Measurement of Short-Lived Fission Product Yields for 237Np via �-ray Spectroscopy November 1, 2020 Sean Burcher LLNL-PRES-816148 This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC Motivation § Accurate Fission Product Yields (FPYs) are important for basic and applied science — FPYs from a fission neutron spectrum is of particular interest § Short-lived (�"⁄# ∼ minutes − hours) FPYs are difficult to measure — Separation methods require time § High resolution �-ray spectroscopy — Count the entire sample — Simultaneous measurement of FPYs for many isotopes — No need to take time to do chemistry/separation 2 LLNL-PRES-816148 Experimental Setup Photo-diode PMT 237 8 § Four Np samples were irradiated in GODIVA Power Multiplication Period ) 0.0680287 (x-264.788) 166.803 PMT Light Saturation 6 critical assembly — Neptunium Nitrate (NpO (NO )) sealed in Quartz 2 3 4 scaled voltage ( tubes Half-Width (27 sec) 2 6.0(1), 10.6(7), 20.3(2), 44.3(5) mg — Max Masses: and - Arb. Units Half Maximum !" — Neutron Flux: ∼ 3 × 10 neutrons/second 0 -100 -50 0 50 100 — Irradiation time: ∼ 50 �� (FWHM) Time (sec) § Samples were retrieved and delivered to �-ray counting setup ∼50 minutes after irradiation § Counting continued for 7 days following irradiation — Short Timescale for first 3 hours • 10.6(7) mg sample — Long Timescale for next 7 days • 26.3(3) mg (6.0 + 20.3) samples 3 LLNL-PRES-816148 Data Analysis : Full Sum Spectrum § The entire �-ray spectrum from the long timescale count Red Triangles indicate peaks used in the current analysis 4 LLNL-PRES-816148 Data Analysis : Time Dependent Spectra § Parse data into time-binned matices § Fit a peak in each in time bin and plot the intensity versus time (decay curve) — Use half-life and �-ray energy to identify isotope § Use decay curve to extract the activity of the isotope immediately after irradiation 5 LLNL-PRES-816148 Data Analysis : Cascade Plots Total Spectrum § Used to build �-ray ‘input deck’ — List of expected �-rays with energy and time windows § Easily identify time dependence of �-ray spectrum Cascade Plot § Helps identify interfering �-rays 6 LLNL-PRES-816148 Data Analysis : Cascade Plots § Used to build �-ray ‘input deck’ — List of expected �-rays with energy and time windows § Easily identify time dependence of �-ray spectrum § Helps identify interfering �-rays 7 LLNL-PRES-816148 Results : Example 93Y �! �"/$ § 93 � = Observed 3 ‘clean’ �-rays from the decay of Y ln 2 Γ �% § Extrapolate Decay Curve fits back to irradiation Γ ∶ �����ℎ��� ����� � ∶ ������ �� �������� time : �# % — Correct for DAQ livetime, detection efficiency, and self- &" attenuation �! � � , � = ? � � �� = �'(&"(�()& − 1) " $ � &! 93 93 93 Activity vs Time (1st order fit) : Y : Eg = 267 keV (Det. 8815) Activity vs Time (1st order fit) : Y : Eg = 947 keV (Det. 8815) Activity vs Time (1st order fit) : Y : Eg = 1918 keV (Det. 8815) �$ = 267 ��� �$ = 947 ��� �$ = 1918 ��� 4 10 103 3 Activity (Counts per hour) Activity (Counts per hour) 10 Activity (Counts per hour) 103 102 102 102 10 20 30 40 50 60 70 Time (hours) 10 15 20 25 30 35 40 45 50 55 5 10 15 20 25 30 35 40 Time (hours) Time (hours) 8 LLNL-PRES-816148 Results : Example 93Y �! �"/$ � = 237 93 Np Cumulative237Np FPY : FPY : Y93 (1stY order fit) ln 2 Γ �% Γ ∶ �����ℎ��� ����� This Work �% ∶ ������ �� �������� 93 Fixed t Y : 1917.9 keV 1/2 ENDF/B VIII.0 93 Y : 947.2 keV 93 Y : 266.9 keV 2 3 4 5 6 7 8 9 Fission Product Yield (%) 9 LLNL-PRES-816148 Determining the Number of Fissions § Four �-rays from isotopes with well-known FPYs were selected as reference yields — Chosen to span a range of: STAYSL PNNL: • �-ray energy 7.2 3 ×10!! issions/gram • Isotope half-life (based on witness foil analysis • Isotope atomic number (Z) performed by B. Pierson PNNL) • Solid and Gas 10 LLNL-PRES-816148 Results: 45 Isotopes/Isomers : 191 �-rays 237 88 Np Cumulative FPY : Kr (1st order fit) 237Np Cumulative FPY : 142La (1st order fit) 88 142 Kr : 2392.4 keV La : 2543.2 keV This Work 142La : 2398.1 keV This Work Fixed t 88 1/2 142 Fixed t Kr : 2232.0 keV La : 2358.6 keV 1/2 ENDF/B VIII.0 142La : 2187.4 keV ENDF/B VIII.0 88 Kr : 2196.1 keV 142La : 2055.6 keV 142La : 2039.0 keV 88 Kr : 2035.7 keV 142 La : 2025.8 keV 142La : 1901.7 keV 88 Kr : 2030.1 keV 88 142 La : 1756.9 keV 142 Kr 142 La La : 1546.1 keV 88 Kr : 1530.0 keV 142La : 1233.3 keV 142La : 1043.9 keV 88 Kr : 834.9 keV 142La : 1011.6 keV 142 88 La : 861.8 keV Kr : 362.1 keV 142La : 641.2 keV 1.4 1.6 1.8 2 2.2 2.4 2.6 2 3 4 5 6 7 8 Fission Product Yield (%) Fission Product Yield (%) 237Np Cumulative FPY : 97Zr (1st order fit) 237Np Cumulative FPY : 130Sb (1st order fit) 97 Zr : 1750.7 keV 130 This Work Sb : 839.6 keV This Work 97 Zr : 1362.8 keV Fixed t Fixed t 1/2 1/2 97 ENDF/B VIII.0 ENDF/B VIII.0 Zr : 1276.3 keV 130 Sb : 793.6 keV 97 Zr : 1148.2 keV 97 Zr : 1021.4 keV 130 Sb : 732.2 keV 97 Zr : 743.5 keV 130 97 97 Zr : 703.7 keV Zr 130 Sb Sb : 331.1 keV 97 Zr : 602.5 keV 97 Zr : 507.8 keV 130 Sb : 182.3 keV 97 Zr : 355.5 keV 4.5 5 5.5 6 6.5 7 7.5 0 0.5 1 1.5 2 2.5 Fission Product Yield (%) Fission Product Yield (%) 11 LLNL-PRES-816148 Results: Investigating Branching Ratios § Example 129Sb: Four �-rays were observed — Three �-rays give consistent result 237 129 237 Np FPY : 129 Sb — One is a clear outlier -> Potential issue Np Cumulative FPY : Sb (1st order fit) with branching ratio for this �-ray? This Work 129 Sb : 915.0 keV Fixed t 1/2 § Requires further investigation ENDF/B VIII.0 — What is ENSDF FPY value based on? 129 Sb : 812.9 keV • Ex. Was it the 761 keV �-ray? — What is the ENSDF branching ratio value based on? 129 Sb : 761.3 keV § Potential to improve accuracy 129 of nuclear data Sb : 544.6 keV 1.2 1.4 1.6 1.8 2 2.2 Fission Product Yield (%) § Highlight areas where future experiments could be focused — Investigate 129Sb branching ratios 12 LLNL-PRES-816148 Conclusion § Fission product yields have been measured for 45 unique isotopes/isomers — Using 191 �-rays — More to come! — Currently investigating discrepancies in results (ex. 129Sb) • Update branching ratios? • Take another look at experiments included in the ENSDF evaluation § Full Results to be published in future Nuclear Data Sheet Article § Results from this experiment will be compared to FPYs of 235U, 238U, 239Pu, and 233U — 235U, 238U, and 239Pu irradiations have been completed — 233U irradiation planned for early/mid 2021 — Self-consistent FPY results for 5 actinides • All irradiations utilized GODIVA • All �-ray count utilized the same experimental setup • All data will be analyzed/re-analyzed with the codes developed in this work 13 LLNL-PRES-816148 Collaborators & Acknowledgements B.D. Pierson L. Greenwood J.T. Harke S.W. Padgett J. Goda P. Zh a o D. Hayes N. Gharibyan J. Hutchinson N. Harward J. Walker K. Roberts G. Slavik A.S. Tamashiro C. Palmer This work was funded by the Office of Defense Nuclear Nonproliferation Research and Development within the United States Department of Energy’s National Nuclear Security Administration. This work was performed under the auspices of the United States Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52- 07NA27344. The National Criticality Experiments Research Center (NCERC), utilized in this work, is supported by the United States Department of Energy Nuclear Criticality Safety Program, funded and managed by the National Nuclear Security Administration for the Department of Energy. 14 LLNL-PRES-816148 Disclaimer This document was prepared as an account of work sponsored by an agency of the United States government. 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GODIVA Burst Neutron Flux determined by witness foil analysis and STAYSL PNNL code Photo-diode PMT 8 Power Multiplication Period ) 0.0680287 (x-264.788) 166.803 PMT Light Saturation 6 4 scaled voltage ( Half-Width (27 sec) 2 Max - Arb. Units Half Maximum 0 -100 -50 0 50 100 Time (sec) Figures generated by Bruce Pierson 16 LLNL-PRES-816148.