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Objectives of the manual are to (1) ensure compliance with requirements of AEC and governmental health agencies, (2) ensure against excessive and unnecessary exposure of personnel to harmful radiation, and (3) prevent contamination of equipment, materials, and environment with radioactive materials.
Following the discovery of the atmospheric cosmogenic radionuclide Be-7 on the Long Duration Exposure Facility (LDEF), we began a search for other known nuclides produced by similar mechanisms. None of the others have the narrow gamma-ray line emission of Be-7 decay which enable its rapid detection and quantification. A search for Be-10 atoms on LDEF clamp plates using accelerator mass spectrometry is described. An unexpected result was obtained.
The Savannah River Site (SRS) is owned and administered by the US Department of Energy (DOE). SRS covers an area of approximately 900 square kilometers. The General Separation Area (GSA) is located roughly in the center of the SRS and includes: radioactive material chemical separations facilities, radioactive waste tank farms, a variety of radioactive seepage basins, and the radioactive waste burial grounds. Radioactive wastes were disposed in the GSA from the mid-1950s through the mid-1990s. Radioactive operations at the F Canyon began in 1954; radioactive operations at H Canyon began in 1955. Waste water disposition to the F and H Seepage Basins began soon after operations started in the canyons. The Old Radioactive Waste Burial Ground (ORWBG) began operations in 1952 to manage solid waste that could be radioactive from all the site operations, and ceased receiving waste in 1972. The Mixed Waste Management Facility (MWMF) and Low Level Radioactive Waste Disposal Facility (LLRWDF) received radioactive solid waste from 1969 until 1995. Environmental legislation enacted in the 1970s, 1980s, and 1990s led to changes in waste management and environmental cleanup practices at SRS. The US Congress passed the Clean Air Act in 1970, and the Clean Water Act in 1972; the Resource Conservation and Recovery Act (RCRA) was enacted in 1976; the Comprehensive Environmental Response Compensation, and Liability Act (CERCLA) was enacted by Congress in 1980; the Federal Facilities Compliance Act (FFCA) was signed into law in 1992. Environmental remediation at the SRS essentially began with a 1987 Settlement Agreement between the SRS and the State of South Carolina (under the South Carolina Department of Health and Environmental Control - SCDHEC), which recognized linkage between many SRS waste management facilities and RCRA. The SRS manages several of the larger groundwater remedial activities under RCRA for facilities recognized early on as environmental problems. All subsequent environmental remediation projects tend to be managed under tri-party agreement (DOE, Environmental Protection Agency, and SCDHEC) through the Federal Facilities Agreement. During 25 years of environmental remediation SRS has stabilized and capped seepage basins, and consolidated and capped waste units and burial grounds in the GSA. Groundwater activities include: pump and treat systems in the groundwater, installation of deep subsurface barrier systems to manage groundwater flow, in situ chemical treatments in the groundwater, and captured contaminated groundwater discharges at the surface for management in a forest irrigation system. Over the last 25 years concentrations of contaminants in the aquifers beneath the GSA and in surface water streams in the GSA have dropped significantly. Closure of 65 waste sites and 4 RCRA facilities has been successfully accomplished. Wastes have been successfully isolated in place beneath a variety of caps and cover systems. Environmental clean-up has progressed to the stage where most of the work involves monitoring, optimization, and maintenance of existing remedial systems. Many lessons have been learned in the process. Geotextile covers outperform low permeability clay caps, especially with respect to the amount of repairs required to upkeep the drainage layers as the caps age. Passive, enhanced natural processes to address groundwater contamination are much more cost effective than pump and treat systems. SRS operated two very large pump and treat systems at the F and H Seepage Basins to attempt to limit the release of tritium to Fourmile Branch, a tributary of the Savannah River. The systems were designed to extract contaminated acidic groundwater, remove all contamination except tritium (not possible to remove the tritium from the water), and inject the tritiated groundwater up-gradient of the source area and the plume. The concept was to increase the travel time of the injected water for radioactive decay of the tritium. The two systems were found to be non-effective and potentially mobilizing more contamination. SRS invested approximately $50 million in construction and approximately $100 million in 6 years of operation. The H Seepage Basin pump and treat system was replaced by a series of subsurface barriers that alters the groundwater velocity; the F Seepage Basin pump and treat system was replaced by subsurface barriers forming a funnel and gate augmented by chemical treatment within the gates. These replacement systems are mostly passive and cost approximately $13 million to construct, and have reduced the tritium flux to Fourmile Branch, in these plumes, by over 70%. SRS manages non-acidic tritiated groundwater releases to Fourmile Branch from the southwest plume of the MWMF with a forest irrigation system. Tritiated water is captured with a sheetpile dam below the springs that caused releases to Fourmile Branch. Water from the irrigation pond is pumped to a filter plant prior to irrigation of approximately 26 hectares of mixed forest and developing pine plantation. SRS has almost achieved a 70% reduction in tritium flux to the Branch from this plume. The system cost approximately $5 million to construct with operation cost of approximately $500K per year. In conclusion, many lessons have been learned in 25 years of relatively aggressive remedial activities in the GSA. Geotextile covers outperform low permeability clay caps, especially with respect to the amount of repairs required to upkeep the drainage layers as the caps age. Passive, enhanced natural processes to address groundwater contamination are much more cost effective than pump and treat systems. In water management situations with non-accumulative contaminants (tritium, VOCs, etc.) irrigation in a forest setting can be very effective.
Cameco Corporation is a world leader in uranium production. Headquartered in Saskatoon, Saskatchewan our operations provide 16% of the world uranium mine production and we have approximately 435 million pounds of proven and probable uranium reserves. Cameco mining operations are located in Saskatchewan, Wyoming, Nebraska and Kazakhstan. Cameco is also a major supplier of uranium processing services required to produce fuel for the generation of clean energy. These operations are based in Blind River, Cobourg and Port Hope, Ontario and are collectively referred to as the Fuel Services Division. The Fuel Services Division produces uranium trioxide from uranium ore concentrate at the Blind River Refinery. Cameco produces uranium hexafluoride and uranium dioxide at the Port Hope Conversion Facility. Cameco operates a fuel manufacturing facility in Port Hope, Ontario and a metal fabrication facility located in Cobourg, Ontario. The company manufactures fuel bundles utilized in the Candu reactors. Cameco's Fuel Services Division produces several types of low-level radioactively contaminated wastes. Internal processing capabilities at both the Blind River Refinery and Port Hope Conversion Facility are extensive and allow for the recycling of several types of waste. Notwithstanding these capabilities there are certain wastes that are not amenable to the internal processing capabilities and must be disposed of appropriately. Disposal options for low-level radioactively contaminated wastes in Canada are limited primarily due to cost considerations. In recent years, Cameco has started to ship marginally contaminated wastes (<500 ppm uranium) to the United States for disposal in an appropriate landfill. The landfill is owned by US Ecology Incorporated and is located near Grand View, Idaho 70 miles southeast of Boise in the Owyhee Desert. The facility treats and disposes hazardous waste, non-hazardous industrial waste and low-activity radioactive material. The site's arid climate, deep groundwater and favourable geology help ensure permanent waste isolation. Combined with a state of the art multi-layer landfill liner system, the Grand View facility represents an ideal choice to minimize environmental liability. Marginally contaminated wastes from operations within the Fuel Services Division are typically loaded into PacTec IP-2 rated Intermediary Bulk Containers and then transported by road to a nearby rail siding. The Intermediary Bulk Containers are then loaded in US Ecology owned gondola rail-cars. The gondolas are then transported via Canadian Pacific and Union Pacific railroads to the US Ecology Rail Transfer facility located in Mayfield, Idaho. The Intermediary Bulk Containers are unloaded into trucks for transport to the disposal facility located approximately 32 miles away. (authors)
The Savannah River Site, which is owned and administered by the US Department of Energy, covers approximately 900 square kilometers. The General Separation Area is located in the center of the site and includes: radioactive material chemical separations facilities, radioactive waste tank farms, radioactive seepage basins, and the radioactive waste burial grounds. Radioactive wastes were disposed in the General Separation Area from the mid-1950's through the mid-1990's. Operations at the F Canyon began in 1954 and at H Canyon began in 1955. Waste water disposition to the F and H Seepage Basins began soon after operations started in the canyons. The Old Radioactive Waste Burial Ground began operations in 1952 to manage solid waste that could be radioactive from all the site operations, and ceased receiving waste in 1972. The Mixed Waste Management Facility and Low Level Radioactive Waste Disposal Facility received radioactive solid waste from 1969 until 1995. Environmental legislation enacted in the 1970's through 1990's led to changes in waste management and environmental cleanup practices. The US Congress passed the Clean Air Act in 1970 and the Clean Water Act in 1972; the Resource Conservation and Recovery Act was enacted in 1976; the Comprehensive Environmental Response Compensation, and Liability Act was enacted by Congress in 1980; and the Federal Facilities Compliance Act was signed into law in 1992. Environmental remediation at the Savannah River Site essentially began with a 1987 Settlement Agreement between the Savannah River Site and the State of South Carolina. The site manages several of the larger groundwater remedial activities under the Resource Conservation and Recovery Act for facilities recognized early on as environmental problems. All subsequent remediation projects are managed under a tri-party agreement (Department of Energy, Environmental Protection Agency, and South Carolina Department of Health and Environmental Control) through the Federal Facilities Agreement. Environmental remediation activities during the past 25 years have stabilized and capped seepage basins as well as consolidated and capped waste units and burial grounds in the General Separation Area. Groundwater activities include: pump and treat systems in the groundwater, installation of deep subsurface barrier systems to manage groundwater flow, in situ chemical treatments in the groundwater, and captured contaminated groundwater discharges at the surface for management in a forest irrigation system. Concentrations of contaminants in the aquifers beneath the General Separation Area and in surface water streams in the General Separation Area have decreased over the past 25 years. Closure of 65 waste sites and 4 Resource Conservation and Recovery Act facilities has been successfully accomplished. Environmental clean-up has progressed to the stage where most of the work involves monitoring, optimization, and maintenance of existing remedial systems. Many lessons have been learned in the process of remediating the General Separations Area. Geo-textile covers outperform low permeability clay caps, especially with respect to the amount of repairs required to upkeep the drainage layers as the caps age. Passive and enhanced natural processes to address contamination are much more cost effective than pump and treat systems. Forest irrigation can be very effective in water management situations with non-accumulative contaminants such as tritium and volatile organic contaminants. (authors)
In the UK, ILW is currently managed using cementitious encapsulation in Portland cement (PC)-based grouts. The long-term behaviour of radionuclides in ILW cementitious waste-forms under varying local conditions of extended interim storage and geological disposal is not well understood and the behaviour of cement minerals in the retention of various radionuclides is poorly constrained. This work focuses on the Ca-Si-[Al,Mg,S] mineral system and how this may evolve with the introduction of radionuclides into the system. Here, we discuss the experimental program aimed at underpinning the uptake and retention mechanisms of a range of key radionuclides (U, Tc, Ce/Pu), with selected cement phases: calcium-silicate-hydrate (C-S-H), hydrotalcite (Mg{sub 6}Al{sub 2}CO{sub 3}(OH)16.4H{sub 2}O) and ettringite (Ca{sub 6}(Al{sub 2}O{sub 6})(SO{sub 4}){sub 3}.32H{sub 2}O). Described here is the syntheses of C-S-H and radionuclide incorporation experiments performed on this phase. Further to this, thermodynamic geochemical modelling has been adopted to explore the Ca-Si-U mineral system, aimed at identifying the mineral phases likely to form on contact of C-S-H phases with aqueous uranium, as a function of pH. (authors)
Once radiological impact is usually considered to be related to nuclear energy accidents and atomic bombs, most of the research on radiation protection has been focused on artificial radionuclides and radioactive waste. Less attention had been given to radiation exposure due to the presence of naturally occurring radioactive materials in raw materials usually considered as not radioactive and used in manufacturing of many building materials. At national level, radiological data from building materials is not available as the control of building materials regarding the content of naturally occurring radionuclides is addressed for the first time in the EU Directive 2013/59/EURATOM. At international level the research developed is largely incomplete: data on the activity concentration measurements of Ra-226, Th-232 and K-40 in building materials used in the construction industry in the EU is non-statistically representative. The data collected are not enough to have an idea of the European situation, but they confirm high concentration of Ra-226, Th-232 and K-40, in some cases. Moreover, most of the research studies carried out in the EU are based on the assessment of the activity concentration index, which was derived for practical monitoring purposes to identify whether a dose criterion is met; to be used only as a screening tool for identifying materials which might be of concern. The dose criterion considers only effective dose due to γ-radiation, but population at home is also exposed to Rn-222 (and Rn-220) from soil, water and building material itself, sometimes to β radiation from superficial materials, and even to Cs-137 from some types of wood. The indoors exposure can be actually much higher than the value assessed with the dose criterion method. Also, in most cases toxic and radioactive components are inseparably. Therefore, all technical questions related to the toxic part of these materials should be addressed: an integrated approach is needed to assess the impacts of using these materials (new materials, recyclates and by-products). Until recently, radiation from natural sources seemed both unremarkable and unalterable - a background phenomenon. It is now known that doses from natural sources and in particular, decay products of radon can be remarkably high within houses in some areas. Therefore, concerning exposure to natural radiation sources, special provisions have been laid down in the EU Directive 1996/28 EURATOM. Still, the radiological evaluation of building materials was not mandatory in this Directive. The most recent EU Directive 2013/59/EURATOM brings some changes concerning the exposure to natural occurring radioactive materials but the previous screening method was kept. An effective dose of 1 mSv/year was set, as a basis for the exposure to radionuclides of natural origin (except for radon). This work seeks to develop an integrated radiological and chemical-mineralogical assessment methodology for realistic exposure scenarios concerning different types of raw materials, by-products and recyclates and used as building materials. The methodology includes the characterization of selected materials accounting for radiological exposure - calculation of effective dose; toxicity assessment - determination of chemical composition and leaching tests, study of changes in the microstructure and consequently in the radon emanation coefficient. (authors)
Microbially induced corrosion (MIC) is an emerging topic that has huge environmental impacts, such as long-term evaluation of microbial interactions with radioactive waste glass, environmental cleanup and disposal of radioactive material, and weathering effects of microbes. Time-of-flight secondary ion mass spectrometry (ToF-SIMS), a powerful mass spectral imaging technique with high surface sensitivity, mass resolution, and mass accuracy, can be used to study biofilm effects on different substrates. Understanding how to prepare biofilms on MIC susceptible substrates is critical for proper analysis via ToF-SIMS. We present here a step-by-step protocol for preparing bacterial biofilms for ToF-SIMS analysis, comparing three biofilm preparation techniques: no desalination, centrifugal spinning (CS), and water submersion (WS). Comparisons of two desalinating methods, CS and WS, show a decrease in the media peaks up to 99% using CS and 55% using WS, respectively. Proper desalination methods also can increase biological signals by over four times for fatty acids using WS, for example. ToF-SIMS spectral results show chemical compositional changes of the glass exposed in a Paenibacillus polymyxa SCE2 biofilm, indicating its capability to probe microbiologically induced corrosion of solid surfaces. This represents the proper desalination technique to use without significantly altering biofilm structure and substrate for ToF-SIMS analysis. ToF-SIMS spectral results showed chemical compositional changes of the glass exposed by a Paenibacillus bacterial biofilm over 3-month inoculation. Finally, possible MIC products include various phosphate phase molecules not observed in any control samples with the highest percent increases when experimental samples were compared with biofilm control samples.
In a radioactive material (RAM) packaging, the formation of eutectic at the Pu/SS (plutonium/stainless steel) interface is a serious concern and must be avoided to prevent of leakage of fissile material to the environment. The eutectic temperature for the Pu/SS is rather low (410 C) and could seriously impact the structural integrity of the containment vessel under accident conditions involving fire. The 9975 packaging is used for long term storage of Pu bearing materials in the DOE complex where the Pu comes in contact with the stainless steel containment vessel. Due to the serious consequences of the containment breach at the eutectic site, the Pu/SS interface temperature is kept well below the eutectic formation temperature of 410 C. This paper discusses the thermal models and the results for the extended fire conditions (1500 F for 86 minutes) that exist in a long term storage facility and concludes that the 9975 packaging Pu/SS interface temperature is well below the eutectic temperature.
In March 2011, the Japanese Fukushima Dai-ichi nuclear reactor was damaged by a 9.0 magnitude earth quake and subsequent 15-meter tsunami. As a result of the nuclear reactor accident, radioactive material from the nuclear reactor and fuel storage pool (primarily radioactive iodine and cesium) was released to the atmosphere and carried by the wind as a plume that spread radioactive contamination across roughly 13,000 square kilometers of the countryside. Amec Foster Wheeler's Radiological Services and Engineering Group mobilized a team of Engineers and Operators to Japan to implement a radiological survey (scan) of roads located in Ichinoseki City, Iwate Prefecture, north of Fukushima, using three of Amec Foster Wheeler's Orion ScanPlotSM advanced radiological scanning systems. The survey was performed in less than two months while the roads were kept open for public use, and was conducted with motorized scooters and battery-assisted bicycles. The survey was performed with operational support from Obayashi, Inc., a large Japanese construction company headquartered in Tokyo. Over a seven-week period, the ScanPlotSM systems covered approximately 1,600 kilometers of roads within Ichinoseki City and surrounding areas of Iwate Prefecture. ScanPlotSM systems recorded GPS locations and radiation dose rate levels from Cs-137 on the road's surface at one-second increments during the survey and displayed the dose rate reading in micro-Sieverts per hour (μSv/h) on the back of the bicycle or motor scooter in real-time on a results monitor so that members of the public would be able to see real-time data. Radiological survey data was provided to Obayashi daily for development of survey result maps for the city. (authors)
High Efficiency Particulate Air (HEPA) filters are routinely used to filter exhaust air at Department of Energy (DOE) National Laboratory facilities that work with radioactive materials. While the HEPA filter configurations are fairly standardized (such as metal framed with glass micro-fiber media), the range and concentrations of radioactive and potentially other hazardous materials in the used filters presents for a variety of characterization approaches as well as challenges. This paper will summarize, compare and contrast the current HEPA filter waste management experience at a selection of DOE National Laboratories. Topic areas to be explored include process knowledge collection, characterization methods, characterization results, waste packaging and disposition pathways, and problems and success stories. (authors)
In a microcalorimetric neutrino mass experiment using the radioactive decay of {sup 163}Ho, the radioactive material must be fully embedded in the microcalorimeter absorber. One option that is being investigated is to implant the radioactive isotope into a gold absorber, as gold is successfully used in other applications. However, knowing the thermal properties at the working temperature of microcalorimeters is critical for choosing the absorber material and for optimizing the detector performance. In particular, it is paramount to understand if implanting the radioactive material in gold changes its heat capacity. We used a bolometric technique to measure the heat capacity of gold films, implanted with various concentrations of holmium and erbium (a byproduct of the {sup 163}Ho fabrication), in the temperature range 70 mK–300 mK. Our results show that the specific heat capacity of the gold films is not affected by the implant, making this a viable option for a future microcalorimeter holmium experiment.
The risk of nuclear or dirty bomb attack by terrorists is one of the most urgent and threatening danger. The Cambodian national strategy to combat weapons of mass destruction (WMD) depicts a layered system of preventive measures ranging from securing materials at foreign sources to interdicting weapons or nuclear or other radioactive materials at ports, border crossings, and within the Cambodian institutions dealing with the nuclear security to manage the preventive programs. The aim of this study is to formulate guidance, to identify scenario of threat and risk, and to pinpoint necessary legal frameworks on nuclear security in the context of counterterrorism based on the International Atomic Energy Agency nuclear security series. The analysis of this study is guided by theoretical review, the review of international laws and politics, by identifying and interpreting applicable rules and norms establishing the nuclear security regime and how well enforcement of the regime is carried out and, what is the likelihood of the future reform might be. This study will examine the existing national legal frameworks of Cambodia in the context of counterterrorism to prevent acts of nuclear terrorism and the threat of a terrorist nuclear attack within the Cambodia territory. It will shed light on departmental lanes of national nuclear security responsibility, and provide a holistic perspective on the needs of additional resources and emphasis regarding nuclear security policy in the context of counterterrorism in Cambodia.
Lynas Advanced Materials Plant (LAMP) has been licensed to produce the rare earths elements since early 2013 in Malaysia. LAMP processes lanthanide concentrate (LC) to extract rare earth elements and subsequently produce large volumes of water leach purification (WLP) residue containing naturally occurring radioactive material (NORM). This residue has been rising up the environmental issue because it was suspected to accumulate thorium with significant activity concentration and has been classified as radioactive residue. The aim of this study is to determine Th-232, U-238 and rare earth elements in lanthanide concentrate (LC) and water leach purification (WLP) residue collected from LAMP and to evaluate the potential radiological impacts of the WLP residue on the environment. Instrumental Neutron Activation Analysis and γ-spectrometry were used for determination of Th, U and rare earth elements concentrations. The results of this study found that the concentration of Th in LC was 1289.7 ± 129 ppm (5274.9 ± 527.6Bq/kg) whereas the Th and U concentrations in WLP were determined to be 1952.9±17.6 ppm (7987.4 ± 71.9 Bq/kg) and 17.2 ± 2.4 ppm respectively. The concentrations of Th and U in LC and WLP samples determined by γ- spectrometry were 1156 ppm (4728 ± 22 Bq/kg) and 18.8 ppm and 1763.2 ppm (7211.4 Bq/kg) and 29.97 ppm respectively. This study showed that thorium concentrations were higher in WLP compare to LC. This study also indicate that WLP residue has high radioactivity of {sup 232}Th compared to Malaysian soil natural background (63 - 110 Bq/kg) and come under preview of Act 304 and regulations. In LC, the Ce and Nd concentrations determined by INAA were 13.2 ± 0.6% and 4.7 ± 0.1% respectively whereas the concentrations of La, Ce, Nd and Sm in WLP were 0.36 ± 0.04%, 1.6%, 0.22% and 0.06% respectively. This result showed that some amount of rare earth had not been extracted and remained in the WLP and may be considered to be reextracted.
This paper compares the Light-Weight Radioisotope Heater Unit (LWRHU) historical testing to Department of Transportation (DOT) Special Form criteria per 49 CFR Part 173, Shippers-General Requirements for Shipments and Packages, Section 469, Tests for special form Class 7 (radioactive) materials as specified in DOE-STD-1027, Hazard Categorization of DOE Nuclear Facilities. Compliance with the aforementioned criteria allows for the exclusion of radioactive sources from the facility’s nuclear material inventory. As part of a new program at Los Alamos National Laboratory (LANL), LWRHUs are planned to be moved into TA-55, PF-5 Power Source Assembly Area (PSAA) for assembly and testing activities. The PSAA Facility is categorized as a low hazard, non-nuclear facility per DOE STD-1027 and is described in TA55-PF-5-FHC-11-001, Facility Hazard Categorization of the PSAA at PF-5, TA-55. The Facility Hazard Categorization document states, there must be documentation that radioactive sources are engineered to pass the special form testing specified by DOT in 49 CFR 173.469, Tests for special form Class 7 (radioactive) materials or ANSI N43.6, Sealed Radioactive Sources - Classification. This paper documents the extensive historical environmental safety testing of the LWRHU and demonstrates its ability to survive potential launch safety accident scenarios. The testing results are used herein to demonstrate through a comparative analysis that the robust design of the LWRHU meets or exceeds the special form testing specifications in 49 CFR 173.469, enabling the LWRHU to be transported and handled in PF-5 in support of testing and assembly program.
The objective of this report is to document the findings from a series of proof-of-concept tests performed by Savannah River National Laboratory (SRNL) R and D Engineering, for the DOE Packaging Certification Program to determine if a viable radio link could be established from within the stainless steel confines of several drum-style DOE certified Type B radioactive materials packagings. Two in-hand, off-the-shelf radio systems were tested. The first system was a Wi-Fi Librestream Onsight™ camera with a Fortress ES820 Access Point and the second was the On-Ramp Wireless Ultra-Link Processing™ (ULP) radio system. These radio systems were tested within the Model 9975 and 9978 Type B packagings at the SRNL. This report documents the test methods and results. A path forward will also be recommended.
A general issue and some selected topics discussed in international projects (ISO, IAEA, OECD) are presented. Long and broad experience in criticality safety is applied to find consistent safety principles for nuclear sites, external transport and final disposal. Support of standards and regulations is a main purpose. An ISO 1709 (criticality safety principles) draft proposes expansion of the scope to transport. Research on the basis for the IAEA Transport Regulations provides insights. Those Regulations are based on criticality safety principles. A general requirement for prevention of criticality during transport is combined with a prescriptive set of requirements on how to get regulatory approval. 'Confinement system' was introduced in 1996 to separate subcriticality from radioactive material containment specifications. The much older intention was to provide technical support, but not safety, for the inter-phases between sites, transport and emergency. The application has changed unintentionally and significantly. A solution is proposed. The principle for determination of a threshold fissile nuclide mass limit for fissile material is used to support acceptability of rounding a Criticality Safety Index value down to zero, similar to determination of the Transport Index. Temperature effects on nuclear properties need to be accounted for. A -40 to 800 Celsius degree temperature range outside a package applies to transport. Burnup credit benchmarks involve high temperatures (depletion) and interpretation of operating reactor measurements for typical water pools (20 to 120 C. degrees). KRITZ critical experiments between 20 and 250 Celsius degrees are currently being evaluated. (author)
Title 10 of the United States (US) Code of Federal Regulations (CFR), Part 71, Packaging and Transportation of Radioactive Material includes requirements for the transport of fissile material in packages. These regulations provide requirements for packaging that is certified by the US Nuclear Regulatory Commission (NRC) to transport fissile material, but the regulations also include provisions that allow for shipment of fissile material in packages that are not required to be certified by the NRC. These provisions include criteria for exemptions from classification as fissile material (10 CFR 71.15) and permit general licenses for limited quantities of fissile material and plutonium-beryllium special form sources (10 CFR 71.22 and 10 CFR 71.23, respectively). These regulations were revised by NRC as part of a broad rulemaking effort in 2004. These regulations are used frequently for a wide-variety of fissile material shipping operations and shippers must interpret the regulations for particular shipping situations. The quantity of fissile material that presents a criticality safety risk depends on the other materials in the system that might absorb neutrons emitted from fission or moderate (slow) those neutrons to lower energies where the probability of them creating an additional fission is highest. Besides the absorption and moderation of neutrons, other parameters that must be considered to ensure criticality safety are: the mass, concentration, or isotopic distribution of the fissile material; and the system geometry and neutron reflection of the package from surrounding materials. These parameters were carefully considered in developing the requirements for the exemptions from the classification of fissile material and the requirements for general licenses for fissile material. This paper will review the technical basis, intent, and anticipated usage of each of the fissile material exemption and general license provisions. Additionally, this paper will discuss the recent regulatory history of the Part 71 fissile material exemptions and general licenses, including the 2015 rulemaking effort. Finally, this paper will outline an upcoming NUREG/CR document regarding the fissile material exemptions and general licenses, and discuss recommendations that are being formulated for potential future revisions to the regulations. (authors)