Recently, a glovebox breach led to the potential exposure of 15 Los Alamos National Laboratory employees to 238Pu. Given what is known about the material involved in the incident, the possibility of ...an intake with a ceramic-type component must be considered. Incidents in which intakes of ceramic solubility-type material is suspected represent a challenge for internal dose assessment via urine bioassay because even relatively large doses cannot be detected in urine until many months after the intake. Ideally, in these situations fecal samples should be collected to assess the intake, but in this case fecal sampling was delayed. This paper presents a method to calculate the maximum possible doses for all individuals involved in an incident using only early time-decreasing urine bioassay measurements.
In addition to a review of theoretical analyses, this work presents an empirical study of nasal swab data from the Los Alamos National Laboratory (LANL) database correlated with intake obtained from ...plutonium internal dosimetry calculations. As a result of this work, several "intake-versus-nasal-swab" models were derived. We advocate quantitative use of nasal swab measurements in dose assessment calculations and discuss ways that this can be done. The best description of the LANL plutonium internal dose database is arguably intake = A + Bx, where A = 2.7 Bq, B = 3.8, and x = summed nasal swab activity. The geometric standard deviation was found to be 8.2. This relationship, obtained using plutonium data, should apply also for other radionuclides.
This work presents an alternate analysis of an in vitro solubility study on the lung dissolution rate of 238PuO2 material involved in a recent inhalation incident at Los Alamos National Laboratory ...(LANL). The original dataset used in this work was retrieved from a recently published report. The present work shows an analysis of the same dataset by modeling the dissolution in separate time intervals rather than modeling the cumulative dissolution.
As with any medical treatment, the decision to excise a wound contaminated with actinides is a risk-benefit analysis. The potential benefits of surgical excision following such contaminated wounds ...are reduction in the probability of stochastic effects, avoidance of local effects, and psychological comfort knowing that radioactive material deposited in the wound is prevented from being systemic. These benefits should be balanced against the potential risks such as pain, numbness, infection, and loss of function due to excision. To that end, the responsibility of an internal dosimetrist is to provide advice to both the patient and the treating physician about the likely benefits of excision that include, but not limited to, averted doses. This paper provides a review of the effectiveness of surgical excisions following plutonium-contaminated wounds and finds that excisions are highly effective at removing plutonium from wounds and at averting the doses they would have caused.
Accidental inhalation of plutonium at the workplace is a non-negligible risk, even when rigorous safety standards are in place. The intake and retention of plutonium in the human body may be a source ...of concern. Thus, if there is a suspicion of a significant intake of plutonium, medical countermeasures such as chelation treatment may be administered to the worker. The present work aimed to interpret the bioassay data of a worker involved in an inhalation incident due to a glovebox breach at Los Alamos National Laboratory's plutonium facility. The worker was treated with intravenous injections of calcium salts of diethylenetriaminepentaacetic acid (DTPA) in an attempt to reduce the amount of plutonium from the body and therefore reduce the internal radiation dose. It is well known in the internal dosimetry field that the administration of chelation treatment poses additional challenges to the dose assessment. Hence, a recently developed chelation model was used for the modeling of the bioassay data. The objectives of this work are to describe the incident, model the chelation-affected and non-affected bioassay data, estimate the plutonium intake, and assess the internal radiation dose.
Inhalation of plutonium is a significant contributor of occupational doses in plutonium production, nuclear fuel reprocessing, and cleanup operations. Accurate assessment of the residence time of ...plutonium in the lungs is important to properly characterize dose and, consequently, the risk from inhalation of plutonium aerosols. This paper discusses the long-term retention of plutonium in different parts of the respiratory tract of two workers who donated their bodies to the US Transuranium and Uranium Registries. The post-mortem tissue radiochemical analysis results, along with the urine bioassay data, were interpreted using Markov Chain Monte Carlo and the latest biokinetic models presented in the Occupational Intakes of Radionuclides series of ICRP publications. The materials inhaled by both workers were found to have solubility between that of plutonium nitrates and oxides. The long-term solubility was also confirmed by comparison of the activity concentration in the lungs and the thoracic lymph nodes. The data from the two individuals can be explained by assuming a bound fraction (fraction of plutonium deposited in the respiratory tract that becomes bound to lung tissue after dissolution) of 1% and 4%, respectively, without having to significantly alter the particle clearance parameters. Effects of different assumptions about the bound fraction on radiation doses to different target regions was also investigated. For inhalation of soluble materials, an assumption of fb of 1%, compared to the ICRP default of 0.2%, increases the dose to the most sensitive target region of the respiratory tract by 258% and that to the total lung by 116%. Some possible alternate methods of explaining higher-than-expected long-term retention of plutonium in the upper respiratory tract of these individuals-such as physical sequestration of material into the scar tissues and possible uptake by lungs-are also briefly discussed.
The three principal pathways for intakes of plutonium are ingestion, inhalation, and contaminated wounds. In August 2018, a glovebox worker at Los Alamos National Laboratory (LANL) sustained a ...puncture from a thread of a braided steel cable contaminated with Pu. The puncture produced no pain, no blood, and little or no visible mark. As a result, the potential for a contaminated wound was not immediately recognized, and a wound count was not conducted until elevated urine bioassay results were received 12 d after the incident. This paper discusses the circumstances of the incident, along with the medical response and dose assessment, and a discussion of the risks and benefits of the medical interventions.
The administration of chelation therapy to treat significant intakes of actinides, such as plutonium, affects the actinide's normal biokinetics. In particular, it enhances the actinide's rate of ...excretion, such that the standard biokinetic models cannot be applied directly to the chelation-affected bioassay data in order to estimate the intake and assess the radiation dose. The present study proposes a new chelation model that can be applied to the chelation-affected bioassay data after plutonium intake via wound and treatment with DTPA. In the proposed model, chelation is assumed to occur in the blood, liver, and parts of the skeleton. Ten datasets, consisting of measurements of C-DTPA, Pu, and Pu involving humans given radiolabeled DTPA and humans occupationally exposed to plutonium via wound and treated with chelation therapy, were used for model development. The combined dataset consisted of daily and cumulative excretion (urine and feces), wound counts, measurements of excised tissue, blood, and post-mortem tissue analyses of liver and skeleton. The combined data were simultaneously fit using the chelation model linked with a plutonium systemic model, which was linked to an ad hoc wound model. The proposed chelation model was used for dose assessment of the wound cases used in this study.
The urinary excretion and wound retention data collected after a Pu-contaminated wound were analyzed using Markov Chain Monte Carlo (MCMC) to obtain the posterior distribution of the intakes and ...doses. An empirical approach was used to model the effects of medical treatments (chelation and excision) on the reduction of doses. It was calculated that DTPA enhanced the urinary excretion, on average, by a factor of 17. The empirical analysis also allowed calculation of the efficacies of the medical treatments-excision and chelation averted approximately 76% and 5.5%, respectively, of the doses that would have been if there were no medical treatment. All bioassay data are provided in the appendix for independent analysis and to facilitate the compartmental modeling approaches being developed by the health physics community.
The plutonium rapid response in vitro bioassay method described here was designed to determine
238
Pu,
239
Pu, and
240
Pu concentration in urine samples from workers with potential internal ...contamination. Results provide quick and actionable information about the level of contamination necessary to assist making further medical decisions, including chelation therapy. The radiochemical procedure can be performed within approximately 48 h, including sample preparation, measurement(s) by alpha spectrometry and/or inductively coupled plasma mass spectrometry (ICP-MS), and data evaluation.
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