Neutron Activation Decay DataRichard 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 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.

Determination of s0/Pg: 24Na

540.

9(25

) b543.

3(35

) b

478(

4) m

bPGAA 540(4) mb

SN 6959.257

24gNaAuthor (year) s0±Ds (mb)

Coltman (1946) 0.47±0.04Pomerance (1951) 0.470±0.024Meadows (1961) 0.47±0.06Brooksbank (1955) 0.50±0.05Koehler (1963) 0.50±0.02Yamamuro (1970) 0.50±0.03Harris (1953) 0.503±0.005Grimeland (1955) 0.51±0.03De Corte (2003) 0.513±0.006Kennedy (2003) 0.515±0.021Heft (1978) 0.523±0.005Ryves (1970) 0.527±0.005Szentmiklosi (2006) 0.527±0.008Bartholomew (1953) 0.530±0.032Wolf (1960) 0.531±0.008Cocking (1958) 0.536±0.006Jowitt (1959) 0.536±0.008Rose (1959) 0.539±0.008EGAF-PGAA 0.540±0.004EGAF-NAA 0.542±0.003Gleason (1975) 0.54±0.02Kaminishi (1963) 0.577±0.008Seren (1947) 0.63±0.13Atlas 0.517±0.004

Summing problemsMay have affectedprevious values.

Determination of s0/Pg: 41K

SN 7533.80

PGAA 1.62(3) b

0.26

9(5)

b

Author (Year)s0±Ds (mb) sg(1525)

Seren (1947) 1.0±0.2Pomerance (1952) 1.19±0.10Koehler (1967) 1.2±0.1Gryntakis (1976) 1.28±0.06De Corte (2003) 1.42±0.02 0.263(2)Gleason (1975) 1.43±0.03 0.257(5)Heft (1978) 1.43±0.03 0.252(5)Lyon (1960) 1.45Ryves (1970) 1.46±0.03Kappe (1966) 1.49±0.03 0.266(8)Kaminishi (1982)* 1.57±0.17EGAF 1.62±0.03 0.269(5)Atlas 1.46±0.03

Author (Year) P g (1566)

Miyahara (1990)* 0.1808(9)

Simoes (2001)* 0.1813(14)

EGAF 0.164(4)

* 4 -pb g measurement not corrected for self-absorption in the target.

A significant problemmay exist with Pg valuesmeasured by 4 -pb g.Many s0 values weremeasured this way

* 4 -pb g Corrected for self-absorption

Determination of s0/Pg: 109Pd

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)

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

Thank you for your attention