Urine Sampling - doe-std-1136-20040121

DOE-STD-1136-2004

Guide of Good Practices for Occupational Radiological Protection in Uranium Facilities

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.

In vivo analysis is most useful for characterizing inhalation exposure of class W or Y compounds of

uranium by lung counting. MDAs are generally not sufficiently low to provide reliable information about

systemic distribution of soluble uranium at occupational levels. The 235U decays with emission of an

energetic (186-keV) photon in high abundance that is used for in vivo monitoring of enriched uranium

workers. The other long- lived uranium isotopes emit only low yields of low-energy photons (<60 keV),

which are easily attenuated by body tissue and have limited usefulness for in vivo analysis. Internal

exposures to aged depleted uranium can be measured in vivo by taking advantage of several photons of

moderate energy (63-93 keV) emitted by the 234mPa daughter of 234Th, which are both short-lived daughters

of 238U.

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 U.S. DOE Phantom Library, operated by the

Pacific Northwest National 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 determine whether 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 essentially nonexistent the potential of very low- level contamination of the sample

from external sources of uranium. Avoidance of very minor external contamination of the samples is

extremely important due to the dosimetric implications of uranium in urine.

Large-volume urine samples are necessary for bioassay monitoring due to the very small urinary

excretion rates. Ideally, 24-hour total samples would be preferred; however, such samples often impose

substantial inconvenience on workers, resulting in noncompliance with the instructions. As an alternative,

total samples can be simulated by either time-collection protocols or volume normalization techniques.

One method of time-collection simulation (NCRP 1987b; Sula et al. 1991) is to collect all urine

voided from 1 hour before going to bed at night until 1 hour after rising in the morning for two

For information on or to request loans from the U.S. DOE Phantom Library, contact In Vivo Radioassay Research Facility, at

(1)

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

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