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Hydrogen infrastructure is expanding. Mobile hydrogen refueling stations are advantageous because they can be moved between locations to provide refueling. However, there are serious concerns over the risk of various accident scenarios as the refueling stations are transported. In this study, we conduct a quantitative risk assessment of a mobile hydrogen refueling station. Risks that may occur at two refueling locations and the transport path between them are analyzed. Our evaluation reveals that risks are mostly in an acceptable zone and to a lesser degree in a conditionally acceptable zone. The greatest single risk factor is an accident resulting from the rupture of the tube trailer at the refueling site. At sites with no tube trailer and during the transport, the risk is greatest from large leaks from the dispenser or compressed gas facility. The mobile hydrogen refueling station can be safely built within acceptable risk levels. [ABSTRACT FROM AUTHOR]

The high velocity compressive response of metallic corrugated core sandwich columns was characterized. One end of a column was compressed, either perpendicular-to-corrugations or parallel-to-corrugations, at a uniform velocity up to 100 m/s whereas the other end was held fixed. Numerical simulations revealed that the response differs from the low velocity response dominated by inertial stabilization; the perpendicular-to-corrugations compressive response was characterized by repetitive densification in a unit cell while the parallel-to-corrugations one occurred during one-way trip of stress wave. The effects of geometric imperfections, column length, compression velocity were investigated through the analysis on rate independent Al6061-T6 corrugated core sandwich columns. On the other hand, the influence of material strain-rate sensitivity was numerically assessed for SS304 corrugated core sandwich columns. As a result, the front end reaction forces increased with imposed velocity while the peak reaction forces on the back end remained invariant. No significant effect of geometric imperfections was observed, and the column length effect was associated with the time scale: the arrival time of stress wave and reaction force variation. Consequently, the analytical expressions for the response were given in terms of sandwich geometric dimensions and loading intensity. [ABSTRACT FROM AUTHOR]

This work was motivated by a necessity of simple and efficient models approximating the responses associated with all the possible failure modes of corrugated core sandwich columns in dynamic compression. In this study, an analytical model was proposed for the prediction of face wrinkling behavior of corrugated core sandwich columns under dynamic compressive loading perpendicular-to-corrugations . The proposed analytical model has been based on the calculation of transverse motion of face ligaments near the front and back ends of a sandwich column. The governing equation for the face ligaments has been a dynamic version of Euler–Bernoulli beam–column equation, and the motions were obtained by employing the Galerkin method to solve the equation. For validation of the proposed model, FE simulations were performed to compare several metrics such as reaction force and the transverse deflection of face ligaments. It was revealed that the dynamic face wrinkling response was also affected by overall column length and the rate of loading unlike the face wrinkling strength of corrugated core sandwich columns in quasi-static compression. Finally, the model׳s limitation and efficiency were discussed. [ABSTRACT FROM AUTHOR]

A theoretical (semi-analytical) approach was proposed to estimate the dynamic in-plane response of corrugated core sandwich columns against suddenly applied loads with a compression rate less than 5m/s. The model has been constructed so as to effectively include various dynamic effects such as stress wave propagation, material rate dependence and lateral inertia. The practical and theoretical complexities caused from the dynamic phenomena and the established governing equations (e.g. coupled non-uniform axial force distribution) have been resolved by employing Galerkin's method. The proposed approach was validated by comparing the calculations from the theoretical model and Finite Element Method (FEM): the load history and deformation shape of extruded Al6061-T6 corrugated core sandwich columns and bending/brazed SS304 corrugated core sandwich columns. The model successfully yielded the imperfection-sensitive, velocity-dependent dynamic response and appearance of higher buckling modes. In addition, it has been demonstrated that the sandwich columns with periodic cellular metals outperform their weight-equivalents, monolithic solid columns, under dynamic conditions. The proposed approach as an efficient tool to explore the dynamic global buckling response in design space can make preliminary studies of weight minimization for dynamic applications. [ABSTRACT FROM AUTHOR]

Abstract: At the Kyoto University Critical Assembly (KUCA), spallation neutrons generated by high-energy proton beams are injected into the thorium-loaded systems on March 2010. By combining the Fixed Field Alternating Gradient (FFAG) accelerator with the thorium-loaded system at KUCA, a series of the ADS experiments is carried out under conditions whereby the spallation neutrons are generated at a tungsten target by 100MeV protons at an intensity of 30pA. Prompt neutron behavior in the time evolution is observed and thorium fission reactions are attained through the experiments and calculations, respectively. And the effects of neutron leakage and spectrum softening are experimentally observed through the neutron multiplication and reaction rate analyses. From the experimental and numerical analyses, in the future, experimental conditions need to be improved to attain further neutron multiplication using the variation of fuels (thorium, highly-enriched and natural uranium) and moderators (graphite, polyethylene, aluminum and beryllium). [Copyright &y& Elsevier]

Abstract: For a core design work of a nuclear transmutation reactor, nuclear data were added to the KAFAX-F22 library based on three master libraries, JEFF3.0, ENDF/B-VI.8 and JENDL3.3. Evaluation of the modified library was done by comparing criticality and the reaction ratio with experimental data. Evaluation of Cm-244 and Np-237 was calculated by TRANSX and DANTSYS for critical assemblies, JEZEBEL and FLATTOP. For the evaluation of minor actinide isotopes for which there was no experiment, calculation results of benchmark problems were compared with MCNP4c2 results. The geometry and composition of these problems are those of the reference model for the Pb–Bi cooled fast spectrum transmutation reactor. There were good agreements among the evaluation data for most of the isotopes except Am-241, Am-243, Cs-135 and Cs-137. In case of Cm-242, results of the KAFAX library from ENDF/B-VI.8 showed a large discrepancy in reactivity worth compared with other libraries. [Copyright &y& Elsevier]

Abstract: One of the lead-alloy cooled fast reactors, PEACER (Proliferation-resistant, Environment-friendly, Accident-tolerant, Continuable-energy, and Economical Reactor), has been designed by a university research team in Korea. This reactor is a medium-size modular fast reactor of 850MWt (300MWe) rated power with lead–bismuth coolant loop. A square lattice fuel assembly with large pitch size might be favorable to ensure sufficient mass flow rate not only in normal operation but also in natural cooling under accidents. A metal fuel of (U,TRU)10%Zr is chosen in this study for the advantage of high thermal conductivity. Multinational energy complex with a closed fuel cycle facilities should provide proliferation resistance with an institutional barrier. Under the material control safeguards, all fuel isotopes and radioactive material should be confined in a complex but as low-level radioactive waste. In order to achieve this goal, efficient transmutation of long-lived minor actinides (LLMAs) and long-lived fission products (LLFPs) should be completed in an LFR core. An energy complex, PEACER-Park, consists of four PEACERs and two collocated pyro-processing plants. Only low-level waste from spent fuel reprocessing plant is designed to be transported out of PEACER-Park. Recovery factors in reprocessing plant, therefore, should be high enough to make low-level tail satisfy US NRC class C classification. However, an interim storage should be collocated in PEACER-Park for storing radioactive fission products having short half-life such as Cs-135 and Sr-90. Parametric studies have been done for a core design to maximize its transmutation capability within safety criteria. [■] When a pitch to diameter ratio (P/D ratio) was increased, the transmutation capability of each LLMA isotope changed in different ways. [■] When neutron leakage was increased by making core shape flat, the transmutation enhanced. [■] It was confirmed that longer cycle length was favorable to transmutation. [■] In the case of feed fuel composition and coolant operation temperature, there were no significant effects on transmutation performance. The final optimized core was designed as follows: a flat core shape with 50cm of active core height and 5m core diameter, pitch to diameter ratio of 2.2 which could be compromised between different transmutation tendencies of Np-237 and Am-241 and three different enrichment zones with 1-year cycle length. This design could achieve a sufficient transmutation capability with a support ratio of 2.085. Maximum pin power peaking was less than 1.5. Large negative radial expansion feedback coefficient and a sufficient shutdown margin could also be guaranteed. [Copyright &y& Elsevier]

Abstract: This study presents a methodology of life prediction of fatigue crack initiation for the cyclically non-stabilized and non-Masing steel. The cyclic behavior of 316L stainless steel was modelled, and the constitutive model was combined with local stress–strain approximations at a notch. The local stress–strain approximation methods were formulated incrementally to get the notch tip stress–strain of the non-Masing material. The local approximations were compared with the FEM results for verification. The prediction of fatigue crack initiation life was carried out by adopting plastic strain energy density (PSED) as a fatigue parameter and all the life prediction results were within factors of two of the experimental results. [Copyright &y& Elsevier]

Abstract: The effects of silicon cross section and neutron spectrum on the radial uniformity of a Si-ingot are examined experimentally with various neutron spectrum conditions. For the cross section effect, the numerical results using silicon single crystal cross section reveal good agreements with experiments within relative difference of 6%, whereas the discrepancy is approximately 20% in free-gas cross section. For the neutron spectrum effect, the radial uniformity in hard neutron spectrum is found to be more flattening than that in soft spectrum. [Copyright &y& Elsevier]

Highlights • Assessment of detectors' locations and number of detectors in PGSFR. • Generation of spatial weighting function using forward fixed-source calculation in MCNPX. • Calculation of transient power during withdrawal of a single control assembly by using FREK. Abstract This paper presents the assessment of the ex-core detectors in the Prototype Gen-IV Sodium-cooled Fast Reactor (PGSFR) in response to the movement of single primary control assembly, to evaluate the detectors' locations and to determine a proper number of detectors. The detectors are located below the containment vessel and distributed in different ranges from the center and different azimuthal angles. Another position considered is in the radial direction of the core, at the sodium coolant gap between the outermost assembly and core shroud. To calculate the detection rate, the contribution of each fuel region to the detector and the core power distribution are required. Initially, the aforementioned contribution is generated by performing a continuous-energy forward fixed-source Monte Carlo calculation using MCNPX. The reactor kinetics code FREK simulates the power change due to an inadvertent withdrawal of a primary control assembly up to 10% from its critical position followed by full insertion of secondary control assemblies. The response from each detector location was evaluated, and consequently, the detectors located below the containment vessel, which can "see" all the fuel assemblies, responded better to the core power increase with a minor error of less than ∼0.6%. In addition, the impact of locating the detector below the containment vessel at different locations from the center or at different azimuthal angles was insignificant but several detectors should be distributed at even azimuthal angles for effective core monitoring and redundancy purposes. [ABSTRACT FROM AUTHOR]

For a metal-fueled SFR (Sodium-cooled Fast Reactor), the negative feedback of the reactivity due to the thermal expansion of fuel has been a principal safety mechanism to guarantee passive reactor shutdown after undercooling accidents. In this paper, an experimental model of the fuel axial expansion reactivity in a metal-fueled SFR was proposed and measured values using the BFS-109-2A critical assembly was compared with calculated values using as-built MCNP models based on the ENDF/B-VII.0 library. The energy-dependent axial expansion reactivity components of the BFS-109-2A model showed good agreement with those of the target core. The difference in the calculation/experiment ratio between the as-built MCNP models and measurements vary from −10.2% to 2.6% for the axial expansion reactivity, meanwhile the suggested axial expansion model showed a 25% discrepancy comparing to the target core. [ABSTRACT FROM AUTHOR]

Abstract: Reaction rate experiments on the accelerator-driven system (ADS) are conducted by combining a critical assembly of a solid-moderated and -reflected core with a pulsed neutron generator. Neutrons (14MeV) generated from the accelerator are injected into a subcritical system and the reaction rates are measured by the foil activation method to obtain neutronic spectrum data. The numerical calculations are executed by MCNPX with ENDF/B-VI.8, JENDL-3.3 and JENDL/D-99 libraries to evaluate the reaction rates of activation foils set in the center of the core. For the ADS experiments with 14MeV neutrons, the C/E values between the experiments and the calculations are found to be well within the relative difference of about 30% in all foils up to subcriticality 1.05%Δk/k. The reaction rates do not depend on the subcriticality level in cases of 115In, 56Fe (purity 99.99%), 27Al, whereas subcriticality dependence is observed in 93Nb. In the critical experiments carried out in the A, B and C cores, special mention should be made of the remarkable effect of the composition rate of 56Fe material. Thus a remarkable improvement is observed in the accuracy of experimental and numerical reaction rates, demonstrating the importance of material impurity for subcritical experiments. [Copyright &y& Elsevier]

Abstract: The neutron multiplication parameters: neutron multiplication M, subcritical multiplication factor ks , external source efficiency φ *, play an important role for numerical assessment and reactor power evaluation of an accelerator-driven system (ADS). Those parameters can be evaluated by using the measured reaction rate distribution in the subcritical system. In this study, the experimental verification of this methodology is performed in various ADS cores; with high-energy (100MeV) proton–tungsten source in hard and soft neutron spectra cores and 14MeV D–T neutron source in soft spectrum core. The comparison between measured and calculated multiplication parameters reveals a maximum relative difference in the range of 6.6–13.7% that is attributed to the calculation nuclear libraries uncertainty and accuracy for energies higher than 20MeV and also dependent on the reaction rate distribution position and count rates. The effects of different core neutron spectra and external neutron sources on the neutron multiplication parameters are discussed. [ABSTRACT FROM AUTHOR]

Abstract: The subcritical multiplication factor ks and the external neutron source efficiency are important parameters in the accelerator-driven system (ADS) performance assessment. The theoretical relation between ks and the effective multiplication factor keff in a subcritical system is discussed in different cases of subcritical system. On the basis of the theoretical background, the dependence of ks and on subcriticality, source position, and energy is numerically investigated using a simple thermal subcritical model. For the sake of experimental evaluation of ks and , the ADS experiments have been carried out in the subcritical systems combined with 14MeV pulsed neutrons of the Kyoto University Critical Assembly (KUCA). The ks and parameters are successfully measured by utilizing the reaction rate distribution obtained by the optical fiber detectors in the subcritical system, within a relative difference of less than 7% and 12% for ks and , respectively, between measured and calculated values for most studied cases. [Copyright &y& Elsevier]

• An experimental model of the radial expansion reactivity in a SFR was proposed. • The model reflects well the spectral component of the radial expansion reactivity. • Measured reactivities during experiment were compared with calculated values. • The difference in the calculation/experiment ratio vary from −4.3% to 9.2%. For a metal-fueled SFR (Sodium-cooled Fast Reactor), the negative reactivity feedback due to the thermal expansion of the support grid which is known as a radial expansion reactivity, provides a principal safety mechanism in most severe accidents. In this paper, an experimental model of the radial expansion reactivity in a metal-fueled SFR is proposed, and experimental models are established in a collaboration between Korea Atomic Energy Research Institute (KAERI) and Institute for Physics and Power Engineering (IPPE). Modeling of the radial expansion reactivity in a realistic experiment condition is very difficult due to physical limitation of experimental facility. Hence, a sparse perturbation method suggested by authors was employed for reasonable modeling of the radial expansion phenomenon. Measured values were compared with calculated ones using the MCNP transport code with the ENDF/B-VII.0 library. The energy-dependent radial expansion reactivity components of the planned experimental model showed good agreement with those of the target Prototype Gen IV SFR core. Errors of C/M (calculation/measurement ratios) varied from −4.3% to 9.2%. Considering the 1 σ uncertainty in the C/M, 5% in maximum, errors of calculation/measurement ratios were within 2 σ uncertainty range. [ABSTRACT FROM AUTHOR]