b. singh and m. birch 02/05/2013beta-delayed neutron data evaluation compilation and evaluation of...

B. Singh and M. Birch02/05/2013 Beta-Delayed Neutron Data Evaluation

Compilation and Evaluation of %Pn and T1/2 Data for β-delayed

Neutron Emitters

Balraj Singh, Michael Birch, Alan ChenMcMaster University

Pre-CRP North American Workshop on Beta-delayed neutron emission 2-3 May 2013 at JIHIR (ORNL, USA)


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


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.

B. Singh and M. Birch

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

02/05/2013 Beta-Delayed Neutron Data Evaluation


Beta-Delayed Neutron Emission in

Potential Precursors identified using AME-2012

A≤72 Mass Region: 1nBeta-Delayed Neutron Emission in

A≤72 Mass Region: 1n



Beta-Delayed Neutron Emission inA≤72 Mass Region: 2n



Beta-Delayed Neutron Emission inA≤72 Mass Region: 3n



Potential Precursors identified using AME-2012, measurements listed in ENSDF database

72<A≤150 Mass Region: 1n






Potential Precursors identified using AME-2012, measurements listed in ENSDF database


Beta-Delayed Neutron Emission in A > 150 Mass Region: 1n

Potential Precursors identified using AME-2012, measurement listed in ENSDF database

Tl-210 ?(1961ST20 report)


Beta-Delayed Neutron PrecursorsMass Region Predicted MeasuredA < 72 1n 203 107

2n 127 193n 76 44n 39 1 (B-17)

72 < A < 150 1n 287 1332n 131 33n 28 0

A > 150 1n 42 1 (Tl-210 ?): TID-14880

2n 1 03n 0 0


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


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.


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


A ≤ 72 Systematics

Fit

•Only data with an uncertainty in Pn ≤ 25% used•Predictions within one order of magnitude

a = 0.0282(53)b = 4.351(81)


Example: 137INSR Reference Half-life (s) %P(n) Method Comments

2013Ye02 6.80(88), 6.88(105), 6.95(76)

Low-energy recoilβ-delayed γ-raysβ singles

2010MaZS ~6.9 n Preliminary Result

1993Ru01* 24.13(12) 7.46(30) n, β-

1980ReZQ* 7.6(8) Ion counting Also 1977Re05,P(n)=8.5(9)

1980Lu04 24.3 6.7(4) n, β- Same group as 1993Ru01

1978Kr15 24.3(8) 6.1(5) fission Also 1974Kr21: mixed activity

1975As04* 24.8(2) 6.1(8) n, β-

1974Gr29 24.5(2) n Same group as 1993Ru01, also 1974Ru08, 1976Lu02

1972Sc48 24.3(8) 6.6(8) fission Adjusted in 1993Ru01 from 5.2(7). Also 1969ScZY

1971De35* 24.7(2) 8.6(12) Gamma,Xe-137

1964Ar24 24 3.0(5) n, β- Outlier: Chauvenet’s criterion

1959Pe28 24.4(4) fission


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


Example: 138I


Example: 64Mn

Reference Pn (%) Method Comments

Hannawald, PhD. Thesis (2000)[2000HaZL]

33(2) n- β counting

Possible problem with neutron and β efficiency?

PRC 86, 064318 (2012)[2012Pa39]

2.7(6) β-γ Level-scheme details not available


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

T1/2 and Qβ-n Syst.

0.144(29)0.110(41)0.38(14)2.96(66)1.87(43)6.0(14)5.9(14)16.0(54)16.1(62)16.7(76)


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


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.

02/05/2013 Beta-Delayed Neutron Data Evaluation

b. singh and m. birch 02/05/2013beta-delayed neutron data evaluation compilation and evaluation of...

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