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All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

The effects of proton exposure on neurochemistry and behavior

Future space missions will involve long-term travel beyond the magnetic field of the Earth, where astronauts will be exposed to radiation hazards such as those that arise from galactic cosmic rays. Galactic cosmic rays are composed of protons, alpha particles, and particles of high energy and charge (HZE particles). Research by our group has shown that exposure to HZE particles, primarily 600 MeV/n and 1 GeV/n 56Fe, can produce significant alterations in brain neurochemistry and behavior. However, given that protons can make up a significant portion of the radiation spectrum, it is important to study their effects on neural functioning and on related performance. Therefore, these studies examined the effects of exposure to proton irradiation on neurochemical and behavioral endpoints, including dopaminergic functioning, amphetamine-induced conditioned taste aversion learning, and spatial learning and memory as measured by the Morris water maze. Male Sprague-Dawley rats received a dose of 0, 1.5, 3.0 or 4.0 Gy of 250 MeV protons at Loma Linda University and were tested in the different behavioral tests at various times following exposure. Results showed that there was no effect of proton irradiation at any dose on any of the endpoints measured. Therefore, there is a contrast between the insignificant effects of high dose proton exposure and the dramatic effectiveness of low dose (<0.1 Gy) exposures to 56Fe particles on both neurochemical and behavioral endpoints. Published by Elsevier Ltd on behalf of COSPAR.

Non-NASA Center↗
DOE OSTI2016

Dose-Escalated Stereotactic Body Radiation Therapy for Patients With Intermediate- and High-Risk Prostate Cancer: Initial Dosimetry Analysis and Patient Outcomes

Purpose: To report the short-term clinical outcomes and acute and late treatment-related genitourinary (GU) and gastrointestinal (GI) toxicities in patients with intermediate- and high-risk prostate cancer treated with dose-escalated stereotactic body radiation therapy (SBRT). Methods and Materials: Between 2011 and 2014, 24 patients with prostate cancer were treated with SBRT to the prostate gland and proximal seminal vesicles. A high-dose avoidance zone (HDAZ) was created by a 3-mm expansion around the rectum, urethra, and bladder. Patients were treated to a minimum dose of 36.25 Gy in 5 fractions, with a simultaneous dose escalation to a dose of 50 Gy to the target volume away from the HDAZ. Acute and late GU and GI toxicity outcomes were measured according to the National Cancer Institute Common Terminology Criteria for Adverse Events toxicity scale, version 4. Results: The median follow-up was 25 months (range, 18-45 months). Nine patients (38%) experienced an acute grade 2 GU toxicity, which was medically managed, and no patients experienced an acute grade 2 GI toxicity. Two patients (8%) experienced late grade 2 GU toxicity, and 2 patients (8%) experienced late grade 2 GI toxicity. No acute or late grade ≥3 GU or GI toxicities were observed. The 24-month prostate-specific antigen relapse-free survival outcome for all patients was 95.8% (95% confidence interval 75.6%-99.4%), and both biochemical failures occurred in patients with high-risk disease. All patients are currently alive at the time of this analysis and continue to be followed. Conclusions: A heterogeneous prostate SBRT planning technique with differential treatment volumes (low dose: 36.25 Gy; and high dose: 50 Gy) with an HDAZ provides a safe method of dose escalation. Favorable rates of biochemical control and acceptably low rates of acute and long-term GU and GI toxicity can be achieved in patients with intermediate- and high-risk prostate cancer treated with SBRT.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Regulatory and Licensing Strategy for Microreactor Technology

With electricity demand on the rise, an increase in the use of nuclear energy is needed in order to meet future energy demands. The use of nuclear energy will not only begin to positively address this demand, but will also mitigate the negative impacts of carbon-induced climate change and provide energy security to the United States. An appropriate option to address the increasing energy demand is the use of advanced reactor systems like microreactors. Microreactors, often referred to as special-purpose reactors or vSMRs, are neutronically simple, factory manufacturable, easily transportable, and designed to produce less than 20 MWt (for classification as Hazard Category 2 per 10 CFR 830, DOE STD 1027). These reactors are decentralized energy sources that have the ability to provide sustainable and affordable power to remote communities and to industrial users, while having self-contained geometry that requires very low maintenance care. In order for microreactors to be approved for operation, they must abide by and successfully complete a rigorous regulatory and licensing process monitored by the Nuclear Regulatory Commission (NRC), the Department of Energy (DOE), or the Department of Defense (DoD). Because microreactors are a relatively new and disruptive technology, there is no clear licensing path for them to follow. Current licensing frameworks are tailored specifically to large, traditional light water reactors (LWRs) that have been developed and understood by the nuclear industry for many years. Unlike LWRs, microreactors have major design differences, specifically in the materials, coolant, reflectors and potential technology applications used. They also have higher in-core operating temperatures, which have the potential to push the materials used past their allowable limits. Because they are much smaller, safety margins, the amount of space required for assembly, and the distances required to meet dose-based regulatory criteria can technically be altered to better fit their new size. The following strategies and recommendations are intended to assure that key licensing issues do not influence the path to microreactor development, demonstration, and commercialization: Nuclear Regulatory Commission • The NRC should address the lack of knowledge and support of risk informed decision-making concepts from staff members and continue to advance and communicate risk initiatives using their Risk Informed Steering Committee • More research should be done into whether or not microreactors, which are small Class 103 facilities, can be licensed using Class 104-type guidance (e.g., NUREG 1537) • The NRC should use frequency-consequence curves to incrementally reduce regulatory uncertainty and risk to facilitate future construction and operation of advanced reactor designs Department of Energy • The DOE should continue to implement their multi-step Phenomena Identification and Ranking Table process in order to help detect and recommend the major design and technology work needed for licensing future reactor systems • The DOE should consider a joint licensing approach with the NRC where microreactors first go through the DOE process, then finish with the NRC process, providing an advantage for both applicants and NRC staff Department of Defense • The DoD should invest in personnel with sufficient expertise, incorporate their military reactors into tactical power systems, and self-regulate using Section 91b of the Atomic Energy Act Transportation • Licensees should convert enriched uranium hexafluoride into metal or oxide at an enrichment facility and then transport them to a fabrication facility • To avoid transportation issues altogether, licensees should consider positioning the enrichment and fabrication facilities on the same site • The DOE should provide their support in developing new shipping packages for safe transport, criticality benchmark data needed to license high-assay low-enriched uranium fuel facilities and transport packages, and provide financial and technical help to the Department of Transportation; and, • The NRC should help transportation efforts by finalizing and developing guidance for implementing 10 CFR 73 and 10 CFR 74 specifically for Category 2 Special Nuclear Material.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2019

Utilizing FLEX Equipment for O&M Cost Reduction in Nuclear Power Plants

There are many ways of reducing the O&M costs; this work presents an innovative framework of reducing O&M costs by utilizing the onsite Flex equipment at NPPs. Flex strategies were postulated by the U.S. Nuclear Regulatory Commission (NRC) in the wake of Fukushima Dai-ichi accident to address beyond-design-basis accidents and improve plant flexibility. Onsite Flex includes equipment such as portable pumps, generators, batteries, compressors, and other supporting equipment or tools, all stored in a dedicated and secure building designed to withstand external hazards. In the past years, several NPPs have invested in procuring and maintaining the onsite Flex asset that stands unutilized most of the time. Recently there have been active efforts to develop strategies through which NPPs can take credit for the Flex equipment. This work focuses on identifying areas where Flex equipment can be utilized during normal plant operation and develop a framework that would aide in reduction of O&M costs without impacting plant safety. Earlier work in the current project, published in INL/EXT 18 51531, had presented the risk- and cost-analysis framework for utilizing FLEX portable equipment during technical specification required shutdown due to component failure. The licensee event report (LER) database of the NRC shows that the commercial NPPs in the US reported 86 technical specification required shutdowns since year 2010. When a component failure or unavailability leads to a technical specification required shutdown, the NPPs suffers both direct costs in terms of loss of revenue arising from the loss of generation and indirect costs in form of reporting and inspection required by the NRC. The earlier work developed the following framework and implemented it on a demonstration probabilistic risk assessment (PRA) model to utilize the portable Flex equipment when a component failure could potentially lead to a technical specification required shutdown: 1. Identify the components, the failure or unavailability of which would result in a 10 CFR 50.73(a)(2)(i)A-reportability requirement, postulated by the NRC for technical specification required shutdown to be reported in NRC’s LER database. 2. Identify the Flex equipment that can be utilized as a standby to the failed component. 3. Develop a probabilistic risk assessment (PRA) model that incorporates the Flex equipment within the current plant PRA model. 4. Perform PRA calculations to determine change in core damage frequency and change in risk-informed allowable outage time. 5. Perform cost-benefit analysis to determine the economic feasibility of implementing the Flex equipment The current work, presented in this report, implement the above framework in a plant PRA model obtained from a US commercial nuclear power plant by prestaging onsite FLEX equipment as a redundancy to the existing auxiliary feedwater system, and pre-coordinating with offsite FLEX centers. The new configuration increased the allowable outage time by about a fifty percent overall for the diesel generator being out of service. The benefits to NPPs of utilizing the Flex equipment during normal operations, and performing the PRA developed in this work, include: 1. A risk-informed plant shutdown alternative to the current technical specification required shutdown. 2. Extension of allowable outage time to initiate technical specification required shutdown. 3. Reducing economic impact of component failure, avoiding plant shutdown, and maximizing generation. 4. Save the direct and indirect costs associated with technical specification required shutdown.

42 ENGINEERING↗
DOE OSTI2016

SU-F-J-64: Comparison of Dosimetric Robustness Between Proton Therapy and IMRT Plans Following Tumor Regression for Locally Advanced Non-Small Cell Lung Cancer (NSCLC)

Purpose: In the light of tumor regression and normal tissue changes, dose distributions can deviate undesirably from what was planned. As a consequence, replanning is sometimes necessary during treatment to ensure continued tumor coverage or to avoid overdosing organs at risk (OARs). Proton plans are generally thought to be less robust than photon plans because of the proton beam’s higher sensitivity to changes in tissue composition, suggesting also a higher likely replanning rate due to tumor regression. The purpose of this study is to compare dosimetric deviations between forward-calculated double scattering (DS) proton plans with IMRT plans upon tumor regression, and assesses their impact on clinical replanning decisions. Methods: Ten consecutive locally advanced NSCLC patients whose tumors shrank > 50% in volume and who received four or more CT scans during radiotherapy were analyzed. All the patients received proton radiotherapy (6660 cGy, 180 cGy/fx). Dosimetric robustness during therapy was characterized by changes in the planning objective metrics as well as by point-by-point root-mean-squared differences for the entire PTV, ITV, and OARs (heart, cord, esophagus, brachial plexus and lungs) DVHs. Results: Sixty-four pairs of DVHs were reviewed by three clinicians, who requested a replanning rate of 16.7% and 18.6% for DS and IMRT plans, respectively, with a high agreement between providers. Robustness of clinical indicators was found to depend on the beam orientation and dose level on the DVH curve. Proton dose increased most in OARs distal to the PTV along the beam path, but these changes were primarily in the mid to low dose levels. In contrast, the variation in IMRT plans occurred primarily in the high dose region. Conclusion: Robustness of clinical indicators depends where on the DVH curves comparisons are made. Similar replanning rates were observed for DS and IMRT plans upon large tumor regression.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Crickets{sup TM} and Curies: Lessons Learned from the Steel Industry - 18221

The global nuclear power industry, and to a lesser extent, the decommissioning and demolition of old nuclear weapons plants, obviously present challenges to those in the radioactive waste management field. Some if not many of these challenges have already been dealt with, and resolved, in the steel industry, including its recycling component. This paper presents proven state-of-the-art radiation detection systems used in steel and related recycling facilities, emphasizing current, reliable and flexible technologies for characterization, volume reduction, and remote handling of recyclable solid wastes contaminated and, just as important, not contaminated, with a wide range of radioactive isotopes. It will also cover features of remotely operated waste handling equipment effective in reducing or eliminating exposure of workers engaged in decontamination and demolition work on active and/or inactive nuclear installations. The industry group identified above has a long-standing policy regarding any radioactivity in potentially recyclable as well as waste materials it receives: if it is detected, it is rejected. The US Steel Manufacturers Association (SMA) put it this way in one of their Public Policy Statements: 'SMA members have not, and will not, accept scrap that is known to be radioactively contaminated' (emphasis included in the original) (1). This policy, adopted around the globe, obviously has major implications for decommissioning and demolition projects. To put it bluntly, if rad-contaminated metal, concrete, or other materials are sent to a facility for possible recycling, reuse or even disposal, they may well be rejected. If so, the materials will be returned to the generator--at the generator's cost-and a new solution will have to be found. This also results in additional costs for the generator. Facilities in the steel making and metal recycling industries have access to, and routinely count on, a wide range of proven detection technologies and techniques for monitoring incoming shipments and sorting the materials in them. The approaches range from using sensitive handheld instruments for pinpointing and isolating small devices such as isotope-containing gauges and radium dials all the way up to technologies effective for large volumes and weights of contaminated construction and demolition material. In this latter realm, the most suitable, robust, and field-proven system for decommissioning and demolition work is a radiation detection system fitted to a grappling and/or magnetic device, known as the Crickets{sup TM} technology, which automatically scans bulk material with no added effort or time in material handling operations. Highly versatile, a Crickets{sup TM} system can be put to work on any material-handling system, including grapples handling volumes ranging from 1 up to 18 cubic yards, while detecting radioactivity in real-time over a very wide dose range, from nSv to Sv levels. Other field-proven real-time measuring radiation detection devices can be fixed to conveyor belts with traverse speeds up 3 meters/second, also measuring in real time and over the same dose range, allowing both recyclable and waste materials with a pre-set level of radioactivity to be diverted off the belt. Finally, there are highly sensitive radiation portal installations for detecting radiation from materials being transported by vehicles, including those with roll-offs, dump trailers, and other containers, again in real-time and for the same dose ranges. For vehicles, the speed must be carefully controlled-the vehicles need to travel from 5 to 10 km/h through the scanning zone to ensure that maximum detection capability is maintained. When radiation detection systems at recycling and steel making facilities detect radioactive material in an incoming shipment, these facilities have a zero tolerance for accepting the cargo. Therefore, it is imperative that material from a demolition operation that is slated to be sent for recycling or other reuse be checked at the point of demolition at similar detection levels to avoid possible rejection later of a shipment because of its radioactivity. In addition to measuring overall radiation levels (for example, total gamma), when necessary, combinations of different radiation detection media can be used to detect the presence and intensities of specific isotopes such as U-235, Cs-137, Co-60, Am-241, etc., again in real-time and over a similar dose range. These detection technologies can be fixed or transportable. More important for the rad-waste management profession, this overall systems approach can be tailored and adapted during use on-site in any dismantling, demolition or remediation project, to allow materials to be thoroughly scanned before being released to the recycling stream for reuse, or to appropriate long-term storage and disposal facilities. Potentially recyclable materials with contamination such as steel beams and rebar will set off alarms at recycling facilities, resulting in unnecessary added expenses to the generator, primarily due to increased transportation costs, time delays and additional rad-waste handling and disposal charges. Additionally, there are situations where relatively lightly contaminated materials, once identified and appropriately characterized, can be reused in new construction applications, such as concrete from demolition being used in the base layer for roads or recycled steel used for repair or construction of bridges. In other cases, specific smaller volumes can be sent to specialized rad-waste disposal sites. These radiation detection systems can also be custom tailored to ensure proper handling and disposition of contaminated materials destined for reuse in specific applications where, for example, acceptable levels of radioactivity in NORM or TENORM can be reused or safely disposed of. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

SU-E-T-226: Junction Free Craniospinal Irradiation in Linear Accelerator Using Volumetric Modulated Arc Therapy : A Novel Technique Using Dose Tapering

Purpose: Spatially separated fields are required for craniospinal irradiation due to field size limitation in linear accelerator. Field junction shits are conventionally done to avoid hot or cold spots. Our study was aimed to demonstrate the feasibility of junction free irradiation plan of craniospinal irradiation (CSI) for Meduloblastoma cases treated in linear accelerator using Volumetric modulated arc therapy (VMAT) technique. Methods: VMAT was planned using multiple isocenters in Monaco V 3.3.0 and delivered in Elekta Synergy linear accelerator. A full arc brain and 40° posterior arc spine fields were planned using two isocentre for short (<1.3 meter height ) and 3 isocentres for taller patients. Unrestricted jaw movement was used in superior-inferior direction. Prescribed dose to PTV was achieved by partial contribution from adjacent beams. A very low dose gradient was generated to taper the isodoses over a long length (>10 cm) at the conventional field junction. Results: In this primary study five patients were planned and three patients were delivered using this novel technique. As the dose contribution from the adjacent beams were varied (gradient) to create a complete dose distribution, therefore there is no specific junction exists in the plan. The junction were extended from 10–14 cm depending on treatment plan. Dose gradient were 9.6±2.3% per cm for brain and 7.9±1.7 % per cm for spine field respectively. Dose delivery error due to positional inaccuracy was calculated for brain and spine field for ±1mm, ±2mm, ±3mm and ±5 mm were 1%–0.8%, 2%–1.6%, 2.8%–2.4% and 4.3%–4% respectively. Conclusion: Dose tapering in junction free CSI do not require a junction shift. Therefore daily imaging for all the field is also not essential. Due to inverse planning dose to organ at risk like thyroid kidney, heart and testis can be reduced significantly. VMAT gives a quicker delivery than Step and shoot or dynamic IMRT.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Filters from taxis air conditioning system: A tool to characterize driver's occupational exposure to bioburden?

Highlights: • Filters from air conditioning system are a suitable method to characterize bioburden in vehicles. • Fungi and bacteria occur widely in taxis and personal vehicles. • The genera Aspergillus, Cladosporium and Penicillium were often detected. • Filters should be more frequently replaced to avoid bioburden proliferation and reaerosolization. • Culture based and molecular methods used in parallel enabled an improved risk characterization. Bioburden proliferation in filters from air conditioning systems of taxis represents a possible source of occupational exposure. The aim of this study was to determine the occurrence of fungi and bacteria in filters from the air conditioning system of taxis used for patient transportation and to assess the exposure of drivers to bioburden. Filters from the air conditioning systems of 19 taxis and 28 personal vehicles (used as controls) operating in three Portuguese cities including the capital Lisbon, were collected during the winter season. The occurrence and significance of bioburden detected in the different vehicles are reported and discussed in terms of colony-forming units (CFU) per 1 m{sup 2} of filter area and by the identification of the most frequently detected fungal isolates based on morphology. Azole-resistant mycobiota, fungal biomass, and molecular detection of Aspergillus species/strains were also determined. Bacterial growth was more prevalent in taxis (63.2%) than in personal vehicles (26.3%), whereas fungal growth was more prevalent in personal vehicles (53.6%) than in taxis (21.1–31.6%). Seven different azole-resistant species were identified in this study in 42.1% taxi filters. Levels of fungal biomass were above the detection limit in 63% taxi filters and in 75% personal vehicle filters. No toxigenic species were detected by molecular analysis in the assessed filters. The results obtained show that bioburden proliferation occurs widely in filters from the air conditioning systems of taxis, including the proliferation of azole-resistant fungal species, suggesting that filters should be replaced more frequently. The use of culture based-methods and molecular tools combined enabled an improved risk characterization in this setting.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Physics and technology considerations for the deuterium–tritium fuel cycle and conditions for tritium fuel self sufficiency

The tritium aspects of the DT fuel cycle embody some of the most challenging feasibility and attractiveness issues in the development of fusion systems. The review and analyses in this paper provide important information to understand and quantify these challenges and to define the phase space of plasma physics and fusion technology parameters and features that must guide a serious R&D in the world fusion program. We focus in particular on components, issues and R&D necessary to satisfy three 'principal requirements': (1) achieving tritium self-sufficiency within the fusion system, (2) providing a tritium inventory for the initial start-up of a fusion facility, and (3) managing the safety and biological hazards of tritium. A primary conclusion is that the physics and technology state-of-the-art will not enable DEMO and future power plants to satisfy these principal requirements. We quantify goals and define specific areas and ideas for physics and technology R&D to meet these requirements. A powerful fuel cycle dynamics model was developed to calculate time-dependent tritium inventories and flow rates in all parts and components of the fuel cycle for different ranges of parameters and physics and technology conditions. Dynamics modeling analyses show that the key parameters affecting tritium inventories, tritium start-up inventory, and tritium self-sufficiency are the tritium burn fraction in the plasma (f b ), fueling efficiency (η f ), processing time of plasma exhaust in the inner fuel cycle (t p ), reactor availability factor (AF), reserve time (tr) which determines the reserve tritium inventory needed in the storage system in order to keep the plant operational for time t r in case of any malfunction of any part of the tritium processing system, and the doubling time (t d ). Results show that η f f b > 2% and processing time of 1–4 h are required to achieve tritium self-sufficiency with reasonable confidence. For η f f b = 2% and processing time of 4 h, the tritium start-up inventory required for a 3 GW fusion reactor is ~11 kg, while it is <5 kg if η f f b = 5% and the processing time is 1 h. To achieve these stringent requirements, a serious R&D program in physics and technology is necessary. The EU-DEMO direct internal recycling concept that carries fuel directly from the plasma exhaust gas to the fueling systems without going through the isotope separation system reduces the overall processing time and tritium inventories and has positive effects on the required tritium breeding ratio (TBR R ). A significant finding is the strong dependence of tritium self-sufficiency on the reactor availability factor. Simulations show that tritium self-sufficiency is: impossible if AF < 10% for any η f f b , possible if AF > 30% and 1% ≤ η f f b ≤ 2%, and achievable with reasonable confidence if AF > 50% and η f f b > 2%. These results are of particular concern in light of the low availability factor predicted for the near-term plasma-based experimental facilities (e.g. FNSF, VNS, CTF), and can have repercussions on tritium economy in DEMO reactors as well, unless significant advancements in RAMI are made. There is a linear dependency between the tritium start-up inventory and the fusion power. The required tritium start-up inventory for a fusion facility of 100 MW fusion power is as small as 1 kg. Since fusion power plants will have large powers for better economics, it is important to maintain a 'reserve' tritium inventory in the tritium storage system to continue to fuel the plasma and avoid plant shutdown in case of malfunctions of some parts of the tritium processing lines. But our results show that a reserve time as short as 24 h leads to unacceptable reserve and start-up inventory requirements. Therefore, high reliability and fast maintainability of all components in the fuel cycle are necessary in order to avoid the need for storing reserve tritium inventory sufficient for continued fusion facility operation for more than a few hours. The physics aspects of plasma fueling, tritium burn fraction, and particle and power exhaust are highly interrelated and complex, and predictions for DEMO and power reactors are highly uncertain because of lack of experiments with burning plasma. Fueling by pellet injection on the high field side of tokamak has evolved to be the preferred method to fuel a burning plasma. Extrapolation from the DIII-D penetration scaling shows fueling efficiency expected in DEMO to be <25%, but such extrapolations are highly uncertain. The fueling efficiency of gas in a reactor relevant regime is expected to be extremely poor and not very useful for getting tritium into the core plasma efficiently. Gas fueling will nonetheless be useful for feedback control of the divertor operating parameters. Extensive modeling has been carried out to predict burn fraction, fueling requirements, and fueling efficiency for ITER, DEMO, and beyond. The fueling rate required to operate Q = 10 ITER plasmas in order to provide the required core fueling, helium exhaust and radiative divertor plasma conditions for acceptable divertor power loads was calculated. If this fueling is performed with a 50–50 DT mix, the tritium burn fraction in ITER would be ~0.36%, which is too low to satisfy the self-sufficiency conditions derived from the dynamics modeling for fusion reactors. Extrapolation to DEMO using this approach would also yield similarly low burn fraction. Extensive analysis presented shows that specific features of edge neutral dynamics in ITER and fusion reactors, which are different from present experiments, open possibilities for optimization of tritium fueling and thus to improve the burn fraction. Using only tritium in pellet fueling of the plasma core, and only deuterium for edge density, divertor power load and ELM control results in significant increase of the burn fraction to 1.8–3.6%. These estimates are performed with physics models whose results cannot be fully validated for ITER and DEMO plasma conditions since these cannot be achieved in present tokamak experiments. Thus, several uncertainties remain regarding particle transport and scenario requirements in ITER and DEMO. The safety standard requirements for protection of the public and release guidelines for tritium have been reviewed. General safety approaches including minimizing tritium inventories, reducing tritium permeation through materials, and decontaminating material for waste disposal have been suggested.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

An editorial to the Special Issue on “Severe climate Risks”

The history of this Special Issue (https://www.sciencedirect.com/special-issue/10JD7LNJNQ0) indirectly dates back to the early 1990s, when the signature of the United Nations Framework Convention on Climate Change kicked-off an international political process based on one overarching and foundational principle: to avoid “dangerous anthropogenic interference with the climate system” at the global level. More than three decades later, such a principle remains central, though complementary aims made their way through the climate negotiation process, such as the importance of ensuring equity and justice, to give just one example here. Scientific knowledge also considerably progressed and we know more about the range of risks that climate change imposes and will continue to impose to the biosphere and humankind, worldwide and at all territorial levels. It is also clear that societal responses to these risks —“climate adaptation” as we know it— are increasingly happening, but definitely not at the pace of climate risk trends (Berrang-Ford et al., 2021, Erisken et al., 2021, Olazabal and Ruiz De Gopegui, 2021, Magnan et al., 2023a, Reckien et al., 2023, UNEP, 2023). As a result, concerns have emerged over the recent years in both the scientific and policy arenas around the idea that societies may not be able to address all climate risks, and that limits to adaptation and induced residual risks need to be considered more seriously. Such concerns further highlight the continuing importance of the imperative to minimise dangerous anthropogenic interference with the climate system, at any scale. But what does “dangerous interference” mean? How can we decide that we are entering the “dangerous” space, compared to a broader range of climate risks that would qualify as problematic but not necessarily “dangerous”? Who should make such a decision? Which conditions drive risk severity over time, including in the future? And what would be the environmental, economic, social and cultural implications of prioritising some climate risks over others? The Intergovernmental Panel on Climate Change (IPCC) was a pioneer in addressing such questions through the development of the “Key Risks” framing that describes those climate risks having the potential to become dangerous or “severe” over the course of this century (Schellnhuber et al., 2006, Schneider et al., 2007, Oppenheimer et al., 2014, O’Neill et al., 2022). The Fifth and Sixth assessment cycles (AR5 and AR6) went a step further by identifying about 120 Key Risks across regions and sectors, and clustering them into 8 “Representative Key Risks” covering a range of geographical systems (low-lying coasts, and to terrestrial and ocean ecosystems), sectors (critical infrastructure, living standards, human health, food security, and water security) and human dimensions (peace and mobility) (Oppenheimer et al., 2014, O’Neill et al., 2022). This Special Issue was born of the efforts of a range of authors, during the development of the IPCC AR6 main Assessment Report between 2019 and 2022, to characterise Key Risks and Representative Key Risks, and advance knowledge on what shapes “severe climate risks” conceptually as well as in the real-world. The series of papers forming this Special Issue is not intended to cover the topic exhaustively, but rather to give readers an overview through the following narrative: defining “severe climate risks” is highly challenging (Magnan et al., 2023b), but knowledge is expanding on the driving climate hazards (Tebaldi et al., 2023) and their implications on geographical systems, sectors and human dimensions, using here food security (Mirzabaev et al., 2023), human mobility (Gilmore et al., 2024) and peace (Buhaug et al., 2023) as illustrative examples. The overall intention is to support especially decision-makers, whatever the scale or sector considered, in asking severity-driven questions to identify sector- and context-specific “priority” risks from climate change.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Benefits of less intrusive remediation alternatives; A review of case studies in Oak Ridge, Tennessee - 15482

Various alternative cleanup strategies have been utilized at Department of Energy facilities in Oak Ridge, Tennessee to avoid costly and potentially ineffective removal of contaminants in soil and sediments, transportation by truck, and long-term storage in landfills. One such example is a remedial decision in the 1990's to not conduct large-scale removal of PCB-contaminated sediments from a large downstream reservoir, and instead implement sediment disturbance controls and monitoring requirements. Monitoring results suggest the decision was a good one with PCB concentrations in fish decreasing substantially over the last 20 years, presumably due to recent cleaner sediments overlying historical sediment layers. At the East Tennessee Technology Park an innovative remediation strategy was developed to reduce human and ecological risks associated with a PCB-contaminated pond, while also enhancing the site's natural resources. Termed the 'Ecological Management and Enhancement' strategy, this remediation option provided an alternative approach to more conventional pond remediation options like sediment and soil removal, draining and capping, and point source/discharge actions. The basic premise of this option is that ecological management, including fish and wildlife management and vegetation management, can interrupt the contaminant exposure pathways that lead to ecological or human receptors. Recent monitoring results have demonstrated both risk reduction and increased natural resource value. Currently under investigation is the use of watershed management approaches that may help ameliorate mercury methylation and bioaccumulation in East Fork Poplar Creek. There is increased recognition that mercury source reduction alone will not achieve the human health risk target level in fish in the downstream environment, where water chemistry and ecological processes are conducive to mercury methylation. Additionally, significant losses in natural resource values are anticipated if major soil and sediment source removal activities are implemented. The Oak Ridge experience suggests that alternative approaches to the conventional 'muck and truck' options to sediment contamination are worth pursuing in some cases. Taking advantage of natural attenuation processes and/or implementing less intrusive water and ecological manipulations could be especially advantageous at contaminated sites where there are multiple or complex sources that are difficult to remediate, conventional source removal is costly, the contaminant of concern is highly bio-accumulative, or where natural resource values could be preserved or enhanced. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Proposed guidance for preparing and reviewing a molten salt non-power production or utilization facility application

Development of non-power molten salt reactors (MSRs) are under consideration to further establish an MSR experience base, support the requirements of Title 10 of the Code of Federal Regulations (10 CFR) Section 50.43(e), and provide any additional analyses needed for development of a full-scale MSR. Guidance provided in this report is based on MSRs operating with liquid fuel (i.e., fuel dissolved within a molten salt). These reactors, unless owned by the DOE or DOD, will require licensing by the US Nuclear Regulatory Commission (NRC) staff. Standard review plan (SRP) guidance for large light water reactors (LWRs) is available in NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants; Light Water Reactor (LWR) Edition. However, NRC staff observed that NUREG-0800 is very cumbersome to apply to non-power reactors “because of the great differences in complexity and hazards between non-power reactors and nuclear power plants.” Therefore, a program to develop performance-based guidance applicable to non-power reactors was initiated. In 1996, NUREG-1537, Parts 1 and 2, Guidelines for Preparing and Reviewing Applications for the Licensing of Non-Power Reactors, was published. Part 1, the format and content guide, suggests a uniform format for presenting information in non-power reactor applications that is acceptable to the NRC staff, but conformance with the format and content is not required. Part 2, the SRP, ensures the quality and uniformity of the staff review of an application. Unfortunately, the application guidelines and SRP do not provide adequate guidance for all advanced non-LWR technologies and applications. This discrepancy eventually led to the 2012 development of interim staff guidance (ISG) for NUREG-1537, which includes criteria for describing and reviewing aqueous homogeneous reactors (AHRs). Specifically, NUREG-1537 ISG, 2012 expanded the original document to address three areas: 1. updated criteria for heterogeneous non-power reactors, 2. criteria for licensing AHRs, and 3. criteria for licensing a Part 50-licensed isotope production facility. In 2015, the US Department of Energy (DOE) opted to build on the AHR NUREG-1537 ISG experience by performing a gap analysis of the guidance that would be used to license a non-power MSR. MSRs represent one of the advanced non-LWR technologies selected by DOE for development through a multiyear cost share award with Southern Company Services. Under this Advanced Reactor Concepts 2015 (DOE Advanced Reactor Concepts [ARC] 15) award program, the DOE tasked Oak Ridge National Laboratory (ORNL) to evaluate the guidance changes that the NRC may need to consider when licensing an MSR non-power reactor. ORNL staff, with support from Boston Government Services, LLC, focused on five system-related chapters in NUREG-1537 that were considered most relevant to inform the effort that would be required for a non-power MSR applicant. ORNL documented this review in a technical report, ORNL/TM-2018/834, Proposed Guidance for Preparing and Reviewing Molten Salt Non-Power Reactor License Applications (NUREG-1537). The report was subsequently shared with industry and the NRC. The 2018 review was limited in scope, focusing on key system chapters based on the expected significance of each chapter relative to expected differences in addressing advanced non-LWR technologies, specifically non-power MSRs, compared with heterogeneously fueled non-power reactors. In the ORNL report, proposed generic adaptations were suggested for the following NUREG-1537 chapters: Chapter 4, “Reactor Description”; Chapter 5, “Reactor Coolant Systems”; Chapter 6, “Engineered Safety Features”; Chapter 9, “Auxiliary Systems”; Chapter 11, “Radiation Protection Program and Waste Management” The inclusion of Chapter 11 in the previous review effort was intended to provide guidance for categorizing the waste-handling process for an MSR operating with homogenous fuel. The introductions from Parts 1 and 2 of the 2012 NUREG-1537 ISG provide guidance for the application and review of production facilities. After a period of operation, non-power MSRs with homogenous fuel will include gaseous and soluble fission products. The gaseous fission products will be collected and held for decay in an off-gas system. There might also be an initiative to polish or filter the soluble fission products in the fuel salt by some mechanical or chemical means. The treatment and handling of fission products in the non-power MSR fuel salt and the description of this process in the safety analysis report (SAR) must be very precise to avoid the waste treatment facility being construed as a co-located special nuclear material (SNM) fuel cycle facility (see Section 2.3 of this report). Subsequent to the release of ORNL/TM-2018/834, NRC staff expressed a desire to continue the regulatory gap analysis that was begun in that report. This would provide additional clarity and information addressed in certain sections of the original report, while also providing new guidance on certain topics not addressed in the original report. This revision would benefit the NRC staff reviewing applications involving non-power MSR designs and would help developers understand how the NRC staff might approach the review of such applications. The focus of this report is to provide infrastructure support to the NRC staff for the regulatory review of non-power MSRs.

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DOE OSTI2019

Challenges in Long-Term Records Preservation and Access - 19549

The US Department of Energy Office of Legacy Management (LM) mission includes preserving records and information about the nation's Cold War-era weapons projects and making that information available for years to come. As LM assumes responsibility for each project, records documenting operations and cleanup activities are absorbed into a central recordkeeping system. Each record category is governed by a federal retention requirement. Routine administrative records are kept just a few years, while the most important records have 'permanent' retention requirements and are transferred to the National Archives typically within 25 years of creation. It is relatively easy for LM to meet retention requirements for these routine and permanent records. LM's big preservation challenge is with records with tremendously long retention requirements. Records with 75-year retention requirements are common, and a small subset of LM records pertaining to waste disposal requires 150-year retention periods. LM must consider the best format for maintaining each of its records collections. Should physical records be boxed up for long-term storage, or should they be digitized? Each option has associated benefits, costs, and risks. Keeping records in paper format avoids digitizing expense and preserves the original media, but the paper must be maintained in a certified storage facility. A vermin infestation or sprinkler malfunction at a certified facility may be rare but could easily destroy records. Keeping the paper and making reference or backup electronic copies reduces the risk of loss but requires diligence and resources to keep the physical records and electronic versions synchronized. This becomes an overwhelming task in a database with millions of records. Entirely replacing paper records with digitized versions as electronic records introduces the risk that records could be lost due to a cybersecurity incident or made inaccessible by evolving technology. LM's early electronic records management efforts were limited to documents saved to PDF format. More recently, LM has embraced the benefits of maintaining records in native formats. (A spreadsheet includes formulas and other details lost when converted to a PDF file.) But whether the file is saved as a Microsoft Excel spreadsheet or PDF document, how do we ensure the file is readable in 75 or 150 years when these records meet their retention requirement? We have no way of knowing for sure from our 2019 vantage point-no more than we would expect to get good technology advice from someone 150 years ago. We cannot predict the technological future, but we can make sure our current electronic records environment is healthy and future ready. This includes making sure the electronic recordkeeping system is built on a modern platform and ensuring that each record in the system is saved in a current format. Quality standards are critical for electronic records to be future ready. Implementing quality involves an organization-wide approach to having consistently formatted file names and complete and descriptive metadata. Quality PDF documents are scanned to settings that ensure characters are machine-readable (with optical character recognition, or OCR). LM is currently replacing its electronic recordkeeping system and simultaneously modernizing its organizational approach to data management; it is replacing a traditional electronic records repository with a system that also manages records stored anywhere across the computer network. This new records management approach will require new thinking in how LM manages a dramatically increased volume of information across the network while not losing focus on its responsibility for long-term records preservation and access. (author)

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DOE OSTI2020

Stakeholder-Engaged Structured Decision Making for the Los Alamos Legacy Cleanup Mission - 20501

The Los Alamos National Laboratory (LANL) environmental legacy cleanup program requires decisions to be made for environmental remediation, decommissioning and disposal or management of radioactive waste. This legacy cleanup program was established to address groundwater contamination, material disposal areas (MDAs) that have been used to dispose of radioactive and other waste material, and 'aggregate areas' that might produce radioactive or other chemical waste as a result of remediation activities. The LANL site is regulated for environmental concerns under the Resource Conservation and Recovery Act (RCRA). However, some parts of LANL, such as material disposal area G (MDA G), have disposed of radioactive waste under DOE Order 435.1, and are subject to other regulations. For example, decommissioning the remote-handled TRU material stored in 33 shafts at MDA G falls under EPA's 40 CFR 191. Collectively, the regulations are all aimed in the same direction of finding the best solution, either through constructs such as 'as low as reasonably achievable' (ALARA), considering balancing factors as opposed to only cost and human health risk, and, under EPA regulations such as RCRA and NEPA, evaluating impact from all chemicals and both human health and ecological endpoints. Despite the basic goals and objectives of the regulations or their guidance, the main challenge is in their implementation. Arguably perhaps, but really in principle, all of these (and similar) regulations are asking for a decision analysis to be performed. Implementation challenges encountered have included lack of understanding of decision analysis in the industry, lack of effective stakeholder engagement in the decision analysis process, and lack of appreciation of the need to separate value judgments from science, the latter leading to developing conservative, or protective, science-based models. Conservative models lead to poor solutions, lack of effective stakeholder engagement leads to long drawn out protracted approaches to finding a solution (which also might never be found with this approach), and lack of understanding of decision analysis and Bayesian statistics causes poor models to be built, which creates unfortunate situations of 'garbage in, garbage out' becoming the basis for decision making. Stakeholder-engaged structured decision making (SDM) is an approach to solving problems that relies on the theory of decision science to involve stakeholders in the decision-making process. This approach incorporates stakeholder values using a scientifically rigorous methodology that separates value judgments from science in a way that helps avoid the pitfalls of biased, protective, or conservative modeling. This approach has its foundation in Keeney's 1992 treatise on value-focused thinking [1]. Keeney advocated a paradigm shift in decision making based on the idea that the standard way of thinking about decisions is backwards. The standard approach of focusing first on identifying alternatives rather than on articulating values results in a reactive approach with the emphasis on mechanics and fixed choices instead of the core values that have meaning to stakeholders. This paradigm shift effectively engages all stakeholders in the decision-making process while using a values focused thinking approach that can lead to the identification of decision opportunities and the creation of better alternatives. The intent is to be proactive and generate solutions that are related directly to values and objectives as identified by stakeholders. There are, perhaps, two overarching reasons why SDM can be used to benefit LANL's environmental legacy cleanup. Some of LANL's remaining waste management and environmental management problems are challenging and complex (for example, the Cr and RDX plumes, and MDAs) and while the traditional approach has, arguably, worked well for relatively simple risk-based problems, it cannot, or should not, be applied to more complex problems if the most effective and efficient solutions are desired. The second reason is cost. This has perhaps become more critical since publication of the Government Accountability Office (GAO) reports that DoE's environmental liability is considered a high-risk concern for the nation [2]. The focus of SDM is on structuring solutions to decision risk problems by first addressing stakeholder and decision maker values and subsequently developing decision objectives and ways to measure those objectives, preference weighting across objectives, identifying decision alternatives that best achieve those values, and characterizing uncertainty in predictions of the measures. Because a complete decision model is created using SDM, it can be evaluated to find the main elements of the model that drive, or predict, the best solution. This approach creates complete decision models that are transparent, traceable, reproducible and technically defensible. The science behind SDM, or decision analysis, is well founded, yet it is not unusual to see ad hoc approaches to decision making implemented under various environmental regulations that are pertinent to the LANL site, including NEPA, RCRA and DOE Order 435.1. Such ad hoc approaches are often not transparent or traceable, and lack reproducibility and technical defensibility. The LANL legacy cleanup program has embarked on using SDM to address the complex problems that remain. Stakeholder meetings have been held, and a prototype version of the stakeholder value system has been developed. Further meetings are expected in the future to address specific project needs. This is a long-term endeavor considering the complex environmental problems faced by DOE EM in Los Alamos (EM-LA), and careful planning, consideration of stakeholder value systems, and engagement with stakeholders throughout the SDM process is expected to lead to a successful endpoint. (authors)

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