Instrumentation Considerations - doe-std-1128-98

DOE-STD-1128-98

The RCTs should be encouraged to pursue registration by the National Registry of

Radiation Protection Technologists.

3.4.3

Staffing Levels

At least one professional health physicist is recommended to be on the staff of each

major plutonium facility as a full-time employee.

There is no rule of thumb for determining the number of RCTs needed for a given

plutonium facility. The number of RCTs should be based on an analysis that

provides for sufficient coverage on each shift, given the number of samples,

surveys, and other work to be performed; the time of training, donning and doffing

protective clothing; shift turnover procedures; and other similar considerations. The

site collective dose and individual dose limits in the facility may also lead to the

need for additional personnel. Consideration should be given to having sufficient

personnel to respond to off-normal conditions and emergencies as well as routine

work. Major maintenance, modifications, or decommissioning activities may

require additional personnel.

3.5

INSTRUMENTATION CONSIDERATIONS

The radiation from the radioactive decay of plutonium includes alpha, beta, gamma, X-ray

(photons), and neutron radiation. An effective monitoring program for plutonium requires

radiation detection instruments that are responsive to all of these forms of radiation. It is

essential that instruments meet the performance criteria outlined in the applicable U.S. and

international standards and be properly calibrated for their intended use.

3.5.1

Types of Instruments and Measurements

Alpha-sensitive instruments are necessary for most contamination control surveys.

Exposure rate surveys are normally conducted with photon-sensitive instruments

with known energy responses. Neutron surveys become important when processing

tens of grams of 238Pu or hundreds of grams of mixed isotopes of plutonium,

particularly compounds (i.e., PuO2, PuF4, etc.). The neutron survey is important in

instances where photon shields, such as leaded glass, are used; such shields

normally stop all of the charged particles, most of the low-energy photons, and

essentially none of the neutrons. Under these circumstances, neutron radiation is

likely to be the major contributor to whole body dose.

Continuous air monitors (CAMs) are used extensively in plutonium facilities.

Continuous air monitors and sample extraction lines that go to CAMs and

continuous radiation dose monitors should be placed outside the glove boxes and

hoods. In-line processing instrumentation is critical to accurately monitor the work

stations and a review should be performed to determine instrument locations.

Continuous air monitors may not have adequate detection capabilities for real-time

monitoring at the DAC level. For 239Pu, the annual limit on intake (ALI) is 4.8 nCi

for class W compounds based on the DAC of 2 x 10-12 Ci/mL, as given in

Appendix A to 10 CFR Part 835 (DOE, 1998a). Representative manufacturers'

specifications on the performance level of such a CAM range from 1 DAC in 4

hours (4 DAC-h) to 1 DAC in 8 hours (8 DAC-h) for alarm (with no radon

present). Continuous air monitors typically have had poor large-particle response

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