Additional Benchmark Evaluation of the NRAD Reactor LEU Core Conversion

1. Additional Benchmark Evaluation of
the NRAD Reactor LEU Core
Conversion
John D. Bess
Margaret A. Marshall
Idaho National Laboratory
2012 ANS Annual Meeting
Chicago, Illinois
June 24-28, 2012
This paper was prepared at Idaho National Laboratory for the U.S.
Department of Energy under Contract Number (DE-AC07-05ID14517)

2. Neutron Radiography (NRAD) Reactor
 250 kW TRIGA Mark II Linear channel
Safety channel 2
 Conversion-type North
beam
tube
 Located at INL G
North beam
aperture
N
 Former PRNC 2-MW reactor I H
Empty grid
J
 60 U(30/20)ErZrH rods location
Graphite
 Formerly HEU FLIP fuel A reflector
assembly
 12 graphite reflectors
B
C East
 3 control rods D
beam
tube
 2 neutron radiography E
East beam
beam lines F
aperture
 Empty positions for in- L
1 2 3 4 5 6
core experimentation K N
 Part of Hot Fuels M Safety channel 1
Log channel
Examination Facility (HFEF)
NW NE
Control rod
SW SE
Fuel cluster assembly
Neutron source (AmBe)
Standard fuel element
Irradiation positions
10-GA50002-04-3
2

3. TRIGA Fuel Conversion
HEU LEU
Nominal
(FLIP) (30/20)
Design Data Core Configuration Operational
Fuel Fuel Number of Fuel Elements 60
Number of Fuel Rods 60 60 Total Mass (g) 2506.5 ± 3.4
Uranium Mass (g) 749.9 ± 2.7
Fuel Type UErZrH UErZrH
235U Mass (g) 148.0 ± 0.6
Uranium Enrichment % 70 19.75 235U Enrichment (%) 19.74 ± 0.02
Uranium Density wt-% 8.42 30 U Mass Content (wt.%) 29.92 ± 0.09
Erbium wt-% 1.48 0.90 H/Zr Ratio 1.58 ± 0.01
Zirconium Rod OD, mm 5.715 5.715 Er Content (wt.%) 0.90 ± 0.02
C Content (wt.%) 0.30 ± 0.02
Fuel Meat OD, mm 34.823 34.823
Fuel Element Length (mm) 380.2 ± 0.4
Fuel Meat L, mm 381 381 Fuel Element Diameter (mm) 34.805 ± 0.003
Clad Thickness, mm 0.508 0.508 Cladding Inner Diameter (mm) 34.894 ± 0.005
Clad Material 304 SS 304 SS Fuel-Clad Difference (mm) 0.089 ± 0.005
3

4. Current Benchmark: NRAD-FUND-RESR-001
 60-fuel-rod critical
configuration
completed
 Available in March
2011 edition of
IRPhEP Handbook
 http://irphep.inl.gov/
 irphep@inl.gov
 Also available in
Sept. 2011 edition of
ICSBEP Handbook
 Useful for storage,
handling, and
transportation of UZrH
4

5. International Handbook of Evaluated Reactor
Physics Benchmark Experiments
March 2012 Edition
 16 Contributing
Countries
 Data from 56
Experimental Series
performed at 32
Reactor Facilities
 Data from 52 out of the
56 series are
published as approved
benchmarks
 Data from 4 out of the
56 series are
published in DRAFT
form
5

6. Summary of the Benchmark Process
6

7. NRAD LEU TRIGA Start-Up Tests
 March 9 – June 7, 2010  Calorimetric power
calibrations
 Fuel loading approach  100, 200, 250 kW
to critical
 Full power operation
 Initial critical  ER
 56 fuel rods
 Graphite reflector
 Rod worths, ER, SDM movements
 Operational core  Dry tube worth
 60 fuel rods  Radiography beam
 Critical, rod worths, ER, characterization
SDM performed after start-
up tests were
completed
7

8. Simplified Benchmark Model – 60 Rods
23.095 Fully
56 Rods
inserted
control rod Water
North
beam
tube
(void)
1.905
13.97
Fully
withdrawn
control rod
S2
East beam
38.1 16.51 tube (void)
Fuel 13.97
C
L
midplane
Graphite
108.73751 65.72251 Fuel Beam
reflector
rod filter tube S1
block
R
D
90
0.123825
5.08 Water
Fuel rod
S1 Shim 1 control rod
19.92
S2 Shim 2 control rod
R Regulating control rod
Dimensions in cm
Graphite reflector block 10-GA50002-145-6
Dimensions in cm
10-GA50002-145-9
8

9. Update to Current Benchmark Model
 Fuel batch data  Zr data from Y-12,
from CERCA CERCA, and EAG
Updated 234U, 236U, measurements
and EBC in fuel Significant
Negligible reduction in Hf
computational bias content in model
50% Reduction in o +0.1 %Δkeff
associated 100% reduction in
uncertainties Hf uncertainty
9

10. Highlights of Benchmark Evaluation
 Water Saturation of  Computational Bias of
Graphite Blocks ~1%
 Other TRIGAs with same
Largest Single problem
Uncertainty o Musashi Mark II (100 kW)
– MCNP+ENDF/B-V
±0.0025 Dk (56 rods) o Slovenia Mark II (250 kW)
– MCNP+ENDF/B-VII
±0.0021 Dk (60 rods)  Bias variation
o Quantity of fuel
o Cross Section Data
 Total Experimental o Monte Carlo Code
– KENO vs MCNP
Uncertainty
 Bias increases with
±0.0028 Dk (56 rods) core size
±0.0024 Dk (60 rods)  ~5¢ per fuel rod
10

11. Effect of Graphite Water Saturation
60-Fuel-Element Core
11

12. Criticality Results – 56 Rods
Experiment keff + Simplification Bias = Benchmark keff
1.0000 + 0.0014 = 1.0014 ± 0.0029 (±$0.39)
Analysis Calculated Bias
Neutron Library
Code keff ± σ Worth ($)
ENDF/B-VII.0 1.00906 ± 0.00007 0.76 1.02
JEFF-3.1 1.00712 ± 0.00007 0.57 0.76
MCNP5
JENDL-3.3 1.00616 ± 0.00007 0.48 0.63
ENDF/B-VI.8 1.00437 ± 0.00007 0.30 0.40
ENDF/B-VII.0
1.00901 ± 0.00007 0.76 1.01
(238-group)
KENO-VI
ENDF/B-VII.0*
1.00898 ± 0.00008 0.76 1.01
(continuous energy)
SERPENT ENDF/B-VII.0 1.00912 ± 0.00008 0.77 1.03
12

13. Criticality Results – 60 Rods
Experiment keff + Simplification Bias = Benchmark keff
1.0000 + 0.0010 = 1.0010 ± 0.0025 (±$0.34)
Analysis Calculated Bias
Neutron Library
Code keff ± σ Worth ($)
ENDF/B-VII.0 1.01029 ± 0.00007 0.93 1.24
JEFF-3.1 1.00822 ± 0.00007 0.72 0.96
MCNP5
JENDL-3.3 1.00731 ± 0.00007 0.63 0.84
ENDF/B-VI.8 1.00558 ± 0.00007 0.46 0.61
ENDF/B-VII.0
1.01041 ± 0.00007 0.94 1.25
(238-group)
KENO-VI
ENDF/B-VII.0*
1.00933 ± 0.00008 0.83 1.11
(continuous energy)
SERPENT ENDF/B-VII.0 1.01032 ± 0.00008 0.93 1.24
13

14. Reactivity Effects Measurements
 Rod measurements  Shim rods
 Uncertainty ~10%  Rod drop
o Technique (6%)  Reg rod
o Shadowing (8%)  Rod drop and
positive period
o Statistical Error (0.2%)
 SDM
 βeff  Rod drop sum
 NRAD = 0.0071  ER
 GA = 0.0078  Positive period
 Range = 0.007-0.008  Graphite blocks
 Benchmark =  Compare recalibrated
ER difference
0.0075 ± 5% (1σ)
 Dry tube
 Compare ER difference
14

15. Location of Dry Tube and Graphite Blocks
North
beam
A5
tube
(void)
C1 13.97
S2
East beam
tube (void)
13.97
S1
R
D1 Dry tube
(void)
D
90
Water
Fuel element
S1 Shim 1 control rod
S2 Shim 2 control rod
R Regulating control rod
Dimensions in cm
Graphite reflector block
F4 11-GA50002-31-6
15

16. Reactivity Effects Results – 56 Rods
Worth Measurement Benchmark ($) MCNP5 ($) C/E
Excess Reactivity 0.37 ± 0.02 0.43 ± 0.02 1.16 ± 0.10
Shutdown Margin -7.54 ± 0.49 -7.83 ± 0.23 1.04 ± 0.07
Shim Rod 1 -2.76 ± 0.31 -3.04 ± 0.15 1.10 ± 0.14
Shim Rod 2 -2.72 ± 0.30 -2.60 ± 0.13 0.96 ± 0.12
Reg Rod -2.43 ± 0.23 -2.62 ± 0.11 1.08 ± 0.10
16

17. Reactivity Effects Results – 60 Rods
Worth Measurement Benchmark ($) MCNP5 ($) C/E
Graphite Block A5 -0.17 ± 0.06 -0.13 ± 0.06 0.79 ± 0.45
Graphite Block C1 -0.41 ± 0.06 -0.39 ± 0.04 0.96 ± 0.18
Graphite Block D1 -0.43 ± 0.06 -0.41 ± 0.04 0.95 ± 0.17
Graphite Block F4 -0.45 ± 0.06 -0.44 ± 0.04 0.98 ± 0.17
Excess Reactivity 1.12 ± 0.05 1.17 ± 0.04 1.05 ± 0.06
Shutdown Margin -6.73 ± 0.47 -6.66 ± 0.23 0.99 ± 0.08
Shim Rod 1 -2.68 ± 0.30 -2.79 ± 0.14 1.04 ± 0.13
Shim Rod 2 -2.75 ± 0.33 -2.63 ± 0.13 0.95 ± 0.12
Reg Rod -2.42 ± 0.16 -2.42 ± 0.08 1.00 ± 0.07
Dry Tube -0.06 ± 0.01 -0.04 ± 0.01 0.69 ± 0.25
17

18. Future Work
 NRAD Upgrade
4 additional fuel North
beam
tube
rods (void)
13.97
4 graphite rods D
90
Repeat start-up
tests at 62 and 64 S2
East beam
rod loadings
tube (void)
13.97
Weigh graphite
S1
R
blocks
Flux measurements
Void effects
Water
Graphite element
Characterize beams
Fuel element
S1 Shim 1 control rod
S2 Shim 2 control rod
R Regulating control rod
Dimensions in cm
Graphite reflector block 11-GA50002-31-3
18

19. Conclusion
 Completed
benchmark evaluation
of cold start-up
measurements
 Large uncertainty in
water saturation of
graphite blocks
 ~1% high
computational bias in
criticality
 Very good agreement
for worth
measurements
 Path forward for
additional benchmark
experiment data
19

20. ¿Questions?
20

21. Extra Slides
21

22. Experiment Evaluation – Biases
 Simplifications were  Noticeable biases
needed Simplification of
 Understand worth fuel rod end fittings
and sensitivity of Removal of steel
various components impurities
 Develop easier to use Use of average fuel
benchmark model composition
 Speed up calculation Replace control rod
time guide tubes with
H2O
 Most simplifications
caused minor Replace beam line
structure with void
changes in keff
22

23. Calculated Spectral Data – 56 rods (MCNP5)
Model Detailed Simple
Cross Section Library ENDF/B-VII.0 ENDF/B-VII.0
keff 1.00765 1.00906
±σk 0.00007 0.00007
Neutron Leakage (%) 0.03 2.28
Thermal
(<0.625 eV) 80.58 80.75
Fission Fraction, Intermediate 16.42 16.27
by Energy (%) Fast
(>100 keV) 2.99 2.98
234U 0.01 0.01
235U 98.74 98.74
Fission Fraction,
236U 0.01 0.01
by Isotope (%)
238U 1.24 1.23
Average Number of
Neutrons Produced 2.444 2.444
per Fission
Energy of Average
Neutron Lethargy 0.26679 0.26275
Causing Fission (eV)
23

24. Calculated Spectral Data – 60 rods (MCNP5)
Model Detailed Simple
Cross Section Library ENDF/B-VII.0 ENDF/B-VII.0
keff 1.00934 1.01029
±σk 0.00007 0.00007
Neutron Leakage (%) 0.04 2.39
Thermal
(<0.625 eV) 80.38 80.54
Fission Fraction, Intermediate 16.60 16.46
by Energy (%) Fast
(>100 keV) 3.02 3.00
234U 0.01 0.01
235U 98.73 98.73
Fission Fraction,
236U 0.01 0.01
by Isotope (%)
238U 1.25 1.24
Average Number of
Neutrons Produced 2.444 2.444
per Fission
Energy of Average
Neutron Lethargy 0.27191 0.26810
Causing Fission (eV)
24

25. Discussion of Cross Section Data
 Cause of Bias?  Er
 Cross section and/or code  KENO and MCNP keff
related values agree when Er is
 Fuel rods significant removed
 235U and 238U  Low-lying resonance
approximations in free-
 Small difference between gas scattering kernels ?
JENDL-3.3 and ENDF/B-
VII.0 data  Currently being
o JENDL thought to be “more investigated
correct” o KUCA
 91Zr and ZrH S(a,b)  Graphite (Cnat)
 Bias identified  (n,g) larger in JENDL-3.3
o Slovenia TRIGA Mark II than ENDF/B-VII.0
o Fuel contains no Er  (n,g) increased further
o ICNC 2011 (Sept.) in JENDL-4.0 base on
 ZrH S(a,b) calculated HTGR research
differently in JEFF-3.1 and
ENDF/B-VII.0
25

26. Future Work – II
 Computational  Additional “To-Do”
Methods Benchmarks
Continue to SNAP 10A/2 water
immersion
investigate Er experiments
o KUCA experiments
Expand NRAD
Investigate thermal benchmark library
scattering S(α,β) Invite other
cross sections members of TRIGA
o Collaborative effort community to
benchmark their
reactors
26

27. References
 Bess, J. D., Maddock, T. L., Marshall, M. A., “Fresh Core Reload of the
Neutron Radiography (NRAD) Reactor with Uranium(20)-Erbium-
Zirconium-Hydride Fuel,” INL/EXT-10-19486, Idaho National
Laboratory (2010).
 International Handbook of Evaluated Reactor Physics Benchmark
Experiments, NEA/NSC/DOC(2006)1, OECD-NEA, Paris, France (2011).
 Matsumoto, T., Hayakawa, N., “Benchmark Analysis of TRIGA Mark II
Reactivity Experiment Using a Continuous Energy Monte Carlo Code
MCNP,” J. Nucl. Sci. Tech., 37(12), 1082-1087 (2000).
 Snoj, L., Žerovnik, G., Trkov, A., “Analysis of Cross Section Libraries
on Zirconium Benchmarks,” Proc. ICNC 2011, Edinburgh, Scotland,
September 19-22 (2011).
 Jeraj, R., Ravnik, M., “TRIGA Mark II Reactor: U(20)-Zirconium Hydride
Fuel Rods in Water with Graphite Reflector,” IEU-COMP-THERM-003,
International Handbook of Evaluated Criticality Safety Benchmark
Experiments, NEA/NSC/DOC(95)03, OECD-NEA, Paris, France (2010).
 Shimakawa, S., Goto, M., Nakagawa, S., Tachibana, Y., “Impact of
Capture Cross-Section of Carbon on Nuclear Design for HTGRs,”
Proc. HTR 2010, Prague, Czech Republic, October 18-20 (2010).
27

28. Detailed Model Development
28

29. Fuel Clusters
Top
Assembly
7.7089
Fuel Rods
3.8862
3.8862
Top View
8.10006
Bottom Dimensions in cm
Assembly 10-GA50002-145-5
10-GA50002-74-2 Dimensions in cm
10-GA50002-145-4
29

30. Top fuel fitting
Fuel Rods
Top end fitting (SS 304/304L)
OD 3.4894 cm Cladding 0.180 MIN.
1.27
Void gap 0.724535
Upper
Top axial reflector (graphite) 8.6868 fuel
reflector
OD 3.27914
Cladding (SS 304/304L)
ID 3.4894, OD 3.591
Zirconium rod
U-Er-Zr-H fuel
ID 0.635, OD 3.4805
23.125 (REF)
38.02 58.73751 + 0.000
25.875 - 0.031
Fuel pellets (3)
Zirconium rod
OD 0.5715
Molybdenum poison disc + 0.003
1.370 - 0.000 I.D.
(REF)
0.079375
Molybdenum poison disc Lower
fuel
OD 3.46964 reflector
Bottom axial reflector (graphite)
OD 3.27914
8.6868
Bottom end fitting (SS 304/304L)
OD 3.4894
1.27
Dimensions in cm Bottom fuel fitting
10-GA50002-145-1
1.414 DIA. Dimensions in inches
NOM. (REF) 10-GA50002-76
30

31. Control Rods Detail of top fitting
2.5
1.25
0.5
Top end fitting (Al 6061) 5/8 flats 0.5 0.625
OD 3.03276
1.9685 0.40 D 1.194 D
1/2-13 UNC-2A 0.125
+ 0.000
0.060 - 0.004
0.1875
Void
Void 17.78
Cladding (Al 6061)
ID 3.03276 1-1/8" O.D. x 0.035" wall
OD 3.175 L 6.5
Al alloy tube
Spacer
1.187 +0.005 O. D.
-
0.000
0.5 D thru
L 0.5
59.436
24.00
REF 23.40
B4C absorber 23.25 1-1/4" O.D. x 0.028" wall
OD 3.01498 L 23.4
Al alloy tube
38.1
15.0
Boron carbide
D 1.187 +0.030
-
0.000
Detail of bottom fitting
D 1.194 0.75
Bottom end fitting (Al 6061) 0.625
OD 3.03276 0.1875 1/16 x 1/16 groove
1.5874
Dimensions in cm
10-GA50002-145-2
0.060 +0.000 0.125
1/16 DIA -0.004
THRU
Dimensions in inches
10-GA50002-90
31

32. Guide Tube
32

33. Graphite Reflectors
Handle
W0170-0089-DE (REF)
Screw, HEX SOC HD
5/8-11 UNC-2A x 2 LG
ALUM 2011-T3
2 REQD
Graphite element
reactor grade
0.9525 cm x 45° chamfer 25.875
± 0.125
65.72251
7.366
7.366
Top View
0.656 +0.002 DIA DRILL
-
0.005
x 0.875 ± 0.060 DP
2 places
5/8-11 UNC-2A THD
Dowel pin Both ends
0.645 DIA x 1-1/2 LG
Alum 2011-T3, 2 REQD
Tie rod + 0.000
D 1.968 - 0.030
5/8 x 7-7/8 LG
ALUM 2011-T3
Adapter
ALUM 2011-T3
Dimensions in cm
Adapter
10-GA50002-145-3
W0170-0090-DD (REF)
0.375 ± 0.030 x 45° ± 5°
Hex nut
Chamfer TYP
5/8-11 UNC-2B THD
ALUM 2011-T3
2.900 +0.100
-
0.000
square
Dimensions in inches 10-GA50002-05-1
33

34. Photograph of NRAD Tank
34