22.251 Systems Analysis of the Nuclear Fuel Cycle
Fall 2009
Laboratory Exercise #3 Solution
a)
Summary of data for normalization:
33.7
Mass,
Kg/MTHM
1000
Energy,
GWe-Y/MTHM
4.6133E-02
50.0
33.7
1000
4.6133E-02
3
75.0
33.7
1000
6.9199E-02
4
7.5
33.2
1000
6.8172E-03
5
20.9
33.2
1000
1.8997E-02
Case
BU, MWth-d/kg
Efficiency
1
50.0
2
Case 1
1.E+08
Case 2
1.E+07
Case 3
Case 4
1.E+06
Case 5
Activity, Ci
1.E+05
1.E+04
1.E+03
1.E+02
1.E+01
1.E+00
1E-01
1E+00
1E+01
1E+02
1E+03
Decay Time, Years
Figure 1: Activity per MTHM
1
1E+04
1E+05
1E+06
Case 1
1.E+05
Case 2
1.E+04
Case 3
Case 4
Decay Heat, W
1.E+03
Case 5
1.E+02
1.E+01
1.E+00
1.E-01
1.E-02
1E-01
1E+00
1E+01
1E+02
1E+03
1E+04
1E+05
1E+06
Decay Time, Years
Figure 2: Decay Heat per MTHM
Case 1
1.E+14
Case 2
1.E+13
Case 3
Case 4
Case 5
1.E+11
3
Ing. Radiotox, m of H2O
1.E+12
1.E+10
1.E+09
1.E+08
1.E+07
1.E+06
1E-01
1E+00
1E+01
1E+02
1E+03
1E+04
Decay Time, Years
Figure 3: Radio-toxicity per MTHM
2
1E+05
1E+06
Case 1
1.E+09
Case 2
1.E+08
Case 3
Case 4
Activity, Ci
1.E+07
Case 5
1.E+06
1.E+05
1.E+04
1.E+03
1.E+02
1E-01
1E+00
1E+01
1E+02
1E+03
1E+04
1E+05
1E+06
Decay Time, Years
Figure 4: Activity per GWe-Y
Case 1
1.E+07
Case 2
1.E+06
Case 3
Case 4
Decay Heat, W
1.E+05
Case 5
1.E+04
1.E+03
1.E+02
1.E+01
1.E+00
1E-01
1E+00
1E+01
1E+02
1E+03
1E+04
Decay Time, Years
Figure 5: Decay Heat per GWe-Y
3
1E+05
1E+06
Case 1
1.E+16
Case 2
1.E+15
Case 3
Case 4
1.E+13
Case 5
1.E+12
3
Ing. Radiotox, m of H2O
1.E+14
1.E+11
1.E+10
1.E+09
1.E+08
1.E+07
1.E+06
1E-01
1E+00
1E+01
1E+02
1E+03
1E+04
1E+05
Decay Time, Years
Figure 6: Radio-toxicity per GWe-Y
b)
Case
1
2
3
4
5
Major
Nuclides
Pu-239
Pu-240
Ra-226
Th-229
Ra-225
Rn-219
Ra-226
Pu-240
Pu-239
Ra-226
Pu-239
Pu-240
Pu-240
Pu-239
4
Fractional
Radiotoxicity
49.8%
39.9%
4.3%
39.8%
31.8%
10.0%
9.3%
44.9%
41.0%
6.9%
60.9%
38.4%
53.7%
43.4%
1E+06
c)
Heat Load – This impacts the flow of groundwater which affects the transport of
nuclides. Additionally it dictates the spacing between the storage tunnels and ultimately
the total physical size of the repository.
Isotope Solubility – The relative ability for a particular isotope to dissolve in water.
Waste Volume – This plays a role on the size of the storage tunnel required; or in other
words how much rock must be mined to make space for the waste.
Modeling Capability – The predictive models used (along with their associated
uncertainties) determine how the repository and the engineered barriers are designed.
d)
On the per energy produced basis, Th fuel is comparable to the rest of the options up to
about 100 years. In the following period up to about 10000 years, Th even offers some
benefits having lower decay heat power than other analyzed cases. Beyond 10000 years,
Th fuel has higher toxicity and heat. However, ThO2 matrix is somewhat more stable in
oxidizing environment than UO2, which may compensate for the higher radiotoxicity.
Thorium fuel is a comparatively less attractive material for proliferators due to the
smaller amount of fissile plutonium and higher radiation barrier.
High burnup PWR has the lowest activity, decay heat and radiotoxicity of all the
analyzed cases.
e)
High burnup reduces the amount of Pu generated per unit energy produced.
Pu isotopic vector becomes more proliferation resistant with higher burnup as relative
fraction of “even” Pu isotopes increases thus increasing the spontaneous fission source.
Pu-238 fraction also increases increasing the heat generation.
ORIGEN predicts Pu isotopes buildup reasonably well if proper cross-section library is
used. For 50MWd/kg case, the discrepancy is below 20%. For the high burnup case
however, no suitable library exists for ORIGEN. Consequently, the discrepancy in Pu
isotopic vector prediction is much larger especially for the higher isotopes. For example,
Pu-242 fraction differs by almost a factor of two between the CASMO and ORIGEN
predictions.
5
Pu-238
Bd = 50 MWd/kg
Bd = 75 MWd/kg
CASMO, ORIGEN,
CASMO, ORIGEN,
Kg/GWe-Y
Kg/GWe-Y
fractional fractional
fractional fractional
0.027
0.031
8.5
0.051
0.056
13.1
Pu-239
0.511
0.533
147.3
0.469
0.478
112.2
Pu-240
0.237
0.253
70.0
0.230
0.308
72.3
Pu-241
0.150
0.126
34.8
0.155
0.105
24.7
Pu-242
0.075
0.057
15.6
0.095
0.054
12.7
Total
1.000
1.000
276.1
1.000
1.000
235.0
1.6E+20
1.4E+20
Pu-238
Atom density, #/cm3
1.2E+20
Pu-239
Pu-240
1.0E+20
Pu-241
Pu-242
8.0E+19
6.0E+19
4.0E+19
2.0E+19
0.0E+00
0
10
20
30
40
50
60
Burnup, MWd/kg
Figure 6: Pu isotopes buildup in PWR assembly
6
70
80
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22.251 Systems Analysis of the Nuclear Fuel Cycle
Fall 2009
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