1.
Benchmark Evaluation of
GROTESQUE, a Complex
Arrangement of HEU Metal Pieces
John D. Bess – INL
Mackenzie L. Gorham – ISU, DOE-ID
(Presenting)
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.
What is GROTESQUE?
 Adjective
Odd or unnatural in shape, appearance, or
character; fantastically ugly or absurd; bizarre.
Fantastic in the shaping and combination of
forms, as in decorative work.
 Noun
Any grotesque object,
design, person, or thing.
2

3.
The GROTESQUE Experiment
 9-units
Smaller HEU
pieces
93.15 wt.% 235U
8 units arranged
around a central
hole in steel
diaphragm
9th unit raised
up through the
hole to achieve
criticality
3

4.
Experiment Background
 June 1964
 Oak Ridge Critical
Experiments
Facility (ORCEF)
Mihalczo, Lynn, and
Taylor
 ORCEF Logbook
15r, “Book 4”, pp.
30-50.
4

5.
Purpose of Experiment
 Original objective:  Later use:
Develop and test Variation used as
neutronics for part of development
GEOM subroutine of early versions of
of the 05R code KENO
Sample Problem 7:
“GROTESQUE
without the
Diaphragm”
available in current
SCALE packages
5

6.
Unit 1
Part Length Width Height Mass
Type
Number (in.) (in.) (in.) (g)
1011 rpp 5 5 7/8 6689
0971 rpp 5 5 1/2 3827
0970 rpp 3 5 1/2 3822
1010 rpp 5 5 7/8 6695
0950 rpp 3 5 1/4 1916
0955 rpp 3 5 1/4 1916
1023 rpp 2 5 1/8 963
1024 rpp 2 5 1/8 963
1048 rpp 2 5 1/8 961
0957 rpp 3 5 1/4 1918
1916 rpp 3 5 1/2 3846
0974 rpp 3 5 1/5 1534
0975 rpp 3 5 1/5 1533
0948 rpp 2 5 1/10 765
0960 rpp 2 5 1/10 768
0995 rpp 1 5 1/10 381
6

7.
Unit 4 (Typical Cylindrical Unit)
Part Height Diameter Mass
Type
Number (in.) (in.) (g)
2278 Cylinder 1.7 3.57 5267
2279 Cylinder 1.7 3.57 5219
2280 Cylinder 1.7 3.57 5234
7

8.
Unit 5
Part Length Width Height Diameter Mass
Type
Number (in.) (in.) (in.) (in.) (g)
945 rpp 5 2 - - 2679
943 rpp 5 2 - - 2680
944 rpp 5 2 - - 2682
946 rpp 5 2 - - 2682
1085 rpp 5 1 - - 1346
942 rpp 5 1 - - 1341
979 rpp 5 1 - - 769
962 rpp 5 1 - - 383
1032 rpp 5 1 - - 192
978 rpp 5 1 - - 768
963 rpp 5 1 - - 383
1014 rpp 5 1 - - 193
2572 cylinder - - 1.7 3.57 5286
8

9.
Unit 9
Part Length Width Height Diameter Mass
Type
Number (in.) (in.) (in.) (in.) (g)
2470 cylinder - - 1.06 4.53 5247
1008 rpp 5 5 7/8 - 6693
1012 rpp 5 5 7/8 - 6684
967 rpp 5 5 1/2 - 3833
3380 hemisphere - - - 4.8 8838
9

10.
Vertical Lift Assembly (Example experiment)
10

11.
Placement
11

12.
Benchmark Experiment
 Dimensions and  Approximately 175
masses measured kg of the 206.5 kg
and reported with a HEU mass placed
high degree of on steel diaphragm
precision Sagging and tilting
 ~Critical of outer 8 units
towards center
ρ = -9.13 ¢
keff = 0.9994
βeff = 0.0067
12

13.
Calculated (MCNP5) Unit Worths
0
-1
-2 Unit 6 Unit 5
Unit 4
-3 Unit 8 Unit 7
Unit Worth (ρ$) Mass (kg)
Relative Unit Worth (r$)
Unit 2
-4 Unit 3
1 -5.32 38.5
2 -2.66 15.8 -5
3 -3.34 23.2 Unit 1
-6
4 -2.41 15.7
5 -2.05 21.4 -7
6 -2.22 15.7 -8
7 -3.12 23.2
-9
8 -2.56 15.8
9 -11.89 31.3 -10
-11
-12 Unit 9
-13
0 5 10 15 20 25 30 35 40 45
Unit Mass (kg)
13

14.
Parameter 1σ
Perturbed Parameter ±keff (1)
Value Uncertainty
Homogenization of Units -- -- Negligible
Uncertainties Holes in Cylindrical Pieces
Gaps between Pieces
--
--
--
--
Negligible
Negligible
Total HEU Mass (g) 206,522 28 Negligible
 Negligible HEU Dimensions (cm) Varies 0.00508 Negligible
0.068 / √2
≤0.00010 Δk
Tilt Angle (°) Varies 0.00017
234
U Content (wt.%) 0.97 0.05 Negligible
 Uncertainty in
235
U Content (wt.%) 93.15 0.05 Negligible
236
βeff
U Content (wt.%) 0.24 0.05 Negligible
Impurity Content (wt.%) Typical ORCEF HEU Metal Negligible
5% Radial Position (cm)
Angular Placement (°)
Varies
--
0.0254
--
0.00080
Negligible
 Radial position Vertical Deflection (cm)
Alternating Vertical Deflection (cm)
Varies
--
0.0127
0.0127
Negligible
Negligible
assumed 100% Centerpiece Vertical Deflection (cm) -1.755 0.0127 Negligible
systematic as Centerpiece (x, y) Position (cm) (0, 0) 0.0127 Negligible
the worth of Stack Order
Stack Alignment
--
--
--
--
Negligible
Negligible
each unit is Support Structure Worth (¢) -10.2 1.14 Negligible
different Room Return
Temperature (K)
--
293
--
2
Negligible
Negligible
Measurement of k eff (¢) -9.13 0.72 Negligible
Experiment Repeatability (¢) -8.17 0.65 Negligible
Total Uncertainty -- -- 0.00082
14

15.
Benchmark Model Development
 Detailed Model  Simple Model
Homogenized units Detailed
neglecting gaps simplifications
between pieces Average HEU
Removed support density and
structure composition
Room return effects No holes in
quantified cylinders
No HEU impurities No tilt and all
pieces on level
 Bias (Δk) plane
-0.00189 ± 0.00009
 Bias (Δk)
-0.00768 ± 0.00041
15

16.
Bias Summary
Bias Description Bias ± 1σ Bias Description Bias ± 1σ
Intra-Unit Gaps and Unit Mass Density Negligible Intra-Unit Gaps and Unit Mass Density Negligible
Removal of Support Structures -0.00068 ± 0.00008 Removal of Support Structures -0.00068 ± 0.00008
Room Return -0.00099 ± 0.00003 Room Return -0.00099 ± 0.00003
Removal of Impurities -0.00022 ± 0.00003 Removal of Impurities -0.00022 ± 0.00003
Removal of Holes in Cylinders -0.00018 ± 0.00003
Total Bias -0.00189 ± 0.00009
Average Fuel Density +0.00053 ± 0.00003
Average Uranium Isotopic Composition -0.00016 ± 0.00003
Placement of All Units on a Level Surface +0.00028 ± 0.00003
Removal of Unit Tilt -0.00560 ± 0.00040
Sum of Individual Biases -0.00702 ± 0.00041
Total Bias -0.00768 ± 0.00041
*Simple model developed for codes that do not have
the capability of geometry rotation.
16

17.
Detailed Model Sample Calculations
CE
Analysis
Code
Neutron Cross
Section Library
Calculated Benchmark
%
σ σ E
(a) MONK9 results keff ± keff ±
provided by ENDF/B-VII.0
ENDF/B-VI.8
0.99391
0.99090
±
±
0.00002
0.00002
-0.36
-0.66
Dave Hanlon MCNP5-1.51
ENDF/B-V.2 0.99462 ± 0.00002 -0.29
from SERCO, JENDL-3.3 0.99222 ± 0.00002 -0.53
UK ENDF/B-VII.0
(continuous 1.00133 ± 0.00008 0.38
(b) COG-11 results energy)
ENDF/B-VII.0
to be provided KENO-VI (238-group) 1.00116 ± 0.00007 0.31
by Dave (SCALE 6.0) ENDF/B-VI.8
(238-group) 0.99814 ± 0.00009 0.06
Heinrichs from ENDF/B-V.2 0.9975 ± 0.0009
LLNL (238-group) 1.00141 ± 0.00009 0.39
*Typically Mihalczo JEF-2.2 0.9899 ± 0.0001 -0.76
HEU metal JEFF-3.1
experiments MONK9(DEV) (a)
0.9914 ± 0.0001 -0.61
calculate ENDF/B-VII.0 0.9943 ± 0.0001 -0.32
slightly low CENDL-3.1 0.9953 ± 0.0001 -0.22
COG-11(b) TBD TBD TBD
17

18.
Simple Model Sample Calculations
CE
Analysis
Code
Neutron Cross
Section Library
Calculated Benchmark
%
σ σ E
(a) MONK9 results keff ± keff ±
provided by ENDF/B-VII.0
ENDF/B-VI.8
0.98810
0.98507
±
±
0.00002
0.00002
-0.37
-0.67
Dave Hanlon MCNP5-1.51
ENDF/B-V.2 0.98877 ± 0.00002 -0.30
from SERCO, JENDL-3.3 0.98644 ± 0.00002 -0.53
UK ENDF/B-VII.0
(continuous 0.99489 ± 0.00009 0.32
(b) COG-11 results energy)
ENDF/B-VII.0
to be provided KENO-VI (238-group) 0.99461 ± 0.00008 0.29
by Dave (SCALE 6.0) ENDF/B-VI.8
(238-group) 0.99160 ± 0.00010 -0.01
Heinrichs from ENDF/B-V.2
LLNL (238-group) 0.99471 ± 0.00008
0.9917 ± 0.0010
0.30
*Typically Mihalczo JEF-2.2 0.9842 ± 0.0001 -0.75
HEU metal JEFF-3.1
experiments MONK9(DEV) (a)
0.9854 ± 0.0001 -0.63
calculate ENDF/B-VII.0 0.9885 ± 0.0001 -0.31
slightly low CENDL-3.1 0.9895 ± 0.0001 -0.21
COG-11(b) TBD TBD TBD
SERPENT1.1.17 ENDF/B-VII.0 0.98805 ± 0.00004 -0.37
18

19.
Conclusions
 Benchmark models  General agreement
have been in calculated
generated for results for some
GROTESQUE contemporary
 Uncertainty is Monte Carlo codes
negligible except
for radial
positioning of
outer 8 units
19

20.
Questions?

21.
Extra Slides
21

22.
HEU Tilt Angle Uncertainty
Center Bottom Bottom Center Middle Reported Angle
Deflection
Unit X,Y Coordinates Z Coordinate X,Y Coordinates Angle Uncertainty
Ratio
(cm) (cm) (cm) (°) (°)
1 0.000, -17.464 0.150 0.000, -17.306 0.0236 1.350 0.066
2 -12.176,-9.343 0.111 -12.051, -9.247 0.0244 1.400 0.068
3 -16.333,1.861 0.174 -16.196, 1.845 0.0205 1.173 0.068
4 -9.539,11.168 0.156 -9.394, 10.999 0.0344 1.970 0.072
5 0.0,15.698 0.290 0.000, 15.400 0.0451 2.580 0.066
6 9.854,10.944 0.134 9.727, 10.803 0.0293 1.680 0.072
7 16.388,1.434 0.140 16.224, 1.419 0.0244 1.400 0.068
8 12.029, -9.398 0.087 11.931, -9.322 0.0192 1.100 0.068
-- -- -- -- -- average 0.068
22

23.
The Benchmark Evaluation Process
23

24.
International Criticality Safety Benchmark
Evaluation Project (ICSBEP)
 Purpose:
 Identify and verify comprehensive sets of critical
benchmark data by reviewing documentation and
talking with experimenters
 Evaluate the data and quantify the overall uncertainty
via sensitivity analyses
 Compile the data into a standardized format
 Perform calculations of each experiment with
standard criticality safety codes
 Formally document work into a single source
 http://icsbep.inl.gov
 icsbep@inl.gov
24

25.
International Handbook of Evaluated Criticality
Safety Benchmark Experiments
September 2011 Edition
 20 Contributing Countries
 Spans approximately 62,600
Pages
 Evaluation of 532
Experimental Series
 4,550 Critical, Subcritical, or
k∞ Configurations
 24 Criticality-Alarm/Shielding
Benchmark Configurations –
numerous dose points each
 155 fission rate and
transmission measurements
and reaction rate ratios for
45 different materials
25