ID | 8 |
---|---|

Type | |

Target | 1-H-2 |

Reaction | (n,el) |

Quantity | DA/DE - Double differential probability distribution by angle and energy |

Incident energy | 0.1 MeV - 1 MeV |

Accuracy | 5 % |

Secondary Energy/Angle | 0-180 Deg |

Field(s) | Fission |

Subfield | Heavy Water Reactors |

Accepted date | 16-Apr-2007 |

Status | Work in progress |

Latest review date | 22-Apr-2022 |

Kenneth KOZIER at CNLCR, CAN

Critical experiments with high enriched uranyl fluoride in heavy water

Different representations of the energy-angle neutron elastic scattering probability distributions (at energies <3.2 MeV) used in various releases of the ENDF/B-VI and JENDL-3.3 evaluated data libraries for deuterium cause differences of about: (1) 1000 pcm in simulations [1,2] of critical experiments involving solutions of high enriched uranyl fluoride solutions in heavy water (specifically the HST-004 and HST-020 series of measurements in the NEA ICSBEP handbook), and (2) 60 pcm in the calculation bias observed [2] in simulations of heavy-water coolant void reactivity (CVR) experiments performed in ZED-2. Moreover, both the HST and ZED-2 simulation results show a rising trend with neutron leakage, suggesting that further revision of the deuterium data evaluations may be needed. Modern measurements may help resolve a small positive bias of about 150 pcm in the simulation of ZED-2 heavy-water CVR experiments (corresponding to about 10% of the calculated CVR).

About 5%, depending on energy and angle. At 220 keV, existing experimental data have uncertainties of about 16% and differ from the evaluated library values by about 35% at backward angles near 180 degrees. At 500 keV, some experimental data have uncertainties of about 5%, but differ from the library values by up to 50% at 180 degrees. At 1.0 MeV, existing experimental data have uncertainties of about 5%, but differ from the library values by up to 33% near 180 degrees. ENDF/B-VI.8 and JENDL-3.3 differ by about 15% at 180 degrees over this energy range. It is estimated that a 5% uncertainty would correspond to a reactivity uncertainty of about 300 pcm in the context of the HST simulations and about 20 pcm in the ZED-2 CVR simulations, and would be adequate to resolve the current discrepancy between results obtained using the ENDF-B/VI.8 (also VII) and JENDL-3.3 deuterium data files.

The available angular scattering experimental data for deuterium were reviewed [3, attached] and found to be 25 to more than 50 years old, sparse and inconsistent, particularly at backward angles near 180 degrees. The experimental data frequently differ from the evaluated library values by several standard deviations, especially at extreme backward and forward angles. In addition to the HST and ZED-2 simulation results [1,2], the neutronic importance of the deuterium scattering data has been investigated in empirical sensitivity studies of simple systems [4, attached], which suggest that the differences arise at energies up to about 1.0 MeV. A recent TSUNAMI sensitivity analysis of the CVR for an Advanced CANDU Reactor (ACR-700) type lattice cell showed [5] a large sensitivity to the deuterium elastic scattering cross section (34% change in CVR per % change in the cross section), although this methodology does not currently address the angular dependence.

References:

1. R.D. Mosteller, J.M. Campbell and R.C. Little, Reactivity Impact of ENDF/B-VI Cross Sections for Deuterium in Heavy-Water Solution Benchmarks, LA-UR-05-0330, 2005 Annual Meeting of the American Nuclear Society, June 5 - 9, 2005, San Diego, CA.

2. R.D. Mosteller, K.S. Kozier, J.M. Campbell and R.C. Little, ''Reactivity Impact of Deuterium Cross Sections for Heavy-Water Benchmarks'', LA-UR-05-0787, proceedings of the International Topical Meeting on Mathematics and Computation, Supercomputing, Reactor Physics, and Nuclear and Biological Applications, Avignon, France, September 12-15, 2005.

3. L.W. Townsend, ''Neutron-Deuterium Cross Section Evaluation'', Final Technical Report, AECL Purchase Order 217739, March 31, 2006 (copy attached).

4. K.S. Kozier, ''Sensitivity of MCNP5 Calculations for a Spherical Numerical Benchmark Problem to the Angular Scattering Distributions for Deuterium'', proceedings of the PHYSOR-2006 ANS Topical Meeting: Advances in Nuclear Analysis and Simulation, Vancouver, BC, September 10-14, 2006 (copy attached; to be issued).

5. M.L. Williams, J.C. Gehin and K.T. Clarno, ''Sensitivity Analysis of Reactivity Responses Using One-Dimensional Discrete Ordinates and Three-Dimensional Monte Carlo Methods'', proceedings of the PHYSOR-2006 ANS Topical Meeting: Advances in Nuclear Analysis and Simulation, Vancouver, BC, September 10-14, 2006 (to be issued).

6. J.P. Svenne, L. Canton, K. Kozier, and L. Townsend, "Re-evaluating low-energy neutron-deuteron elastic scattering using three-nucleon theory", International Conference on Nuclear Data for Science and Technology 2007, Contrib. #208.

7. K.S. Kozier, "Assessment of evaluated (n,d) energy-angle elastic scattering distributions using MCNP simulations of critical measurements and simplified calculation benchmarks", International Conference on Nuclear Data for Science and Technology 2007, Contrib. #594

Additional sensitivity studies are in progress. We are also looking into the possibility of having someone review the theoretical basis for the two distinctly different quantum mechanical formalisms used by ENDF/B & JENDL for the deuterium elastic scattering energy-angle distributions, and potentially undertake some new Faddeev three-body model calculations.

At the ND2007 in Nice two contributions were presented summarising the status at the time of the conference (April 2007, refs. 6 and 7). Theoretical calculations by L. Canton solving the AGS three-body equations using the Bonn-B nuclear potential tend to support the higher degree of backscattering in the ENDF/B-IV.4 evaluation. A 5% experimental accuracy for the differential cross section at 180 degrees would be sufficient to discriminate between ENDF/B-VI.4 and theory on the one hand and ENDF/B versions VI.5 to VII.0 on the other hand. Possibilities for experimental efforts are being investigated in the US and in Europe. Further theoretical efforts are planned to study the impact of three body forces and the use of other nucleon-nucleon potentials on the angular distribution.

Work in progress (as of SG-C review of May 2018)

Please report any missing information to hprlinfo@oecd-nea.org

Experiments

- J.A. Frenje, et al., Measurements of the Differential Cross Sections for the Elastic n-3H and n-2H Scattering at 14.1 MeV by Using an Inertial Confinement Fusion Facility, PRL 107 (2011) 122502, EXFOR 14305
- M. Stanoiu, et al., Neutron-Deuteron Elastic Scattering Measurements, Journal of the Korean Physical Society 59 (2011) 1825
- N. Nankov, et al., The Angular Distribution of Neutrons Scattered from Deuterium below 2 MeV, ND2013, NDS 119 (2014) 98
- R. Nolte, et al., Measurement of the differential neutron-deuteron scattering cross section in the energy range from 100 keV to 600 keV using a proportional counter, ERINDA workshop, CERN Proceedings 2014-002, p.187
- G.J. Weisel, et al., Neutron-deuteron analyzing power data at En=22.5 MeV (of interest to theoretical models for evaluations), PRC 89 (2014) 054001, EXFOR 14395
- E. Pirovano, et al., Backward-forward reaction asymmetry of neutron elastic scattering on deuterium, PRC 95 (2017) 024601, EXFOR 23335
- E. Pirovano, et al., Measurement of the angular distribution of neutrons scattered from deuterium below 3 MeV, EPJ Web of Conferences 239 (2020) 01016

Theory/Evaluation

- J.P. Svenne, et al., Re-evaluating low-energy neutron-deuteron elastic scattering using three-nucleon theory, ND2007 proceedings, EDP Sciences p.243
- 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

Validation

- D. Roubtsov, et al., Reactivity Impact of 2H and 16O Elastic Scattering Nuclear Data on Critical Systems with Heavy Water, ND2013, NDS 118 (2014) 414