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 improved cross sections and emission spectra and their accuracies for 238U(n,inel) is an important issue that emerges for five of the eight cases studied. The most stringent requirements for this case arise from the GFR and the LFR.
Improvements of the nuclear data for 238U(n,inel) are important for estimates of keff for the GFR, LFR, ABTR and SFR (in order of significance), the peak power of a GFR and the void coefficient of an SFR.
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 | ABTR | SFR | EFR | GFR | LFR |
| 6.07-19.6 MeV | 29 | 12 | | | 7 | |
| 2.23-6.07 MeV | 20 | 3 | 5 | 4 | 2 | 3 |
| 1.35-2.23 MeV | 21 | 4 | 5 | 4 | 2 | 2 |
| 0.498-1.35 MeV | 12 | 7 | 6 | 5 | 2 | 2 |
| 67.4-183 keV | 11 | 7 | | 9 | 7 | 4 |
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. This request is of high priority.
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
- M. Kerveno et al., (n,xn gamma) reaction cross section measurements for (n,xn) reaction studies, EPJ Conferences 42 (2013) 01005, EXFOR 22795
- A.M. Daskalakis et al., Quasi-differential neutron scattering from 238U from 0.5 to 20 MeV, Annals of Nuclear Energy 73 (2014) 455
- M. Kerveno, et al., From gamma emissions to (n,xn) cross sections of interest: the role of GAINS and GRAPhEME in nuclear reaction modelling, Eur. Phys. J. A, 51 12 (2015) 167
- M. Kerveno, et al., Measurement of 238U(n,n'γ) cross section data and their impact on reaction models, Phys. Rev. C 104 (2021) 044605
Theory/Evaluation
- A. Santamarina et al., Improvement of 238U Inelastic Scattering Cross Section for an Accurate Calculation of Large Commercial Reactors, ND2013, Nuclear Data Sheets 118 (2014) 118-121
- R. Capote et al., IAEA CIELO Evaluation of Neutron-induced Reactions on 235U and 238U Targets, NDS 148 (2018) 254
Validation
Additional file attached:SG26-report.html
Additional file attached:
| Request ID | 36 |
Type of the request | High Priority request |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 92-U-238 | (n,g) SIG | 20 eV-25 keV | | See details | Y |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action |
| Fission | Fast and Thermal Reactors | 15-SEP-08 | 15-SEP-08 | |
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 | ABTR | SFR | EFR | GFR | LFR | VHTR | EPR |
| | λ=1 | λ≠1,a | λ≠1,b | 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 | λ=1 | λ≠1,a |
|
| 9.12 - 24.8 keV | 9 | 3 | 2 | 2 | 4 | 3 | 3 | 3 | 2 | 2 | 1 | 2 | 2 | | | 5 | 4 |
| 2.03 - 9.12 keV | 3 | | | | | | | | | 1 | 1 | | | | | | |
| 22.6 - 454 eV | 2 | | | | | | | | | | | | | 1 | 1 | 1 | 1 |
Justification document:
1. 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).
2. OECD/NEA WPEC Subgroup 7 (SG-7) Final Report: "Nuclear data standards" (link to WPEC Subgroup 7 Report in PDF format, 450kb).
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:
In this particular case high accuracy is required throughout the energy range. Only the groups shown above have initial uncertainties larger than the target uncertainties. The low initial uncertainty is a result of the standards evaluation (see SG-7 report above). Concerns have been raised that despite the excellent efforts of this subgroup an independent check is in order to verify the present view on required corrections to experimental work for the unresolved resonance range.
Entry Status:
Completed (as of SG-C review of May 2018) - New time-of-flight measurements have been performed worldwide, e.g., at LANSCE [Ullmann:2014], JRC-Geel [Kim:2016] and n_TOF [Mingrone:2017;Wright:2017]. These experimental data have been used in the CIELO evaluation [Sirakov:2017,Capote:2018] and for the evaluation of the standards [Carlson:2018]. The CIELO evaluated data have been adopted in ENDF/B-VIII.0 and JEFF-3.3; the evaluated uncertainties match the requested accuracy.
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Experiments
- A. Wallner et al., Novel Method to Study Neutron Capture of 235U and 238U Simultaneously at keV Energies, PRL 112 (2014) 192501, EXFOR 23170
- J.L. Ullmann, et al., Cross section and g-ray spectra for 238U(n,g) measured with the DANCE detector array at the Los Alamos Neutron Science Center, PRC 89 (2014) 034603, EXFOR 14310
- H.I. Kim et al., Neutron capture cross section measurements for 238U in the resonance region at GELINA, EPJ A 52 (2016) 170, EXFOR 23302
- F. Mingrone et al., Neutron capture cross section measurement of 238U at the CERN n_TOF facility in the energy region from 1 eV to 700 keV, PRC 95 (2017) 034604, EXFOR 23234
- T. Wright et al., Measurement of the 238U(n,g) cross section up to 80 keV with the Total Absorption Calorimeter at the CERN n_TOF facility, PRC 96 (2017) 064601
Theory/Evaluation
- H. Derrien et al., R-Matrix Analysis of 238U High-Resolution Neutron Transmissions and Capture Cross Sections in the Energy Range 0 to 20 keV, NSE 161 (2009) 131
- R. Dagan et al., Impact of the Doppler Broadened Double Differential Cross Section on Observed Resonance Profiles, ND2013, NDS 118 (2014) 179
- Kopecky et al., Status of Evaluated Data Files for 238U in the Resonance region, JRC Technical Report, EUR 27504 EN (2015)
- I. Sirakov et al., Evaluation of cross sections for neutron interactions with 238U in the energy region between 5 keV and 150 keV, EPJ A 53 (2017) 199
- R. Capote et al., IAEA CIELO Evaluation of Neutron-induced Reactions on 235U and 238U Targets, NDS 148 (2018) 254
- A.D. Carlson et al., Evaluation of the Neutron Data Standards, NDS 148 (2018) 143
Validation
Additional file attached:SG26-report.html
Additional file attached:
| Request ID | 55 |
Type of the request | Special Purpose Quantity |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 92-U-238 | (n,g) SIG/SPA | 235U(n,f) | | 2-5 | Y |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action |
| Dosimetry | Fast fission, D-T fusion | 06-OCT-17 | 06-OCT-17 | |
Requester: Dr Stanislav SIMAKOV at KIT, GER
Email: intersurfen@gmail.com
Project (context): IRDFF project
Impact:
The International Reactor Dosimetry and Fusion File (IRDFF) aims at providing evaluated neutron dosimetry reactions validated for all applications related to fission reactors and fusion technology development [IAEA2017].
Accuracy:
2%-5%
Justification document:
Accurate cross sections as well as spectrum-averaged cross sections (SACS) in relevant and well-characterized neutron fields are essential for improvement and validation of the evaluated data [Simakov2017].
Comment from requester:
New measurements of the spectrum-averaged cross section are requested to solve C/E discrepancy. See SPA_CE_U235.pdf below.
References
- [IAEA2017] IAEA CRP on Testing and Improving the International Reactor Dosimetry and Fusion File (IRDFF),
http://www-nds.iaea.org/IRDFFtest/.
- [Simakov2017] S. Simakov, et al., “Proposals for new measurements for IRDFF community and HPRL”, September 2017.
Review comment:
Non-threshold reactions measured in fast spectra such as the 252Cf(sf) and 235U(nth,f) spectrum tend to have their spectrum averaged cross section dominated by scattering contributions and ‘room-return’ neutrons. Experiments should be designed to minimize these contributions and maximize the reaction rate from the primary source. For new experiments best estimates must be provided by detailed Monte Carlo calculation of the spectrum realized in the experiment and the Monte Carlo model must be made available to IRDFF to facilitate validation of new proposals for the cross section. In all cases it is advised to publish both the fully corrected SACS and the measured reaction rates of the primary reaction and the monitor reactions used for normalization and validation of the model. The measured reaction rates must be provided with a full covariance matrix.
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
Additional file attached:Simakov2017.pdf
Additional file attached:SPA_CE_U235.pdf
| Request ID | 65 |
Type of the request | Special Purpose Quantity |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 92-U-238 | (n,2n) SIG/SPA | 252Cf(sf)-235U(n,f) | | 2-5 | Y |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action |
| Dosimetry | Fast fission, D-T fusion | 06-OCT-17 | 06-OCT-17 | |
Requester: Dr Stanislav SIMAKOV at KIT, GER
Email: intersurfen@gmail.com
Project (context): IRDFF project
Impact:
The International Reactor Dosimetry and Fusion File (IRDFF) aims at providing evaluated neutron dosimetry reactions validated for all applications related to fission reactors and fusion technology development [IAEA2017].
Accuracy:
2%-5%
Justification document:
Accurate cross sections as well as spectrum-averaged cross sections (SACS) in relevant and well-characterized neutron fields are essential for improvement and validation of the evaluated data [Simakov2017].
Comment from requester:
New measurements of the spectrum-averaged cross section are requested to solve C/E discrepancy and for improvement of the prompt fission neutron spectrum at high energy. See CE_Cf252U235_and_HighThreshold.pdf below.
References
- [IAEA2017] IAEA CRP on Testing and Improving the International Reactor Dosimetry and Fusion File (IRDFF),
http://www-nds.iaea.org/IRDFFtest/.
- [Simakov2017] S. Simakov, et al., “Proposals for new measurements for IRDFF community and HPRL”, September 2017.
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
Additional file attached:Simakov2017.pdf
Additional file attached:CE_Cf252U235_and_HighThreshold.pdf
| Request ID | 101 |
Type of the request | Special Purpose Quantity |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 92-U-238 | (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 |
Requester: Dr Roberto CAPOTE NOY at IAEA, AUT
Email: roberto.capotenoy@iaea.org
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
- A.D. Carlson, et al., Evaluation of the Neutron Data Standards, Nuclear Data Sheets 148, 143-188 (2018)
- Z.W. Miller, A Measurement of the Prompt Fission Neutron Energy Spectrum for 235U(n,f) and the Neutron-induced Fission Cross Section for 238U(n,f), PhD Thesis, University of Kentucky (2015); https://uknowledge.uky.edu/physastron_etds/29/
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:
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
- B. Marcinkevicius, S. Simakov, V. Pronyaev, 209Bi(n,f) and natPb(n,f) cross sections as a new reference and extension of the 235U, 238U and 239Pu(n,f) standards up to 1 GeV, IAEA Report INDC(NDS)-0681
- A.D. Carlson et al., Evaluation of the Neutron Data Standards, NDS 148 (2018) 143
Additional file attached:
Additional file attached: