[en] Experience with Type C thermocouples operating for long periods in the 1400 to 1600 C temperature range indicate that significant decalibration occurs, often leading to expensive downtime and material waste. As part of an effort to understand the mechanisms causing drift in these thermocouples, the Idaho National Laboratory conducted a long duration test at 1500 C containing eight Type C thermocouples. As report in this document, results from this long duration test were adversely affected due to oxygen ingress. Nevertheless, results provide key insights about the impact of precipitate formation on thermoelectric response. Post-test examinations indicate that thermocouple signal was not adversely impacted by the precipitates detected after 1,000 hours of heating at 1,500 C and suggest that the signal would not have been adversely impacted by these precipitates for longer durations (if oxygen ingress had not occurred in this test)

[en] Because of the impact that melt relocation and vessel failure may have on subsequent progression and associated consequences of a Light Water Reactor (LWR) accident, it is important to accurately predict heating and relocation of materials within the reactor vessel, heat transfer to and from the reactor vessel, and the potential for failure of the vessel and structures within it. Accurate predictions of such phenomena require high temperature thermal and structural properties. However, a review of vessel and structural steel material properties used in severe accident analysis codes reveals that the required high temperature material properties are extrapolated with little, if any, data above 1000 K. To reduce uncertainties in predictions relying upon extrapolated high temperature data, Idaho National Laboratory (INL) obtained high data for two metals used in LWR vessels: SA 533 Grade B, Class 1 (SA533B1) low alloy steel, which is used to fabricate most US LWR reactor vessels; and Type 304 Stainless Steel SS304, which is used in LWR vessel piping, penetration tubes, and internal structures. This paper summarizes the new data, and compares it to existing data

[en] This paper will introduce and demonstrate the 'Risk-Informed' criticality process developed to investigate the pre and post closure potential for criticality at a high-level waste repository. This process is based on the US Nuclear Regulatory Commission (NRC), Title 10 Code of Federal Register (CFR) Part 63. The risk-informed, performance-based methodology presented is consistent with the Code of Federal Regulations (CFR) Title 10, Part 63 (64 FR 8640). Part 10 CFR 63 specifies the overall performance objectives of the potential repository at Yucca Mountain prior to closure and during postclosure. The overall performance of the repository is specified for postclosure (10 CFR 63.113) in terms of expected annual dose to the average member of the critical group. There are no specific design criteria for postclosure criticality control in 10 CFR 63. This regulation is a risk-informed, performance-based regulation, which treats criticality as one of the processes or events that must be considered for the overall system performance assessment. (author)

[en] At the Los Alamos Neutron Science Center (LANSCE), spallation neutrons are produced by an 800-MeV proton beam interacting with tungsten targets. Gun-barrel-type penetrations through the heavy concrete and steel shielding that surround the targets collimate neutrons to form neutron beams used for scattering experiments. Two liquid hydrogen moderators of one-liter volume each are positioned adjacent to the neutron-production targets. Some of the neutrons that pass through a moderator interact with or scatter from protons in the hydrogen. The neutron-proton interaction reduces the energy or moderates neutrons to lower energies. Lower energy 'moderated' neutrons are the most useful for some neutron scattering experiments. We provide a description of the LANSCE hydrogen-moderator system and its cryogenic performance with proton beams of up to 125 micro-amp average current

[en] Angular correlation measurements have been made between the deuterons and the ¹²C g.s. product nuclei in the reaction ¹³C(p,d)¹²C^*(15.11 MeV, 1⁺)(→ ¹²C g.s. + γ) at deuteron scattering angles of 40⁰, 50⁰, 60⁰, and 75⁰, and a proton bombarding energy of 41.3 MeV. These measurements yield information concerning the k=2 polarisation tensors (t_2q) of the excited ¹²C nucleus produced in the direct (p,d) reaction. Cross-section angular distributions to the strongly excited g.s., 4.43, 12.71, 15.11 and 16.11 MeV states are also reported. Monte Carlo simulations of the laboratory distribution functions associated with the individual t_kq were performed, incorporating the effects of finite geometry (beam spot and detector sizes), beam divergence, energy loss and multiple scattering of the ¹²C nuclei in the target. Finite range DWBA calculations were perfomed describing the polarisation tensors and cross sections, assuming a 1p neutron pickup. DWBA calculations for both conventional (elastic) and adiabatic d + ¹²C potentials were performed. Also, the effects of spin-orbit and the T_r and T_l tensor potential were studied. The results confirmed that the ''standard'' DWBA formalism using an elastic d + ¹²C potential is inadequate for describing the recoil nucleus polarization. The use of adiabatic potentials, which arise from three-body effects, produced an improvement in the description of the extracted data. The DWBA calculations showed only a modest sensitivity to inclusion of spin-orbit and the T_r and T_l tensor terms in the deuteron optical potential. (orig.)

[en] The authors deduced a time dispersion of (0.49+-0.03) ns (fwhm) for the combined effects of the burst width and the residual phase drift after phase compensation of the 135 MeV proton beam at the IUCF. This result is based on cosmic-ray coincidence measurements yielding an intrinsic time resolution of (334+-13) ps (fwhm) for a 5 in. X 40 in. NE-102 counter; on an observed time resolution of 0.66 ns (fwhm) for prompt γ-rays produced by 135 MeV protons on C; and on the assumption that the various time dispersions combine in quadrature. Also the measured width of 0.83 ns (fwhm) for 116 MeV neutrons from the ¹²C(p,n)¹²N(g.s.) reaction at 135 MeV is consistent with the above values for the detector and beam contributions. Effective detector thicknesses of 90 mm and 79 mm were deduced for the γ-ray and neutron data, respectively. The smaller effective thicknesses result from charged recoils exiting the counter without depositing enough energy to be detected above the threshold. (Auth.)

[en] The cross-sections, vector analysing powers, and proton polarisation have been measured for the ¹¹⁶Sn(d vector, p)¹¹⁷Sn reaction at 12.2 and 15.1 MeV. Optical model analyses have been performed for the elastic scattering data. The reaction data have been compared with DWBA calculations. The analysis also includes the data previously obtained by Cadmus and Haeberli for the same reaction at 8.2 MeV. (orig.)

[en] Parity non-conservation was studied for seventeen states in the compound nucleus ²³⁹U by measuring the helicity dependence of the p-wave resonance cross section for epithermal neutrons scattered from ²³⁸U. The root-mean-squared parity-violating matrix element for the mixing of p-wave and s-wave states was determined to be M = 0.58_-0.25^+0.50 meV. This corresponds to a parity-violating spreading width of Γ^PV = 1.0 x 10^-7 eV. This gives a value of 4 x 10^-7 for α_p, the ratio of strengths of the P-odd and P-even effective nucleon-nucleon interactions in ²³⁹U. In this paper the implications of these results for studies of Time Reversal Symmetry in the compound nucleus is discussed

[en] The capability of performing accurate absolute measurements of neutron beam polarization opens a number of exciting opportunities in fundamental neutron physics and in neutron scattering. At the LANSCE pulsed neutron source we have measured the neutron beam polarization with an absolute accuracy of 0.3% in the neutron energy range from 40 meV to 10 eV using an optically pumped polarized ³He spin filter and a relative transmission measurement technique. ³He was polarized using the Rb spin-exchange method. We describe the measurement technique, present our results, and discuss some of the systematic effects associated with the method

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