BetaDelayedNeutronCompilationandEvaluationinthe.pptVIP

Compilation and Evaluation of Beta-Delayed Neutron emission probabilities and half-lives of precursors in the Non-Fission Region (A ≤ 72) M. Birch and B. Singh (McMaster University) D. Abriola (NDS-IAEA) T.D. Johnson, E.A. McCutchan and A.A. Sonzogni (NNDC, BNL) Presented by B. Singh at DDEP workshop, Oct 8-10, 2012 LNHB/CEA Saclay, France Beta Delayed Neutron Emission Process In neutron rich nuclei, if the Q-value of the beta decay of the parent (precursor) is greater than the neutron separation energy of the daughter then neutron unbound levels in the beta-daughter nuclide may be populated which decay by neutron emission We define this energy window as Qβ-n = Qβ(A,Z) – Sn(A,Z+1) Need Qβ-n 0 for delayed neutron emission to occur Beta Delayed Neutron Emission Process Previous Evaluations of the A ≤ 72 Region Only a few nuclides were present in earlier evaluations: L. Tomlinson, ADNDT 12, 179 (1973): 5 nuclides 8He, 9Li, 12Be, 13B, 17N P. del Marmol, ADNDT A6, 141 (1969): 8He, 9Li, 12Be, 17N Since 1973 many new measurements have been made in this mass region Current work is the first comprehensive compilation and evaluation of Pn for this mass region Potential Precursors in the A ≤ 72 Region The delayed neutron emission probabilities have been experimentally measured for 101 precursors. These measurements have been compiled and evaluated. 112 additional nuclides have been identified as potential precursors based on Qβ-n 0 using mass values from G. Audi et al., 2011 interim mass evaluation file (2011AuZZ) For 172 of these nuclides (including all but one of the 101 measured precursors) half-life measurements are also available. These too have been compiled and evaluated. Potential Precursors in the A ≤ 72 Region Some of these nuclides can emit two or more delayed neutrons if Qβ S2n or Qβ S3n Potential Precursors in the A ≤ 72 Region P2n P3n Number of cases with measured P2n , P3n 19 4 Potential number of precursors (2011AuZZ) 115 80 Each measured multip