Deficiencies in Nuclear Data Evaluations and Uncertainty Assessment

In this document, Roberto Capote from IAEA discusses deficiencies in neutron data evaluations and statistical models for uncertainty assessment. The content covers topics such as USU definition, identification of outliers, and what is not considered USU. Various neutron data standards and evaluation results are presented, including uncertainties in measurements for different materials. The document emphasizes the importance of accurate data assessment in nuclear research.

• Nuclear Data
• Evaluation
• Uncertainty Assessment
• Neutron Standards
• Roberto Capote

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1. arXiv 5 Nov. 2019, under review Nuclear Data Sheets CSWEG 2019, BNL, Upton, NY, November 4-6 2019 Roberto Capote, IAEA Nuclear Data Section e-mail: R.CapoteNoy@iaea.org Web: http://www-nds.iaea.org Nuclear Data Week, CSWEG 2019* 4-6 November 2019, BNL, Upton, NY 1 R.CapoteNoy@iaea.org http://www-nds.iaea.org

2. Deficiencies in ND evaluations: USU in Neutron Data Standards A.D. Carlson et al, Nucl. Data Sheets148 (2018) 143-188 Evaluation of the Neutron Data Standards Roberto Capote, IAEA Nuclear Data Section e-mail: R.CapoteNoy@iaea.org Web: http://www-nds.iaea.org Nuclear Data Week, CSWEG 2019* 4-6 November 2019, BNL, Upton, NY 2 R.CapoteNoy@iaea.org http://www-nds.iaea.org

3. Deficiencies in ND evaluations: USU in Neutron Data Standards 1H(n,n) : 0.34% 6Li(n,t) : 0.5 % C(n,n) : 0.8% 10B(n, ) : 0.5 % 197Au(n, ) : 1.7 % 238U(n, ) : 1.7-2.4 % 235U(n,f) : 1.2 % valid for all actinides measured with fission chambers 252Cf(s.f.) tot : 0.4% valid for all actinides RC & D. Neudecker arXiv 1908.00272 (2019) Roberto Capote, IAEA Nuclear Data Section e-mail: R.CapoteNoy@iaea.org Web: http://www-nds.iaea.org Nuclear Data Week, CSWEG 2019* 4-6 November 2019, BNL, Upton, NY 3 R.CapoteNoy@iaea.org http://www-nds.iaea.org

4. USU definition and statistical model Statistical model to estimate USU uncertainties mean value i counting statistics i systematic errors i USU Roberto Capote, IAEA Nuclear Data Section e-mail: R.CapoteNoy@iaea.org Web: http://www-nds.iaea.org Nuclear Data Week, CSWEG 2019* 4-6 November 2019, BNL, Upton, NY 4 R.CapoteNoy@iaea.org http://www-nds.iaea.org

5. Before identifying USU Assess INPUT values, uncertainties & correlations Identification and removal of outliers Roberto Capote, IAEA Nuclear Data Section e-mail: R.CapoteNoy@iaea.org Web: http://www-nds.iaea.org Nuclear Data Week, CSWEG 2019* 4-6 November 2019, BNL, Upton, NY 5 R.CapoteNoy@iaea.org http://www-nds.iaea.org

6. What is not USU? 235U(n,f) 20keV-1MeV Poenitz GLSQ eval. (1970) Evolution of measured 235U(n,f) with time THIS IS NOT USU ! Roberto Capote, IAEA Nuclear Data Section e-mail: R.CapoteNoy@iaea.org Web: http://www-nds.iaea.org Nuclear Data Week, CSWEG 2019* 4-6 November 2019, BNL, Upton, NY 6 R.CapoteNoy@iaea.org http://www-nds.iaea.org

7. What is not USU? Some targets contained water ! THIS IS NOT USU ! Roberto Capote, IAEA Nuclear Data Section e-mail: R.CapoteNoy@iaea.org Web: http://www-nds.iaea.org Nuclear Data Week, CSWEG 2019* 4-6 November 2019, BNL, Upton, NY 7 R.CapoteNoy@iaea.org http://www-nds.iaea.org

8. Deficiencies in ND evaluations Too small evaluated uncertainties, <1% (*) arXiv IRDFF-II: A new neutron Why <1% are too small? Expert judgement !! (*) Disclaimer: There are also people worried about too large uncertainties also expert judgement Roberto Capote, IAEA Nuclear Data Section e-mail: R.CapoteNoy@iaea.org Web: http://www-nds.iaea.org Nuclear Data Week, CSWEG 2019* 4-6 November 2019, BNL, Upton, NY 8 R.CapoteNoy@iaea.org http://www-nds.iaea.org

9. Clues pointing to the need of USU Roberto Capote, IAEA Nuclear Data Section e-mail: R.CapoteNoy@iaea.org Web: http://www-nds.iaea.org Nuclear Data Week, CSWEG 2019* 4-6 November 2019, BNL, Upton, NY 9 R.CapoteNoy@iaea.org http://www-nds.iaea.org

10. 252Cf(sf) nubar measurements, USU? 3.86 111 Boldeman 116 Spencer 121 Hopkins 125 Asplund 127 White 128 Axton 129 COLV/AXT 130 COLV/ULL 138 Alek-Rov 139 Smith 140 Edwards 141 Boz-nesh 142 DeVolpi 143 Zhang 144 Spiegel USU nubar: 0.4% (0.6%) 1977 1982 1963 1963 1968 1985 1966 1965 1981 1984 1982 1977 1972 1981 1981 3.7549 3.7831 3.7767 3.7910 3.8194 3.7547 3.7299 3.7405 3.7618 3.7678 3.7641 3.7475 3.7507 3.7534 3.7828 N=15 3.84 3.82 252Cf(sf) nubar 3.80 3.78 3.76 3.74 3.72 3.70 1 2 3 4 5 6 7 8 9 101112131415 Measurement number All measurements: 3.765 +/-0.023 (0.6%) GMA value (GLSQ): 3.764 +/-0.005 (0.13%) Indep. Exp. ! ?.??% ?.?% ?? Roberto Capote, IAEA Nuclear Data Section e-mail: R.CapoteNoy@iaea.org Web: http://www-nds.iaea.org Nuclear Data Week, CSWEG 2019* 4-6 November 2019, BNL, Upton, NY 10 R.CapoteNoy@iaea.org http://www-nds.iaea.org

11. USU in 252Cf(s.f.)? Indep. Exp. ! ?.??% ?.?% ?? Roberto Capote, IAEA Nuclear Data Section e-mail: R.CapoteNoy@iaea.org Web: http://www-nds.iaea.org Nuclear Data Week, CSWEG 2019* 4-6 November 2019, BNL, Upton, NY 11 R.CapoteNoy@iaea.org http://www-nds.iaea.org

12. USU in 252Cf(s.f.) Std 2009: 0.13% (too small) Std 2017: 0.42% (slightly large?) PUB upper: 0.38% PUB min. real.: 0.23% Roberto Capote, IAEA Nuclear Data Section e-mail: R.CapoteNoy@iaea.org Web: http://www-nds.iaea.org Nuclear Data Week, CSWEG 2019* 4-6 November 2019, BNL, Upton, NY 12 R.CapoteNoy@iaea.org http://www-nds.iaea.org

13. Deficiencies in benchmark evaluations: USU in benchmarks (too small uncert.?) HEU Roberto Capote, IAEA Nuclear Data Section e-mail: R.CapoteNoy@iaea.org Web: http://www-nds.iaea.org Nuclear Data Week, CSWEG 2019* 4-6 November 2019, BNL, Upton, NY 13 R.CapoteNoy@iaea.org http://www-nds.iaea.org

14. Summary and conclusions USU definition given First action : UQ based on recognized uncertainties Second : Outlier removal Third: estimate USU (if any) following clues Examples given of what is not USU USU~200 pcm for HMF benchmarks (sph. vs cyl.) Important 252Cf(s.f.) nubar ( ) to be reevaluated: Expected from 0.23% up to 0.38% (PUBs) Std 2009 (/B-VII)=0.13%; Std 2017 (/B-VIII)=0.42% USU estimates: Roberto Capote, IAEA Nuclear Data Section e-mail: R.CapoteNoy@iaea.org Web: http://www-nds.iaea.org Nuclear Data Week, CSWEG 2019* 4-6 November 2019, BNL, Upton, NY 14 R.CapoteNoy@iaea.org http://www-nds.iaea.org