| 161. |
- Rochman, D., et al.
(författare)
-
A Bayesian Monte Carlo method for fission yield covariance information
- 2016
-
Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 95, s. 125-134
-
Tidskriftsartikel (refereegranskat)abstract
- The present work proposes a Bayesian method to combine theoretical fission yields with a set of reference data. These two sources of information are merged using a Monte Carlo process, and leads to a so-called Bayesian Monte Carlo update. Examples are presented for the independent fission yields of four major actinides, using the GEF code as a source of theoretical calculations and an evaluated library of fission yields for the reference data. The impact of the updated fission yields and their covariances is shown for two distinct applications: a UO2 pincell with burn-up up to 40 GWD/tHM and decay heat calculations of a thermal neutron pulse on U-235 and Pu-239.
|
|
| 162. |
- Rochman, D., et al.
(författare)
-
Correlation (nu)over-bar(p) - sigma for U-Pu in the thermal and resonance neutron range via integral information
- 2019
-
Ingår i: The European Physical Journal Plus. - : SPRINGER HEIDELBERG. - 2190-5444. ; 134
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents an application of the Backward-Forward Monte Carlo (BFMC) method using measured critical boron concentrations for a specific PWR cycle. The considered prior nuclear data are the fission cross sections, nu for U-235 and Pu-239 and the capture cross section of U-238. The posterior nuclear data exhibit cross-isotope correlations, moderate changes for the average quantities and reduced uncertainties. This work is the first one considering the BFMC method and an integral system mostly sensitive to thermal neutrons. It contributes to show the impact of integral experimental data for the evaluation of nuclear data and their covariance matrices, leading to cross-isotope correlations and a nuclear data uncertainty reduction.
|
|
| 163. |
- Rochman, D., et al.
(författare)
-
Nuclear data uncertainty for criticality-safety : Monte Carlo vs. linear perturbation
- 2016
-
Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 92, s. 150-160
-
Tidskriftsartikel (refereegranskat)abstract
- This work is presenting a comparison of results for different methods of uncertainty propagation due to nuclear data for 330 criticality-safety benchmarks. Covariance information is propagated to key using either Monte Carlo methods (NUSS: based on existing nuclear data covariances, and TMC: based on reaction model parameters) or sensitivity calculations from MCNP6 coupled with nuclear data covariances. We are showing that all three methods are globally equivalent for criticality calculations considering the two first moments of a distribution (average and standard deviation), but the Monte Carlo methods lead to actual probability distributions, where the third moment (skewness) should not be ignored for safety assessments.
|
|
| 164. |
- Rochman, D., et al.
(författare)
-
Re-evaluation of the thermal neutron capture cross section of Nd-147
- 2016
-
Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 94, s. 612-617
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we are proposing a re-evaluation of the thermal-neutron induced capture cross section of Nd-147. A unique measurement exists from which this cross section was calculated in 1974. This original calculation is based on an assumed value for a specific gamma-ray fraction (called F-2), taken from the neighboring nucleus Nd-145. With the availability of reaction codes such as TALYS, such fraction can nowadays be calculated using specific reaction models and parameters. The new value of F-2 indicates a decrease of the thermal cross section by 45%, leading to 243 barns, instead of the 440 barns previously reported. This new cross section impacts the calculation of the number density for the well-known burn-up indicator Nd-148, but as shown, the change is close to the usual experimental uncertainties for the 148Nd number densities, thus having a limited impact on burn-up calculation.
|
|
| 165. |
- Rochman, Dimitri, et al.
(författare)
-
The TENDL library : Hope, reality and future
- 2017
-
Ingår i: Nd 2016 Bruges. - Les Ulis : EDP Sciences. - 9782759890200
-
Konferensbidrag (refereegranskat)abstract
- The TALYS Evaluated Nuclear Data Library (TENDL) has now 8 releases since 2008. Considerable experience has been acquired for the production of such general-purpose nuclear data library based on the feedback from users, evaluators and processing experts. The backbone of this achievement is simple and robust: completeness, quality and reproducibility. If TENDL is extensively used in many fields of applications, it is necessary to understand its strong points and remaining weaknesses. Alternatively, the essential knowledge is not the TENDL library itself, but rather the necessary method and tools, making the library a side product and focusing the efforts on the evaluation knowledge. The future of such approach will be discussed with the hope of nearby greater success.
|
|
| 166. |
- Zagaynova, Valeria, et al.
(författare)
-
The influence of boron doping on magnetic properties of oxygen-eroded graphite
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A series of nanoporous oxygen-eroded graphites prepared by a redox reaction in a closed system between graphite and CuO, with varying amounts of boron, has been studied. We have found that introduction of boron affects the defect-induced magnetism of disordered nanoporous carbon in a complex way, changing both paramagnetic and diamagnetic contributions. Small concentrations of boron dopant enhance magnetic response from the system, while higher concentrations suppress magnetism due to annihilation of localized states.
|
|
