UNCLASSIFIEDManaged by Triad National Security, LLC for the U.S. Department of Energy’s NNSA

Pu Evaluations

LA-UR-19-xxxxx

Patrick TalouLos Alamos National Laboratory

CSEWG, NNDC, BNL, Nov. 5-6, 2019

Plutonium Isotopes

Slide 2

xs (fast) xs (RRR) xs (URR) PFNS Nu-bar Covariances236 JENDL-4.0 JENDL-4.0 JENDL-4.0 JENDL-4.0 JENDL-4.0 31,32,33,34,35

237 JENDL-4.0 JENDL-4.0 JENDL-4.0 JENDL-4.0 JENDL-4.0 31,32,33,34,35

238 ENDF/B-VII.1 JENDL-4.0 JENDL-4.0 ENDF/B-VII.1 ENDF/B-VII.1 31,33,35

239 ENDF/B-VIII ENDF/B-VIII ENDF/B-VIII ENDF/B-VIII ENDF/B-VIII 31,32,33,35

240 ENDF/B-VII.1 ENDF/B-VIII ENDF/B-VII.1 ENDF/B-VII.1 ENDF/B-VII.1 31,32,33,35

241 ENDF/B-VI ENDF/B-VI ENDF/B-VI ENDF/B-VI ENDF/B-VI ENDF/B-VII

242 JENDL-4.0 ENDF/B-VII ENDF/B-VII JENDL-4.0 JENDL-4.0 31,33,34,35

243 ENDF/B-V-VI ENDF/B-V-VI ENDF/B-V-VI ENDF/B-V-VI ENDF/B-VIII

244 JENDL-4.0 JENDL-4.0 JENDL-4.0 JENDL-4.0 ENDF/B-VIII 31,32,33,34,35

245 ENDF/B-VIII? ENDF/B-VIII? ENDF/B-VIII? From Pu243 From Pu243

246 JENDL-4.0 JENDL-4.0 JENDL-4.0 JENDL-4.0 ENDF/B-VIII 31,33,34,35

ENDF/B-VIII.0

Older ENDF/B

Recent, OK

Needs work

Bad

Nothing

Other evaluation

A plethora of inconsistent physics models…

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Slide 3

– A=236, 237, 5/18, CCONE (JENDL-4.0)– A=238, 5/18, LAM (ENDF/B-VII.1)– A=239, 5/18, LAM+Chi-Nu (B-VIII.0) to be finalized– A=240, 5/18, LAM (B-VII.1, 2010)– A=241, 5/18, Maxwellian, (B-VI, 1990)– A=242, 5/18, CCONE (JENDL-4.0)– A=243, 5/18, Maxwellian (B-VI.1)– A=244, 5/18, CCONE (JENDL-4.0)– A=245, 5/18, adopted from Pu243– A=246, 5/18, CCONE (JENDL-4.0)

Prompt Fission Neutron Spectra

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Slide 4

§ Emission of neutron(s) prior to fission (of residual nucleus)– First-chance (n,n’f), second-chance (n,2nf), …– It ties together the suite of isotopes

§ But it’s not a trivial connection!§ Fission observables

– Cross Sections, PFNS,kinetic energy of fragments, FPY, etc

– It places constraints on sophisticated fission physics models

The role of multi-chance fission

n

n’

g

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Slide 5

§ Fission cross section modeling– R-matrix, Bouland, Lynn, Talou, PRC 88,

054612 (2013)– Optical model, Sin, Capote, Herman, Trkov,

PRC 93, 034605 (2016)– Multi-dimensional fission paths?– Fission fragment angular distributions– (n,gf) process (also ties to <n> fluctuations)

Lynn, Talou, Bouland, PRC 97, 064601 (2018)§ Prompt fission data (PFNS, PFgS, …)

– Statistical decay of fission fragments (CGMF, FREYA, BeOH)

– Ties together Y(A,Z), TKE, PFNS, <n>, PFG … without the need for Jezebel!

– Randrup, Talou, Vogt, PRC 99, 054619 (2019)

More sophisticated physics models are needed to make use of those correlations as constraints

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Slide 6

§ See FPY Session§ Ties prompt and b-delayed fission data to IFY and CFY

Fission Product Yield Evaluation efforts will also help!

0

0.02

0.04

0.06

0.08

0.1(a) Thermal

Fiss

ion

Yiel

d

JENDLpre

post(b) Fast JENDL

prepost

0

0.02

0.04

0.06

0.08

0.1

60 80 100 120 140 160 180

(c) 3 MeV

Fiss

ion

Yiel

d

Mass Number

prepost

60 80 100 120 140 160 180

(d) 5 MeV

Mass Number

prepost

235U

Krishichayan et al, PRC 100, 014608 (2019)Okumura, Kawano et al, JNST (2018)

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Slide 7

§ Latest 239Pu ChiNu data (see Lee’s talk) + new evaluation§ Other isotopes? New data?§ Modeling with CGMF/FREYA? PFNS too soft?§ RPI quasi-integral (n,xn) experiments (see Danon’s talk)

Prompt Fission Neutron Spectrum (PFNS)

Kelly et al, PRL 122, 072503 (2019)

0.5

1

1.5

2

2.5

0.01 0.1 1 10

PFN

S / M

axw

ellia

n (T

=1.4

2 M

eV)

Outgoing Neutron Energy (MeV)

239Pu(n14 MeV,f)

Chi-Nu,liquids, 14.5 MeVChi-Nu,LiGl, 14.5 MeV

ENDF/B-VIII.0JEFF-3.3

Eval.+Chi-Nu

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Slide 8

§ Not too bad: covariances available for many isotopes and reactions§ Consistent across suite of isotopes: no§ Realistic: probably not – needs validation§ Lots of UQ work on PFNS, sf, <n> for 239Pu only (Neudecker et al)§ Model limitations w/o data?

Status of uncertainties & correlations

Neudecker et al, NDS 148, 293 (2018)

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Slide 9

§ NIFFTE fissionTPC data to be finalized, but new measurements in ratio to 6Li(,nt) in progress

§ New modeling should tie measured angular distributions to cross sections

Fission Cross Section

0.9

1

1.1

1.2

1.3

1.4

1.5

1.6

1.7

0.1 1 10

Rat

io s

f (Pu

-239

) / s

f (U

-235

)

Incident Neutron Energy (MeV)

Carlson,1978Staples,1998

Lisowski,1991Shcherbakov,2001

Tovesson,2010Standards, 2007

Ratio 239Pu/235U s(n,f)

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Slide 10

§ P(n;Einc) now available for 239Pu; can be calculated for all other Pu isotopes, given reasonable Y(A,Z,TKE;Einc)

§ Still too large uncertainties for <n>(Einc) à new measurements?

Prompt Fission Neutron Multiplicity (<n>) and P(n)

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Slide 11

§ Model calculations of PFGS reproduce well recent exp. data

§ Role of isomers in time-dependent PFGS

§ Multiplicity-dependent spectra§ Problem with total g-ray energy

and/or multiplicity

Prompt Fission g-Ray Data

10-3

10-2

10-1

100

101

0 1 2 3 4 5 6

239Pu (nth,f)

PF

GS

(1/

MeV

)

Outgoing gamma-ray energy (MeV)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0.0 0.5 1.0 1.5 2.0

PF

GS

(1/

MeV

)

Outgoing gamma-ray energy (MeV)

Gatera, 2017Chyzh (s), 2014Chyzh (b), 2014Verbinski, 1973Ullmann, 2014

CGMFENDF/B-VII.1

JENDL 4.0JEFF 3.3

ENDF/B-VIII.0

239Pu(nth,f)

4

5

6

7

8

9

10

11

12

13

14

0 2 4 6 8 10 12 14 16 18 20

239Pu (n,f)

⟨νγ⟩

Incident Neutron Energy (MeV)

ENDF/B-VII.1Oberstedt, 2017

Chyzh, 2014Ullmann, 2013

Verbinski, 1973Drake, inferred

Nellis, inferredCGMF

Oberstedt, 2017JEFF 3.3JENDL 4

ENDF/B-VIII

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Slide 12

§ 239Pu (n,g) cross section measurement [Mosby et al, NDS 148, 312 (2018)] à ENDF/B-VIII.0

§ Impact of M1 “scissors” mode on other Pu capture cross sections

Capture Cross Section

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Slide 13

§ Small change to 239Pu(n,2n) cross section near threshold, motivated by PROFIL studies and internal LANL data testing

§ No other changes to elastic/inelastic§ Quasi-integral RPI scattering experiments (see Danon’s talk)§ LLNL Pulsed-spheres § New scattering experiments (Bernstein) à n,g correlated exp/sim

(n,xn) Cross Sections

Pu, 0.7 mfp, NE213-A, 117

10-4

10-3

10-2

10-1

100

Flux

/ Sou

rce

Neu

tr./ n

s

UCID-16372ENDF/B-VIII.0+Chi-NuFeb19

ENDF/B-VIII.0

0.60.8

11.21.41.6

150 200 250 300 350 400 450 500

C/E

Time (ns)

ENDF/B-VIII.0+Chi-NuFeb19ENDF/B-VIII.0

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Jezebel and Flaptop-Pu Spectral indices

PMF assemblies, poor situation; more work needed for Pu data !!

Credit: R.Capote (IAEA)

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Dosimetry reactions in plutonium fast critical assemblies

Chadwick et al., CIELO Collaboration, NDS118, 1-25 (2014)

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Slide 16

§ Advanced physics models provide tighter and correlated constraints on evaluated data

§ Experimental data on suite of isotopes promise correlated information

§ Realistic UQ would benefit from consistency across suite of isotopes§ Some advances made on major isotopes should benefit more minor

ones

Final remarks

Thanks to:

Conlin, Haeck, Herman, Kawano, Mumpower, Neudecker, Parsons, Stetcu