JEFF, NEA WPEC Subgroup 27
Impact:
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.
Accuracy:
7.5% on the total gamma energy. 7.5% on the multiplicity.
Best accuracy achievable for the gamma spectrum shape.
Justification document:
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.
Comment from requester:
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.
Review comment:
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.
Entry Status:
Work in progress (as of SG-C review of May 2018)
Pending new evaluation or validation (as of SG-C review of June 2019)
Pending new evaluation or validation (as of SG-C review of May 2021) with recommendations for priority validation of the latest evaluations
Completed (as of SG-C review of May 2022) - The characteristics of the PFGS have been measured at thermal and fast energies for both U-235 and Pu-239. Experimental data have been combined with model calculations to evaluate the prompt gamma properties as a function of incident neutron energy for JEFF-3.3 and ENDF/B-VIII.0.
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Experiments
- A. Chyzh, et al., Total prompt g-ray emission in fission of U-235, Pu-239,241, and Cf-252, PRC 90 (2014) 014602, EXFOR 14361
- S. Oberstedt, et al., Future research program on prompt g-ray emission in nuclear fission, Eur. Phys. J. A (2015) 51:178
- A. Gatera, et al., Prompt-fission g-ray spectral characteristics from 239Pu(nth,f), PRC 95 (2017) 064609
Theory/Evaluation
- O. Serot et al., Prompt Fission Gamma Spectra and Multiplicities for JEFF-3.3, JEF/DOC-1828, JEFF Meeting, OECD, Paris (2017)
- D. Brown et al., ENDF/B-VIII.0: The 8th Major Release of the Nuclear Reaction Data Library with CIELO-project Cross Sections, New Standards and Thermal Scattering Data, NDS 148 (2018) 1
- I. Stetcu et al., Evaluation of the Prompt Fission Gamma Properties for Neutron Induced Fission of U-235,238 and Pu-239, NDS 163 (2020) 261
- A. Tudora, Prompt gamma-ray results of two deterministic modelings of prompt emission in fission, Eur. Phys. J. A 56 (2020) 128
Additional file attached:HPRLgammafission.pdf
Additional file attached:
| Request ID | 19 |
Type of the request | High Priority request |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 94-PU-238 | (n,f) SIG | 9 keV-6 MeV | | See details | Y |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action |
| Fission | Fast Reactors (ADMAB) | 31-MAR-08 | 11-SEP-08 | Y |
Requester: Prof. Massimo SALVATORES at CADARACHE, FR
Email:
Project (context): NEA WPEC Subgroup 26
Impact:
Design phases of selected reactor and fuel cycle concepts require improved data and methods in order to reduce margins for both economical and safety reasons. A first indicative nuclear data target accuracy assessment was made within WPEC Subgroup 26 (SG-26). The assessment indicated a list of nuclear data priorities for each of the systems considered (ABTR, SFR, EPR, GFR, LFR, ADMAB, VHTR, EPR). These nuclear data priorities should all be addressed to meet target accuracy requirements for the integral parameters characterizing those systems (see the accompanying requests originating from SG-26).
The request for the improved cross section and uncertainties for 238Pu(n,f) emerges for five of the eight cases studied. The most stringent requirements for this case arise from the SFR, LFR and ADMAB.
Improvements of the nuclear data for 238Pu(n,f) are important for estimates of keff for the SFR, LFR, ADMAB and GFR (in order of significance), the peak power of ADMAB and the void coefficient of an SFR.
Requested accuracy is required to meet target accuracy for burnup for an Accelerator-Driven Minor Actinides Burner (ADMAB). Details are provided in the SG-26 report: "Uncertainty and Target Accuracy Assessment for Innovative Systems Using Recent Covariance Data Evaluations" (link to WPEC Subgroup 26 Report in PDF format, 6 Mb).
Accuracy:
Target accuracies are specified per system and per energy group when they are not met by the BOLNA estimate of the current (initial) uncertainties.
| Energy Range | Initial versus target uncertainties (%) |
| Initial | SFR | EFR | GFR | LFR | ADMAB |
| 2.23 - 6.07 MeV | 21 | 6 | | 7 | 8 | 7 |
| 1.35 - 2.23 MeV | 34 | 6 | 24 | 8 | 7 | 6 |
| 0.498 - 1.35 MeV | 17 | 3 | 10 | 5 | 3 | 3 |
| 183 - 498 keV | 17 | 4 | 12 | 6 | 3 | 4 |
| 67.4 - 183 keV | 9 | 5 | | | 5 | |
| 24.8 - 67.4 keV | 12 | 6 | | 7 | 6 | |
| 9.12 - 24.8 keV | 11 | 7 | | 7 | 7 | |
Justification document:
OECD/NEA WPEC Subgroup 26 Final Report: "Uncertainty and Target Accuracy Assessment for Innovative Systems Using Recent Covariance Data Evaluations" (link to WPEC Subgroup 26 Report in PDF format, 6 Mb).
Comment from requester:
Given the present state of knowledge the above target accuracies are very tight. However, any attempt that significantly contributes to reducing the present accuracy for this quantity is strongly encouraged. Any such attempt will significantly enhance the accuracy with which reactor integral parameters may be estimated and will therefore impact economic and safety margins.
Review comment:
Entry Status:
Work in progress (as of SG-C review of May 2018)
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Experiments
- T. Granier et al., New measurement of the 238Pu(n,f) cross-section, AIP Conf. Proc. 1175 (2009) 227, EXFOR 14273
- J.J. Ressler et al., Surrogate measurement of the 238Pu(n,f) cross section, PRC 83 (2011) 054610, EXFOR 14292
- R.O. Hughes et al., 236Pu(n,f), 237Pu(n,f), and 238Pu(n,f) cross sections deduced from (p,t), (p,d), and (p,p') surrogate reactions, PRC 90 (2014) 014304, EXFOR 14396
- A. Pal et al., Determination of 238Pu(n,f) and 236Np(n,f) cross sections using surrogate reactions, PRC 91 (2015) 054618, EXFOR 33095
- Ongoing work by a CENBG-CEA-IPNO+ collaboration on surrogate measurements
Theory/Evaluation
- M.B. Chadwick et al., ENDF/B-VII.1 Nuclear Data for Science and Technology: Cross Sections, Covariances, Fission Product Yields and Decay Data, p.2937 in NDS 112 (2011) 2887
- Pu-238 evaluation was proposed to be part of INDEN (CIELO follow-up) initial program of work (as of Dec. 2017)
Validation
Additional file attached:SG26-report.html
Additional file attached:
| Request ID | 35 |
Type of the request | High Priority request |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 94-PU-241 | (n,f) SIG | 0.5 eV-1.35 MeV | | See details | Y |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action |
| Fission | Fast and Thermal Reactors | 04-APR-08 | 12-SEP-08 | Y |
Requester: Prof. Massimo SALVATORES at CADARACHE, FR
Email:
Project (context): NEA WPEC Subgroup 26
Impact:
Distinct requests for this fission cross section are made at higher energies for fast reactor applications and also at lower energies for thermal reactor applications. Requested accuracy is required to meet target accuracy for k-eff for the GFR, SFR, LFR and ABTR and to meet k-eff and burnup for EFR. Requested accuracy is also required to meet target accuracy for k-eff for the VHTR and k-eff and burnup for the PWR. Details are provided in the OECD/NEA WPEC Subgroup 26 Final Report: "Uncertainty and Target Accuracy Assessment for Innovative Systems Using Recent Covariance Data Evaluations" (Final Draft attached).
Accuracy:
Target accuracies are specified per system and per energy group when they are not met by the BOLNA estimate of the current (initial) uncertainties. The weighting factor λ is explained in detail in the accompanying document. Changes from the reference value of λ=1 show the the possible allowance for other target uncertainties. Two cases (A and B) are distinguished for λ≠1 (see Table 24 of the report).
| Energy Range | Initial versus target uncertainties (%) |
| Initial | ABTR | SFR | EFR | GFR | LFR | ADMAB | VHTR | EPR |
| | λ=1 | λ≠1,b | λ=1 | λ≠1,b | λ=1 | λ≠1,a | λ=1 | λ=1 | λ=1 | λ=1 | λ≠1,a | λ=1 | λ≠1,a |
|
| 0.498 - 1.35 MeV | 17 | 12 | 9 | 3 | 3 | 8 | 7 | 4 | 4 | 2 | | | | |
| 183 - 498 keV | 14 | 9 | 7 | 3 | 2 | 7 | 6 | 3 | 3 | 2 | | | | |
| 67.4 - 183 keV | 20 | 9 | 7 | 3 | 2 | 6 | 5 | 3 | 3 | 2 | | | | |
| 24.8 - 67.4 keV | 9 | | | 3 | 3 | 6 | 6 | 3 | 3 | 2 | | | | |
| 9.12 - 24.8 keV | 11 | | | 4 | 3 | 7 | 6 | 3 | 4 | 2 | | | | |
| 2.03 - 9.12 keV | 10 | | | 5 | 5 | 8 | 7 | 2 | 5 | 2 | | | | |
| 0.454 - 2.03 keV | 13 | | | 4 | 4 | 7 | 6 | 3 | | 3 | | | | |
| 22.6 - 454 eV | 19 | | | 9 | 8 | | | 5 | | 7 | 6 | 8 | 5 | 6 |
| 0.54 - 4.00 eV | 27 | | | | | | | | | | 9 | 12 | 8 | 10 |
Justification document:
OECD/NEA WPEC Subgroup 26 Final Report: "Uncertainty and Target Accuracy Assessment for Innovative Systems Using Recent Covariance Data Evaluations" (link to WPEC Subgroup 26 Report in PDF format, 6 Mb).
Comment from requester:
Given the present state of knowledge the above target accuracies are very tight. However, any attempt that significantly contributes to reducing the present accuracy for this quantity is strongly encouraged. Any such attempt will significantly enhance the accuracy with which reactor integral parameters may be estimated and will therefore impact economic and safety margins.
Review comment:
See appendix A of the attached report.
Entry Status:
Work in progress (as of SG-C review of May 2018)
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Experiments
- F. Tovesson, T.S. Hill, Cross Sections for 239Pu(n,f) and 241Pu(n,f) in the Range En = 0.01 eV to 200 MeV, Nuclear Science and Engineering 165 (2010) 224, EXFOR 14271
- V.V. Desai, Determination of 241Pu(n,f) cross sections by the surrogate-ratio method, PRC 87 (2013) 034604, EXFOR 33053
Theory/Evaluation
- H. Derrien et al., Reevaluation and Validation of the 241Pu Resonance Parameters in the Energy Range Thermal to 20 eV, NSE 150 (2005) 109
- Pu-241 evaluation was proposed to be part of INDEN (CIELO follow-up) initial program of work (as of Dec. 2017)
Validation
Additional file attached:SG26-report.html
Additional file attached:
| Request ID | 37 |
Type of the request | High Priority request |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 94-PU-240 | (n,f) SIG | 0.5 keV-5 MeV | | See details | Y |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action |
| Fission | Fast Reactors | 15-SEP-08 | 15-SEP-08 | Y |
Requester: Prof. Massimo SALVATORES at CADARACHE, FR
Email:
Project (context): CEA Cadarache
Impact:
Design phases of selected reactor and fuel cycle concepts require improved data and methods in order to reduce margins for both economical and safety reasons. A first indicative nuclear data target accuracy assessment was made within WPEC Subgroup 26 (SG-26). The assessment indicated a list of nuclear data priorities for each of the systems considered (ABTR, SFR, EPR, GFR, LFR, ADMAB, VHTR, EPR). These nuclear data priorities should all be addressed to meet target accuracy requirements for the integral parameters characterizing those systems (see the accompanying requests originating from SG-26).
Accuracy:
Target accuracies are specified per system and per energy group when they are not met by the BOLNA estimate of the current (initial) uncertainties. The weighting factor λ is explained in detail in the accompanying document. Changes from the reference value of λ=1 show the the possible allowance for other target uncertainties. Two cases (A and B) are distinguished for λ≠1 (see Table 24 of the report).
| Energy Range | Initial versus target uncertainties (%) |
| | Initial | SFR | EFR | GFR | LFR | ADMAB |
| | | λ=1 | λ≠1,a | λ≠1,b | λ=1 | λ≠1,a | λ=1 | λ≠1,a | λ=1 | λ≠1,a | λ=1 | λ≠1,a |
|
| 2.23 - 6.07 MeV | 5 | 3 | 3 | 3 | | | 3 | 3 | 3 | 3 | | |
| 1.35 - 2.23 MeV | 6 | 3 | 3 | 2 | | | 3 | 3 | 3 | 3 | 3 | 3 |
| 0.498 - 1.35 MeV | 6 | 2 | 2 | 2 | 4 | 3 | 2 | 3 | 2 | 2 | 2 | 2 |
| 0.454 - 2.03 keV | 22 | 13 | 13 | 11 | | | 9 | 10 | | | | |
Justification document:
OECD/NEA WPEC Subgroup 26 Final Report: "Uncertainty and Target Accuracy Assessment for Innovative Systems Using Recent Covariance Data Evaluations" (link to WPEC Subgroup 26 Report in PDF format, 6 Mb).
Comment from requester:
Given the present state of knowledge the above target accuracies are very tight. However, any attempt that significantly contributes to reducing the present accuracy for this quantity is strongly encouraged. Any such attempt will significantly enhance the accuracy with which reactor integral parameters may be estimated and will therefore impact economic and safety margins.
Review comment:
Entry Status:
Work in progress (as of SG-C review of May 2018)
Pending new evaluation or validation (as of SG-C review of May 2021)
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Experiments
- A.B. Laptev et al., Int. Conf. on Fission and Properties of Neutron-Rich Nuclei, Sanibel Island, USA, p.462, 2007, EXFOR 41487
- F. Tovesson et al., Neutron induced fission of 240,242Pu from 1 eV to 200 MeV, PRC 79 (2009) 014613, EXFOR 14223
- P. Salvador et al., Neutron-induced fission cross section of 240Pu from 0.5 MeV to 3 MeV, PRC 92 (2015) 014620, EXFOR 23281
- F. Belloni et al., Neutron induced fission cross section measurements of 240Pu and 242Pu, EPJ Conf. 146 (2017) 04062
- A. Stamatopoulos et al., Investigation of the 240Pu(n,f) reaction at the n_TOF/EAR2 facility in the 9 meV-6 MeV range, PRC 102 (2020) 014616, EXFOR 23458
- Ongoing work from a JRC-PTB-NPL collaboration and from a CENBG-CEA-JRC collaboration (ANDES and EMRP projects)
Theory/Evaluation
- D. Brown et al., ENDF/B-VIII.0: The 8th Major Release of the Nuclear Reaction Data Library with CIELO-project Cross Sections, New Standards and Thermal Scattering Data, NDS 148 (2018) 1
- Pu-240 evaluation was proposed to be part of INDEN (CIELO follow-up) initial program of work (as of Dec. 2017)
Validation
Additional file attached:SG26-report.html
Additional file attached:
| Request ID | 38 |
Type of the request | High Priority request |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 94-PU-240 | (n,f) nubar | 200 keV-2 MeV | | See details | Y |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action |
| Fission | Fast Reactors | 15-SEP-08 | 15-SEP-08 | Y |
Requester: Prof. Massimo SALVATORES at CADARACHE, FR
Email:
Project (context): CEA Cadarache
Impact:
Design phases of selected reactor and fuel cycle concepts require improved data and methods in order to reduce margins for both economical and safety reasons. A first indicative nuclear data target accuracy assessment was made within WPEC Subgroup 26 (SG-26). The assessment indicated a list of nuclear data priorities for each of the systems considered (ABTR, SFR, EPR, GFR, LFR, ADMAB, VHTR, EPR). These nuclear data priorities should all be addressed to meet target accuracy requirements for the integral parameters characterizing those systems (see the accompanying requests originating from SG-26).
Accuracy:
Target accuracies are specified per system and per energy group when they are not met by the BOLNA estimate of the current (initial) uncertainties. The weighting factor λ is explained in detail in the accompanying document. Changes from the reference value of λ=1 show the the possible allowance for other target uncertainties. Two cases (A and B) are distinguished for λ≠1 (see Table 24 of the report).
| Energy Range | Initial versus target uncertainties (%) |
| Initial | SFR | EFR | GFR | LFR | ADMAB |
| | λ=1 | λ≠1,a | λ≠1,b | λ=1 | λ≠1,a | λ=1 | λ≠1,a | λ=1 | λ≠1,a | λ=1 | λ≠1,a |
|
| 1.35 - 2.23 MeV | 3 | 2 | 2 | 2 | | | | | | | | |
| 0.498 - 1.35 MeV | 4 | 2 | 2 | 1 | 3 | 2 | 2 | 2 | 1 | 1 | 2 | 2 |
| 183 - 498 keV | 5 | 3 | 3 | 3 | | | | | 3 | 3 | | |
Justification document:
OECD/NEA WPEC Subgroup 26 Final Report: "Uncertainty and Target Accuracy Assessment for Innovative Systems Using Recent Covariance Data Evaluations" (link to WPEC Subgroup 26 Report in PDF format, 6 Mb).
Comment from requester:
Given the present state of knowledge the above target accuracies are very tight. However, any attempt that significantly contributes to reducing the present accuracy for this quantity is strongly encouraged. Any such attempt will significantly enhance the accuracy with which reactor integral parameters may be estimated and will therefore impact economic and safety margins.
Review comment:
Entry Status:
Work in progress (as of SG-C review of May 2018)
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Theory/Evaluation
- Pu-240 evaluation was proposed to be part of INDEN (CIELO follow-up) initial program of work (as of Dec. 2017)
Validation
Additional file attached:SG26-report.html
Additional file attached:
| Request ID | 39 |
Type of the request | High Priority request |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 94-PU-242 | (n,f) SIG | 200 keV-20 MeV | | See details | Y |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action |
| Fission | Fast Reactors | 15-SEP-08 | 15-SEP-08 | Y |
Requester: Prof. Massimo SALVATORES at CADARACHE, FR
Email:
Project (context): CEA Cadarache
Impact:
Design phases of selected reactor and fuel cycle concepts require improved data and methods in order to reduce margins for both economical and safety reasons. A first indicative nuclear data target accuracy assessment was made within WPEC Subgroup 26 (SG-26). The assessment indicated a list of nuclear data priorities for each of the systems considered (ABTR, SFR, EPR, GFR, LFR, ADMAB, VHTR, EPR). These nuclear data priorities should all be addressed to meet target accuracy requirements for the integral parameters characterizing those systems (see the accompanying requests originating from SG-26).
Accuracy:
Target accuracies are specified per system and per energy group when they are not met by the BOLNA estimate of the current (initial) uncertainties. The weighting factor λ is explained in detail in the accompanying document. Changes from the reference value of λ=1 show the the possible allowance for other target uncertainties. Two cases (A and B) are distinguished for λ≠1 (see Table 24 of the report).
| Energy Range | Initial versus target uncertainties (%) |
| Initial | SFR | EFR | GFR | LFR | ADMAB |
| | λ=1 | λ≠1,b | λ=1 | λ≠1,a | λ=1 | λ≠1,a | λ=1 | λ≠1,a | λ=1 |
|
| 6.07 - 19.6 MeV | 37 | 15 | 14 | | | | | | | |
| 2.23 - 6.07 MeV | 15 | 5 | 5 | | | 6 | 6 | 7 | 8 | 7 |
| 1.35 - 2.23 MeV | 21 | 5 | 4 | | | 5 | 6 | 7 | 7 | 5 |
| 0.498 - 1.35 MeV | 19 | 4 | 3 | 11 | 9 | 4 | 4 | 4 | 4 | 4 |
| 183 - 498 keV | 19 | 9 | 8 | | | | | | | |
Justification document:
OECD/NEA WPEC Subgroup 26 Final Report: "Uncertainty and Target Accuracy Assessment for Innovative Systems Using Recent Covariance Data Evaluations" (link to WPEC Subgroup 26 Report in PDF format, 6 Mb).
Comment from requester:
Given the present state of knowledge the above target accuracies are very tight. However, any attempt that significantly contributes to reducing the present accuracy for this quantity is strongly encouraged. Any such attempt will significantly enhance the accuracy with which reactor integral parameters may be estimated and will therefore impact economic and safety margins.
Review comment:
Entry Status:
Work in progress (as of SG-C review of May 2018)
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Experiments
- F. Tovesson et al., Neutron induced fission of 240,242Pu from 1 eV to 200 MeV, PRC 79 (2009) 014613, EXFOR 14223
- A. Tsinganis, et al., Measurement of the 242Pu(n,f) Cross Section at the CERN n_TOF Facility, NDS 119 (2014) 58-60
- P. Salvador-Castineira, Neutron-induced fission cross sections of Pu242 from 0.3 MeV to 3 MeV, PRC 92 (2015) 044606, EXFOR 23280
- C. Matei, et al., Absolute cross section measurements of neutron-induced fission of 242Pu from 1 to 2.5 MeV, PRC 95 (2017) 024606, EXFOR 23334
- P. Marini, et al., 242Pu neutron-induced fission cross-section measurement from 1 to 2 MeV neutron energy, PRC 96 (2017) 054604
- F. Belloni et al., Neutron induced fission cross section measurements of 240Pu and 242Pu, EPJ Conf. 146 (2017) 04062
- T. Koegler et al., Fast-neutron-induced fission cross section of 242Pu measured at the neutron time-of-flight facility nELBE, PRC 99 (2019) 024604
Theory/Evaluation
- M. Herman et al., COMMARA-2.0 Neutron Cross Section Covariance Library, Report BNL-94830-2011, Brookhaven National Laboratory (2011)
- Pu-242 evaluation was proposed to be part of INDEN (CIELO follow-up) initial program of work (as of Dec. 2017)
Validation
Additional file attached:SG26-report.html
Additional file attached:
| Request ID | 99 |
Type of the request | High Priority request |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 94-PU-239 | (n,f) nubar | Thermal-5 eV | | 1 | Y |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action |
| Fission | | 23-MAR-18 | 12-APR-18 | Y |
Requester: Dr Roberto CAPOTE NOY at IAEA, AUT
Email: roberto.capotenoy@iaea.org
Project (context):
Impact:
Cf. Ref. [1,2]. A similar, but stronger than in U-235, resonance nubar effect is expected for Pu-239 due to the 1/2 GS spin.
Accuracy:
Accuracy below 1% is required on the evaluated data. New measurements must strive to achieve a relative uncertainty below about 1% on the ratio to Cf-252(sf) nubar, as done in the best past experiments [3].
Statistical precision below about 1% at the resonances is required in order to unambiguously identify resonant fluctuations.
Justification document:
A new evaluation of the PFNS [4] in the thermal energy range has determined a lower value of the average neutron energy than that reported in the existing evaluated nuclear data libraries. This value is in agreement with Rising et al and Neudecker independent evaluations. However, a number of thermal-solution benchmarks has shown that the combined use of the new Thermal Neutron Constants and a softer prompt fission neutron spectrum at thermal energy yields k-eff values that are larger than measurements by a margin that increases as the above-thermal-leakage fraction (ATLF) increases (see Ref. [5]). Therefore a reduced criticality is needed for high-leakages solutions. Such reduced criticality may arises due to the (n,gf) process in Pu-239 resonance nubar.
Unfortunately, only measurements from the 70s and 80s are available, a critical region below 5 eV needs to be remeasured with higher incident-energy resolution and higher accuracy and precision to improve existing evaluated data files.
References
- M.T. Pigni, et al., n+235U resonance parameters and neutron multiplicities in the energy region below 100 eV, EPJ Web of Conferences 146, 02011 (2017)
- E. Fort et al., Evaluation of prompt nubar for 239Pu: Impact for applications of the fluctuations at low energy, Nuclear Science and Engineering 99, 375 (1988)
- Gwin et al., Measurements of the energy dependence of prompt neutron emission from 233U, 235U, 239Pu, and 241Pu for En = 0.005 to 10 eV relative to emission from spontaneous fission of 252Cf, Nuclear Science and Engineering 87, 381 (1984)
- R. Capote, et al., Prompt Fission Neutron Spectra of Actinides, Nuclear Data Sheets 131, 1-106 (2016)
- C. De Saint Jean (coordinator), Co-ordinated Evaluation of Plutonium-239 in the Resonance Region, Nuclear Energy Agency, International Evaluation Cooperation, NEA/WPEC-34, Report NEA/NSC/WPEC/DOC(2014)447 (2014)
Comment from requester:
Additionally to changes in nubar changes in resonance parameters may be required. We cannot split those effects on studied criticality benchmarks.
Review comment:
Entry Status:
Work in progress (as of SG-C review of May 2018)
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Experiments
- F.J. Hambsch, et al., Prompt fission neutron emission in resonance fission of 239Pu, ND2004, Santa Fe (NM), USA, September 2004, AIP 769 (2005) 644
Theory/Evaluation
- J.E. Lynn, P. Talou and O. Bouland, Reexamining the role of the (n,gf) process in the low-energy fission of 235U and 239Pu, PRC 97 (2018) 064601
Additional file attached:
Additional file attached: