neutron-induced fission studies and reactions on specific nuclei · 2018-03-12 · 235u, 238u and...
TRANSCRIPT
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
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
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
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
?
?
?
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:
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)
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
169Tm(n,3n)167Tm209Bi(n,4n)206Bi
Diagnostic tool for National Ignition Facility at LLNL
169Tm(n,3n)167Tm209Bi(n,4n)206Bi
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
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
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
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