In Vivo Monitoring - doe-std-1128-98

DOE-STD-1128-98

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 inside 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 urine.

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

Pacific Northwest Laboratory, telephone (509) 376-6102.

5-19