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ENDF/B-VII.0 Data Testing of 233U/Th ICSBEP Benchmarks

A. C. (Skip) Kahler

Los Alamos National Laboratory

IAEA Consultants Meeting to Review Benchmarking of Nuclear Data for the

U/Th Fuel Cycle

December, 2010 This work was carried out under the auspices of the National Nuclear Security Adminis-tration of the U.S. Department of Energy at Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396.

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Introduction

What’s in the ICSBEP Handbook?

ENDF/B-VII.0 Data Testing

Strengths, Weaknesses & What Comes Next?

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What is in the ICSBEP Handbook?

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ICSBEP Benchmark/Category Comments

U233-MET-FAST-xxx Bare and reflected systems are defined. UMF1 and UMF6 (LANL “Jezebel” and “Flattop”) configurations were calculated during ENDF/B-VII.0 testing; others have been calculated since then.

U233-MET-THERM-001 India’s Kamini Reactor; BeO reflected and H2O moderated. Not calculated during ENDF/B-VII.0 testing, but the evaluators report a kcalc of 0.9890(3) with ENDF/B-VI cross sections.

U233-COMP-THERM-001 LWBR SB (Seed-Blanket) Experiments. A suite of 8 critical experiments. Run during ENDF/B-VII.0 data testing with decks from Andre Trkov and/or Russ Mosteller.

U233-COMP-THERM-004

D2O moderated lattice of 233UO2 – 232ThO2. Approved at the May, 2010 annual meeting. The benchmark keff is 1.0017(13); sample MCNP kcode calculations with ENDF/B-V, ENDF/B-VI and ENDF/B-VII cross sections yield kcalc’s of 0.9933(1), 0.9877(1) and 0.9964(1), respectively.

U233-SOL-INTER-001 Uranyl-fluoride solution assemblies. Spherical geometry with various combinations of beryllium, steel and polyethylene reflectors (33 configurations).

U233-SOL-THERM-xxx Uranyl-Nitrate and uranyl-fluoride solution assemblies in simple (sphere, cylinder) geometry. Systems are bare or H2O reflected. Over 100 critical configurations are modeled.

Pu-MET-FAST-008 (Thor) A spherical Pu (93.6 w/o 239Pu) core surrounded by a 232Th cylinder.

FUND-IPPE-FR-MULT-RRR-001

Reaction rate ratio (to 235U(n,f)) measurements in a fast spectrum reactor. Includes 232Th(n,f), 232Th(n,γ), 232Th(n,2n) and 233U(n,f), among other structural and actinide cross sections. This evaluation appears in the 2009 edition of the ICSBEP Handbook.

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Data Testing – Fast Assemblies

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Benchmark ID Evaluation Data Benchmark keff and Uncertainty

ENDF/B-VII.0 kcalc and Unc Comments

U233-MET-FAST-001 9/30/1999, rev. 3 1.000(1) 0.99964(4) Unreflected (233U Jezebel)

U233-MET-FAST-002 9/30/1998, rev. 2 1.0000(10) 1.0000(11)

0.99907(4) 1.00050(4)

1.2 cm or 2.0 cm thick HEU reflector, ~1/4 to ~1/3 of fission

occurs in 235U.

U233-MET-FAST-003 3/31/1995, rev. 0 1.000(1) 1.000(1)

0.99450(4) 1.00016(4)

Same core as UMF2, 2.3 cm or 5.3 cm thick natU reflector, ~10%

to 15% of fission is in the re- flector, 235U/238U ratio is < 10%.

U233-MET-FAST-004 3/31/1995, rev. 0 1.0000(7) 1.0000(8)

1.00459(4) 1.00500(4)

Same core as UMF2, 2.4 cm or 5.8 cm thick natW reflector, high kcalc is consistent with other W

bearing benchmarks.

U233-MET-FAST-005 9/30/1999, rev. 1 1.0000(30) 1.0000(30)

0.99427(4) 0.99248(4)

Same core as UMF2, 2.0 cm or 4.2 cm thick Be metal reflector,

with < 1% oxygen. Model includes Be kernel but with

>90% fast fission it is not relevant.

U233-MET-FAST-006 9/30/2000, rev.1 1.0000(14) 0.99928(4)

19.9 cm thick natU reflector (Flattop), ~10% of fission occurs

in the reflector and 235U/238U ratio is ~25%.

Pu-MET-FAST-008 9/30/1999, rev.2 1.0000(6) 0.99800(3) Spherical Pu core; cylindrical Th

reflector.

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Data Testing – Be & Poly Reflected Solutions

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0.97000

0.97500

0.98000

0.98500

0.99000

0.99500

1.00000

1.00500

1.01000

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800

k cal

cC/

E

Above-Thermal Fission Fraction, ATFF

233U Solution Benchmarks with Be and/or Polyethylene Reflectors

USI1/Be

USI1/Poly

USI1/Be&Poly

UST15/Be

UST15/Poly

UST15/Be&Poly

MCNP5 eigenvalue calculations use ENDF/B-VII.0 Cross Sections.

kcalc uncertainty is typically 10 pcm, or less.

Average benchmark uncertainty is ~ 600pcm.

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Data Testing – Bare & H2O Reflected Solutions

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0.99000

0.99500

1.00000

1.00500

1.01000

1.01500

1.02000

1.02500

0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400

k cal

cC/

E

Above-Thermal Fission Fraction, ATFF

233U Solution Benchmarks, Bare or H2O Reflected

UST, Bare

UST, Water Reflected

MCNP5 eigenvalue calculations use ENDF/B-VII.0 Cross Sections.

kcalc uncertainty is typically 10 pcm, or less.

Average benchmark uncertainty is ~ 400pcm.

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Data Testing – 233UO2/ThO2 Lattice

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0.99000

0.99500

1.00000

1.00500

1.01000

1.01500

1.02000

1.02500

0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400 0.450 0.500

k cal

cC/

E

Above-Thermal Fission Fraction, ATFF

233UO2 Seed - Blanket Lattice Experiments, UCT001

235UO2-ZrO2/ThO2

233UO2-ZrO2/ThO2

233UO2-ZrO2

233UO2-ZrO2/233UO2-ThO2

235UO2-ZrO2/233UO2-ThO2

235UO2-ZrO2/ThO2

233UO2-ZrO2/ThO2

233UO2-ZrO2/233UO2-ThO2

MCNP5 eigenvalue calculations use ENDF/B-VII.0 Cross Sections.

kcalc uncertainty is typically 10 pcm, or less.

Average benchmark uncertainty is ~ 260pcm.

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Data Testing – Combined Results

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0.97000

0.97500

0.98000

0.98500

0.99000

0.99500

1.00000

1.00500

1.01000

1.01500

1.02000

1.02500

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800

k cal

cC/

E

Above-Thermal Fission Fraction, ATFF

233U Benchmarks: Bare or Reflected Solutions and SB Lattices

USI1/Be

USI1/Poly

USI1/Be&Poly

UST15/Be

UST15/Poly

UST15/Be&Poly

UST, Bare

UST, Water Reflected

UCT1, Lattice

MCNP5 eigenvalue calculations use ENDF/B-VII.0 Cross Sections.

kcalc uncertainty is typically 10 pcm, or less.

Average benchmark uncertainties vary from ~ 260 pcm to ~600pcm.

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Data Testing – Reaction Rate Ratios

FUND-IPPE-FR-MULT-RRR-001 Reaction Benchmark Value Benchmark Value

Uncertainty Calculated Value Calculated Value

Uncertainty C / E

232Th(n,2n) 0.00924 0.00050 0.01084 0.00006 1.173 ± 0.064 232Th(n,f) 0.0430 0.0013 0.03898 0.00002 0.907 ± 0.027 232Th(n,γ) 0.109 0.004 0.10194 0.00008 0.935 ± 0.034 233U(n,f) 1.54 0.03 1.5546 0.0007 1.009 ± 0.020

Historical LANL Critical Assembly Reaction Rate Data 232Th(n,f) – PMF8 232Th(n, γ) – “ 232Th(n,2n) – “

0.26 1.20 1.04

0.01 0.06 0.03

0.242 1.322 0.880

0.0003 0.001 0.005

0.93 ± 0.04 1.10 ± 0.06 0.85 ± 0.02

233U(n,f)- HMF1 1.59 0.03 1.5690 0.0004 0.987 ± 0.019

233U(n,f)- HMF28 1.608 0.003 (0.03?) 1.5676 0.0008 0.975 ± 0.002 233U(n,f) – PMF1 1.578 0.027 1.556 0.002 0.986 ± 0.017 233U(n,f) – IMF7 1.58 0.03 1.545 0.004 0.978 ± 0.019

Notes: - HMF1 = Godiva. - HMF28 = Flattop. - PMF1 = Jezebel. - IMF7 = Big-10. - PMF8 = Thor; 232Th(n,X) reaction rate ratios are relative to 238U(n,X). - All remaining reaction rate ratios are relative to 235U(n,f).

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Observations

With ENDF/B-VII.0 Cross SectionsFast Critical Assembly calculated eigenvalues are accurate.

Intermediate and Thermal Spectrum calculated eigenvalues for solution assemblies exhibit a decreasing trend with increasing average fission energy.

233UO2/232ThO2 fuelled lattice assembly calculated eigenvalues are accurate, but are consistent with the solution assembly trend line.

233U(n,f) reaction rate ratios are calculated accurately.

232Th(n,2n), (n,f) and (n,g) reaction rate ratios are not calculated accurately.

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