Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 1 LLNL-PRES-XXXXXX This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA Lawrence Livermore National Security, LLC TUNL Seminar September 12,

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 2 2 TUNL Duke C. BHATIA M. BHIKE B. FALLIN C. HOWELL W. TORNOW N.C. State Univ. M. GOODEN J. KELLEY LLNL J. BECKER R. HENDERSON J. KENNEALLY R. MACRI C. RYAN S. SHEETS M. STOYER A. TONCHEV LANL C. ARNOLD E. BOND T. BREDEWEG M. FOWLER W. MOODY R. RUNDBERG G. RUSEV D. VIEIRA J. WILHEMY Acknowledgements

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 3 1.Motivation 1.Energy Dependence of Fission-Product Yields 2.Experimental technique 3.Results 4.Future plans

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 4  Resolve the long-standing difference between LLNL and LANL with respect to selected fission product data  Joint LANL/LLNL fission product review panel endorsed a possible energy dependence of 239 Pu(n,f) 147 Nd fission product yield with fission neutrons: 4.7%/MeV from 0.2 to 1.9 MeV (M. Chadwick) 3.2%/MeV from 0.2 to 1.9 MeV (I. Thompson)  Mostly low energy data from critical assembly or fast reactors 239 Pu(n,f) 147 Nd M.B. Chadwick et al. Nuclear Data Sheets 111 (2010) 2923; H.D Selby et al. Nuclear Data Sheets 111 (2010) P. Baisden et al, LLNL-TR , 2010; R. Henderson et al. LLNL-TR DRAFT; I. Tompson et al. Nucl. Sci. Eng. 171, 85 (2012) There are no 147 Nd data between 1.9 and 14 MeV  Very scarce experimental data at the MeV- range  Large discrepancy (~20%) at 14 MeV

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 5 Scission point % KE Prompt n-emission Prompt  -emission Beta decay, delayed n,  Credit: Encyclopædia Britannica, Inc Saddle point Distance between fragments (cm) time (s)

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 6 Pre-actinides ((e.g.W,Au,Pb,Bi) Heavy (Es to Lr) Medium (U to Cf) Asymmetric Symmetric Light (Th, Pa ) Triple humped

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 7  Y i E (A) = fractional yields of mass chain ‘A’ (after  decays) from initial actinide ‘i’ for neutron energy ‘E’.  How does the asymmetry evolve with neutron energy for 235,238 U, 239 Pu? Depends on actinideDepends on neutron energy Goal: Develop high-precision FPY energy dependence from 1 to 15 MeV

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 8 DENIS source FN TANDEM 10MV Shielded neutron source area 2 H(d,n) 3 He; Monoenergetic neutrons: 4.0 – 7.7 MeV 3 H(p,n) 3 He; Monoenergetic neutrons: 0.5 – 7.7 MeV Quasi-monoenergetic neutrons 7 Li(p,n) 7 Be; Monoenergetic neutrons: 0.1 – 0.65 MeV 3 H(d,n) 4 He; Monoenergetic neutrons: 14.8 – 20.5 MeV

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Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 10 2 H gas From VdG accelerator p or d n One thick target ~0.2 g/cm 2 Two thin targets ~10 μg/cm 2 Dual fission chamber n-detector

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 11 Fission_counts = m f  σ n,f ε f t f Gamma_counts ( 147 Nd) = m γ  σ n,f FPY I γ ε γ t γ m γ ( m f ) = atoms in the 239 Pu thick (thin) target  = neutron flux (n.cm -2.s -1 ) σ n,f = 239 Pu(n,f) fission cross section (cm 2 ) FPY = fission product yield of 147 Nd per 239 Pu fission I γ = branching ratio of E  ε γ (ε f ) = counter efficiency of  -ray (fission) detection t γ ( t f ) = time factor for irradiation and counting periods of  -ray (fission) (Gamma_count / Fission_count) = (m thick / m thin ) * FPY * C  FPY = (Gamma_count) / Fission_count) * (m thin / m thick ) * C

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 12 Relative FPY Ratio (This is what we have promised) 1. Statistical uncertainties of  -ray peak counts (1-2%) 2. Relative HPGe detector efficiency (1-2% including the fit) Absolute FPY energy dependency: 1.Statistical error of  -ray peak counts (1-3%) 2.Absolute detector efficiency (2% including the fit) 3.Branching ratios (0.2 – 8% ( 147 Nd)) 4.Absolute FC efficiency (3% experimentally, 0.5% simulation) 5.Low energy neutrons (<1%) 6.Neutron fluence rate fluctuation (<0.3%) 7.Efficiency conversion ratio between close and standard geometry (<1%) 8.True coincidence summing (<1%) 9.Random coincidence summing (<0.2%) 10. Sample weight (<0.1%) 11. Self-absorption of  -ray ( %)

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 13  Room returns neutrons – at ToF area  ToF spectrum from neutron and 3 He monitors  Fission chamber design and characteristics

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 14 Region of interest Not desirable events in our measurements

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 15 Reactions studied 115 In(n, n') 115m In 197 Au(n, 2n) 196 Au 27 Al(n,  ) 24 Na 235 U (n, f) 133 I and 135 I Room return neutrons ~ 10 5 times smaller than primary flux on target

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 16  Room returns neutrons – at ToF area  ToF spectrum from neutron and 3 He monitors  Fission chamber design and characteristics

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 17 Neutron and gamma are well separated Break up – Negligible Neutron and gamma are well separated Break up – Negligible

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 18  Room returns neutrons – at ToF area  ToF spectrum from neutron and 3 He monitors  Fission chamber design and characteristics

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 19  Design and fabricate three fission chambers: one for 239 Pu, one for 235 U, and one for 238 U  Dedicated thin (~10 μg/cm 2 ) 235,238 U and 239 Pu foils electroplated on 0.5” titanium backing ★  Dedicated thick ( mg/cm 2 ) 235 U (93.27%) 238 U (99.97%) and 239 Pu (98.4%) targets  Fission chamber efficiency confirmed: 100%, confirmed with activation measurements ★ Made by LANL Gas flow in and out FC gas cell

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 20 Excellent  / fission separation alpha fission

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 21 in cadmium without cadmium 9 MeV / Background neutrons = 150 / 1

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 22 Experimental Results

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 23 FP/ 99 Mo Present Data Present Data Present Data Present Data Gindler 1 et al. LANL 2 Selby et al. Saclay 3 J. Laurec et al. England 4 et al. LANL 5 LLNL 6 Nethaway 4.6 MeV9 MeV14.5 MeV14.8 MeV4.5 MeV MeV 14.7 MeV 14 MeV 14.8 MeV 87 Kr 91 Sr 92 Sr 97 Zr 105 Ru 131 I 132 Te 133 I 140 Ba 142 La 143 Ce 147 Nd 0.21 ± 5.3% 0.52 ± 2.2% 0.56 ± 4.3% 0.96 ± 3.3% 0.96 ± 3.7% ± 5.2% 1.18 ± 5.0% 0.89 ± 3.8% ± 3.9% 0.37 ± 5.1% 0.22 ± 5.3% 0.48 ± 1.4% 0.51 ± 3.7% 0.89 ± 2.9% 0.85 ± 2.2% 0.93 ± 3.3% 0.76 ± 4.0% 1.03 ± 3.5% 0.82 ± 3.0% 0.80 ± 2.1% 0.64 ± 2.6% 0.34 ± 3.9% 0.22 ± 5.5% 0.52 ± 1.4% 0.52 ± 3.7% 0.97 ± 2.1% 0.86 ± 2.0% 1.03 ± 3.0% 0.80 ± 4.0% 1.09 ± 3.9% 0.84 ± 2.3% 0.85 ± 2.0% 0.64 ± 2.3% 0.35 ± 3.2% 0.21 ± 5.3% 0.53 ± 1.8% 0.52 ± 3.8% 0.86 ± 2.7% ± 4.9% 0.88 ± 3.7% 0.85 ± 2.8% 0.90 ± 3.4% ± 4.6% 0.22 ± 4.5% 0.51 ± 4.8% 0.58 ± 6.4% 0.93 ± 0.6% 0.87 ± 6.0% ± 0.7% 1.11 ± 0.6% 0.88 ± 0.6% 0.79 ± 5.9% 0.65 ± 0.6% ± 4.5% ± 4.2% ± 5.2% 0.34 ± 3.5% ± 3.3% ± 3.5% 0.81 ± 4.5% 0.99 ± 6.2% 0.82 ± 3.1% ± 3.2% 0.31 ± 5.2% ± 7.1 % 0.74 ± 6.0 % 0.97 ± 5.2 % 0.61 ± 7.9 % 0.74 ± 5.7 % 0.74 ± 5.8 % ± 6.3 % 0.86 ± 7.1 % ± 7.1% ± 7.1 % ± 7.1 % 1 J.E.Gindler et al. Phys. Rev. C 27 (1983) H.D.Selby et al. Nucl. Data Sheets 111(2010) J. Laurec et al. Nucl. Data Sheets 111(2010) T.R. England and B.F. Rider, LA-UR M. Mac Innes, M.B. Chadwick, and T. Kawano, Nuclear Data Sheets 112 (2011) 3135– D.R.Nethaway and B. Mendoza, Phys. Rev. C 6 (1972) 1827

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 24 FP/ 99 Mo Present Data Present Data Present Data Glendenin et al. 1 ANL Selby et al. 2 LANL Laurec et al. 3 Saclay Maeck mass- spectrometry 4 England et al. 5 Innes et al. 6 LANL Nethaway et al. 7 LLNL 4.6 MeV 9 MeV14.5 MeV3.9 MeV~1.4 MeV14.7 MeV MeV14 MeV 14.8 MeV 238 U 97 Zr 105 Rh 131 I 132 Te 135 Xe 140 Ba 141 Ce 143 Ce 147 Nd 0.86 ± 2.6 % 0.55 ± 3.0 % ± 4.3 % ± 2.9 % ± 3.2 % 0.35 ± 3.5 % 0.85 ± 2.4 % 0.62 ± 3.3 % 0.60 ± 2.7 % 0.74 ± 4.5 % ± 2.8 % ± 3.1 % 0.37 ± 2.8 % 0.97 ± 2.2 % 0.76 ± 3.4 % 0.71 ± 2.2 % 1.18 ± 5.4 % 1.15 ± 3.4 % 0.93 ± 2.5 % 0.88 ± 2.4 % 0.87 ± 2.6 % 0.40 ± 3.5 % 0.94 ± 0.2 % 0.73 ± 0.4 % 0.56 ± 0.2 % 0.82 ± 0.3 % ± 0.5 % ± 0.4 % 0.45 ± 0.4 % ± 3.6 % ± 3.8 % 0.89 ± 3.4 % 0.58 ± 5.0 % 0.70 ± 3.4 % 0.81 ± 4.7 % 0.99 ± 4.8 % 0.79 ± 3.3 % 0.67 ± 3.5 % 0.77 ± 3.2 % 0.34 ± 5.4 % ± 2.4 % ± 1.8 % ± 6.1 % 0.57 ± 14.7 % 0.71 ± 5.6 % 0.82 ± 5.9 % ± 5.9 % 0.75 ± 5.9 % ± 5.6 % 0.88 ± 6.5 % ± 7.2 % ± 7.2 % 0.36 ± 7.0 % 235 U 97 Zr 105 Rh 131 I 132 Te 140 Ba 143 Ce 147 Nd 1.04 ± 4.4 % 0.37 ± 2.5 % ± 4.6 % 0.99 ± 3.6 % 0.93 ± 3.8 % 0.35 ± 4.3 % 1.04 ± 2.4 % 0.39 ± 2.4 % 0.91 ± 3.6 % 1.08 ± 4.2 % 1.05 ± 2.9 % 0.93 ± 3.8 % 0.30 ± 3.0 % 1.02 ± 1.8 % 0.37 ± 1.8 % 0.84 ± 2.4 % 1.10 ± 3.3 % 1.06 ± 2.5 % 0.92 ± 2.6 % 0.38 ± 2.7 % 1.09 ± 0.4 % ± 0.3 % 0.94 ± 0.4 % 1.07 ± 0.4 % 0.86 ± 0.5 % 0.41 ± 0.3 % ± 3.3 % ± 3.4 % 0.98 ± 3.6 % ± 3.3 % 0.81 ± 4.7 % 0.89 ± 3.3 % 0.72 ± 3.3 % 0.30 ± 5.5 % ± 1.4 % ± 1.4 % ± 6.6 % 0.37 ± 6.0 % 0.89 ± 5.8 % 0.81 ± 5.5 % 0.89 ± 5.5 % ± 5.8 % 1 ± 13.9 % ± 10.6 % ± 11.9 % 1 L. E. Glendenin et al. Phys. Rev. C 24 (1981) H. D. Selby et al. Nucl. Data Sheets 111(2010) J. Laurec et al. Nucl. Data Sheets 111(2010) W.J. Maeck et al., ENICO – 1028 (1980). 5 T.R. England and B.F. Rider, LA-UR M. Mac Innes, M.B. Chadwick, and T. Kawano, Nuclear Data Sheets 112 (2011) 3135– D. R. Nethaway and B. Mendoza, Phys. Rev. C 6 (1972) 1827.

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Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx Our absolute magnitude of the 147 Nd FPY below 2.5 MeV and at 14.5 MeV neutron energies are slightly higher than the predicted values. 2. We can rule out the two low- yield data at 14.8 MeV. 3. The slope of 147 Nd FPY from 4.6 to 14.8 MeV is slightly negative (- 1% / MeV). 4. There is no energy dependence (or it is below our experimental sensitivity) for 140 Ba and 99 Mo fragments. Model calculation ___ Uncertainties ___ J. Lestone. Nuclear Data Sheets 112 (2011) 3120

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 35 Summary We start delivering precise (< 2% relative uncertainty) information on FPY ratios obtained at SIX energies in case of 239 Pu and at FOUR energies for 235 U and 238 U We will deliver accurate (4-5% absolute uncertainty) information on the energy dependent fission product yields covering an energy range from 1 < E n < 15 MeV Potential experiments:  Reduce 147 Nd branching ratio uncertainty from the current 8%  High-accuracy measurements in the 0-2 MeV range to clarify 144 Ce and 147 Nd neutron-energy dependence Strong LLNL-LANL-TUNL Collaborative Effort

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Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 37 Further Experiment & Theory Needed Future experiments (2013 – 2015):  Reduce 147 Nd branching ratio uncertainty from the current 8% (submitted LLNL LDRD proposal)  Developing a high-intensive 7 Li(p,n) neutron source at TUNL  High-accuracy measurements in the 0-2 MeV range to clarify 147 Nd neutron- energy dependence using 7 Li(p,n) and 3 H(p,n) reactions  Two measurements at the both sides of the 2 nd chance fission, i.e. E n = 5 and 7 MeV  Thermal measurement at the MIT reactor Potential theory work:  Guidance on shape from onset of 2nd-chance fission

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 38 FragmentE  (keV)'T 1/2 I  % 95 Zr d % Zr h % Rh h % Sb d % I d % I h % Te d 1388 % I h % Xe h 290 % Ba d % Ce d % Ce h % Nd d % 11

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Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 47 1.Precise FPY measurements on 239 Pu, 235 U and 238 U E n = 1.5, 2.6, 4.6, 9.0, 14.5, and 14.8 MeV 2. From September 2011 to April 2013: Total beam on target ~ 1000 hours Funded by NNSA AA (Multiply by ~$300 / h) 3. Counting time at TUNL: more than a year of continuous fission products measurement

Lawrence Livermore National Laboratory LLNL-PRES-xxxxxx 48 Reducing fission-product  -ray branching-ratio uncertainties 147 Ce Q  =3.4 MeV 56.4 s IY: 1.91% 147 Pr Q  =2.7 MeV 13.4 m IY: 0.18% 147 Nd Q  =0.9 MeV d IY: 0.001%    Produce pure sources using mass- separated CARIBU fission-product beam… (  M/M~10 -4 … only need  M/M~10 -2 ) (10 10 atoms after 1 day) …collaborate with TAMU for high-precision  and  -ray spectroscopy At TAMU, they have a unique HPGe detector laboriously calibrated to ~0.2% for efficiency count  decays with low- threshold 4   counter (~100% efficient for  s) N. Scielzo: ER-LDRD proposal