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[en] Piping in the Defense Waste Processing Facility (DWPF) at the Savannah River Site (SRS) must withstand the stresses involved during an unlikely but potential deflagration event. One method proposed for protection and reinforcement of piping during such an event is the use of a carbon fiber-reinforced epoxy composite (Diamond-Wrap(regsign)). In the DWPF, this reinforcement composite product would be required to maintain its safety function for a 20-year service life. This product has been ASME-approved (nuclear code case 589) for post-construction maintenance and is DOT-compliant per 49CFR 192 and 195. However, its radiation resistance properties have not been evaluated. This report documents initial radiation resistance testing of the product and microstructural effects. Additional testing is recommended to evaluate radiation effects on specific properties such as burst strength, chemical resistance/weeping and for service life prediction in critical applications
[en] Carbon fiber-reinforced bisphenol-A epoxy matrix composite was evaluated for gamma radiation resistance. The composite was exposed to total gamma doses of 50, 100, and 200 Mrad. Irradiated and baseline samples were tested for tensile strength, hardness and evaluated using FTIR (Fourier transform infrared) spectroscopy and DSC (differential scanning calorimetry) for structural changes. Scanning electron microscopy was used to evaluate microstructural behavior. Mechanical testing of the composite bars revealed no apparent change in modulus, strain to failure, or fracture strength after exposures. However, testing of only the epoxy matrix revealed changes in hardness, thermal properties, and FTIR results with increasing gamma irradiation. The results suggest the epoxy within the composite can be affected by exposure to gamma irradiation
[en] TYPE I and II (ASTM 285-B) - Experienced stress corrosion cracking (SCC), 2 have been closed; 22 scheduled for closure by 2017, and No active leak sites today. TYPE III (ASTM A516-70 and A537 Class I) - Post-fabrication relief of weld residual stresses, Improved resistance to SCC and brittle fracture, No leakage history, and Receives new waste. The objectives are to utilize statistical methods to reduce conservatism in current chemistry control program; and express nitrite inhibitor limits in terms of pitting risk on waste tank steel. Conclusions are: (1) A statistically designed experimental study has been undertaken to improve the effectiveness of the minimum nitrite concentrations to inhibit pitting corrosion; (2) Mixture/amount model supports that pitting depends on the ratio of aggressive to inhibitive anions, as well as the concentration of each species; (3) Secondary aggressive species, Cl- and SO42-, significantly effect the corrosion response; and (4) Results support the reduction of the chemistry control nitrite inhibitor concentrations in the regime of 0.8-1.0 M nitrate.
[en] Various recycle strategies have been proposed to manage the inventory of transuranics in commercial spent nuclear fuel (CSNF), with a particular goal of increasing the loading capacity of spent fuel and reprocessing wastes in the Yucca Mountain repository. Transuranic recycling in commercial LWRs can be seen as a viable means of slowing the accumulation of transuranics in the nationwide CSNF stockpile. Furthermore, this type of approach is an important first step in demonstrating the benefits of a nuclear fuel cycle which incorporates recycling, such as envisioned for Generation-IV reactor systems under development. Recycling strategies of this sort are not proposed as an attempt to eliminate the need of a geologic nuclear waste repository, but as a means to enhance the usefulness of the repository currently under construction in the U.S., perhaps circumventing the need for a second facility. A US-DOE Secretarial recommendation on the need for the construction of a second geologic repository is required by 2010. The Advanced Fuel Cycle Initiative (AFCI) has supported a breadth of work to evaluate the ideal transuranic separation and recycle strategy. Previous AFCI studies of LWR-based transmutation have considered the benefits of homogeneously recycling plutonium, plutonium and neptunium, and all transuranic (TRU) species. A study of a wide range of hypothetical separation schemes (Pu, Pu+Np, Pu+Np+Am, etc.) with multi-recycling has also been performed, focusing on the proliferation resistance of the various fuel cycles and fuel handling issues. The direct recycle of the recovered TRU from spent inert-matrix fuel (IMF) into new IMF was found to be quite limited due to the rapid burndown of the fissile plutonium. The IMF is very effective at destroying the fissile fraction of the TRU with destruction rates in excess of 80% of the fissile material without recycling the IMF. Blending strategies have been proposed to mitigate the rapid burndown of the fissile plutonium by mixing high fissile feed from new sources (e.g., spent UO2 pins) with the low fissile material recovered from the recycled transmutation fuel. The blending of the fuels is anticipated to aid the multi-recycle of the transuranics. A systematic study of blending strategies (for both IMF and MOX) has been initiated and is currently ongoing. This work extends the previous study that considered separation strategies for plutonium, neptunium, and americium recycling in MOX, CORAIL, and IMF6 by considering blending schemes and approach to continuous recycle. Plutonium and americium are recycled in order to reduce the intermediate term (100 to 1500 years after spent fuel irradiation) decay heat of the disposed waste which accounts for the bulk of the repository heating. Since the long-term released dose from the repository is dominated by neptunium, it is sensible to consume it by transmutation in a reactor, as well. Curium accounts for ∼0.6% of the TRU mass in spent UO2 fuel (∼0.008% of the heavy metal), but does constitute significantly higher fractions in spent transmutation fuels. This initial evaluation will focus on blending strategies for the multirecycling of Pu+Np+Am. The impact of curium recycle will be investigated as part of the systematic study of blending strategies. The initial study focuses on understanding a simple strategy for IMF recycle and blending. More complex strategies (i.e., heterogeneous assemblies) will be evaluated later in the year, including enriched uranium support options. Currently, a preliminary study of a serial blending strategy has been performed in order to evaluate the impact of blending on the performance of the IMF recycle and to evaluate the potential for continuous or infinite recycle. The continuous recycle of Pu+Np+Am in IMF would allow for complete destruction of all heat contributing actinides in the same LWRs that originally produced them. The only transuranics sent to the repository would be those lost in reprocessing and curium if it is not eventually recycled
[en] The Savannah River Site (SRS) is currently storing plutonium materials in the K-Area Materials Storage (KAMS) facility. The materials are packaged per the DOE 3013 Standard and transported and stored in KAMS in Model 9975 shipping packages, which include double containment vessels sealed with dual O-rings made of Parker Seals compound V0835-75 (based on Viton(regsign) GLT). The outer O-ring of each containment vessel is credited for leaktight containment per ANSI N14.5. O-ring service life depends on many factors, including the failure criterion, environmental conditions, overall design, fabrication quality and assembly practices. A preliminary life prediction model has been developed for the V0835-75 O-rings in KAMS. The conservative model is based primarily on long-term compression stress relaxation (CSR) experiments and Arrhenius accelerated-aging methodology. For model development purposes, seal lifetime is defined as a 90% loss of measurable sealing force. Thus far, CSR experiments have only reached this target level of degradation at temperatures (ge) 300 F. At lower temperatures, relaxation values are more tolerable. Using time-temperature superposition principles, the conservative model predicts a service life of approximately 20-25 years at a constant seal temperature of 175 F. This represents a maximum payload package at a constant ambient temperature of 104 F, the highest recorded in KAMS to date. This is considered a highly conservative value as such ambient temperatures are only reached on occasion and for short durations. The presence of fiberboard in the package minimizes the impact of such temperature swings, with many hours to several days required for seal temperatures to respond proportionately. At 85 F ambient, a more realistic but still conservative value, bounding seal temperatures are reduced to ∼158 F, with an estimated seal lifetime of ∼35-45 years. The actual service life for O-rings in a maximum wattage package likely lies higher than the estimates due to the conservative assumptions used for the model. For lower heat loads at similar ambient temperatures, seal lifetime is further increased. The preliminary model is based on several assumptions that require validation with additional experiments and longer exposures at more realistic conditions. The assumption of constant exposure at peak temperature is believed to be conservative. Cumulative damage at more realistic conditions will likely be less severe but is more difficult to assess based on available data. Arrhenius aging behavior is expected, but non-Arrhenius behavior is possible. Validation of Arrhenius behavior is ideally determined from longer tests at temperatures closer to actual service conditions. CSR experiments will therefore continue at lower temperatures to validate the model. Ultrasensitive oxygen consumption analysis has been shown to be useful in identifying non-Arrhenius behavior within reasonable test periods. Therefore, additional experiments are recommended and planned to validate the model.
[en] Changes at the data analysis center are summarized. The most dramatic change in the operation of the Data-Analysis Center (DAC) has been the implementation of a VAX cluster. The cluster is a network of loosely coupled VAX computers tied together with a high-speed network and sharing common disks. System software was enhanced with the addition of DECalc, a spread-sheet program for the VAX. EUNICE, a UNIX environment package that is layered on VMS, was added to VAX machine MPFG0. Networking capabilities in the DAC were significantly increased during 1984. Specifically, access to remote networks, such as TELENET, was made easier through the C-Division computers. In addition, the DAC acquired dial-out modems and software so that users could transfer files between DAC machines and other computers over phone lines. A major project in the data-acquisition section in the past year was a special-purpose multiprocessor system to analyze data generated at LAMPF. During the year requirements for the system have been defined, hardware for a prototype system (PDP-11/730s and Ethernet) has been selected, and the system software has been designed. During 1984 both Q replay and data acquisition using VAXes and the VMS operating system were fully implemented and released to users. VAX data acquisition was used successfully in experiments at EPICS at LAMPF, at the Bates Linear Accelerator in Massachusetts, and at the Bevalac at Lawrence Berkeley National Laboratory. The EPICS VAX-11/730 system was upgraded to a VAX-11/750 at the end of 1984 to improve on-line response and performance. Another VAX-11/750 is being purchased for HRS
[en] A series of experiments to monitor the aging performance of Vitonreg. GLT O-rings used in the Model 9975 package has been ongoing for six years at the Savannah River National Laboratory. Sixty-seven mock-ups of 9975 Primary Containment Vessels (PCVs) were assembled and heated to temperatures ranging from 200 to 450 F. They were leak-tested initially and have been tested at nominal six month intervals to determine if they meet the criterion of leaktightness defined in ANSI standard N14.5-97. Fourteen additional tests were initiated in 2008 with GLT-S O-rings heated to temperatures ranging from 200 to 400 F. High temperature aging continues for 36 GLT O-ring fixtures at 200--350 F. Room temperature leak test failures have been experienced in 5 of the GLT O-ring fixtures aging at 300 and 350 F, and in all 3 of the GLT O-ring fixtures aging at higher temperatures. No failures have yet been observed in GLT O-ring fixtures aging at 200 F for 30--48 months, which is still bounding to O-ring temperatures during storage in KAMS. High temperature aging continues for 6 GLT-S O-ring fixtures at 200--300 F. Room temperature leak test failures have been experienced in all 8 of the GLT-S O-ring fixtures aging at 350 and 400 F. No failures have yet been observed in GLT-S O-ring fixtures aging at 200 or 300 F for 19 months. For O-ring fixtures that have failed the room temperature leak test and been disassembled, the O-rings displayed a compression set ranging from 51--95%. This is significantly greater than seen to date for packages inspected during KAMS field surveillance (23% average). For GLT O-rings, service life based on the room temperature leak rate criterion is comparable to that predicted by compression stress relaxation (CSR) data at higher temperatures (350--400 F). While there are no comparable failure data yet at aging temperatures below 300 F, extrapolations of the data for GLT O-rings suggests that CSR model predictions provide a conservative prediction of service life relative to the leak rate criterion. Failure data at lower temperatures is needed to verify this apparent trend. Insufficient failure data exist currently to perform a similar comparison for GLT-S O-rings. Aging and periodic leak testing will continue for the remaining fixtures.
[en] The Model 9975 shipping package specifies the materials of construction for its various components. With the loss of availability of material for two components (cane fiberboard overpack and Viton(regsign) GLT O-rings), alternate materials of construction were identified and approved for use for transport (softwood fiberboard and Viton(regsign) GLT-S O-rings). As these shipping packages are part of a long-term storage configuration at the Savannah River Site, additional testing is in progress to verify satisfactory long-term performance of the alternate materials under storage conditions. The test results to date can be compared to comparable results on the original materials of construction to draw preliminary conclusions on the performance of the replacement materials.
[en] This report summarizes the research activities of WP-1754. The study focusses on the environmental factors influencing formation of lead free whiskers on electrodeposited tin coatings over copper (or copper containing) substrates. Much of the initial results are summarized in an interim report. From the initial results, two main areas were chosen to be the focus of additional research: the demonstration of effects of elastic stress state in the nucleation of whiskers and the confirmation of the effect of oxygen/nitrogen ratio in the formation of whiskers. Different levels of elastic stress were induced with the incorporation of a custom designed fixture that loaded the substrates in a four-point bending configuration and were maintained in an environmental chamber under conditions deemed favorable for whisker growth. The results show that induced elastic stress slightly increased the concentration of nucleation sites of whiskers. The effects of oxygen content were studied by aging substrates in gas vials of varying absolute pressure and different oxygen/nitrogen ratios. The concentration of whiskers were measured and appear to be sensitive to absolute pressure but are not sensitive to oxygen content (as previously observed)