Structural material for fusion power reactors
Impact:
SiC is a potential very low activation structural material for a fusion power reactor. Al-27 produced from neutron irradiation of Si generates Al-26 via the Al-27(n,2n) reaction. Al-26 is a long-lived radionuclide with a half life of 720,000 years emitting high energy gammas. The concentration of Al-26 in SiC determines whether the decommissioned fusion blanket qualifies for recycling.
Accuracy:
The request for 20% accuracy is based on what seemed feasible for the nuclear data community to achieve and probably would be sufficient for applications as well. It is not based on any sensitivity calculations.
Justification document:
The estimates consider waste generated by four full power years at 5 MW/m2 neutron wall load and are based on a particular scenario for waste handling using evaluations for Si-28(n,x)Al-27 provided by ENDF/B-VI and ADL-3 which are adopted in FENDL/A-2.0. Estimated concentration limits for Si are a factor 10 higher than earlier estimates, so that SiC would qualify as a truly low-activation material. The request asks for experimental data to validate these estimates and a subsequent re-evaluation. No direct experimental data exist.
Reference 1: E.T.Cheng, Jour. Nucl. Mat.,258-263(1998)1767
Reference 2: E.T. Cheng, Proc. of the Int. Conf. on Nuclear Data for Science and Technology, eds. G. Reffo, A. Ventura and C. Grandi, SIF, Bologna, 1158 (1997)
Comment from requester:
Two methods to measure this reaction cross section have been suggested by Herbert Vonach and others. These include (1) Measurement of Na24 activity with high-purity Si samples and intense neutron sources, and (2) Measurement of total production in Si and then subtracting the well known (n,p) cross sections to obtain the (n,n'p) values. An attempt to measure this cross section data at 14 MeV a few years ago failed due to the contamination of the Si samples with the impurity Al. The request for 20% accuracy is based on what seemed feasible for the nuclear data community to achieve and probably would be sufficient for applications as well. It is not based on any sensitivity calculations.
Review comment:
The accuracy is not known. Estimates from present and earlier evaluations differ by a factor of ten.
The request appears to imply application to post-ITER fusion reactors in view of the high neutron dose required to generate relevant quantities of Al-26.
Reference [1] refers primarily to the Si-28(n,np) reaction, whereas the production of Al-27 from Si-28 is important. This therefore also implies the (n,d) reaction since the respective thresholds are 12 and 9.7 MeV.
Quantitative information is supplied that seems to suggest directly that 20% accuracy is of interest to the application. Stoichiometric SiC has 70 wt% of Si, whereas the scenario assumed for the estimates of Ref. [1] results in an upper limit of 85 wt% Si for recycling.
This request qualifies as a General request primarily since the project end time is unspecified.
Entry Status:
Completed (as of SG-C review of May 2018) - Development in state-of-the-art nuclear reaction codes such as TALYS and EMPIRE allowed to fulfil this request. The uncertainties in the main evaluated files (ENDF/B-VIII.0, JEFF-3.3, TENDL-2015) are all consistent above the threshold reaction and vary within a 15-25% band between 13 MeV and 20 MeV.
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Experiments
Theory/Evaluation
- M. Herman et al., COMMARA-2.0 Neutron Cross Section Covariance Library, Report BNL-94830-2011, Brookhaven National Laboratory (2011)
Additional file attached:
Additional file attached:
| Request ID | 5 |
Type of the request | High Priority request |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 72-HF-0 | (n,g) SIG | 0.5 eV-5.0 keV | | 4 | Y |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action |
| Fission | LWR | 28-APR-06 | 16-APR-07 | |
Requester: Dr Gilles NOGUERE at CAD-DER, FR
Email: gilles.noguere@cea.fr
Project (context): JEFF
Impact:
In nuclear industry hafnium is used as neutron absorbing material to regulate the fission process. Interpretations of critical experiments with UOx fuel conducted by CEA in the AZUR zero-power reactors has shown systematic underestimation of the reactivity worth that may be attributed to an overestimated natural hafnium capture cross section in the epi-thermal energy range [1,2].
Accuracy:
Requested accuracy can be found in the CEA Report "Correlations entre données nucleaires et experiences integrales a plaques, le cas du hafnium", Jean-Marc Palau, CEA-R-5843 (1997). The target accuracy on the effective capture integral has to be lower than 4%
Justification document:
[1] David Bernard, "Determination des incertitudes liés aux grandeurs neutroniques d'interet des reacteurs a eau presurisee a plaques combustibles et application aux etudes de conformite", University Blaise Pascal, Clermont-Ferrand II, France (2001).
[2] G. Noguere, A. Courcelle, J.M. Palau, O.Litaize, "Low neutron energy cross sections of the hafnium isotopes", JEFDOC-1077.pdf, OECD-NEA, Issy-les-Moulineaux, France (2005).
[3] G. Noguere, A. Courcelle, P. Siegler, J.M. Palau, O. Litaize, "Revision of the resolved resonance range of the hafnium isotopes for JEFF-3.1", Technical note CEA Cadarache NT-SPRC/LEPH-05/2001 (2005).
Comment from requester:
Neither the JENDL3.3 nor the JEFF3.1 libraries, that were recently issued, solve the problem. In fact, this was observed for JENDL3.3 before the JEFF3.1 file was constructed. As a result the JEFF3.1 file has been produced with this problem in mind taken into consideration the recent data from Trbovich et al. obtained at RPI [3]. Finally, a 400 pcm underestimation remains that is likely due to interfering isotopic contributions in the resolved energy region. New high resolution measurements appear needed, and would be particularly valuable if they can distinguish the contributions of different isotopes.
Review comment:
Calculations on the AZUR configuration using the JEFF3.1 library give a Hf reactivity worth of about -300 pcm [2].
Entry Status:
Completed (as of SG-C review of May 2018) - The measurements performed at RPI [Trbovich:2009] and JRC-Geel [Ware:2010] allowed to significantly improve the Hf isotopes in JEFF, which now gives satisfactory results for reactivity worth due to Hf data [Noguere:2009].
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Experiments
- A.K.M. Meaze et al. (G.N. Kim), Measurement of the Total Neutron Cross-Sections and the Resonance Parameters of Natural Hafnium at the Pohang Neutron Facility, J. Korean Phy. Soc. 46 (2005) 401, EXFOR 31689
- K. Wisshak, et al., Fast neutron capture on the Hf isotopes: Cross sections, isomer production, and stellar aspects, PRC 73 (2006) 045807, EXFOR 22926
- M.J. Trbovich, et al., Hafnium resonance parameter analysis using neutron capture and transmission experiments, NSE 161 (2009) 303, EXFOR 14239
- T. Ware, Measurement and analysis of the resolved resonance cross sections of the natural hafnium isotopes, PhD thesis, University of Birmingham (2010); etheses.bham.ac.uk//id/eprint/807
- M. Budak, et al., Experimental determination of effective resonance energies for 158Gd(n,g)159Gd and 179Hf(n,g)180mHf reactions, ANE 38 (2011) 2550
Theory/Evaluation
Additional file attached:JEFDOC-1077.ppt
Additional file attached:NT_Hafnium.pdf
| Request ID | 7 |
Type of the request | General request |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 26-FE-56 | (n,xn) SIG,DDX | 7 MeV-20 MeV | 1MeV-20MeV | 30 | |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action |
| Fission,ADS | Shielding, Medical, SNS | 13-JUL-06 | 16-APR-07 | |
Requester: Prof. Arjan KONING at NRGPETTEN, NED
Email:
Project (context): JEFF, Model calculations
Impact:
New double differential experimental data for the Fe(n,xn) reaction will allow a crucial test of the pre-equilibrium models underlying neutron transport libraries for spallation neutron sources. They will thereby enhance the confidence in neutron transport calculations for spallation neutron sources such as envisioned for accelerator driven systems.
Accuracy:
30% for the double-differential spectra
Justification document:
A global pre-equilibrium analysis from 7 to 200 MeV based on the optical model potential, A.J. Koning and M.C. Duijvestijn,
Nucl. Phys. A744, 15 (2004).
Comment from requester:
There are hundreds of (p,xp) and (p,xn) spectra in the 20-200 MeV range available, several (n,xp) spectra, but there are basically no
double-differential (n,xn) spectra available. The presence of such data would heavily constrain the pre-equilibrium model parameters and thereby result in a much better prediction of neutron-induced spectra in the entire 50-200 MeV range. Since high-energy spectra are rather structureless the choice of target is less essential.
Review comment:
Entry Status:
Completed (as of SG-C review of May 2018) - The experimental program performed at Uppsala [Sagrado:2011] combined with improvements in nuclear reaction models allow modern evaluations to address this request, see e.g. [Herman:2018].
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Experiments
- I.C. Sagrado Garcia et al., Neutron production in neutron-induced reactions at 96 MeV on 56Fe and 208Pb, PRC 84 (2011) 044619
Theory/Evaluation
- M. Herman et al., Evaluation of Neutron Reactions on Iron Isotopes for CIELO and ENDF/B-VIII.0, NDS 148 (2018) 214
Additional file attached:
Additional file attached:
| Request ID | 10 |
Type of the request | General request |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 79-AU-197 | (n,tot) SIG | 5 keV-200 keV | | 5 | |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action |
| Fusion,Science | Dosimetry | 18-MAY-07 | 06-JUN-07 | |
Requester: Dr Roberto CAPOTE NOY at IAEA, AUT
Email: roberto.capotenoy@iaea.org
Project (context): Dosimetry
Impact:
INDC(NDS)-0507 Summary Report of Consultants’ Meeting Review the Requirements to Improve and Extend the IRDF library (International Reactor Dosimetry File (IRDF-2002)), IAEA Headquarters, Vienna, Austria 20-21 April 2006, prepared by L.R. Greenwood and Alan L. Nichols (IAEA, Vienna, January 2007)
Accuracy:
5%
Justification document:
Gold is an extremely important material in nuclear applications: the capture on gold is a standard neutron cross-section, gold has been proposed as a high energy neutron dosimeter (see below), Au-197(n,2n) is a reactor dosimetry reaction considered in all recent IRDF files, etc. Reactions on gold are also of interest for nuclear model code testing as gold is a mono-isotopic element being amenable to detailed calculations.
Taken from INDC(NDS)-0507 "... proposed high energy dosimetry reactions 197Au(n,2n)196Au, 197Au(n,3n)195Au, and 197Au(n,4n)194Au require the extension of the gold evaluation up to 60 MeV"
To our surprise we found large discrepancies in the measured total cross section data of gold in the 5-200 keV energy range (URR) as can be seen from the attached plots. The only existing evaluation (Young et al in red in the figures) has been carried out in the early nineties and has been adopted for all subsequent libraries with minor modifications. This evaluation follows the Seth et al. data measured in 1965, which is in contradiction with several new measurements (for example Purtov 1994 and Wishak 1995-2006). The spread of the Wishak measurements is puzzling.
Comment from requester:
A new dispersive coupled-channel optical model potential (5 keV - 200 MeV) derived using the requested data (plus the existing database above 200 keV) will have a direct impact on future evaluations of neutron induced reactions on gold.
Review comment:
While considerable data exist for the 5-200 keV total cross section, there is considerable scatter in these data. The measurement range is well suited for time-of-flight facilities and may also be accessed with quasi-monoenergetic beams using the Li(p,n) neutron source reactions. For a transmission measurement optimal conditions are obtained with a transmission factor close to 0.5, which implies that getting a sample might be costly, but purity and chemical issues should not be concerns. A measurement which overlaps with the region of the Au capture standard (200 keV to 2.5 MeV) would be of interest to allow a consistency check.
Entry Status:
Completed (as of SG-C review of May 2018) - The JEFF-3.2 evaluation [Sirakov:2013] based on new JRC-Geel measurements [Sirakov:2014;Massimi:2014] is significantly below the target accuracy. The evaluation has been validated against the Grenoble LSDS integral experiment [Zerovnik:2013].
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Experiments
- R. Hannaske, et al., Neutron total cross section measurements of gold and tantalum at the nELBE photoneutron source, EPJA 49 (2013) 137, EXFOR 23199
- I. Sirakov, et al., Results of total cross section measurements for 197Au in the neutron energy region from 4 to 108 keV at GELINA, EPJA 49 (2014) 144, EXFOR 23222
- C. Massimi et al., Neutron capture cross section measurements for 197Au from 3.5 to 84 keV at GELINA, EPJA 50 (2014) 124, EXFOR 23253
Theory/Evaluation
- A.B. Smith, Neutron Scattering from the Standard 197Au, ANL/NDM-161, 2005
- I. Sirakov et al., Evaluation of neutron induced reaction cross sections on gold, Report JRC 78690, EUR 25803, 2013
- B. Becker, et al., Evaluation of the Covariance Matrix of Estimated Resonance Parameters, NDS 118 (2014) 381
- A.D. Carlson et al., Evaluation of the Neutron Data Standards, NDS 148 (2018) 143
Validation
Additional file attached:AU197_NTOT_RECENT.ps
Additional file attached:AU197_WISHAK.ps
| 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 | |
Requester: Dr Yasunobu NAGAYA at JAEA, JPN
Email: nagaya.yasunobu@jaea.go.jp
Project (context): JENDL, NEA WPEC Subgroup 29
Impact:
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.
Accuracy:
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.)
Justification document:
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.
Comment from requester:
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.
Review comment:
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.
Entry Status:
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).
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Experiments
- M. Jandel et al., New Precision Measurements of the 235U(n,g) Cross Section, PRL 109 (2012) 202506, EXFOR 14149
- A. Wallner et al., Novel Method to Study Neutron Capture of 235U and 238U Simultaneously at keV Energies, Phys. Rev. Lett. 112 (2014) 192501, EXFOR 23170
- J. Balibrea et al., Measurement of the neutron capture cross section of the fissile isotope 235U with the CERN n_TOF Total Absorption Calorimeter and a fission tagging based on Micromegas detectors, NDS 119 (2014) 10
- Y. Danon, et al., Simultaneous measurement of 235U fission and capture cross sections from 0.01 eV to 3 keV using a gamma multiplicity detector, Nucl. Sci. and Eng. 187 (2017) 191
- J. Balibrea et al., Measurement of the neutron capture cross section of the fissile isotope 235U with the CERN n TOF total absorption calorimeter and a fission tagging based on micromegas detectors, EPJ Conferences 146 (2017) 11021
Theory/Evaluation
- R. Capote et al., IAEA CIELO Evaluation of Neutron-induced Reactions on 235U and 238U Targets, NDS 148 (2018) 254
Validation
- O. Iwamoto et al., Uranium-235 Capture Cross-section in the keV to MeV Energy Region, International evaluation cooperation, Report NEA/WPEC-29, OECD NEA (2011)
- M. Salvatores, et al., Methods and Issues for the Combined Use of Integral Experiments and Covariance Data: Results of a NEA International Collaborative Study, Nuclear Data Sheets 118 (2014) 38
- G. Palmiotti, et al., Combined Use of Integral Experiments and Covariance Data, Nuclear Data Sheets 118 (2014) 596
Additional file attached:U235proposal.pdf
Additional file attached:Viewgraph.U235proposal.pdf
| Request ID | 13 |
Type of the request | General request |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 24-CR-52 | (n,xd),(n,xt) SIG | Threshold-65 MeV | | 20 | Y |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action |
| Fusion | IFMIF, First wall | 23-OCT-07 | 07-NOV-07 | |
Requester: Dr Robin A. FORREST at UKAEA/CUL, UK
Email:
Project (context): JEFF, EFF
Impact:
See attached report EFF/DOC-1015, "Preparatory work for the evaluation of Cr-52 high energy neutron data for EFF", P. Pereslavtsev.
Accuracy:
No experimental data are available for this reaction apart from one point at 14 MeV. Therefore, new experimental results with 20% accuracy are still valuable.
Justification document:
The reactions that need to be considered are Cr-52(n,d+n'p)V-51 and Cr-52(n,t+n'd)V-50. These are important both for modelling and for fusion technology applications. They are discussed in the UKAEA FUS 509 document (Handbook of activation data).
Comment from requester:
Attempts to measure the split in (n,d) and (n,np) to the production of 51V and the split in (n,t), (n,nd) and (n,2np) contributions to the production of 50V would be valuable.
Review comment:
In view of the stable end product both for the (n,d) and (n,nd) reaction, double differential measurements detecting the deuteron are recommended. Such measurements may also provide important additional data for modeling in the form of (n,xp) and (n,xt) double differential cross sections. Measurements with the 'activation-technique' would need to employ a combination of two reactions. Such measurements are complicated, since traces of natural vanadium are a major source of contamination and because the induced activity will be very low. Accelerator Mass Spectrometry is deemed not feasible on account of the background resulting from the wide spread use of vanadium in structural parts. In view of these difficulties it is unlikely that experimentally the cross section for the production of a specific isotope will be accessible. Modeling would have to be invoked.
According to the attached report a single measurement at 14 MeV exists. Above that energy two recent evaluations divergence by nearly a factor 2.
Cr-52 has been under re-evaluation several times in the recent past. For this particular reaction it appears that no progress can be made without new experimental data. In view of the predicted trends in the cross section, it appears that the emphasis of new experimental work should be in the domain above 14 MeV. However, the energy range between threshold (8441 keV) and 14 MeV may be important in an actual fusion reactor.
Entry Status:
Completed (as of SG-C review of May 2018) - This request didn't trigger any measurement and should its priority rise again it will have to be resubmitted. Nevertheless, it has been partially addressed by the JEFF-3.2 evaluation using state-of-the-art nuclear reaction codes [Pereslavtsev:2011].
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Theory/Evaluation
Additional file attached:effdoc-1015.pdf
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: massimo.salvatores@cea.fr
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 | 40 |
Type of the request | High Priority request |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 14-SI-28 | (n,inl) SIG | 1.4 MeV-6 MeV | | See details | Y |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action |
| Fission | Fast Reactors | 15-SEP-08 | 15-SEP-08 | |
Requester: Prof. Massimo SALVATORES at CADARACHE, FR
Email: massimo.salvatores@cea.fr
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).
This request is specific to the gas-cooled fast reactor.
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 | GFR |
| | λ=1 | λ≠1,a |
|
| 2.23 - 6.07 MeV | 14 | 3 | 4 |
| 1.35 - 2.23 MeV | 50 | 6 | 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:
Completed (as of SG-C review of May 2018) - The measurement performed at JRC-Geel [Negret:2013] and the latest evaluations (JEFF-3.3, ENDF/B-VIII.0) all match the requested accuracy.
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Experiments
- A. Negret et al., Cross sections for inelastic scattering of neutrons on 28Si and comparison with the 25Mg(a,n)28Si reaction, PRC 88 (2013) 034604, EXFOR 23173
- A. Negret et al., Neutron inelastic scattering measurements for background assessment in neutrinoless double beta decay experiments, PRC 88 (2014) 027601
Theory/Evaluation
- M. Herman et al., COMMARA-2.0 Neutron Cross Section Covariance Library, Report BNL-94830-2011, Brookhaven National Laboratory (2011)
Additional file attached:SG26-report.html
Additional file attached:
| Request ID | 44 |
Type of the request | High Priority request |
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 93-NP-237 | (n,f) SIG | 200 keV-20 MeV | | 2-3 | Y |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action |
| Fission | fast reactors | 11-MAY-15 | 18-MAY-15 | |
Requester: Dr Fredrik TOVESSON at LANL, USA
Email: tovesson@lanl.gov
Project (context): Los Alamos National Laboratory
Impact:
- The Np-237 fission cross section has impact for certain fast nuclear reactor designs. A sensitivity study by Aliberti et al. [1] pointed to a target accuracy of 8% for this cross section for Sodium-cooled Fast Reactor of the Gen-IV type (high level waste recycling).
- WPEC Subgroup-26 [2]: Present uncertainty (BOLNA) 6-8% from 0.5-6 MeV. Required uncertainty for an Accelerator Driven Minor Actinide Burner (ADMAB): 1.5-4 %.
- For many measurements the 237Np(n,f) is a reference cross section that is valuable on account of its low fission threshold and moderate activity.
Accuracy:
Uncertainties of 2-3%
Justification document:
There is a discrepancy of about 6-9% between a recent measurement performed by the n_TOF collaboration and ENDF/B-VII (C. Paradela et al. [3]).
The higher n_TOF values are supported by a validation exercise by Leong et al. [4].
A recent independent result in the energy range from 4.8 to 5.6 MeV yields cross sections that in function of energy first agree with ENDF/B-VII and then with the n_TOF result (M. Diakaki et al. [5]).
Independently an issue was recently found when cross sections for Pu-isotopes referred to the 238U(n,f) cross section were compared to the same cross sections referred to the 237Np(n,f) cross section in the same measurement arrangement (P. Salvador et al. [6]).
Comment from requester:
The request is well motivated and of some concern also to reactor dosimetry when using spectral indices and/or reaction rates of 237Np fission chambers (IRDFF [7]).
References:
- [1] G. Aliberti et al., Annals of Nuclear Energy 33 (2006) 700-733.
- [2] M. Salvatores et al., Nuclear Science NEA/WPEC-26, www.oecd.org.
- [3] C. Paradela et al., Phys. Rev. C 82 (2010) 034601; Korean Physical Society 59 (2011) 1519.
- [4] L.S. Leong et al., Annals of Nuclear Energy 54 (2013) 36
Review comment:
Entry Status:
Completed (as of SG-C review of May 2018) - The request was related to a discrepancy between measurements performed at LANSCE [Tovesson:2007] and n_TOF [Paradela:2010]. New measurements using improved PPAC detectors have shown that the overestimation of the n_TOF data was caused by different roughness of the surface of the Np and U samples [Tassan-Got:2019].
Main references:
Please report any missing information to hprlinfo@oecd-nea.org
Experiments
- O. Shcherbakov et al., Neutron-Induced Fission of 233U, 238U, 232Th, 239Pu, 237Np, natPb and 209Bi Relative to 235U in the Energy Range 1-200 MeV, Jour. of Nuclear Science and Technology Suppl. 2 (2002) 230, EXFOR 41455
- F. Tovesson and T. Hill, Neutron induced fission cross section of 237Np from 100 keV to 200 MeV, PRC 75 (2007) 034610, EXFOR 14130
- M.S. Basunia, The (3He, t f) as a surrogate reaction to determine (n,f) cross sections in the 10-20 MeV energy range, NIM B 267 (2009) 1899, EXFOR 31673
- C. Paradela, et al., Neutron-induced fission cross section of 234U and 237Np measured at the CERN Neutron Time-of-Flight (n_TOF) facility, PRC 82 (2010) 034601, EXFOR 23126
- M. Diakaki et al., Determination of the 237Np(n,f) reaction cross section for En = 4.5-5.3 MeV using a MicroMegas detector assembly, EPJA 49 (2013) 62, EXFOR 23189
- M. Diakaki et al., Neutron-induced fission cross section of 237Np in the keV to MeV range at the CERN n_TOF facility, PRC 93 (2016) 034614, EXFOR 22742
- L. Tassan-Got et al., Fission program at n_TOF, EPJ Web of Conferences 211, 03006 (2019)
Theory/Evaluation
- M.B. Chadwick et al., ENDF/B-VII.0: Next Generation Evaluated Nuclear Data Library for Nuclear Science and Technology, NDS 107 (2006) 2931
Validation
Additional file attached:1-s2.0-S0306454906000296-main.pdf
Additional file attached: