Plutonium Contamination Detection - STD-1128-98master0114

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

-- That it has never been used or stored in an area controlled for contamination purposes

(i.e., a Contamination Area, High Contamination Area, or Airborne Radioactivity Area)

-- That it has never come into contact with unsealed radioactive material

-- That it has not been stored or used in a Radiological Buffer Area (RBA) surrounding

a Contamination Area, High Contamination Area, or Airborne Radioactivity Area.

This material may be considered to be not contaminated and an instrument survey is not

necessary according to the DOE standard, Radiological Control (DOE, 1999a). A material

history release form should be used to document the release of material that is known to be

free of contamination by its history of use. If the material history release form cannot be

completed, or if the history of the material is unknown, an instrument survey must be made

of the material. Material released from RBAs around Contamination Areas, High

Contamination Areas, or Airborne Radioactivity Areas should also be evaluated using an

instrument survey.

The material evaluation process should also consider the nuclides to which the material was

potentially exposed. If the material was exposed to significant quantities of nuclides that are

difficult to detect, including tritium, 14C, 125I, or 129I, an appropriate survey methodology

should be applied.

4.2.6 Plutonium Contamination Detection

The detection and measurement of plutonium contamination is necessary to ensure control

of contamination and compliance with DOE requirements. Typically, detection of

plutonium contamination has been performed using survey instruments that detect the alpha

activity. Routinely used health physics instruments (i.e., alpha survey instruments) may not

be adequate for some D&D operations. Self-absorption of plutonium alpha particles within

the source or in an irregular surface area may require the use of special X-ray and low-

energy photon instruments (e.g., a NaI detector). The NaI detector should also be used to

detect plutonium contamination that has been painted over.

Discussions of methods used to detect plutonium contamination for past D&D operations

can be found in publications by Umbarger (1982) and West et al. (1991). Umbarger

reported on nondestructive assay techniques (including portable field instrumentation and

laboratory-based methods) for sorting waste in low-level (class A) and TRU waste. Portable

field instruments included the field FIDLER (i.e., thin NaI detector), phoswich detector (i.e.,

thin NaI detector coupled with a thicker CsI detector), ZnS alpha scintillation detector, a

portable multichannel analyzer, and a hand-held gamma-ray spectrometer gun. The

advantage of a phoswich detector over a NaI detector is its lower operating background. In

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