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Neutron Activation Decay Data. Richard B. Firestone Isotopes Project, Lawrence Berkeley National Laboratory, Berkeley, CA 94720. The Evaluated Gamma-ray Activation File (EGAF).
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Neutron Activation Decay Data Richard B. Firestone Isotopes Project, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 DDEP Workshop 8-10 October 2012
The Evaluated Gamma-ray Activation File (EGAF) • The EGAF database was developed to manage the first measurements of prompt and delayed g-ray cross sections at the Budapest Reactor. • These data were compiled under an IAEA CRP and are available in • Database of Prompt Gamma Rays from Slow Neutron Capture for Elemental Analysis, R.B. Firestone, et al, IAEA STI/PUB/1263, 251 pp (2007). • Handbook of Prompt Gamma Activation Analysis with Neutron Beams, edited by G.L. Molnar (Kluwer Publishers, 2004). • EGAF Contents • Eg, sg for prompt g-rays from thermal (n,g) on all isotopic targets • Eg, sg, t1/2, for g-rays from all thermal (n,g) activation products • s0 derived from sg data and other measurements • Adopted Levels, Gammas, Sn for all (n,g) product nuclei (RIPL)
Evaluation of Neutron Activation Products • The Evaluated Gamma-ray Activation File (EGAF) contains adopted decay data for all activation products. I propose that these data be evaluated under DDEP guidelines. • Important for reactor decay heat calculations • Important for neutron transport calculations • Important for neutron activation analysis (NAA) • Important for national security and nonproliferation • Important for nuclear medicine • Special decay scheme normalization constraints • 303 Isotopes, 81 isotopes evaluated by DDEP
Activation Product List • DDEP evaluated
Data Resources • Cross sections • EGAF activation product sg, s0 • IUPAC NAA k0 compilation • Mughabghabs0, Atlas of Neutron Resonances • Literature • Radioactive decay data • DDEP evaluations • ENSDF evaluations • XUNDL compilations • Literature • Decay energies • Audi atomic mass evaluations
Decay Scheme Normalization s0=Ssg(GS)=Ssg(CS) s0=sg/Pg If s0 is determined from prompt sgor other data and decay sg is known, then Pg is uniquely determined. Both sg and s0 can be measured in the same experiment.
Determination of s0 Z<20 decay scheme complete s0=Ssg(GS)=Ssg(CS) 2. Z≥20 must correct for continuum Continuum – calculated with statistical model code DICEBOX Below Ecrit – measured primary, secondary g-rays from EGAF. Level scheme from ENSDF, modified to RIPL standard and consistency with DICEBOX s0=Ssg(GS)expt+Ssg(GS)calc
Population/Depopulation Plots Comparison of cross sections populating levels (DICEBOX) and depopulating them (EGAF) helps chose statistical model parameters.
Improved Adopted Level Properties Jp=4-based upon ag(t) in 104Ru(α,2ng) is inconsistent with 3- from statistical model calculations. Further investigation indicates adopted Jp is based on weak partially obscured g-rays and inconsistent with g-ray decay to 2+ levels.
SN 6959.257 PGAA 540(4) mb 478(4) mb 543.3(35) b 540.9(25) b Determination of s0/Pg: 24Na Summing problems May have affected previous values.
SN 7533.80 PGAA 1.62(3) b 0.269(5) b Determination of s0/Pg: 41K A significant problem may exist with Pg values measured by 4pb-g. Many s0 values were measured this way * 4pb-gCorrected for self-absorption * 4pb-g measurement not corrected for self-absorption in the target.
Determination of s0/Pg: 109Pd For s0 (EGAF)=8.6(6) b (s0 (Atlas)=7.6(5) b)
Conclusions • EGAF database provides an opportunity to evaluate a complete thermal neutron activation database • Evaluations should be consistent with DDEP standards • Addition of s0 cross sections • Improved Pg measurements • Move towards a common decay data evaluation standard for all databases (EGAF, ENSDF, DDEP) - discussion
