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At least 775 records · Page 43

Friendly Extensible Transfer Tool Beta Version

Often data transfer software is designed to meet specific requirements or apply to specific environments. Frequently, this requires source code integration for added functionality. An extensible data transfer framework is needed to more easily incorporate new capabilities, in modular fashion. Using FrETT framework, functionality may be incorporated (in many cases without need of source code) to handle new platform capabilities: I/O methods (e.g., platform specific data access), network transport methods, data processing (e.g., data compression.).

Collins, William P.↗

B61-12 Life Extension Program (Maintaining the Stockpile)

The B61 nuclear gravity bomb, deployed from U.S. Air Force and North Atlantic Treaty Organization (NATO) bases, has almost 50 years of service, making it the oldest and most versatile weapon in the enduring U.S. stockpile. Numerous modifications have been made to improve the B61’s safety, security, and reliability since the first B61 entered service in 1968, and four B61 variants remain in the stockpile: the 3, 4, 7, and 11. However, the aging weapon system requires a life extension to continue deterring potential adversaries and reassuring our allies and partners of our security commitments to them.

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W76-1 Life Extension Program (Maintaining the Stockpile)

The W76-1 is a refurbished W76-0 warhead, which is a submarine-launched ballistic missile system that was first introduced into the stockpile for the Navy in 1978. The W76-1 Life Extension Program extends the originally designed warhead service life of 20 years to 60 years. The W76-1 continues to meet all missions and capabilities of the original W76-0 warhead and does not provide new military capabilities. NNSA completed refurbished warhead production at the Pantex Plant in December 2018.

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W80-4 Life Extension Program (Maintaining the Stockpile)

In close coordination with the Department of Defense,NNSA is extending the life of the W80-1 warhead through the W80-4 Life Extension Program (LEP) for use in the U.S. Air Force’s Long Range Standoff (LRSO) cruise missile. Together, the W80-4 and LRSO will help ensure the long-term effectiveness of the bomber leg of the Nation’s nuclear triad. The W80-4 LEP will also extend the warhead’s service life while enhancing its safety, security, and reliability.

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Deterministic Selection of Design Extension Condition without Core Melt

The concept of beyond design basis accidents (BDBA) recently has been changed to design extension conditions (DEC). DEC is required to be considered in the design process, and it comprises conditions in events without core melt and conditions in events with core melt. DEC with core melt is a part of severe accident. A systematic and deterministic approach to select DEC without core melt for a pressurized water reactor (PWR) is introduced.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

Extension of the DIF3D Code for Molten Salt Reactor Analysis

The molten salt reactor (MSR) with the fuel dissolved into the liquid salt has been selected as one of the six Generation-IV reactors due to its excellent characteristics in the aspects of sustainability, economy, passive safety, and resource utilization. In a MSR, the fuel salt is circulated throughout the whole system and thus some of delayed neutron precursors generated in the core decay in position of low importance or even out of the core. As a result, the multiplication factor (k-eff) of MSR is smaller than that of a reactor of stationary fuel when all the other conditions are same. Therefore, the neutronics code developed for stationary fuel cannot be applied directly to MSR analysis. In this paper, we describe the extension and application of the DIF3D code to MSR neutronics analysis. The DIF3D code system is a multi-group steady-state neutron diffusion and transport theory solver. It provides three flux solution options: finite-difference diffusion theory, nodal diffusion theory, and variational nodal transport theory methods. Eigenvalue, adjoint, fixed source and criticality (concentration) search problems are permitted. The DIF3D code has recently been modified to model the flowing fuel. To verify the new capability of DIF3D, the MSFR [4] core was analyzed with a wide range of velocity field of fuel salt and time spent outside of the core.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

A new track finding algorithm based on a multi-dimensional extension of the Hough Transform

We introduce a new pattern recognition algorithm for track finding in High Energy Physics Experiments based on an extension of the Hough Transform to multiple dimensions. A remarkable property of this algorithm is that the execution time is simply proportional to the total number of the hits to be processed, making it particularly attractive for high occupancy situations. The algorithm needs to be trained using a sufficiently large set of simulated tracks. The same track finding algorithm can be used for very different detector geometries and only the set of simulated tracks used for training needs to be changed. The particular structure of the algorithm also lends itself naturally to parallel hardware implementations which, combined with its intrinsic flexibility, should provide a most powerful tool for triggering at future colliders.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Extensive sensitivity study of PWR fuel assay data - 14301

Accurate calculations of the isotopic composition of spent nuclear fuel play a fundamental role in several parts of nuclear energy. An important example is the use of burnup credit in criticality safety analysis, where the results gained from depletion calculations are used to determine the fuel composition in subsequent criticality calculations. The work presented here is a sensitivity study for depletion calculations of high-burnup fuel samples from the Vandellos II PWR that entails an unusually detailed evaluation of assay data. In addition to investigating the impacts of experimental uncertainties on the calculated isotopic composition, the consequences of various modelling approaches are studied to give quantitative estimations of the impact on accuracy. Furthermore, the reactivity of the calculated fuel composition is tracked, because this is the integral characteristic of the irradiated fuel that one is actually interested in for burnup credit applications. While the sensitivity study is performed only for one of the nine experimental samples of the Vandellos II assay data, the lessons learned lead to evaluation models with different levels of model detail for all fuel samples. The results show that the discrepancies between the measured and calculated isotopic compositions are considerably larger than the uncertainties inherent in the measurement and the calculation method would indicate. This is not unexpected, since large discrepancies are a common result of assay data recalculations. However, the unusually extensive sensitivity study performed here allows to exclude some possible sources of error: since the influence of experimental uncertainties like fuel assembly geometry and reactor parameters on the isotopic composition is shown to be small, one valuable conclusion of this study is to focus more on the measurement uncertainties of the chemical assay itself, and the nuclear data that the calculation is based upon. The study also demonstrates that using the reactivity of the depleted fuel as an additional comparison point between measurement and calculation can provide some orientation regarding the importance of the manifold influences on calculation results. Tracking this integral characteristic of the depleted fuel is very helpful in focusing on the actual impact of the depletion calculation uncertainties on criticality safety. (author)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

Extension of the high-resolution thermal-hydraulics code ESCOT to hexagonal core geometries for multi-physics calculations

The extension of the capabilities of the pin-level nuclear reactor core thermal-hydraulics (T/H) code ESCOT to analyze hexagonal fueled cores and its performance are presented. ESCOT is an accurate yet fast core thermal-hydraulics solution aiming at high-fidelity and high-resolution multi-physics core analysis in the framework of massively parallel computing platforms. Its algorithm solution is based on the four-equation drift-flux model for two-phase calculations, these are numerically solved by applying the Finite Volume Method (FVM) and the Semi-Implicit Method for Pressure-Linked Equation (SIMPLE)-like algorithm in a staggered grid system. Constitutive models such as turbulent mixing, pressure drop, and vapor generation are employed to simulate key phenomena in subchannel-scale analysis. ESCOT is parallelized by a double (radial and axial) domain decomposition that enables its highly parallelized execution. The coupling of the code with the neutronics whole core solver for hexagonal geometries nTRACER is described. The newly implemented ESCOT features are validated by comparing single assembly and full core steady state nTRACER-ESCOT solutions with nTRACER standalone internal one-dimensional T/H solver results. The validation problems are based on the VVER 440 and VVER 1000 cores. ESCOT results show differences within an acceptable range with respect to the simple 1D nTRACER built-in solver. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

Nanosecond-level time synchronization of autonomous radio detector stations for extensive air showers

To exploit the full potential of radio measurements of cosmic-ray air showers at MHz frequencies, a detector timing synchronization within 1 ns is needed. Large distributed radio detector arrays such as the Auger Engineering Radio Array (AERA) rely on timing via the Global Positioning System (GPS) for the synchronization of individual detector station clocks. Unfortunately, GPS timing is expected to have an accuracy no better than about 5 ns. In practice, in particular in AERA, the GPS clocks exhibit drifts on the order of tens of ns. We developed a technique to correct for the GPS drifts, and an independent method used for cross-checks that indeed we reach nanosecond-scale timing accuracy by this correction. First, we operate a “beacon transmitter” which emits defined sine waves detected by AERA antennas recorded within the physics data. The relative phasing of these sine waves can be used to correct for GPS clock drifts. In addition to this, we observe radio pulses emitted by commercial airplanes, the position of which we determine in real time from Automatic Dependent Surveillance Broadcasts intercepted with a software-defined radio. From the known source location and the measured arrival times of the pulses we determine relative timing offsets between radio detector stations. We demonstrate with a combined analysis that the two methods give a consistent timing calibration with an accuracy of 2 ns or better. Consequently, the beacon method alone can be used in the future to continuously determine and correct for GPS clock drifts in each individual event measured by AERA.

47 OTHER INSTRUMENTATION↗

Lifetime Extension of the Gas Discharge Detectors with Plasma Etching of Silicon Deposits in 80%CF{sub 4} + 20%CO{sub 2}

A method of elimination of silicon compounds from the anode wire of an aged proportional counter is presented. The aging of a counter with a 70%Ar + 30%CO{sub 2} and a 60%Ar + 30%CO{sub 2} + 10%СF{sub 4} working mixture was stimulated by a {sup 90}Sr β source. To accelerate the process of aging, the gas mixture flow to the counter was supplied through a pipe with RTV coated wall. As a result, the amplitude of the signal decreased 70% already at accumulated charge of Q = 0.03 C/cm. The etching of the silicon compounds on the wire surface with an 80%CF{sub 4} + 20%CO{sub 2} gas mixture discharge led to full recovery of the operating characteristics of detector and an increase in the lifetime. A scanning electron microscopy and X-ray spectroscopy analysis of the recovered wire surface were performed. In accordance with the results, a good quality of wire cleaning from SiO{sub 2} compounds was obtained.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

The Search for High-Energy Photons and Neutrinos Producing Extensive Air Showers with Energies E > 10{sup 18} eV and Zenith Angles θ > 70{sup °} in the Yakutsk Array Data

The method of searching for showers generated by neutral particles such as high-energy gamma quanta and astrophysical neutrinos is described, and the results of this search are presented. These results were obtained in the combined analysis of data on electrons, muons, and Cherenkov radiation of EASs and their temporal responses in scintillation and Cherenkov detectors. An upper limit on the flux of gamma quanta with energies of 3 × 10{sup 1}8, 10{sup 1}9, and 3 × 10{sup 1}9 eV was obtained. The multiparameter analysis of shower characteristics did not reveal EASs produced by neutrinos.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

MOOSE IPL Extensions (Documentation)

In FY-2015, The development of MOOSE was driven by the needs of the NEAMS MOOSE-based applications, BISON, MARMOT, and RELAP-7. An emphasis was placed on the continued upkeep and improvement MOOSE in support of the product line integration goals. New unified documentation tools have been developed, several improvements to regression testing have been enforced and overall better software quality practices have been implemented. In addition the Multiapps and Transfers systems have seen significant refactoring and robustness improvements, as has the “Restart and Recover” system in support of Multiapp simulations. Finally, a completely new “Control Logic” system has been engineered to replace the prototype system currently in use in the RELAP-7 code. The development of this system continues and is expected to handle existing needs as well as support future enhancements.

99 GENERAL AND MISCELLANEOUS↗