In Vivo Monitoring - STD-1128-98master0141

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

5.5.1 In Vivo Monitoring

The scheduling and measurement process for obtaining in vivo measurements is usually

straightforward. Workers are scheduled for the measurements and results are available

shortly after the measurement is completed. Counting times for in vivo 241Am measurements

range from about 15 minutes to an hour or more, depending on the type of measurement and

sensitivity required. The long counting times can impose limitations on the throughput of

workers through a measurement facility, making scheduling an important issue. Procedures

should be in place to assure that workers arrive for scheduled measurements and that follow-

up occurs when a measurement is not completed or a worker fails to show.

Occasionally, workers are found who are claustrophobic when placed in an in vivo counter

cells. Leaving the cell door partially open may help reduce some of the anxiety, but will

also likely compromise the low background for which the system is designed.

Many workers want to know the results of their measurements. While a simple statement by

the in vivo measurement technician may be adequate, a form letter stating that results were

normal (or showed no detection of any of the nuclides of concern) can provide permanent

verification. If results are not normal, a form letter can also be used to explain what happens

next.

An important aspect of any in vivo measurement program is the calibration and verification

testing of the measurement equipment. In vivo measurement results are highly dependent on

the determination of a background result. Likewise, calibration using known activities in

appropriate phantoms is also important. Phantoms are available commercially or by loan

from the USDOE Phantom Library, operated by the Pacific Northwest Laboratory.(1)

5.5.2 Urine Sampling

Urine sampling programs can be effectively administered using either workplace or home

collection protocols. Workplace sampling protocols must assure that adequate precautions

are taken to prevent external contamination of the sample by levels of activity well below

the detection capabilities of friskers and workplace monitors. Home collection protocols

have the advantage of being sufficiently removed from the workplace to render as

essentially nonexistent the potential of very low-level contamination of the sample from

external sources of plutonium. Avoidance of very minor external contamination of the

samples is extremely important due to the dosimetric implications of plutonium in an in

urine.

(1) For information on or to request loans from the USDOE Phantom Library, contact In an in Vivo Radioassay Research Facility, at the Pacific

Northwest Laboratory, telephone (509) 376-6102.

5-19