[en] The work performed under this giant included an analysis of the multiple-step helium production mechanism discovered in iron following long-term mixed-spectrum reactor exposure, the measurement of a large number of samples irradiated in fast-neutron environments for cross section determinations, the initial mapping of the neutron fluence distribution for a high-fluence T(d,n) irradiation experiment, the initial measurements of helium production in materials irradiated by 10-MeV neutrons, and the initiation of a joint experiment with ANL to measure the spectrum-integrated Be(n,2n) cross section at lower neutron energies. This work is summarized in the present report. The work is ongoing, and this document thus provides a status report rather than final numerical data

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[en] The objectives of this work are to apply helium accumulation neutron dosimetry to the measurement of neutron fluences and energy spectra in mixed-spectrum fission reactors utilized for fusion materials testing, and to measure helium generation rates of materials in these irradiation environments. Helium generation measurements have been made for several Fe, Cu Ti, Nb, Cr, and Pt samples irradiated in the mixed-spectrum High Flux Isotope Reactor (HFIR) and Oak Ridge Research Reactor (ORR) at the Oak Ridge National Laboratory. The results have been used to integrally test the ENDF/B-V Gas Production File, by comparing the measurements with helium generation predictions made by Argonne National Laboratory using ENDF/B-V cross sections and adjusted reactor spectra. The comparisons indicate consistency between the helium measurements and ENDF/B-V for iron, but cross section discrepancies exist for helium production by fast neutrons in Cu, Ti, Nb, and Cr (the latter for ORR). The Fe, Cu, and Ti work updates and extends previous measurements

[en] Helium generation measurements have been performed for Fe, Cu, and Ti samples irradiated in the Experimental Breeder Reactor-II (EBR-II) experiment X287 and for iron samples irradiated in the Oak Ridge Research Reactor (ORR) experiment MFE4A2. These measurements are part of a program to measure total helium production rates over the range of fission reactor spectra and fluences used for fusion materials testing, and to use the results for integral cross section testing. The present results are significantly different from the ENDF/B-V cross section evaluations for all three materials, with the largest difference being for titanium (approx. 270%). The Ti and Cu samples from EBR-II also contained significant quantities of ³He, presumably accumulated by the absorption and subsequent decay of tritium from the reactor environment

[en] Helium generation measurements have been made for Ti and Cu samples irradiated in the Oak Ridge Research Reactor (ORR) experiment MFE4A2. The results are significantly different from helium generation predictions based on ENDF/B-V cross section evaluations, providing evidence that the ENDF/B-V files for helium generation in Ti and Cu require revision for fission reactor neutron spectra. Similar discrepancies have previously been observed in analyses of samples irradiated in the Experimental Breeder Reactor-II (EBR-II). Measurements were also made using platinum-encapsulated samples to test helium retention in Ti, Cu, and Fe in the severe ORR irradiation environment. Preliminary results show less than 1% loss from iron, but losses of approx.3.5% and approx.6% from Ti and Cu, respectively

[en] This paper reports the first direct measurement of ¹⁰B capture rate in a mockup control rod in a critical assembly. The experiment used the helium accumulation fluence monitor (HAFM) technique. 13 refs

[en] Spectrum integrated cross sections for ⁶Li and ¹⁰B from five benchmark fast reactor neutron fields are compared with calculated values obtained using the ENDF/B-V Cross Section Files. The benchmark fields include the Coupled Fast Reactivity Measurements Facility (CFRMF) at the Idaho National Engineering Laboratory, the 10% Enriched U-235 Critical Assembly (BIG-10) at Los Alamos National Laboratory, the Sigma-Sigma and Fission Cavity fields of the BR-1 reactor at CEN/SCK, and the Intermediate Energy Standard Neutron Field (ISNF) at the National Bureau of Standards. Results from least square analyses using the FERRET computer code to obtain adjusted cross section values and their uncertainties are presented. Input to these calculations include the above five benchmark data sets. These analyses indicate a need for revision in the ENDF/B-V files for the ¹⁰B and ⁶Li cross sections for energies above 50 keV

[en] Information is presented concerning the development and performance testing of helium accumulation fluence monitors and the measurement of helium distribution in irradiated unfueled Type 316 stainless steel fuel cans

[en] Information is presented concerning the development and performance testing of helium accumulation fluence monitors

[en] A tritium extraction facility has been built for the purpose of measuring the absolute tritium concentration in neutron-irradiated lithium metal samples. Two independent calibration procedures have been used to determine what fraction, if any, of tritium is lost during the extraction process. The first procedure compares independently measured ⁴He and ³H concentrations from the ⁶Li(n,α)T reaction. The second procedure compared measured ⁶Li(n,α)T/¹⁹⁷Au (n,γ)¹⁹⁸Au thermal neutron reaction rate ratios with those obtained from Monte Carlo calculations using well-known cross sections. Both calibration methods show that within experimental errors (approx. 1.5%) no tritium is lost during the extraction process