purposes qualify factors should

be applied for extremity exposures.

6.3.4

Criticality Accident Dosimetry

A criticality safety program, which includes material control, criticality alarms,

and criticality accident dosimetry, is required as outlined in DOE Order 420.1A

(DOE, 2003a). The requirements in 10 CFR 835.1304 require that fixed nuclear

accident dosimeters (NADs) and personnel nuclear accident dosimeters (PNADs)

shall be worn by all individuals entering a controlled area that contains certain

quantities of fissile materials, such as those required in DOE Order 420.1A

(DOE, 2003a); which requires installed criticality alarms. The criticality accident

dosimetry system should follow the provisions of ANSI/ANS 13.3-1988,

Dosimetry for Criticality Accidents (ANSI, 1969a); this standard is currently

being revised. Information on criticality accident dosimetry is also available from

the International Atomic Energy Agency (IAEA, 1982).

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