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Compilation and Evaluation of %P n and T 1/2 Data for β - delayed Neutron Emitters

Compilation and Evaluation of %P n and T 1/2 Data for β - delayed Neutron Emitters. Balraj Singh, Michael Birch, Alan Chen McMaster University Pre-CRP North American Workshop on Beta-delayed neutron emission 2-3 May 2013 at JIHIR (ORNL, USA). Outline.

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Compilation and Evaluation of %P n and T 1/2 Data for β - delayed Neutron Emitters

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  1. Compilation and Evaluation of %Pn and T1/2 Data for β-delayed Neutron Emitters Balraj Singh, Michael Birch, Alan Chen McMaster University Pre-CRP North American Workshop on Beta-delayed neutron emission 2-3 May 2013 at JIHIR (ORNL, USA) Beta-Delayed Neutron Data Evaluation

  2. Outline • Status of available compilations/evaluations • Current status of beta-delayed neutron probability measurements • Compilation/Evaluation procedures • A<72 compilation, evaluation, systematics • Examples • Future plan for A>72, fission region • Conclusions Beta-Delayed Neutron Data Evaluation

  3. Status of available compilations/Evaluation • G. Rudstam, K. Aleklett, L. Sihver: ADNDT 53, 1 (1993): evaluation and measurements: Cu-75 to La-150: 93 nuclides : only 31 references cited. • B. Pfeiffer, K.L. Kratz, P. Moller: Prog. Nucl. Energy 41, 39 (2002): compilation Cu-73 to La-150: 129 nuclides. No documentation or source references. -- M.C. Brady: Ph.D. Thesis (Texas A&M, 1989; LA-11534-T): evaluation and calculations: Cu-75 to La-149: 89 nuclides. F.M. Mann, M. Schreiber, R.E. Schenter, T.R. England: Nucl. Sci. Eng. 87, 418 (1984): 72 nuclides T. Izak-Biran, S. Amiel: Nucl. Sci. Eng. 57, 117 (1975): 42 nuclides from As-85 to Cs-146 L. Tomlinson: ADNDT 12, 179 (1973): 41 nuclides (Ga-79 to Cs-146; 5 in non-fission region) P. del Marmol: ADNDT A6, 141 (1969): 30 nuclides (As-85 to Cs-144; 4 in non-fission region) Since 2002, many new measurements in all regions up to A=150 No evaluation for non-fission region A<72 No separation of multiple (P2n,P3n )neutron emission ENSDF coverage of these data is non-uniform and in many cases inadequate. NUBASE-12 takes data mostly from ENSDF. Beta-Delayed Neutron Data Evaluation

  4. Status of available measurements For all mass regions: potential beta-delayed neutron precursors for 1n, 2n, 3n decays; and those for which measurements have been reported, based on Q values from 2012-AME Beta-Delayed Neutron Data Evaluation

  5. Beta-Delayed Neutron Emission in Beta-Delayed Neutron Emission in A≤72 Mass Region: 1n A≤72 Mass Region: 1n Potential Precursors identified using AME-2012 Beta-Delayed Neutron Data Evaluation

  6. Beta-Delayed Neutron Emission in A≤72 Mass Region: 2n Potential Precursors identified using AME-2012 Beta-Delayed Neutron Data Evaluation

  7. Beta-Delayed Neutron Emission in A≤72 Mass Region: 3n Potential Precursors identified using AME-2012 Beta-Delayed Neutron Data Evaluation

  8. Beta-Delayed Neutron Emission in Beta-Delayed Neutron Emission in 72<A≤150 Mass Region: 1n 72<A≤150 Mass Region: 1n Potential Precursors identified using AME-2012, measurements listed in ENSDF database Beta-Delayed Neutron Data Evaluation

  9. Beta-Delayed Neutron Emission in 72<A≤150 Mass Region: 2n Potential Precursors identified using AME-2012, measurements listed in ENSDF database Beta-Delayed Neutron Data Evaluation

  10. Beta-Delayed Neutron Emission in 72<A≤150 Mass Region: 3n Potential Precursors identified using AME-2012 Beta-Delayed Neutron Data Evaluation

  11. Beta-Delayed Neutron Emission in A > 150 Mass Region: 1n Tl-210 ? (1961ST20 report) Potential Precursors identified using AME-2012, measurement listed in ENSDF database Beta-Delayed Neutron Data Evaluation

  12. Beta-Delayed Neutron Precursors Beta-Delayed Neutron Data Evaluation

  13. Compilation/Evaluation Policies • Compile all experimental data, include • T1/2, Pn , methodology • Method: see NDC(NDS)-0599 p. 47; and 1993Ru01 for details) • Neutron-beta coincidences • Neutron and beta counting • γ- γ, β-γ, β-γ-n • Ion counting • Comparison with a standard • Fission yields • New method: recoil fragment, fragment-γ coincidence • Whether neutron spectrum measured • Comments concerning experiment/paper Preferred Beta-Delayed Neutron Data Evaluation

  14. Evaluation Policies • Not just averaging of all experimental numbers, critical assessment of individual measurements • Recommended value is the weighted average of the most reliable measurements; or the most reliable measurement out of a set. • Most recent value taken when measurements repeated by a group over time using same method. • When an average is taken, the assigned uncertainty is not lower than the lowest experimental uncertainty in the dataset that is being averaged. • Full documentation is kept concerning how the evaluated result was obtained, e.g. which results were considered for averaging, and why. • Primary versus secondary (grey) literature; latter used with caution, and if possible in consultation with the authors. Beta-Delayed Neutron Data Evaluation

  15. Work Done So Far: A ≤ 72 • The P1n (including P2n, P3n) probabilities and/or half-lives have been evaluated for a total of 110 nuclides in the A ≤ 72 mass region; another 63 for half-lives only; total of ~200 papers consulted. McMaster+IAEA+GSI+BNL: • M. Birch, B. Singh, D. Abriola, I. Dillmann, A. Sonzogni, E. McCutchan, T. Johnson • Systematics: • The Kratz-Herrmann Formula (KHF: ZP 263 (1973) 435) does not make accurate predictions in this mass region • The ratio of Pn to T1/2 shows a better correlation with the Q(β-n) energy window for the decay Beta-Delayed Neutron Data Evaluation

  16. A ≤ 72 Systematics Fit a = 0.0282(53) b = 4.351(81) • Only data with an uncertainty in Pn ≤ 25% used • Predictions within one order of magnitude Beta-Delayed Neutron Data Evaluation

  17. Example: 137I Beta-Delayed Neutron Data Evaluation

  18. Example: 137I • P(n) : weighted average (LRSW) = 7.29 (33) %, reduced χ2=1.0. Uncertainty of 0.30 in 1993Ru01 increased to 0.46 to limit its relative weight to 50%. Recommended values in 1993Ru01: 7.14 (23) %; 2002Pf04: 7.02 (54) % • T1/2 :24.13(12) s from 1993Ru01 or 24.60(19) s: weighted average (NRM) of 1993Ru01, 1975As04, 1971De35. ENSDF value: 24.5(2) from 1974Gr29. NUBASE-12 value: 24.13(12)s

  19. Example: 138I

  20. Example: 64Mn Beta-Delayed Neutron Data Evaluation

  21. Other 2000HaZL Pn Measurements • Only measurements available for most Mn isotopes; remained unpublished in regular literature • Due to possible discrepant data for 64Mn, new measurements should be made for these isotopes Beta-Delayed Neutron Data Evaluation

  22. Future evaluation plan • Checks on first draft of A<72 region. Plans to publish this in NDS by the end of 2013. • Compilation/evaluation of A=72-150 region starts next week. Much bigger task than A<72 region • Hope to complete first draft by the end of 2014. • Checking may take another six months or so. • Next step is to think about database development: its contents, design, place, who? • Database: contents: • experimental data, systematics, theory, literature, etc Beta-Delayed Neutron Data Evaluation

  23. Conclusions • We feel that a dedicated evaluation of %B-n data and associated half-lives with full details will be useful. It may provide initiative for new experiments where data are lacking or inadequate. • McMaster’s group has completed a first draft of evaluation of A<72 region nuclei. It is being checked by collaborators. • Work on A=73-150 region will soon start with estimated first draft in about a year and half. Probably ~300 papers. • Will keep track of new measurements, and incorporate these in the evaluation of two mass regions as needed. • We will take part in discussions of a suitable database of these data. Beta-Delayed Neutron Data Evaluation

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