Inherently Safe Subcritical Assembly (ISSA) Benchmark Evaluation - - PowerPoint PPT Presentation

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Inherently Safe Subcritical Assembly (ISSA) Benchmark Evaluation - - PowerPoint PPT Presentation

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LLNL-PRES-770146 NCSP NUCLEAR CRITICALITY SAFETY PROGRAM Inherently Safe Subcritical Assembly (ISSA) Benchmark Evaluation Presented at the Nuclear Criticality Safety Program (NCSP) Technical Program Review March 26-27 2019 Tony Nelson, Soon

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SLIDE 1

Inherently Safe Subcritical Assembly (ISSA) Benchmark Evaluation

Lawrence Livermore National Laboratory, P.O. Box 808, L-384, Livermore, CA 94551-0808 This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344

Tony Nelson, Soon Kim, Will Zywiec, Dave Heinrichs

Lawrence Livermore National Laboratory

LLNL-PRES-770146

NCSP

NUCLEAR CRITICALITY SAFETY PROGRAM

Presented at the Nuclear Criticality Safety Program (NCSP) Technical Program Review March 26-27 2019

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SLIDE 2

Inherently Safe Subcritical Assembly (ISSA)

2

  • Subcritical benchmark

experiments for ICSBEP

  • Existing asset as a

training assembly

  • Validate time dependent

radiation transport modules

  • Validate nuclear data
  • Subcritical multiplication

monitoring

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SLIDE 3

ISSA Fuel

  • Originally fabricated for the Omega West

Reactor

  • Modified at LLNL
  • 93.16% 235U
  • U3O8 powder + aluminum powder
  • Sandwiched between aluminum plates
  • 19 curved plates per assembly
  • 232 g 235U per assembly
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SLIDE 4

Experiments

  • 5 experiments:

–1, 2, 4, 6, and 9 fuel assemblies

  • Multiplication ranging

from 1.2-10

4

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SLIDE 5

0.5 1 1.5 2 2.5 3 3.5 4 50 100 150 200 250 300 350

Time, s (9 Assemblies) Neutron Counts

9 Assemblies

Experimental Results

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SLIDE 6

Fission Chains

0.5 1 1.5 2 2.5 3 3.5 4 50 100 150 200 250 300 350

Time, s (9 Assemblies) Neutron Counts

9 Assemblies

Experimental Results

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SLIDE 7

Fission Chain

20 40 60 80 100 120 140 160 180 0.5 1 1.5 2 2.5 3 3.5 4 50 100 150 200 250 300 350

Time, s (1 Assembly) Time, s (9 Assemblies) Neutron Counts

9 Assemblies 1 Assembly Fission Chains

Experimental Results

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SLIDE 8

Experimental Results

8

1E-07 1E-06 1E-05 1E-04 1E-03 1E-02 1E-01 1E+00 1E+01 50 100 150 200 250 300 350 400 450 500

Time Until Next Detection Event, s Neutron Counts

9 Assemblies

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SLIDE 9

Experimental Results

9

Fission Chains Random Source

1E-07 1E-06 1E-05 1E-04 1E-03 1E-02 1E-01 1E+00 1E+01 50 100 150 200 250 300 350 400 450 500

Time Until Next Detection Event, s Neutron Counts

9 Assemblies

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SLIDE 10

Experimental Results

10

1E-07 1E-06 1E-05 1E-04 1E-03 1E-02 1E-01 1E+00 1E+01 50 100 150 200 250 300 350 400 450 500

Time Until Next Detection Event, s Neutron Counts

9 Assemblies 1 Assembly

Fission Chains Random Source

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SLIDE 11

Analysis

0.5 1 1.5 2 2.5 3 3.5 4 50 100 150 200 250 300 350

Time, s (9 Assemblies) Neutron Counts

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SLIDE 12

Analysis

0.5 1 1.5 2 2.5 3 3.5 4 50 100 150 200 250 300 350

Time, s (9 Assemblies) Neutron Counts

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SLIDE 13

Analysis

0.01 0.02 0.03 0.04 0.05 0.06

4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100 104 108 112 116 120 124 128 132

Fraction of Segments with k Counts (bk) Number (k) of Counts Recorded in Segment

ISSA Experimental Data Poisson Distribution

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SLIDE 14

Analysis

14

0.5 1 1.5 2 2.5 3 3.5 4 50 100 150 200 250 300 350

Time, s (9 Assemblies) Neutron Counts

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SLIDE 15

Analysis

15

0.5 1 1.5 2 2.5 3 3.5 4 50 100 150 200 250 300 350

Time, s (9 Assemblies) Neutron Counts

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SLIDE 16

Analysis

16

0.5 1 1.5 2 2.5 3 3.5 4 50 100 150 200 250 300 350

Time, s (9 Assemblies) Neutron Counts

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SLIDE 17

Analysis

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5000 10000 15000 20000 25000 30000

Y2F Time Gate, µs

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SLIDE 18

Analysis

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5000 10000 15000 20000 25000 30000

Y2F Time Gate, µs

1 Assembly 2 Assemblies 4 Assemblies 6 Assemblies 9 Assemblies

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SLIDE 19

Simulation

19

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SLIDE 20

20

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SLIDE 21

Simulation Results

0.00 0.05 0.10 0.15 0.20 0.25 0.30

100 200 300 400 500

Y2F Time Gate Size, ms

Experimental

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SLIDE 22

Simulation Results

0.05 0.1 0.15 0.2 0.25 0.3

100 200 300 400 500

Y2F Time Gate Size, ms

COG Experimental

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SLIDE 23

Simulation Results

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 500 1000 1500 2000 2500

Time Until Next Detection, s

Time, s

  • Neutron start time determined

by: (Random Number) X (Total simulation duration)

  • Random number generator is

single precision

  • Smallest difference between

random numbers is ~1E-7

  • For simulation duration 1E6 s,

smallest time between source neutrons is 1E-7*1E6 = 0.1 s

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SLIDE 24

Simulation Results

0.00 0.05 0.10 0.15 0.20 0.25 0.30

100 200 300 400 500

Y2F Time Gate Size, ms

COG Experimental

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SLIDE 25

Simulation Results

0.05 0.1 0.15 0.2 0.25 0.3

100 200 300 400 500

Y2F Time Gate Size, ms

Fixed COG COG Experimental

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SLIDE 26

Simulation Results

26

  • 20.00%
  • 15.00%
  • 10.00%
  • 5.00%

0.00% 5.00% 10.00% 15.00% 20.00% 1 2 3 4 5 6 7 8 9

R2F (C-E)/E

Number of Assemblies

COG with ENDF/B-VII.1

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SLIDE 27

Simulation Results

27

  • 20.00%
  • 15.00%
  • 10.00%
  • 5.00%

0.00% 5.00% 10.00% 15.00% 20.00% 1 2 3 4 5 6 7 8 9

R2F (C-E)/E

Number of Assemblies

COG with ENDF/B-VII.1 COG with ENDF/B-VIII.0

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SLIDE 28

Simulation Results

28

  • 20.00%
  • 15.00%
  • 10.00%
  • 5.00%

0.00% 5.00% 10.00% 15.00% 20.00% 1 2 3 4 5 6 7 8 9

R2F (C-E)/E

Number of Assemblies

COG with ENDF/B-VII.1 COG with ENDF/B-VIII.0 MORET with ENDF/B-VII.1 MORET with JEFF3.2 MORET with JEFF3.2 and FREYA

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SLIDE 29

Conclusions –Identified non-physical artifact in radiation transport code –Demonstrated improvement of nuclear data from ENDF/B-VII to ENDF/B-VIII –Points towards further improvements from FREYA –Provided a dataset for multiplicity community to validate new theories and techniques

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SLIDE 30

Acknowledgements

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA273444 and was made possible through the support of:

–Wilfried Monange, Jesson Hutchinson, Boukhmès Mechitoua –DOE Nuclear Criticality Safety Program –DOE Office of Fissile Materials Disposition –DOE NNSA Livermore Field Office –LLNL Nuclear Operations Directorate

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SLIDE 31

Questions?

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