Effective Application of Partitioning and Transmutation Technologies to Geologic Disposal
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Transcript of Effective Application of Partitioning and Transmutation Technologies to Geologic Disposal
Effective Application of Partitioning and Transmutation Technologies to
Geologic Disposal
Joonhong AhnDepartment of Nuclear Engineering
University of California, Berkeley Tetsuo Ikegami
O-arai Engineering Center, Japan Nuclear Cycle Development Institute, Japan
November 9-11, 20048-th Information Exchange Meeting, OECD/NEA
Las Vegas, Nevada
Background• Effects of P/T on safety of a geologic repository have be
en measured by – the radiological exposure dose rate,
• which is insensitive to P/T application due to solubility-limit mechanisms
– the radio-toxicity of solidified HLW,• which does not indicate repository performance.
• Performance of geologic repositories assessed by considering canister-multiplicity shows that– initial mass loading of toxic radionuclides and canister-array conf
iguration in the repository affect repository performance, and – environmental impact, if it is measured as radiotoxicity of radionu
clides existing in the environment, can be reduced by reducing the initial mass loadings of radionuclides in a waste canister.
Objectives of the present study• To develop models for evaluation of
environmental impact as functions of – repository-configuration parameters,– radionuclide-mobility parameters, and– waste-package parameters.
• To investigate quantitative relationships, for LWR and for FBR– between the capacity and environmental impact of the
repository, and– between the initial mass loadings of radionuclides in
waste canisters and environmental impact of the repository.
Environmental Impact from nuclide i
Radionuclide mass: Mi(t)
repository
Uncontaminated groundwater
Environmental Impact,
Contaminated groundwater
Ny
Nx
310 3
/s 1000 g kg /molm -water kg-nuclide
g/mol 3.7 10 Bq/Ci MPC Ci mi A
ii i
NC
M
ˆ oiMMass loading in a canister
ˆi ix i
oy iMI N N C P
Pi is the ratio of the peak mass in the environment to the total initialloading in the repository, of radionuclide i.
Mass of Np-237 in Environment
1.E-4
1.E-3
1.E-2
1.E-1
1.E+0
1.E-1 1.E+0 1.E+1 1.E+2 1.E+3
Normalized time
Nor
mal
ized
mas
s of
Np-
237
in e
nviro
nmen
t
Nx=10
Nx=100
Nx=1
Initial mass loading per canister = 3.9 molPeak
Mass of Cs-135 in Environment
1.E-5
1.E-4
1.E-3
1.E-2
1.E-1
1.E+0
1.E+1
1.E+2
1.E+3
1.E+0 1.E+2 1.E+4 1.E+6
time, year
Mas
s in
env
ironm
ent,
mol
Nx=1
Nx=10
Nx=200 Rp=1.3ep=0.5K = 48e=0.3S=0.905 m2D=10 mV=4.525 m3L=0.98 mV=1 m/yrTL=10,000 yrh.l. = 2.3E6 yrMo=3.48 mol/can
Peak
Formulas for Factor Pi
• Pi is a function of:– canister-array configuration,
• such as Nx,– repository design,
• such as engineered-barrier dimensions,– radionuclide-transport parameters,
• such as groundwater velocity, solubilities, diffusion coefficients and retardation factors of radionuclides,
– waste-package parameters,• such as package failure time, initial mass loadings of radionuclides,
waste-matrix dissolution time.• Two analytical formulas have been derived:
– for congruent-release radionuclides, and– for solubility-limited release radionuclides.
Waste conditioning model to determine initial mass loading in waste package
the waste composition In a canister
Canister dimensions
Radiation conditions
the radionuclidecomposition vector
from separation process Number of canisters
Repository conditions
Storage conditions
Materials conditions
Repository performance
HLW Glass
Mass: Mass:
canister
GWS MMM
Composition vector:
Composition vector: Composition vector:
Solidification of HLW
Wn Gn
(1 )S W Gr r n n n(r = HLW loading fraction)
Solidified Waste
Mass:
WM GM
Standard form of LP problem
Linear Programming (LP) Model
0xbAxcx
andtosubject
fMaximize ,
where c = row vector of coefficients of objective function, x = column vector of independent variables, A = matrix of coefficients of constraint inequalities, b = column vector of RHS of constraint inequalities.
Objective function
Constraints
LP model for optimizing HLW conditioning- For objective function: c = [1, 0], x = [MW, MG]T
- For constraints: A and b are determined based on regulations/specifications imposed on solidified HLW products.
Canistered waste weight ≤ 500 [kg] Canistered waste fill height ≤ volume of an empty
canister Vcan = 0.15 m3
Canistered waste heat generation ≤ 2300 [W/canister]
MoO3 content ≤ 2 wt%
Na2O content ≤ 10 wt%
HLW loading ≤ 25 wt%
Considered Constraints for JNC-HLW
Filled canister weight
Filled HLW glass volume (Approximate)
HLW loading limit
Heat generation
Mo-limit
Na-limit
kgMM GW 400
073
GW MM
][3.238 kgMW
0544.0 GW MM
0417.0 GW MM
4.547508.1 GW MM
(1)
(2)
(6)
(4)
(5)
(3)
Summary of Constraints
MG [kg]
MW [kg]
200
400
200 400
400 GW MM
600
600
800
800
(Heat)
(Filled waste volume)
(Filled canister weight)
(25 wt% waste loading)GW MM 333.0
(Mo- limit )GW MM 544.0
(Na- limit )GW MM 417.0
kgMMax W 0.99%)0.25( wt
4.547508.1 GW MM
3.238WM
(1)
(3)
(2)
(6)
(4)
(5)
Graphical representation of optimum
Composition Vector of HLW Glass Product:
GWWG NrNrN
)1(
WN
= composition vector of HLW before vitrification (known)
GN
= composition vector of glass frit before vitrification (known)
r = HLW waste loading fraction (determined by LP model)
where
GWWG NNN
75.025.0 For r = 0.25
Canisters produced from 1 MTU of PWR-Spent Fuel
=The amount of HLW from 1 MTU of PWR-spent fuel [kg]
The amount of HLW loaded into a canister [kg]
78.12 [ ] 0.79 [Can/MT]99.0 [ ]
kgkg
=
HLW Glass Compositions & Number of Canisters per ton
PWR vs FBR• PWR
– 0.79 canister/MT– 11.7 GWd-e/canister– 1420 GWy for 40,000-
canister repository
• FBR– 1.25 canister/MT– 21.3 GWd-e/canister– 2590 GWy for 40,000-
canister repositoryLWR (mol/canister) FBR (mol/canister) Nuclide
Lumped Lumped Am 243 4.35E-1 3.04E-3 Pu 239 1.55E-2 4.51E-1 1.93E-1 1.96E-1 Pu 241 3.67E-3 1.20E-2 Am 241 9.27E-1 7.23E-3 Np 237 2.04E+0 2.97E+0 1.12E-3 2.04E-2 I 129 1.28E+0 2.58E+0
Cs 135 2.64E+0 1.39E+1 Tc 99 7.06E+0 1.05E+1
Environmental impact from 40,000 canister repository (LWR)
1.E+07
1.E+08
1.E+09
1.E+10
1.E+11
1.E+12
1 10 100 1000
Number of canisters connected in a row, Nx
Env
ironm
enta
l im
pact
, m3 , f
rom
repo
sito
ry
Np-237
Pu-239
Tc-99
I-129
Cs-135
after reduction ofAm and Np by 1/100
Environmental impact from 40,000 canister repository (FBR)
1.E+07
1.E+08
1.E+09
1.E+10
1.E+11
1.E+12
1 10 100 1000
Number of canisters connected in a row, Nx
Env
ironm
enta
l im
pact
, m3 , f
rom
repo
sito
ry
Np-237
Pu-239
Tc-99
I-129
Cs-135after reduction of
Am and Np by 1/100 and Pu by 1/10
Initial mass loading vs. EI
1.E+8
1.E+9
1.E+10
1.E+11
1.E+12
1.E-3 1.E-2 1.E-1 1.E+0 1.E+1Initial mass loading per canister, Mol
Env
ironm
enta
l im
pact
, m3 , f
rom
rep
osito
ry Np-237
Pu-239
40,000 canisters of HLWin a repository
Initial loading in a canisterfrom LWR spent fuel
Initial loading after reductionof Am and Np by a factor of100 from LWR canister
Initial loading in a canisterfrom FBR spent fuel
Initial loading after reductionof Am and Np by a factor of100 and Pu by a factor of 10from a FBR canister
EI from Repository
• LWR only– 1.7E8 m3/GWy
• LWR + P/T that reduces Np+Am by a factor of 200– 4.0E6 m3/GWy
• FBR– 4.4E6 m3/GWy
Toxicity of depleted uranium and mill tailings
1.E+4
1.E+5
1.E+6
1.E+7
1.E+8
1.E+9
1.E+10
1.E+11
1.E+2 1.E+3 1.E+4 1.E+5 1.E+6 1.E+7 1.E+8Time, year
Toxic
ity (m
3 -wat
er) p
er G
Wy
Total
Pb210Po210Ra226
Th230
Ac227
Pa231
U238
Ra223
U235
Bi210
Th227
U234
Depleted U
1.E+4
1.E+5
1.E+6
1.E+7
1.E+8
1.E+9
1.E+10
1.E+11
1.E+2 1.E+3 1.E+4 1.E+5 1.E+6 1.E+7 1.E+8Time, year
Toxic
ity (m3 -w
ater
) per
GW
y Total
Pb210Po210
Ra226Th230
Ac227
Pa231
U238, U234
Ra223
U235
Bi210
Th227
Mill Tailings
1GWyr(e), LWR, Thermal efficiency 0.325; Capacity factor 0.8; 33GWday/ton; 27.4 ton of 3.3% enriched U fuel; Reprocessing; 26 ton of recovered U returned to enrichment; Depleted U from enrichment contains 0.3% of U-235; Mill tailings contain all decay daughters of uranium isotopes that were in secular equilibria in the ore and 7% of U isotopes; 181 tons of natural uranium in the ore.
EI from Repository + Depleted Uranium
• LWR only1.7E8 m3/GWy + 1.0E10 m3/GWy = +1.0E10 m3/GWy
• LWR + P/T that reduces Np+Am by a factor of 2004.0E6 m3/GWy + 1.0E10 m3/GWy = +1.0E10 m3/GWy
• FBR that consumes 1 ton of DU/GWy4.4E6 m3/GWy – 5.3E7 m3/GWy = – 4.9E7 m3/GWy
Summary• If a P/T system is applied to the LWR system to reduce the environmental
impact from the repository, the target nuclide would be Np-237 and Am-241. The reduction of these nuclides would be meaningful until the environmental impact of Np-237 is reduced to the level of environmental impacts of dominating FP nuclides, such as I-129 and Cs-135.
• The repository filled with 40,000 HLW canisters from FBR operation would result in the environmental impact smaller than that from the LWR repository by a factor of 20. If compared on a per GWyear basis, the advantage of FBR is even greater (a factor of 40). Because the dominating radionuclides are FP nuclides, P/T application for a FBR system to reduce actinides is not attractive.
• The possibility of decreasing the environmental impact from the entire cycle, including legacy depleted uranium, by the FBR system has been indicated. On the other hand, with the LWR + P/T system, depleted uranium will continue to be generated and dominate the environmental impact.