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This presentation is on the SG 51 Proposal: unresolved evaluations. This lecture includes URR evaluations with a look at measurements, linking RRR and URR, and unified RRR and URR. This talk ends with a discussion.
This presentation discusses the ENDF format and its implication for experimental data. The effect of self-shielding on measured cross sections some call this effect transmission enhancement (to be explained). Additionally discussed: from experiment to evaluation. And finally, Processing “high energy resolution” transmission for URR evaluation.
63,65 Cu angular distributions resolved for ENDF/B-VIII.1, consistent with both differential data and integral benchmark performance. 139 La RRR and URR evaluations will be merged with the LANL high energy evaluation, and to be submitted to the future ENDF-B release (post-VIII.1). 14 N RRR evaluation is planned to produce n+ 14 N, p+ 14 C, and a+ 11 B contributions to be submitted to the future ENDF-B release (post-VIII.1). 181 Ta covariances repaired and reported as intended in an errata to ENDF/B-VIII.1.
The Critical Unresolved Region Integral Experiment (CURIE) critical experiment was performed at the National Criticality Experiments Research Center (NCERC) at the Device Assembly Facility (DAF) at the Nevada Nuclear Security Sites (NNSS) in 2020. The objective of CURIE was to improve the quality of integral nuclear data in the uranium-235 ( 235 U) unresolved resonance region (URR) by performing benchmark integral experiments that were sensitive to the URR energy ranges. The CURIE experiment was evaluated for the International Criticality Safety Benchmark Evaluation Project (ICSBEP) handbook and the benchmark evaluation was accepted in 2022. The URR is a region within the intermediate neutron energy range (the intermediate energy ranges from 0.7 eV to 100 keV). The observed resonance structure in neutron cross sections is due to discrete energy levels in the nucleus and are characterized by resonance parameters. In the URR region, the resonance parameters are only partially resolved as the resolution of the experiment techniques becomes comparable to the average width of the resonances themselves, and the resonances are so close to one another that the structure cannot be determined empirically. The ENDF/B-VIII.0 and JEFF-3.3 nuclear data libraries define the URR as beginning at 2.25 keV and continuing until 25 keV. There are minimal intermediate neutron energy benchmarks available in the ICSBEP benchmark handbook, and aside from CURIE there are none that are highly sensitive in the URR energy region. There is a current need for additional experiments sensitive to the URR energy region. There is a new proposed subgroup for the Organization for Economic Co-operation and Development and Nuclear Energy Agency (OECD NEA) Working Party on International Nuclear Data Evaluation Cooperation (WPEC), so any new models or information will need experimental validation and testing. The NEA Working Party on Nuclear Criticality Safety (WPNCS) recent experimental needs and priority list includes intermediate energy 235 U and 238 U experiments, as does the recent Integral Experiments to Address Nuclear Criticality Safety Needs Meeting (May 2023). A variant on the original CURIE experiment called the Multiple Critical Unresolved Region Integral Experiment (MCURIE) is proposed to provide further investigation of the intermediate and URR energy region for uranium. MCURIE will utilize existing fuels at NCERC but use alternative moderators and reflectors to modify the neutron absorption, scattering, and fission spectra of the experiments, allowing for precise targeting of nuclear data sensitivities. The overall goal of MCURIE is to develop a framework for designing and performing integral benchmark experiments with high sensitivities in the intermediate and URR energy regions for nuclear data validation.
This presentation finds that new measurement at LANSCE combining DANCE and NEUANCE at the end of 2020 and 2021. Additionally, two samples of 10 mg and 20 mg of 233 U have been prepared at LANL by Evelyn M. Bond (December 2020). Data analysis has been finished and results of the capture-to-fission ratio on 233 U in the neutron energy region from 0.7 eV to 250 keV have been provided. The focus was to provide data from 1-300 keV. We are providing data from 0.7 eV to 1 keV in addition. The result has been normalized to the ENDF/B-VIII.0 broadened capture-to-fission cross section ratio in the neutron energy region recommended by the Luiz Leal and Marco Pigni, between 8.1 and 14.7 eV. This is the first measurement of the capture-to-fission ratio between 2 - 30 keV. The data show some small differences in the RRR with the evaluation though the general trend is consistent. In the URR this data shows a smaller capture-to-fission ratio than the evaluation from 10 to 150 keV
Uranium-233 plays an important role in the Th-U fuel cycle, which has been proposed as an alternative to the U-Pu fuel cycle due to its reduced amount of transuranium elements. The available experimental 233 U(n,γ) cross section data in the literature are scarce [1, 2, 3], from which the capture to fission ratio is shown in figure 1. In 2008, the 233 U(n,γ) cross section was investigated at LANL using the DANCE detector combined with a PPAC, however the statistics in the keV regime were inadequate for a reliable extraction of the cross section at 100 keV. Large discrepancies are found between the evaluations, especially in the Unresolved Resonance Region (URR), see figure 1. An accurate measurement of the 233 U(n,γ) cross section is required by the NCSP to complete the neutron-induced cross section data; a new evaluation reported the need of 233 U capture data.
There are new evaluation methods being explored for combined RRR + URR. Simple example demonstrated in SAMMY code using. Potential to be applied to future LoFi, Medium-Fi covariance efforts. Much more work needs to be done to fully correlate regions.
NASA has specific processes and requirements that must be followed for tests involving human subjects to be conducted in a safe and effective manner. There are five distinct phases of test operations. Phase one, the test request phase, consists of those activities related to initiating, processing, reviewing, and evaluating the test request. Phase two, the test preparation phase consists of those activities related to planning, coordinating, documenting, and building up the test. Phase three, the test readiness phase consists of those activities related to verifying and reviewing the planned test operations. Phase four, the test activity phase, consists of all pretest operations, functional checkouts, emergency drills, and test operations. Phase five, the post test activity phase, consists of those activities performed once the test is completed, including briefings, documentation of anomalies, data reduction and archiving, and reporting. Project management processes must be followed for facility modifications and major test buildup, which include six phases: initiation and assessment, requirements evaluation, preliminary design, detailed design, use readiness review (URR) and acceptance. Compliance with requirements for safety and quality assurance are documented throughout the test buildup and test operation processes. Tests involving human subjects must be reviewed by the applicable Institutional Review Board (IRB).
Minimal updates to current capabilities (SAMMY/AMPX) and to the ENDF format are proposed to include threshold reaction for outgoing charged-particle channels in the URR formalism. If average resonance parameters are reported, probability tables for newly defined reactions channels may be needed, implemented, and tested. Nuclear data evaluation of n+ 35 Cl reactions can be considered the best case to apply the proposed updates.
Satellite XCO 2 retrievals could improve the estimates of surface carbon fluxes, but it remains unknown on what scales these estimates are robust. Here, we use the time-dependent Bayesian synthesis top-down method and prior net ecosystem exchanges (NEEs) from 12 terrestrial biosphere models (TBMs) to infer the monthly carbon fluxes of 51 land regions with constraints by GOSAT XCO 2 retrievals. We find that the uncertainty (standard deviation of 12 TBMs) reduction rates (uncertainty reduction rate (URR)) decrease significantly at decreasing spatial scales. On the continental-scale, the mean URR is about 57%, and the annual and seasonal cycle estimates of NEE are rather robust. The evaluation shows that the posterior CO 2 concentrations are significantly improved at the continental scale. Our study suggests that the GOSAT XCO 2 can only promise a robust continental-scale NEE estimate and improving the XCO 2 accuracy is an effective way to achieve robust estimates on smaller scales under current spatial coverage.
This presentation touches on the covariance data in unresolved range. This presentation talks about how the URR has several limitations and the focus on covariance information. The talk briefly outlines the limitations and fosters a discussion that can lead to format proposals.
This presentation discusses SAMMY releases and states that all of its dependencies are freely available. It also discusses version control and confirms that versions will be tagged as needed. Additionally, SAMMY program flow is discussed and states that the program flow was improved to allow for easier external access to SAMMY routines. Modernization of SAMMY is continued with the Doppler and Resolution broadening modules. The presentation concludes by stating that documentation updates are in progress.
This presentation provides overviews of uraniums, 233 U and 235 U, plutonium research including motivations, current status in ENDF/B-VIII.0, the inclusion of sub-thermal data, and the inclusion of LANL ratio capture-to-fission data. Additionally, the preliminary fit of Mosby’s data as reported, fluctuating neutron multiplicities, uncertainty in evaluated libraries, and experimental effects are also presented. The presentation concludes by providing a summary of plans for the U and Pu evaluation work.