| Request ID | 4 | Type of the request | High Priority request | ||
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 92-U-235 | (n,f) prompt g | Thermal-Fast | Eg=0-10MeV | 7.5 | Y |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action | |
| Fission | LWR, Gen-IV | 10-MAY-06 | 12-MAY-06 | Y | |
Requester: Prof. Gerald RIMPAULT at CAD-DER, FR
Email: gerald.rimpault@cea.fr
Project (context): JEFF, NEA WPEC Subgroup 27
Impact:
Accuracy:
Justification document:
Comment from requester:
Review comment:
Entry Status:
Main references: Experiments Theory/Evaluation Additional file attached:HPRLgammafission.pdf
Requester: Dr Yasunobu NAGAYA at JAEA, JPN
Project (context): JENDL, NEA WPEC Subgroup 29
Impact:
Accuracy:
Justification document:
Comment from requester:
Review comment:
Entry Status:
Main references: Experiments Theory/Evaluation Validation Additional file attached:U235proposal.pdf
Requester: Dr Roberto CAPOTE NOY at IAEA, AUT
Project (context):
Impact: Improvements in the standard cause all measurements relative to that standard to be improved. See Ref. [1].
Accuracy: 5% of the cross-section
Justification document: There are discrepancies (see Fig. 24 in section III.E, pp.161-162 of Ref. [1]) between different theoretical calculations, data estimated from the (p,f) reaction, and the only measured data set of U-238(n,f) cross section at those energies [2]. New measurements of absolute cross sections of U-235 or U-238 (n,f) and/or U-235 or U-238 (p,f) reactions in the energy range where pion channels begin to play an important role (100-500 MeV) are needed to solve the discrepancies and to reduce the uncertainties of the Neutron Standards in that energy range. References
Comment from requester: At high-energy the (n,f) cross-section can be inferred with rather low uncertainty from (p,f) cross-section measurements, and thanks to this can be used in the neutron standards evaluation.
Review comment:
Entry Status:
Main references: Experiments Theory/Evaluation
The four fast reactor systems of GenIV feature innovative core characteristics for which gamma-ray heating estimates for non-fuel zones require an uncertainty of 7.5% [1]. For the experimental Jules Horowitz Reactor (RJH) at Cadarache a similar requirement appears [2]. Recent studies show evidence of discrepancies on integral measurement in MASURCA, EOLE and MINERVE, from which it is clear that the expectations for GenIV systems and the RJH thermal reactor are not met [3]. Gamma-ray energy release is dominated by Pu-239 and U-235.
7.5% on the total gamma energy
7.5% on multiplicity
Best accuracy achievable for the gamma spectrum shape
Reference 1: G. Rimpault, Proc. Workshop on Nuclear Data Needs for Generation IV, April 2005, Antwerp, Belgium
Reference 2: D. Blanchet, Proc. M&C 2005, Int. Topical Meeting on Mathematics and Computation, Supercomputing, Reactor Physics and Nuclear and Biological Applications, Sep. 2005, Avignon, France
Reference 3: 'Needs for accurate measurements of spectrum and multiplicity of prompt gammas emitted in fission', G. Rimpault, A. Courcelle and D. Blanchet, CEA/Cadarache – DEN/DER/SPRC.
Forty percent of the total gamma-ray energy release results from prompt decay of fission products. No comprehensive analytic expressions exist and Hauser-Feshbach model calculations are involved and presently lack sufficient knowledge to warrant a solution of the problem. New measurements would be needed to guide new evaluation efforts. Present evaluations are based on measurements from the seventies.
Discrepancies observed for C/E ratios in various benchmarks range from 10 to 28%. The request is well motivated and based on a considerable effort.
Work in progress (as of SG-C review of May 2018)
Pending new evaluation or validation (as of SG-C review of June 2019)
Please report any missing information to hprlinfo@oecd-nea.org
Additional file attached:
Request ID 12
Type of the request High Priority request
Target Reaction and process Incident Energy Secondary energy or angle Target uncertainty Covariance
92-U-235 (n,g) SIG,RP 100 eV-1 MeV 3 Y
Field Subfield Date Request created Date Request accepted Ongoing action
Fission FBR, Thermal reactors 29-AUG-07 06-NOV-07
Email: nagaya.yasunobu@jaea.go.jp
U-235 cross sections are very important not only for major thermal reactors but for FBRs because lots of critical experiments for FBRs have been performed at critical assemblies where UO2 fuels are used as driver fuels. Experimental data obtained at such critical assemblies have a great impact on design work for FBRs. Recent studies show that calculated sodium void reactivity worths for BFS experiments underestimate the experimental results by 30-50% [1].
The significant discrepancies not only exceed the target accuracy of 20% for a FBR design but also deteriorate the design accuracy estimated with the cross-section adjustment and bias factor techniques. Thus such experimental data cannot be employed in these techniques.
The requested accuracies (relative one standard deviation) are given for energy-averaged cross sections as follows:
Energy interval and accuracy
100eV - 500eV: 5%
500eV - 1keV: 5%
1keV -2.25keV: 5%
2.25keV- 5keV: 8%
5keV - 10keV: 8%
10keV - 20keV: 8%
20keV - 30keV: 8%
30keV - 40keV: 3%
40keV - 90keV: 3%
90keV -200keV: 3%
200keV-400keV: 3%
400keV-900keV: 3%
900keV - 1MeV: 3%
(It is assumed that the resolved resonance region is below 2.25 keV and the unresolved resonance region is between 2.25 keV and 30 keV. The boundaries for the resonance regions are the same as for JENDL-3.3.)
Reference 1: first attached document, O. Iwamoto, "WPEC Subgroup Proposal" JAEA, March 9 (2007).
Reference 2: second attached document, viewgraph for Dr. Iwamoto's proposal at the 19th WPEC meeting.
The re-evaluation of U-235 cross sections has been already proposed at the 19th WPEC meeting on 18 - 20 April 2007, at the NEA Headquarters, Issy-les-Moulineaux, France.
The proposal seems well motivated. Concerns were expressed in view of the recent changes to the evaluation that emerged from the activities of NEA/WPEC Subgroup 22 "Nuclear Data for Improved LEU-LWR Reactivity Predictions" and ENDF/B-VII benchmarking. The wider impact that new evaluations of U-235 will have, should be considered and duly accounted for by new efforts. Although, the sensitivity of the cross section for the target application is well argued, the documentation does not reveal if the problem must be uniquely attributed to the capture cross section of U-235 in the specified energy range.
Work in progress (as of SG-C review of May 2018)
Completed (as of SG-C review of June 2019) - The request was related to an issue in the keV region identified by the JENDL project in the early 2000's. Some preliminary evaluation work was performed in the framework of WPEC/SG29 [Iwamoto:2011]. The new measurements performed at LANSCE [Jandel:2012], RPI [Danon:2017] and n_TOF [Balibrea:2017] have been used in the CIELO evaluation [Capote:2018]. The issue is now solved in all major libraries (JENDL-4.0, JEFF-3.3, ENDF/B-VIII.0).
Please report any missing information to hprlinfo@oecd-nea.org
Additional file attached:Viewgraph.U235proposal.pdf
Request ID 100
Type of the request Special Purpose Quantity
Target Reaction and process Incident Energy Secondary energy or angle Target uncertainty Covariance
92-U-235 (n,f),(p,f) SIG 100 MeV-500 MeV 5 Y
Field Subfield Date Request created Date Request accepted Ongoing action
Standard ADS 23-MAR-18 11-APR-18 Y
Email: roberto.capotenoy@iaea.org
Work in progress (as of SG-C review of May 2018)
Please report any missing information to hprlinfo@oecd-nea.org