Testing Decision Level (DL) and Minimum Detectable Amount (MDA) for Hanford In Vivo Counting Systems.

Testing the decision level (DL) and minimum detectable amount (MDA) of a radionuclide for a direct bioassay (in vivo) counting system is a requirement for in vivo monitoring programs across the DOE complex. Bottle manikin absorption (BOMAB) and torso phantoms are used in conjunction with point sources to facilitate the testing. This paper describes a method of testing the DL and MDA values of in vivo counting systems with equipment commonly used by in vivo programs.

Excreta Sampling as an Alternative to In Vivo Measurements at the Hanford Site.

The capabilities of indirect radiobioassay by urine and fecal sample analysis were compared with the direct radiobioassay methods of whole body counting and lung counting for the most common radionuclides and inhalation exposure scenarios encountered by Hanford workers. Radionuclides addressed by in vivo measurement included 137Cs, 60Co, 154Eu, and 241Am as an indicator for plutonium mixtures. The same radionuclides were addressed using gamma energy analysis of urine samples, augmented by radiochemistry and alpha spectrometry methods for plutonium in urine and fecal samples.

Disaggregating measurement uncertainty from population variability and Bayesian treatment of uncensored results.

In making low-level radioactivity measurements of populations, it is commonly observed that a substantial portion of net results is negative. Furthermore, the observed variance of the measurement results arises from a combination of measurement uncertainty and population variability. This paper presents a method for disaggregating measurement uncertainty from population variability to produce a probability density function (PDF) of possibly true results.

Case study: three acute 241Am inhalation exposures with DTPA therapy.

Three workers incurred inhalation exposures to Am oxide as a result of waste sorting and compaction activities. The exposure magnitudes were not fully recognized until the following day when an in-vivo lung count identified a significant lung deposition of Am in a male worker, and DTPA chelation therapy was initiated. Two additional workers (one female and one male) were then identified as sufficiently exposed to also warrant therapy.

Twenty-four years of follow-up for a Hanford plutonium wound case.

A 1985 plutonium puncture wound resulted in the initial deposition of 48 kBq of transuranic alpha activity, primarily 239+240Pu and 241Am, in a worker's right index finger. Surgical excisions in the week following reduced the long-term residual wound activity to 5.4 kBq, and 164 DTPA chelation therapy administrations over 17 mo resulted in urinary excretion of about 7 kBq.

A historically significant shield for in vivo measurements.

Due to the ubiquitous nature of ionizing radiation, in vivo measurement systems designed to measure low levels of radionuclides in people are usually enclosed within a high-density shield. Lead, steel, earth, and water are just some of the materials that have been and are being used to shield the detectors from radiations of cosmic, atmospheric, man-made, and terrestrial origin. At many Department of Energy sites, the counting room shields are constructed of pre-World War II steel to reduce the background levels in order to perform measurements that have low minimum detectable activities.

Six-year follow-up of an acute 241Am inhalation intake.

A 38-y-old Caucasian male who suffered an acute accidental inhalation intake of 6.3 kBq of 241Am was monitored over 2,135 d using periodic in vivo measurements of the activity in the lungs, liver, and skeleton. Lung clearance was described by a two-compartment exponential model with half-times of 110 d and 10,000 d.