ORAU TEAM Dose Reconstruction Project for NIOSH

Document No. ORAUT-TKBS-0041 Revision No. 01 Effective Date: 06/02/2009 Page 44 of 89
plutonium from Hanford. If the actual age of the fuel is known (such as from an incident investigation
report), then that age can be used in the intake and dose analysis.
5.2 IN VITRO BIOASSAY
The bioassay program for NUMEC workers primarily involved urine and fecal sampling for isotopes of
uranium, plutonium, 241 Am. Occasional analyses were performed for fission products (FPs) and 232 Th.
The reported bioassay data generally includes a measurement error that indicates the detection level.
The bioassay analyses are described in the following sections.
Table 5-3. Activity composition of Hanford reference fuel-grade plutonium mixture (12%). a
Mixture
designation Specific Activity (Ci/g)
Years of
0-yr 5-yr 10-yr 15-yr 20-yr
aging b
Pu-238 1.71E-02 1.64E-02 1.58E-02 1.52E-02 1.46E-02
Pu-239 5.26E-02 5.26E-02 5.26E-02 5.26E-02 5.26E-02
Pu-240 2.72E-02 2.72E-02 2.72E-02 2.72E-02 2.72E-02
Pu-241 3.09E+00 2.43E+00 1.91E+00 1.50E+00 1.18E+00
Pu-242 3.93E-06 3.93E-06 3.93E-06 3.93E-06 3.93E-06
Am-241 0.00E+00 2.19E-02 3.89E-02 5.22E-02 6.24E-02
a. Source: ORAUT (2007a).
b. Time since separation of the Am-241 from the plutonium mix.
Several bioassay vendors were used to evaluate in vitro bioassay samples for the NUMEC sites. The
SEC evaluations for the NUMEC Apollo site (NIOSH 2007c) and the NUMEC Parks Township site
(NIOSH 2008) indicated that Controls for Environmental Pollution has been implicated in the
falsification of data and that its bioassay analyses provided to NUMEC cannot be considered reliable.
Bioassay data from Controls for Environmental Pollution should only be used to indicate the potential
for exposure to a particular radionuclide on a particular date. The data cannot be used in a dose
reconstruction to evaluate intakes or assign internal dose.
The in vitro bioassay records for individuals nearly always include an indication of the detection level
for the measurement. Dose reconstructors should use the listed detection level information in
evaluation of intakes for specific radionuclides when available, except as noted below for urine
bioassay data from Controls for Radiation in the early years (1961 to 1965).
5.2.1
Plutonium Urine and Feces Bioassay
Plutonium might have been present at the NUMEC facilities in several forms that include type M,
type S, and possibly type Super S material solubility categories. The intake analysis based on
bioassay monitoring results should evaluate intakes based on all three types and use the type
providing the highest dose estimate.
5.2.1.1 Plutonium Urine Minimum Detectable Concentrations and Frequencies
Plutonium-239 was analyzed in urine from about 1962 to 1999, and 241 Am was analyzed starting in
about 1966. The minimum detectable concentrations (MDCs) are listed in Table 5-4 for NUMEC
facilities. If an MDC value is needed prior to the dates listed in the table, the values for the earliest
date should be used. Note that no bioassay monitoring results were found between 1985 and 1999.
In addition, because one health physics department was responsible for the bioassay program at both
the Apollo and Parks Township sites, it is difficult to determine from the reported bioassay results if
the employee worked at the Apollo or Parks Township site. It is likely that much of the plutonium
bioassay results were for work at the Parks Township site.