Neutron-Induced Fission Studiesand

Reactions on Specific Nuclei

Presenter: Werner Tornow (PI)Duke University & TUNL

Co-PI: C.R. Howell, Duke University & TUNL

Co-authors: Megha Bhike, B. Fallin, S. Finch, KrishichayanIsabel Newsome, Jennifer Soter, Sarah Wildenhain

Duke University & TUNL&

T. Bredeweg, M. Fowler, M. Gooden, D. Vieira, J. WilhelmyLANL

&J. Silano, M. Stoyer, A. Tonchev

LLNL

Outline

1. Fission product yield measurements for 235,238U(n,f) and 239Pu(n,f) between En=0.0 and 15 MeV

2. (Nuclear Forensics: Fission Isomers 134mTe and 136mXe)

3. 238U(n,)239U

4. NIF: 169Tm(n,2n)168Tm, 169Tm(n,3n)167Tm), and 209Bi(n,4n)206Bi

5. Interpretation of nuclear test results: 191,193Ir(n,2n)190,192Ir

6. Future work

Fission Product Yields (FPYs)• Shape and energy

evolution of FPY mass distribution is a sensitive probe of the fission process

• Need for high-precision FPY data– Stockpile Science– Nuclear Energy– Nuclear Forensics– Antineutrino Anomaly– Benchmark for Microscopic

Fission Models Data from T.R. England and B.F. Rider, LA‐UR‐94‐3106 (1994)

Fission Product Yields Landscape• Neutron-rich fission

products β-decay to stability

• Identify with E and t1/2

• Determine cumulative & independent yields Fission Products

Stable Nuclei

Resolve the long-standing difference between LLNL and LANL with respect to selected fission product data

Joint LANL/LLNL fission product review panel suggested the possible energy dependence239Pu(n,f)147Nd fission product yield:

4.7%/MeV from 0.2 to 1.9 MeV (M. Chadwick) 3.2%/MeV from 0.2 to 1.9 MeV (I. Thompson)1

Relative slope (%) = 100* [(FPY(E2)-FPY(E1)) / (E2-E1)] / FPY(E1)

Mostly low energy data from critical assemblies or fast reactors

M.B. Chadwick et al. Nuclear Data Sheets 111 (2010) 2923; H.D Selby et al. Nuclear Data Sheets 111 (2010) 2891.P. Baisden et al, LLNL-TR-426165, 2010; R. Henderson et al. LLNL-TR-418425-DRAFT; I. Thompson et al. Nucl. Sci. Eng. 171, 85 (2012)

There are no 147Nd data between 1.9 and 14 MeV

Not many data exist in the MeV range

Large discrepancy (~20%) at 14 MeV

239Pu(n,f)147Nd

239Pu(n,f)147Nd

J. Lestone. Nuclear Data Sheets 112 (2011) 3120T. Kawano et al. J. Nucl. Sci. Technol. 50 (2013) 1034

GEF Code, Version 2.2, 2013

Approach

Mono-energetic neutron beams

Dual fission chambers to get absolute yields

High-resolution -ray spectroscopy

Floor Plan of TUNL (Triangle Universities Nuclear Laboratory)

For neutron energies below En=0.6 MeV: 7Li(p,n)7Be

For neutron energies below En=4 MeV: 3H(p,n)3He

For neutron energies above En=4 MeV: 2H(d,n)3He

For neutron energies above En=14.5 MeV and below 30 MeV: 3H(d,n)4He

Thick Target Thin Monitor Foils

Fission ChambersGas Inflow

Dual Fission Chamber

2H gas

From VdG accelerator

p or dn

One thick target ~0.2 g/cm2

Two thin targets ~10 μg/cm2

Dual fission chamber n-detector

(Gamma_count / Fission_count) = (mthick / mthin) * FPY * C

9 MeV datum not corrected for off-energy neutrons from the 2H(d,n)3He reaction

9 MeV datum not corrected for off-energy neutrons from 2H(d,n)3He reaction

Datum at 9 MeV not corrected for off-energy neutrons from the 2H(d,n)3He reaction

9 MeV datum not corrected for off-energy neutrons from 2H(d,n)3He reaction

At higher energies, 5 – 15 MeV,all is consistent with what we know

The symmetric FPYs increase

The two asymmetric FPY’s slightly decrease

The very asymmetric FPY’s (the wings) slightly increase

At higher energies, 5 – 15 MeV,all is consistent with what we know

The symmetric FPYs increase

The two asymmetric FPY’s slightly decrease

The very asymmetric FPY’s (the wings) slightly increase

At lower energies, 0.5 –5 MeV,a new phenomenon

Expand effort on basic theory of fission to understand evolution of yields at low neutron energies

Conjecture: Interplay between pairing and shell effects

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Short Lived FPY Measurementsht

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• Expose to neutron beam for 1 hr, begin counting immediately after (<5 min) and count continuously for 3-4 days

• Reduce activity from long lived FPs, halving background

Decay Time:

Fission Product -Ray Spectra at En = 9 MeV

Decay Time:

FPY Mass Distribution: Long & Short Irradiation

• Self-consistent, systematic approach to measuring FPYs

• Long-lived (days or weeks)

• Short-lived (minutes or hours)

• Constrain the mass distribution

10-2

10-1

100

10-2

10-1

100

101

70 80 90 100 110 120 130 140 150 16010-2

10-1

100

238U(n,f)Long irradiation ( ) and short ( ) data

235U(n,f)

En= 9 MeV

Long irradiation ( ) and short ( ) data

Long irradiation ( ) and short ( ) data

Fiss

ion

Prod

uct Y

ield

(%)

Product Mass Number

239Pu(n,f)

10-2

10-1

100

10-2

10-1

100

101

70 80 90 100 110 120 130 140 150 16010-2

10-1

100

238U(n,f)Long irradiation ( ) and short ( ) data

235U(n,f)

En= 9 MeV

Long irradiation ( ) and short ( ) data

Long irradiation ( ) and short ( ) data

Fiss

ion

Prod

uct Y

ield

(%)

Product Mass Number

239Pu(n,f)

239Pu235U 238U

Independent Cumulative Fission Product Yields

238U(n,)239U

Uγ)U(n, 23992

23892

Np23993

- T1/2

= 23.45(2) m

- T1/2

= 2.356(3) d

Pu23994

238U(n,)239U

238U pill box

238U 197Au197Au

1/16”wall thickness

238U

3H(p,n)3He

AMS: Accelerator Mass Spectroscopy, Wallner et al.

National Ignition Facility (NIF)at LLNL

Inertial Confined Fusion, 192 laser beams, DT capsule in hohlraum

Ratio of secondary and tertiary neutrons to primary neutrons is a measureof the density of the DT plasma

RIF

RIF Studies

En (MeV) 17.5 – 21.5 23.5 – 30

169Tm(n,3n)167Tm209Bi(n,4n)206Bi

Diagnostic tool for National Ignition Facility at LLNL

169Tm(n,3n)167Tm209Bi(n,4n)206Bi

169Tm(n,2n)168TmDiagnostic tool for National Ignition Facility at LLNL

169Tm(n,2n)168Tm

191,193Ir(n,2n)190,192Ir

Medical uses

Material for constructing activation detector

191Ir(n,2n)190mIr

What are the plans for the future?

Fission Product Yield at thermal energy on 239Pu, 235U and 238UTest run at the MIT reactor: Week of March 19, 2018Production run during the summer 2018 at the MIT reactor

Fission Product Yield at 11.0 MeV for 235U

Fission Product Yield at 13.2 MeV for 235U, 238U

Continue 238U(n,)239U between 0.2 and 3 MeV

Continue 169Tm(n,2n)168Tm and 169Tm(n,3n)167Tm

Continue 191,193Ir(n,2n)190,192Ir

Recent publications:

“Energy Dependence of Fission Product Yields from 235U, 238U and 239Pu for Incident Neutron Energies between 0.5 and 14.8 MeV”, M.E. Gooden, C.W. Arnold, J.A. Becker, C. Bhatia, M. Bhike, E.M. Bond, T.A. Bredeweg, B. Fallin, M.M. Fowler, C.R. Howell, J.H. Kelley, Krishichayan, R. Macri, G. Rusev, C. Ryan, S.A. Sheets, M.A. Stoyer, A.P. Tonchev, W. Tornow, D.J. Vieira, and J.B. Wilhelmy, Nuclear Data Sheets 131, 319 (2016).

“Measurement of the 169Tm(n,3n)167Tm cross section and the branching ratios in the decay of 167Tm”, B. Champine, M. Bhike, M.E. Gooden, Krishichayan, E.B. Norman, N.D. Scielzo, M.A. Stoyer, K.J. Thomas, A.P. Tonchev, and W. Tornow, Phys. Rev. C 89, 014611 (2016).

“Measurement of the 209Bi(n,4n)206Bi and 169Tm(n,3n)167Tm cross sections between 23.5 and 30.5 MeV relevant to reaction in flight neutron studies at the National Ignition Facility”, M.E. Gooden, T.A. Bredeweg, B. Champine, D.C. Combs, S. Finch, A. Hayes-Sterbenz, E. Henry, Krishichayan, R. Rundberg, W. Tornow, J. Wilhelmy, and C. Yeamans, Phys. Rev. C 96, 024622 (2017).

“Measurements of the 169Tm(n,2n)168Tm cross section from threshold to 15 MeV”, J. Soter, M. Bhike, S.W. Finch, Krishichayan, and W. Tornow, Phys. Rev. C 96, 064619 (2017).

Recent Presentations:

A. Tonchev, Recent Results from Fission Product Yield Measurements. Tri-Lab Nuclear Data Workshop, Aldermaston, UK, May 18, 2016.

W. Tornow, Energy Dependence of Fission-Product Yields from 235U, 238U and 239Pu for Incident Energies between 0.5 and 15 MeV, Technical Meeting on "Fission Yields: current status and perspective in measurements, theory and evaluations", IAEA, Vienna, Austria, 23-26 May 2016.

M.E. Gooden, Energy Dependence of Fission Product Yields from 235U, 238U and 239Pu for Incidence Neutron Energies Between Thermal and 14.8 MeV, International Conference on Nuclear Data for Science and Technology, Bruges, Belgium, September 2016.

Where are they now?

Robert A. Macri: staff member at LLNL

A. Hutcheson: Staff member at Office of Naval Research

Elaine Kwan: Staff member at NCL, MSU

Gencho Y. Rusev: Staff member at LANL

Anton P. Tonchev: Staff member at LLNL

Matthew E. Gooden: Staff member at LANL

Sample

Sample

d +d

d +T

up to 21.5 MeV

above 21.5 MeV

Use a mixture of 124Xe and 136Xe or Kr as tracer nuclei

The (n) reaction with Q=0 MeV probes the low-energy neutroncomponent

The (n,2n) reaction with Q>9 MeV probes the high-energy neutron component

(ablator)or SiO2

169Tm(n,3n)167Tm

N=82 even-even closed shell nuclei

ENDF for prompt fission products

Nuclear Forensics

ExperimentTUNL 10 MV Tandem accelerator

• 8 MeV neutrons produced by D(d,n) reaction

• Shielded neutron source area– Copper collimator – Finely sized neutron beam– Low beam related

backgrounds• Two clover HPGe detectors

– HPGe detectors offer superior energy resolution

• Targets– 1.5 g 235U– 2.1 g 238U

Tandem Experiment

for 238U

ResultsEn=8 MeV

For 235U(n,f) there is an intrinsic background line at the energy of 134mTe

For 235U(,f) no problem: see C.R. Howell’s talk

63,65Cu(n,γ)64,66Cu

Used in many nuclear physics applications

submitted

63Cu(n,γ)64Cu65Cu(n,γ)66Cu