| Request ID | 78 | Type of the request | Special Purpose Quantity | ||
| Target | Reaction and process | Incident Energy | Secondary energy or angle | Target uncertainty | Covariance |
| 83-BI-209 | (n,3n) SIG/SPA | 252Cf(sf)-235U(n,f) | 5-10 | Y | |
| Field | Subfield | Date Request created | Date Request accepted | Ongoing action | |
| Dosimetry | High-energy | 06-OCT-17 | 06-OCT-17 | ||
Requester: Dr Stanislav SIMAKOV at KIT, GER
Email: intersurfen@gmail.com
Project (context): IRDFF project
Impact:
Accuracy:
Justification document:
Comment from requester: References
Review comment:
Entry Status:
Main references: Experiments Theory/Evaluation Additional file attached:Simakov2017.pdf
Requester: Dr Stanislav SIMAKOV at KIT, GER
Project (context): IRDFF project
Impact:
Accuracy:
Justification document:
Comment from requester: References
Review comment:
Entry Status:
Main references: Experiments Theory/Evaluation Additional file attached:Simakov2017.pdf
Requester: Dr Alexey STANKOVSKIY at SCK-CEN, BLG
Project (context): MYRRHA and Gen-IV reactors with lead-bismuth coolants
Impact: Polonium-210, a rather short-lived alpha emitter (half-life 138.4 days), determines the radiological burden associated with the use of lead-bismuth heavy metal coolants of fast reactors, MYRRHA accelerator-driven system currently designed at SCK•CEN, Belgium is one of the examples. It is produced via neutron capture on 209Bi forming the ground state of 210Bi (half-live 5 days) which rapidly decays into 210Po. 210Bi has also long-lived (3 My) metastable state that can also be produced via neutron capture and that decays to 206Tl. Thus the knowledge of branching ratio between these two neutron capture channels is important to accurately predict the inventory of Polonium-210.
Accuracy: 10% on the capture cross sections both to ground and metastable states of 210Bi. The analysis performed in [Fiorito2018] reveals high sensitivity of 210Po production to the neutron capture cross section at first (801.6 eV) and neighbouring resonances up to 10 keV, as well as to the data around 100-300 keV where the neutron spectrum is peaked. The spread in prediction of 210Po concentration between nuclear data libraries reaches 40% while the propagation of existing covariance data for the capture cross section results in uncertainties between 5 and 20%. Furthermore, the covariance data on the branching ratio are not provided in the evaluated data files although they are likely to contribute significantly to the final 210Po concentration uncertainty.
Justification document: Significant differences between evaluations were observed in the neutron capture cross section and branching ratio, which were proved to pose a severe constraint for the correct 210Po content prediction in MYRRHA and other lead-bismuth cooled reactor concepts. The covariance matrices found in the 209Bi evaluations result in different uncertainty profiles and energy correlations. The 210Po concentration uncertainty (intended as one standard deviation) after one irradiation cycle of MYRRHA is ranging between 5% and 20%. This level of uncertainty does not cover the deviation between 210Po concentration values assessed with the evaluated files coming from different libraries, even when three standard deviations are considered. Furthermore, branching ratio covariances were not propagated since they are not provided in the evaluated files, although they are likely to add a significant uncertainty contribution to the polonium content. Significant efforts are necessary to reduce the discrepancies between evaluated data. In particular, accurate measurements should be carried out to obtain the reliable branching ratio not only at thermal energies and for the first resonance at about 800 eV, but also in the energy ranges of interest for lead-bismuth-cooled reactors such as MYRRHA, as made clear by the sensitivity plots in [Fiorito2018]. Because of the disagreement between libraries, a consistent evaluation for the branching ratios should be elaborated that also includes the energy-dependent behaviour in the resonance region and above. Although the BROND-3.1 [Blokhin2016] evaluation seems providing most accurate branching ratio among evaluated libraries, it also relies only on few experimental energy points [Saito2003, Saito2004, Borella2008, Borella2011] in the range 800 eV – 10 keV. The future evaluation thus should be supported by additional experimental measurements. References
Comment from requester:
Review comment:
Entry Status:
Main references: Experiments
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].
5%-10%
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].
Following a recommendation from the IAEA Data Development Project on Neutron Standards [Pronyaev2013], the IRDFF project supports SACS measurements of high-threshold (above 10 MeV) dosimetry cross-sections in well-characterized 252Cf(sf) and 235U(nth,f) neutron fields in order to improve the cross sections and/or the high-energy part of the prompt fission neutron spectra.
Measurements of the spectrum-averaged cross section are missing for validation purposes and for improvement of the cross section and prompt fission neutron spectrum above 10 MeV. See Cf252U235_HighThreshold.pdf below.
http://www-nds.iaea.org/IRDFFtest/.
Work in progress (as of SG-C review of May 2018)
Please report any missing information to hprlinfo@oecd-nea.org
Additional file attached:Cf252U235_HighThreshold.pdf
Request ID 93
Type of the request Special Purpose Quantity
Target Reaction and process Incident Energy Secondary energy or angle Target uncertainty Covariance
83-BI-209 (n,xn) x=3-10 SIG 20MeV/Thr.-150 MeV 5-10 Y
Field Subfield Date Request created Date Request accepted Ongoing action
Dosimetry High-energy 06-OCT-17 06-OCT-17
Email: intersurfen@gmail.com
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].
5%-10%
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].
The IRDFF project strives to evaluate, and eventually add to the library, high-threshold reactions with cross section plateaus located between 15/20 MeV and 100/150 MeV to meet the requirements of the accelerator-driven high-energy neutron sources. Note that it is important to know the cross section tail up to 100/150 MeV in order to allow the deconvolution of high-energy quasi-monoenergetic neutron source spectra.
http://www-nds.iaea.org/IRDFFtest/.
Work in progress (as of SG-C review of May 2018)
Please report any missing information to hprlinfo@oecd-nea.org
Additional file attached:Bi(n,xn)_HighEnDos.pdf
Request ID 114
Type of the request High Priority request
Target Reaction and process Incident Energy Secondary energy or angle Target uncertainty Covariance
83-BI-209 (n,g)Bi-210g,m BR 500 eV-300 keV 10 Y
Field Subfield Date Request created Date Request accepted Ongoing action
ADS,Fission 26-OCT-18 09-NOV-18 Y
Email: alexey.stankovskiy@sckcen.be
In addition to 209Bi(n,g) branching ratio or activation measurements, complementary transmission measurements may be needed to fix the resonance parameters in the re-evaluation of the 209Bi capture cross section. Moreover, integral benchmarks dedicated to 209Bi activation/cooling in representative spectra are required to better assess the performance of evaluated data.
Work in progress (as of SG-C review of June 2019)
Please report any missing information to hprlinfo@oecd-nea.org