Fission Surface Power for the Lunar Surface

1. Assessment of Zero Power
Critical Experiments and
Needs for a Fission Surface
Power System
James Parry
John Bess
Idaho National Laboratory
Brad Rearden
Oak Ridge National Laboratory
Gary Harms
Sandia National Laboratories
Nuclear and Emerging Technologies for Space
ANS Annual Meeting, Atlanta, GA
June 14-19, 2009

2. Objective
Assess current computational
modeling capabilities and
associated biases for the design
of the lunar Fission Surface Power
system to minimize necessary
nuclear experiments and tests
2

3. Fission Surface Power (FSP) System
Lunar outpost
power supply
20 – 50 kW
<8 yr operation
Ready for launch
by 2020
Provide a power-
rich mission
environment
3

4. Experimental Needs
Non-nuclear performance tests
¤ Steady-state, transient, & system response
¤ Verify and validate design
¤ Use in neutronics calculations
Neutronics
¤ Critical mass, fission rate, control drum worth,
accident scenarios, reactivity effects
¤ Validate with existing criticality data
Desire to minimize testing and validate
system performance within acceptable risk
4

5. Evaluation of Benchmark Data
International Handbook of Evaluated
Criticality Safety Benchmark
Experiments
Ideal benchmark would be a fast-
spectrum, NaK-cooled, SS-clad, HEU-
O2, Be-reflected system
Handbook contains a conglomerate of
experiments
¤ ZPPR-20 – mockup of SP-100
¤ 4 configurations
5

6. MCNP Bias Assessment
Select critical experiments
modeled in MCNP v.5.1.40
ENDF/B-V.0, -VI.6, -VII.0 cross
sections
Assess the calculated eigenvalues
and the expected benchmark
eigenvalues from the experiments
6

7. Average Bias ( k)
∆
HE
U
Fa
st
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
S pe
IE c tru
U m
Fa
s tS
pe
HE c
U tru
m
M
ix
ed
In Sp
ter ec
m tru
m
ed
iat
e
ENDF/B-V
Sp
ec
Th tr um
erm
al
Sp
ec
tru
m
ENDF/B-VI
Be
ryll
ium Su
bc
Re r iti
fl e ca
cto l
r/M
ENDF/B-VII
od
er
ato
St
ee r
lR
ef
lec
ted
B4
C
Co
ntr
ol
7

8. Results from MCNP Bias Assessment
Some insight into effects from major
components
¤ Definitive conclusions not possible due to
mixture of experiment designs
Some improvement with ENDF/B-VII.0
data, but not for IEU fast-spectrum and
subcritical experiments
¤ Need to reduce uncertainty in subcritical
experiments for validation of launch
accident configurations
8

9. Beryllium Reflector Bias Assessment
Assessment of worth of beryllium
using a selection of benchmarks
Evaluated for both fast- and
mixed-neutron systems
¤ HEU-MET-FAST-058
¤ HEU-MET-FAST-066
¤ MIX-MET-FAST-007
9

10. 10

11. 11

12. Results from Beryllium Bias Assessment
Bias increases as reflector worth
increases
¤ Up to 0.5% ∆k/k in HEU systems
¤ Up to 1.0% ∆k/k in mix-fuel systems
Implies a cross section bias
¤ Improvement in cross section data
for Be should improve analysis
capabilities of the FSP
12

13. ZPPR-20 Benchmark Data
 ZPPR-20C(105)
¤ HEU-MET-FAST-075
¤ Critical Core
 ZPPR-20D(129)
¤ HEU-MET-MIXED-012
¤ Critical Water Immersion
Accident
 ZPPR-20D(136)
¤ SUB-HEU-MET-MIXED-001
¤ Subcritical Water
Immersion Accident
 ZPPR-20E(160)
¤ SUB-HEU-MET-FAST-001
¤ Subcritical Earth Burial
Accident
13

14. TSUNAMI Analysis
Tools for Sensitivity and Uncertainty
Analysis Methodology Implementation in
Three Dimensions (TSUNAMI-3D)
¤ Comprehensive analysis of relative deviation of
keff due to cross-section covariance data
TSUNAMI-IP (Indices and Parameters)
¤ Comparison of TSUNAMI-3D analyses for
multiple configurations
¤ Compute relational parameters between two
configurations to assess a degree of simularity
 i.e. proposed designs to existing experimental data
14

15. TSUNAMI-3D Results for FSP Model
Total Component
Covariance Major
Uncertainty Uncertainty
Library Components
(%Δk/k) (%Δk/k)a
235U(n, γ) 1.9576 0.0006
235U(ν-bar) 0.5651 0.0000
Be(n, n) 0.3559 0.0023
SCALE 6 2.0872 235U(n, n’) 0.2261 0.0009
235U(n, fission) 0.1864 0.0000
235U(n, n) to
235U(n, γ) -0.1297 0.0003
a Negative value represents anticorrelations
between two reactions in the covariance data 15

16. Correlation Coefficient, ck
Rigorous uncertainty analysis
¤ Propagates tabulated cross-section
uncertainty information to keff
¤ Energy-dependent sensitivity coefficients
Represents estimate of the correlated
uncertainty between systems
Measures degree of similarity of the
systems in terms of relative
uncertainty
16

17. TSUNAMI-3D Results
SCALE 6 Covariance Data
Model Cross-Section
ck
Uncertainty (%)
ZPPR-20C(105) 0.9753 ± 0.0036 2.0684
ZPPR-20D(129) 0.9453 ± 0.0021 1.7137
ZPPR-20D(136) 0.9327 ± 0.0020 1.6520
ZPPR-20E(160) 0.9323 ± 0.0041 1.5943
17

18. Penalty Assessment (TSUNAMI-IP)
Determine additional margins of uncertainty
where experimental information is
unavailable
Provides added measure of safety where
validation coverage is lacking
Covariance data uncertainty reduced to 0.29
%∆k/k, which is mostly from the Be(n,n)
reaction uncertainty
Can be used to assess bias and bias
uncertainty for additional margins in
subcriticality experiments to account for
lack of experimental coverage for beryllium
18

19. Future Efforts
Utilize TSUNAMI to analyze the benchmarks
identified in the MCNP study
Apply advanced bias techniques with
SCALE 6 TSURFER
Evaluate reactor physics data for the ZPPR-
20C benchmark
¤ Control rod worth, material worth, temperature
effects, reaction rates
¤ MCNP and SCALE 6 TSAR
Perturbation analysis of key reactor
parameters to reduce uncertainties in
margin prediction
Improve uranium and beryllium cross
section data
19

20. Conclusions
ENDF/B-VII data reduced
eigenvalues biases except for
subcritical and IEU benchmarks
Beryllium reflector has a bias
trend for increasing reflector
worth
ZPPR-20 data should preclude the
necessity of a FSP cold critical
experiment
20

21. Acknowledgments
Support and guidance provided by
NASA Marshall Space Flight
Center and NE-34.
Technical advice and guidance
provided by Harold McFarlane, Jim
Werner, and Steve Aumeier at the
INL and Paul Turinsky at NCSU.
21

22. This work was performed under the management of the Department of Energy, Office of Nuclear
Energy under DOE Idaho Operations Office Contract DE-AC07-05ID14517, for the NASA 22
Exploration Technology Development Program as part of the Fission Surface Power Project.