Michael T. Ryan

Limitations on upper bound dose to adults due to intake of 129I in drinking water and a total diet-implications relative to the proposed Yucca Mountain high level radioactive waste repository.

Abstract— The purpose of this report is to comment on the potential annual doses due to the intake by adults of 129I, an important radionuclide in the proposed high-level radioactive waste repository at Yucca Mountain. An often overlooked, but significant, factor is that, in this case, the ground water, which would be the primary transport vehicle for any releases, contains relatively high concentrations of stable iodine (127I); in fact, the median concentration in the ground water in the vicinity of the proposed repository is 5.0 μg L−1. In comparison, the maximum concentration of 129I in the ground water, due to potential releases of 129I during the first 10,000 y following closure of the repository, is estimated to be ~3.7 × 10−7 Bq L−1 (~10−5 pCi L−1). This would result in a 127I to 129I ratio in the water of almost 90 million to one. Assuming no other sources of these two isotopes were being consumed, this would place an upper bound on the annual committed thyroid dose of 1.2 × 10−5 mSv (1.2 × 10−3 mrem), less than one thousandth of the Ground Water Protection Standard of 4 mrem y−1. When the additional intake of stable and radioactive iodine in other components of the diet is considered, the overall ratio of 127I to 129I would be more than 2 billion to one. The would place an upper bound on the annual committed effective dose of ~2.5 × 10−8 mSv (~2.5 × 10−6 mrem), less than one millionth of the Individual Protection Standard of 0.15 mSv (15 mrem).

Supplemental digital content.

Supplementary Materials Figure 1. Sustained administration of the COMT inhibitor OR486 leads to increased mechanical and thermal pain sensitivity in male and female rats. Figure 2. Male and female adrenalectomized rats fail to develop OR486-induced pain sensitivity. Figure 3. Sustained peripheral, intrathecal or intracerebroventricular administration of βAR antagonists, in the absence of systemic administration of OR486, does not alter pain sensitivity. Figure 4. Intrathecal administration of high dose propranolol does not alter OR486-induced pain sensitivity. Figure 5. Intracerebroventricular administration of high dose propranolol does not alter OR486-induced pain sensitivity.

Improving the regulation and management of low-activity radioactive wastes.

This paper summarizes the first phase of a study in progress by a committee of the National Research Councils Board on Radioactive Waste Management. The Board initiated the study after observing that statutes and regulations administered by the federal and state agencies that control low-activity radioactive wastes have developed as a patchwork over almost 60 y. These controls usually reflect the enterprise or process that produced the waste rather than the wastes radiological hazard. Inconsistencies in the regulatory patchwork or its application may have led to overly restrictive controls for some low-activity wastes while others were neglected in comparison. In the first phase of this study, the committee reviewed current low-activity waste inventories, regulations, and management practices. This led the committee to develop five categories that encompass the spectrum of low-activity wastes and serve to illustrate gaps and inconsistencies in current regulations and management practices. The committee completed its first phase with four findings that will lead into the final phase of the study. This paper is excerpted from the committees interim report that was issued in October 2003.

Effects of Back Pressure on Condensed-Phase Properties Within Supercritical Ethylene Jets

The effects of ambient pressure on the liquid contents and droplet size inside condensed ethylene jets injected at the supercritical conditions were studied both experimentally and numerically. The small angle X-ray scattering (SAXS) technique available at the Argonne National Laboratory was utilized to measure droplet size and liquid volume fraction inside the condensed jets. Two different ambient pressures inside the injection chamber were selected for testing. A companion numerical model, based on previously developed approaches, was used to provide insight into droplet properties and growth processes. It was found that the measured droplet size is on the order of 1000-2000 A (100-200 nm) for the conditions tested in the present study. The measurements also show that an elevated ambient pressure can increase droplet size and reduce the liquid volume fraction within the condensed jet for a given injection condition. This experimentally observed trend, however, contradicts the present numerical results. The contributing factors for the observed discrepancies should be addressed in the future. Both measurements and numerical calculations show that the Mach disk inside the under-expanded jet exhibits large influences on droplet size and liquid volume fraction for the condensed jet injected into an elevated ambient pressure. CFD predictions show that droplets inside the jet discharged into a low ambient pressure exhibit a higher evaporation rate to reach a smaller droplet size and a lower liquid volume fraction at the downstream locations. Both measured and predicted liquid volume fraction and mass fraction within the condensed jets are fairly small.

Simulation of Supercritical Ethylene Condensation using Homogeneous Nucleation Theory

*† ‡ § AFRL-RZA, WPAFB, OH Numerical simulations of condensate formation during the rapid expansion of a supercritical ethylene jet are presented in this work. A homogeneous nucleation model that accounts for droplet temperature variations is used to model the formation and growth of a condensed phase consisting of small liquid droplets. Numerical predictions for average liquid volume fraction and average droplet diameter are computed along different lines of sight through the expanding ethylene jet. These results are compared with experimental measurements obtained using small angle x-ray scattering (SAXS). Computational predictions are most sensitive to the inclusion of droplet temperature variations. The droplet temperature lags the mean-flow temperature, leading to a reduction in the effective condensation rate. This leads to smaller droplet sizes which are in good overall agreement with SAXS measurements except near the outer boundaries of the jet. The experimental data-reduction process for liquid volume fraction is sensitive to the assumed value of liquid ethylene density in the free-jet expansion region. By incorporating computed values of this quantity into the data reduction method, much better agreement between experimental measurements and computational predictions of liquid volume fraction is obtained.

Significance of 14C and 228Ra in terms of the proposed Yucca Mountain high-level radioactive waste repository.

14C and 228Ra are two of the radionuclides that have either been identified as being potentially significant in terms of releases from the proposed Yucca Mountain high-level radioactive waste repository, or are specifically cited for consideration and evaluation in the regulations promulgated by the U.S. Nuclear Regulatory Commission. The purpose of this study was to estimate the concentrations and associated doses for these two radionuclides, if released under conditions of a scenario assumed to apply to a repository containing some of the features of the one proposed at Yucca Mountain, NV, and to compare these estimates to the regulatory limits for that facility. For 14C, the postulated condition was that an annual fractional release of 10−5 of its total remaining inventory occurs beginning at 10,000 y after repository closure. For 228Ra, the same fractional release rate was assumed, but in this case it was presumed to occur when the 228Ra inventory was projected to reach a maximum at more than 108 y after repository closure. The estimated concentrations and doses were, in turn, compared to the concentration limit, specified in the Ground Water Protection Standards (GWPSs) in the case of 228Ra, or derived, in the case of 14C, on the basis of the regulatory dose rate limit. Due to the small inventory of 14C in the waste, and its short half-life relative to the performance period evaluated, its estimated concentration in the ground water would be slightly more than 4% of the derived GWPS. Due to the relatively small initial inventory of 232Th, the precursor of 228Ra, and the correspondingly small quantities of higher atomic number actinides that could, through decay, produce additional quantities of 232Th, its estimated concentration in the ground water would be less than 3% of the GWPS, leaving the remaining portion of the limit for potential contributions from 226Ra. At the same time, however, it must be recognized that, in this case, the regulations require that any contributions of naturally occurring 226Ra and 228Ra already present in the ground water must be included in the determination of compliance. If this is done, the total concentration of 228Ra, combined with the naturally occurring concentration of 226Ra, would be about 10.5% of the limit. In a similar manner, the committed doses due to the annual consumption of each of these two radionuclides in ground water and food, produced in the local biosphere, were evaluated in terms of the Individual Protection Standard (IPS). Based on these analyses, the estimated effective dose for 14C, using the coefficients in Federal Guidance Report (FGR) No. 13, was 4.15 &mgr;Sv y−1, less than 3% of the IPS. For 228Ra, the comparable estimate at the time of maximum inventory, excluding in this case the contributions from naturally occurring 226Ra and 228Ra, was 7.39 &mgr;Sv y−1, representing about 5% of the IPS. Based on the value assumed for the fractional release rate (10−5 y−1), it was concluded that neither 14C nor 228Ra will be significant in terms of either the applicable GWPS or the IPS. While it was recognized that, due to the time spans involved, these analyses were primarily an academic exercise, it is believed that the perspectives and accompanying insights are useful.

Factors affecting dose estimates for long-term performance assessments : Case study-Armagosa valley

The purpose of this study was to review and evaluate some of the factors that influence the dose estimates to members of the public due to chronic, long-term releases of radioactive materials into the environment. Although the examples discussed are based on data from the Amargosa Valley located near the proposed Yucca Mountain high-level radioactive waste repository, the factors evaluated are common to any such assessment. While it is recognized that such factors include those related to both the environmental transport of radionuclides from the point of release through the environmental media to the receptor, and the influence of his/her location and living habits, the assessments that follow are primarily limited to the latter. The specific goal in all cases was to illustrate how the assumptions and input values relative to certain factors influence the dose estimates and to quantify, to the extent possible, their relative significance. At the same time, it must be recognized that the assessments presented here were limited to doses due to the ingestion of food and water; those due to the inhalation of airborne radionuclides and external exposures were not considered. The factor that proved most important from the standpoint of the overestimation of doses (i.e., conservatism) was the implementation of the regulatory requirements pertaining to the withdrawal of groundwater from the local aquifer. Another significant source of conservatism was the dose estimates provided by the U.S. Department of Energy, assuming that the Reasonably Maximally Exposed Individual (RMEI) resided at the U.S. EPA designated site, 18 km from the repository, vs. the Amargosa Valley, about 35 km away. Also important, for selected radionuclides, was the impact of their effective half-lives on the committed doses, as estimated, in comparison to those that would actually be received. Having lesser impacts were the status of a local aquaculture farm on the intake of 14C, and the intake of stable iodine on dose estimates for 129I. On the basis of these evaluations, one can reasonably conclude that the overall conservatism in the dose assessments, based on these sources that were identified, approaches an order of magnitude. The sole factor that led to an underestimation of the doses (i.e., non-conservatism) was the regulatory requirement that the concept of the RMEI, as defined by U.S. EPA, in contrast to that of the Critical Group (CG), as recommended by the International Commission on Radiological Protection, be applied in estimating the doses to potentially affected population groups. Rather than dwell on the differences in the impacts of the application of each of these two concepts, the next step should be to subject each concept to a systematic and rigorous analysis, the goal being to gain an understanding of the range of dose estimates that would be yielded, the underlying reasons for the differences that are observed, and the lessons to be learned in terms of improving the methodologies for estimating doses due to environmental radionuclide releases.

A simple method for assessing exposure to internal emitters

One of the most challenging aspects of regulatory compliance can be demonstrating compliance with internal dosimetry requirements. For long-lived alpha-emitting radionuclides in particular, the sensitivity and accuracy of bioassay analysis and whole body counting may not allow for adequate assessment of intakes. Simple and effective measures can be used to control the workplace for the internal hazards associated with long-lived radioactive material using methods that measure directly the air to which workers are exposed. This paper provides an easy assessment tool that uses direct measurement of the specific activity of dusts in breathing zone air to evaluate internal exposures. Using this method, sensitive assessments can be made to determine if intakes are likely to have occurred and, if so, at what magnitude. It is not a substitute for confirmatory bioassay or whole body counting but a simple method to evaluate expectations for internal exposures.

HPS publications implement society's "SI Only" position.

The Health Physics Society (HPS) publications team is taking the next step in using the International System (SI) of units (NIST 2008) exclusively to express radiological quantities in Society communications. Traditional units are not acceptable in HPS position statements and publications such as Health Physics, Operational Radiation Safety, and Health Physics News and will no longer be permitted in other postings on the HPS website, including fact sheets and the Ask the Experts (ATE) feature. The SI-derived units for radiological quantities are becquerel (Bq), gray (Gy), and sievert (Sv). In the United States, national policy on SI was set by the Metric Conversion Act (1975), and President George H.W. Bush reinforced national policy with the issuance of Executive Order 12770 (1991). In 1985, in NCRP Report No. 82, the National Council on Radiation Protection and Measurements called for the gradual adoption of SI units over a five-year transition period (NCRP 1985). Health Physics adopted the use of SI in 1984 (Roessler 1984). At that time, traditional units in parentheses were permitted to be used during what was seen as a transition period. Health Physics News has also followed this guideline. The SI base units and the SI coherent derived units, including those with special names, have the important advantage of forming a coherent setVunit conversions are not required when inserting particular values for quantities into quantity equations. Because the SI is the only system of units that is globally recognized, the HPS believes it also has a clear advantage for establishing a worldwide dialogue. Teaching science and technology to the next generation will be simplified if everyone uses this system. If the traditional units continue to be used, the advantages of SI are lost. The HPS publications team of editors is continuing the decision to use SI units in an exclusive manner (not allowing traditional units in parentheses) in all HPSpublished materials to fully implement the Society’s dictate proposed and adopted by the HPS in its February 2012 position statement, PS025-0, ‘‘Exclusive Use of SI to Express Radiological Quantities’’ (HPS 2012). In addition to radiological quantities, the editors also decided to expand the use of SI to other commonmetricunits suchas length, mass, area, volume, and speed. HPS editors recognize the valid concerns that have been expressed relating to the decision to adopt this SI-only policy. Certainly it is contrary to the perpetuation of the use of the traditional units by U.S. government agencies. In addition, apprehension has been expressed about safety in the nuclear industry if a new system of units is imposed. However, nearly all countries in the world, including many with well-established nuclear industries, have effected this transition successfully without compromising health and safety. The adoption of SI only is more challenging for Society publications that reach readers other than radiation professionals (such as website documents and ATE). ATE editors are implementing a two-step process to meet the SI-only position and yet maintain a communication form that is public-friendly. First, personal correspondence with questioners will use the terms and units the questioners use. For instance, if they use rem, the answer will be in rem; if they use sievert, the answer will be in sievert. However, when the question and answer are posted on the website, the posted response will use SI exclusively. Second, each of these answers will include a footnote that leads toapublic-friendly document outlining a guide to a conversion chart showing traditional and SI unit relationships and to a chart that puts the values of these units in perspective. The editors hope this decision will assist Society members in becoming accustomed to the SI system by reading and writing in the system and, ultimately, thinking in terms of SI exclusively instead of continually making the errorprone conversion from traditional units to SI units. It is inevitable that the United States will need to convert to the worldwide-accepted SI system exclusively at some time. Continued delayonlyprolongsconfusioncaused by the simultaneous use of two systems of units. It is expected that the HPS experience in effecting this transition successfully will demonstrate that the complete conversion to international units is possible and practical. The authors declare no conflicts of interest. This article has been reprinted from Health Physics 105.1, July 2013. Editorial

100 volumes of Health Physics.

I am pleased to note that this issue marks the occasion of the publication of Volume 100, No. 1, of the Health Physics Journal. Back in 1958, a group of scientists led by the first Editor-in-Chief, K. Z. Morgan, compiled Volume 1, No. 1, in an effort to begin the process of sharing research being conducted in the burgeoning field of radiological health physics. That first issue contained 13 papers, one note, one news item, and a list of future articles. All were by now-renowned authors including John Auxier, Lauriston Taylor, Lewis Cochran, and Walter Snyder, to name just a few. The topics covered in that inaugural effort included interactions of radiation with matter, instrumentation, dosimetry, and a most interesting article on “Health Physics Responsibilities to Management” by G. Hoyt Whipple (Health Phys 1:71– 75; 1958). Those pioneers who laid the foundation for today’s health physics scientists could not have known at the time that in 2010 their publication would have become a widely-respected scientific journal with a readership from every continent on the globe. Fifty-two years and over 600 issues later, it is fitting that Volume 100, No. 1, is a special issue including the Proceedings of the 45th Annual Meeting of the NCRP that took place in March 2009 with the theme, “The Future of Nuclear Power Worldwide: Safety, Health and Environment.” The contributing authors for this issue include practitioners from across Europe and North America writing about topics of international consequence facing us in the 21st century. Many thanks to all the authors, reviewers, and editorial staff who work so diligently to produce a high quality and scientifically significant publication every month, including Dick Burk and everyone at Burk and Associates. I would be remiss if I did not also thank all those who preceded me as Editor-in-Chief: Karl Morgan, Wade Patterson, Gen Roessler, Rich Vetter, and Ken Miller. Much of the success of the Journal is due to the efforts of these wonderful folks. Thanks too to all our advertisers, without whom it would have been difficult to reach this important milestone. And finally thanks to all our Health Physics Society members past and present, and our institutional and individual subscribers from around the world. I hope you enjoy this special issue of the Health Physics Journal, Volume 100, No. 1!