Determination of gamma-ray transition probabilities and decay

Report
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
• Mughabghab s0, 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 sg or 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
1.
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 3from statistical model calculations. Further investigation
indicates adopted Jp is based on weak partially obscured grays and inconsistent with g-ray decay to 2+ levels.
Determination of s0/Pg:
24Na
SN
PGAA
540(4) mb
6959.257
Summing problems
May have affected
previous values.
24gNa
Author (year)
Coltman (1946)
Pomerance (1951)
Meadows (1961)
Brooksbank (1955)
Koehler (1963)
Yamamuro (1970)
Harris (1953)
Grimeland (1955)
De Corte (2003)
Kennedy (2003)
Heft (1978)
Ryves (1970)
Szentmiklosi (2006)
Bartholomew (1953)
Wolf (1960)
Cocking (1958)
Jowitt (1959)
Rose (1959)
EGAF-PGAA
EGAF-NAA
Gleason (1975)
Kaminishi (1963)
Seren (1947)
Atlas
s0±Ds (mb)
0.47±0.04
0.470±0.024
0.47±0.06
0.50±0.05
0.50±0.02
0.50±0.03
0.503±0.005
0.51±0.03
0.513±0.006
0.515±0.021
0.523±0.005
0.527±0.005
0.527±0.008
0.530±0.032
0.531±0.008
0.536±0.006
0.536±0.008
0.539±0.008
0.540±0.004
0.542±0.003
0.54±0.02
0.577±0.008
0.63±0.13
0.517±0.004
Determination of
s0/Pg: 41K
SN 7533.80
PGAA
1.62(3) b
A significant problem
may exist with Pg values
measured by 4pb-g.
Many s0 values were
measured this way
s0±Ds
Author (Year)
(mb)
Seren (1947)
1.0±0.2
Pomerance (1952) 1.19±0.10
Koehler (1967)
1.2±0.1
Gryntakis (1976) 1.28±0.06
De Corte (2003)
1.42±0.02
Gleason (1975)
1.43±0.03
Heft (1978)
1.43±0.03
Lyon (1960)
1.45
Ryves (1970)
1.46±0.03
Kappe (1966)
1.49±0.03
Kaminishi (1982)* 1.57±0.17
EGAF
1.62±0.03
Atlas
1.46±0.03
sg(1525)
0.263(2)
0.257(5)
0.252(5)
0.266(8)
0.269(5)
* 4pb-g Corrected for self-absorption
Author (Year)
Pg (1566)
Miyahara (1990)* 0.1808(9)
Simoes (2001)*
0.1813(14)
EGAF
0.164(4)
* 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)
Eg (keV)
sg (IUPAC)
Pg (IUPAC)
Pg (DDEP)
311.4
0.00217(1)
0.00033(3)
0.000314(21)
647.3
0.00285(4)
0.000252(18) 0.000252(14)
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

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