Timothy P. Lynch

USTUR whole body case 0262: 33-y follow-up of Puo2 in a skin wound and associated axillary node

This whole body donation case (USTUR Registrant) involved two suspected PuO2 inhalation intakes, each indicated by a measurable Pu alpha activity in a single urine sample, followed about 1(1/2) y later by a puncture wound to the thumb while working in a Pu glovebox. The study is concerned with modelling simultaneously the biokinetics of deposition and retention in the respiratory tract and at the wound site; and the biokinetics of Pu subsequently transferred to other body organs, until the donors death. Urine samples taken after the wound incident had readily measurable Pu alpha activity over the next 14 y, before dropping below the minimum detectable excretion rate (<0.4 mBq d(-1)). The Registrant died about 33 y after the wound intake, at the age of 71, from hepatocellular carcinoma with extensive metastases. At autopsy, all major soft tissue organs were harvested for analysis of their 238Pu, 239+240Pu and 241Am content. The amount of 239+240Pu retained at the wound site was 68 +/- 7 Bq (1 SD), measured by low-energy planar Ge spectrometry. A further 56.0 +/- 1.2 Bq was retained in an associated axillary lymph node, measured by radiochemistry. Simultaneous mathematical analysis (modelling) of all in vivo urinary excretion data, together with the measured lung, thoracic lymph node, wound, axillary lymph node and systemic tissue contents at death, yielded estimated intake amounts of 757 and 1504 Bq, respectively, for the first and second inhalation incidents, and 204 Bq for the total wound intake. The inhaled Pu material was highly insoluble, with an estimated long-term absorption rate from the lungs of 2 x 10(-5) d(-1). The Pu material deposited at the wound site was mixed: approximately 14% was rapidly absorbed, approximately 49% was absorbed at the rate of about 6 x 10(-5) d(-1), and the remainder ( approximately 37%) was absorbed extremely slowly (at the rate of about 5 x 10(-6) d(-1)). Thus, it was estimated that only approximately 40% of the Pu initially deposited in the wound had been absorbed systemically over the 33-y period until the donors death. The biokinetic modelling also indicated that, in this individual case, some of the parameter values (rate constants) incorporated in the ICRP Publication 67 Pu model were up to a factor of 2 different from ICRPs recommended values (for reference man).

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 workers 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. The case was published in 1988, but now 24 y of follow-up data are available. Annual bioassays have included in-vivo measurements of 241Am in the wound, skeleton, liver, lung, and axillary lymph nodes, and urinalyses for plutonium and 241Am. These measurements have shown relatively stable levels of 241Am at the wound site, with gradually increasing amounts of 241Am detected in the skeleton. Liver measurements have shown erratic detection of 241Am, and the lung measurements indicate 241Am but as interference from activity in the axillary lymph nodes and skeleton rather than activity in the lung. Urine excretion of 239+240Pu since termination of chelation therapy has typically ranged from 10 to 20 mBq d−1, with 241Am excretion about 10% of that for 239+240Pu. Annual routine medical exams have not identified any adverse health effects associated with the intake.

CASE STUDY: THREE ACUTE 241Am INHALATION EXPOSURES WITH DTPA THERAPY

Three workers incurred inhalation exposures to 241Am 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 241Am 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. In-vivo bioassay measurements were performed over the ensuing 6 mo to quantify the 241Am activity in the lungs, liver, and skeleton. Urine and fecal samples were collected and showed readily detectable 241Am. Clinical lab tests and medical evaluations all showed normal results. There were no significant adverse clinical health effects from the therapy. The estimated 241Am inhalation intakes for the three workers were 1,800 Bq, 630 Bq, and 150 Bq. Lung retention showed somewhat longer pulmonary clearance half-times than standard inhalation class W or absorption Type M assumptions. The three subjects underwent slightly different therapy regimens, with therapy effectiveness factors (defined as the ratio of the reference doses without therapy relative to the final assessed doses) of 4.5, 1.9, and 1.7, respectively.

In Vivo Radiobioassay and Research Facility

Bioassay monitoring for intakes of radioactive material is an essential part of the internal dosimetry program for radiation workers at the Department of Energys (DOE) Hanford Site. This monitoring program includes direct measurements of radionuclides in the body by detecting photons that exit the body and analyses of radionuclides in excreta samples. The specialized equipment and instrumentation required to make the direct measurements of radionuclides in the body are located at the In Vivo Radiobioassay and Research Facility (IVRRF). The construction of the IVRRF was completed in January 1959 and was designed expressly for the in vivo measurement of radioactive material in Hanford workers. The IVRRF is located in Richland, WA, in the southeastern corner of the state. Most routine in vivo measurements are performed annually and special measurements are performed as needed. The primary source terms at the Hanford Site include fission and activation products (primarily 137Cs and 90Sr), uranium, uranium progeny, and transuranic radionuclides. The facility currently houses five shielded counting systems, mens and womens change rooms, and an instrument maintenance and repair shop. These systems are used to perform an average of 7,000 measurements annually. This includes approximately 5,000 whole body measurements analyzed for fission and activation products and 2,000 lung measurements analyzed for americium and uranium. Various other types of measurements are performed periodically to estimate activity in wounds, the thyroid, the liver, and the skeleton. The staff maintains the capability to detect and quantify activity in essentially any tissue or organ. The in vivo monitoring program that utilizes the facility is accredited by the Department of Energy Laboratory Accreditation Program for direct radiobioassay. This manuscript provides an overview of the facilities and equipment at the IVRRF and the in vivo measurement methods used to monitor workers with a potential for an occupational intake of radioactive material.

Radiation Doses to Hanford Workers from Natural Potassium-40

The chemical element potassium is an essential mineral in people and is subject to homeostatic regulation. Natural potassium comprises three isotopes, 39K, 40K, and 41K. Potassium-40 is radioactive, with a half life of 1.248 billion years. In most transitions, it emits a β particle with a maximum energy of 0.560 MeV, and sometimes a gamma photon of 1.461 MeV. Because it is ubiquitous, 40K produces radiation dose to all human beings. This report contains the results of new measurements of 40K in 248 adult females and 2,037 adult males performed at the Department of Energy Hanford Site in 2006 and 2007. Potassium concentrations diminish with age, are generally lower in women than in men, and decrease with body mass index (BMI). The average annual effective dose from 40K in the body is 0.149 mSv y−1 for men and 0.123 mSv y−1 women respectively. Averaged over both men and women, the average effective dose per year is 0.136 mSv y−1. Calculated effective doses range from 0.069 to 0.243 mSv y−1 for adult males, and 0.067 to 0.203 mSv y−1 for adult females, a roughly three-fold variation for each gender. The need for dosimetric phantoms with a greater variety of BMI values should be investigated. From our data, it cannot be determined whether the potassium concentration in muscle in people with large BMI values differs from that in people with small BMI values. Similarly, it would be important to know the potassium concentration in other soft tissues, since much of the radiation dose is due to beta radiation, in which the source and target tissues are the same. These uncertainties should be evaluated to determine their consequences for dosimetry.

Hanford Radiological Protection Support Services Annual Report for 2000

During calendar year 2000, the Pacific Northwest National Laboratory performed its customary radiological protection support services in support of the U.S. Department of Energy Richland Operations Office and the Hanford contractors. These services included: (1) external dosimetry, (2) internal dosimetry, (3) in vivo monitoring, (4) radiological records, (5) instrument calibration and evaluation, and (6) calibration of radiation sources traceable to the National Institute of Standards and Technology. Each program summary describes the routine operations, program changes and improvements, program assessments, supporting technical studies, and professional activities.

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

AbstractThe 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. It was concluded that in vivo whole body counting and lung counting capability should be maintained at the Hanford Site for the foreseeable future, however, urine and fecal sample analysis could provide adequate, though degraded, monitoring capability for workers as a short-term alternative, should in vivo capability be lost due to planned or unplanned circumstances.

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. The pre-World War II steel is commonly called low background steel in the in vivo industry vernacular. The low background descriptor comes from the fact the steel was manufactured prior to the beginning of atmospheric testing of nuclear weapons in the 1940s. Consequently, the steel is not likely to be contaminated with fission or activation products from fallout. For high energy photons (600 keV < E < 1500 keV), 30 cm of steel shielding significantly reduces the measured background radiation levels. This is the story of the unique steel that began as the hull of the U.S.S. Indiana and now forms a shielded room at the In Vivo Radiobioassay and Research Facility in Richland, Washington.

Summing coincidence errors using 152Eu lungs to calibrate a lung-counting system: are they significant?

The use of a lung phantom containing 152Eu/241Am activity can provide a sufficient number of energy lines to generate an efficiency calibration for the in vivo measurements of radioactive materials in the lungs. However, due to the number of energy lines associated with 152Eu, coincidence summing occurs and can present a problem when using such a phantom for calibrating lung-counting systems. A Summing Peak Effect Study was conducted at three laboratories to determine the effect of using an efficiency calibration based on a 152Eu/241Am lung phantom. The measurement data at all three laboratories showed the presence of sum peaks. While one of the laboratories found only small biases (<5%) when using the 152Eu/241Am calibration, the other facilities noted up to 30% positive bias in the 140 keV to 190 keV energy range that prevents the use of the 152Eu/241Am lung phantom for routine calibrations. Although manufactured by different vendors, the three facilities use similar types of germanium detectors (38 cm2 by 25 mm thick or 38 cm2 by 30 mm thick) for counting. These results underscore the need to evaluate the coincidence summing effect, which appear system dependent, when using a nuclide such as 152Eu for the calibration of low-energy lung counting systems and highlight the problem of using a general calibration curve in place of specific nuclide calibration factors.

Hanford Radiological Protection Support Services Annual Report for 2001

The report describes the 2001 activities associated with the External Dosimetry Program, Internal Dosimetry Program, In Vivo Monitoring Program, Hanford Radiation Records Program, Instrumentation and Technology Program and the Radiation Standards and Calibrations Program. The programs are managed by the Pacific Northwest National Laboratory for the U.S. Department of Energy Richland Operations Office, the Office of River Protection and the Hanford Site contractors.