Technical Meeting on the Disposal of ILW
September 9-13, 2013
Vienna, IAEA
JNFL Sub-Surface Disposal Plan and Safety Strategy
for Relatively Higher LLW
Kazuyuki KATO
Japan Nuclear Fuel Limited
(JNFL)
Contents
Classification of radioactive waste disposal
Basic concept of sub-surface disposal
Target waste and facility design activity
Safety strategy for sub-surface disposal
2
Classification of
Radioactive Waste Disposal
3
Disposal Concepts for Radioactive Waste in Japan
JNFL(In operation)
Near-surface disposal without
engineered barrier (Trench disposal)
Category 2
(VLLW) (L3)
< 50m
Near-surface disposal with
engineered barrier
(Relatively lower LLW) (L2)
Category 1
Sub-surface disposal with
engineered barrier
(Relatively higher LLW) (L1)
50m <
ILW in IAEA’s
classification
300m <
Geological disposal
(LLW highly contaminated TRU)
Geological disposal
(High-level radioactive waste)
K. KATO, FEPC, Intermediate Depth Disposal of Radioactive Waste: The Safety Basis and its Realization - International Workshop, Korea, 8-12 December, 2008
4
Upper Bounds of Concentration for each LLW Disposal Concept
VLLW
Relatively lower LLW
Relatively higher LLW
(L3)
(L2)
(L1)
Disposal Depth
Engineered Barrier
System (EBS)
Active control period
Near-surface: < 50m
Sub-surface: 50m <
without EBS
with EBS
Trench
Concrete pit
~50 years
with High
Performance EBS
~300-400 years
Upper Bounds of Concentration
(Bq/ton-waste)
C-14
-
1E+11
1E+16
Cl-36
-
-
1E+13
Co-60
1E+10
1E+15
-
Ni-63
-
1E+13
-
Sr-90
1E+07
1E+13
-
Tc-99
-
1E+09
1E+14
I-129
-
-
1E+12
1E+08
1E+14
-
-
1E+10
1E+11
Cs-137
alpha
Upper Bounds of Radioactive Concentration for Burial of Low-Level Radioactive Solid Waste (in Japanese), NSC, May 2007.
5
Basic Concept of Sub-Surface Disposal
6
Regulatory Requirement for Disposal Depth
Foundation of
motorway and train
overpass
0
0m
20
20m
Foundation of of
high
Foundation
rise building and
High-rise
building
Water
its basement
subway Water
Subway
And
basement
pipe
pipe
underground
Foundation of
Foundation
of
ordinary house
ordinary house
multipurpose
40 m
40
Sewerage
sewerage
duct
underground
multipurpose
duct
Example
of sub-surface
concept
Example of sub
- surface disposal disposal
concept
Tunnel type
Tunnel type
Silo type
LLW for sub
Sufficient depth to avoid normal use of
underground
50-100m).
underground
(ex. 50 (e.g.
- 100m).
Sufficient depth against normal use of
Silo type
-
LLW
for
surface disposal
Sub-surface disposal
The depth of sub-surface disposal is defined over 50m in law
7
Concept of Sub-Surface Disposal
(1) Depth
Sufficient depth to avoid normal use of underground (over
50m).
(2) Candidate site
The place that has the function to prevent or mitigate the
migration of the radioactive nuclides to the environment
(3) Disposal facility
The function to reduce the flux of radioactive nuclides from
the facility is more enhanced than L2
(4) Institutional control
Several hundred years until the radioactive nuclides
significantly decay
8
Target Waste and Facility Design Activity
9
Target Waste for Sub-Surface Disposal
MOX Fuel
Uranium Fuel
Spent Fuel
Nuclear
Power Plant
Uranium Enrichment Plant
/Fuel Fabrication Plant
Low-level waste
・ Concrete pit Disposal(L2)
・ Trench Disposal (L3)
Recovered Uranium
/Plutonium
Reprocessing
Plant
MOX Fuel
Fabrication Plant
High-level
waste
Low-level waste
・ Geological Disposal
（vitrified waste, hull, end-piece ）
Sub-surface Disposal (L1)
(Reactor core internal etc.)
Metallic piping,
Plastic material
Incombustibles
Concentrated
liquid waste
Incombustibility thing
Channel box
(CB)
－BWR－
Control
Rod
Control
Rod
Burnable poison
(BP)
Ion
exchange
resin
Inflammables
－PWR－
（Note） CB/BP are generated from not only the power stations but also a reprocessing plant.
10
Example of the Waste Inventory for SubSurface Disposal
[Bq/ton]
Ni-63
[Bq/ton]
Ni-63
C-14
Ni-59
Zr-93
Time after generation [y]
Operational waste from power station
(activated metal)
Radioactive concentration
Radioactive concentration
Ni-59
Zr-93
C-14
Time after generation [y]
Waste from JNFL (Reprocessing Plant and MOX Plant)
Source: NSC: Figure 1, Figure 4, Document No. 11-1, Sub-committee on Category 2 Waste
Disposal 11th Meeting, Special committee on Radioactive waste/Decommissioning (2008)
11
Objectives of Site Investigation in Rokkasho
stream
2) Groundwater
Approx.100m
-Hydraulic characteristics
-Geochemical characteristics
marsh
1) Geology
3) Rock mechanics
Stability of cavern
Permeable zone
-Geological structure
-Properties of faults/fractures
12
Test Cavern and Exploratory Drifts
Entrance
Exploratory drift
(for accessing)
6.５
7 m
Test cavern
16ｍ
m
18ｍ
13
Effective Diffusion Coefficient De [m2/s]
The difference of EBS performance
10-5
Near-surface disposal(in operation)
10-10
Sub-surface disposal
10-15
10-15
10-10
10-5
Hydraulic Conductivity Kw [m/s]
T. Shimizu, The Fourth Annual RadWaste Summit, September 7-10, 2010, Las Vegas, Nevada
14
Engineered Barrier System of Sub-Surface Disposal
Liner
concrete
Backfill (soil, concrete)
Host Rock
(sedimentary rock)
Bentonite
(Low permeability layer)
Mortar
(Low diffusivity layer)
Reinforced
concrete pit
Mortar fill
Waste packages
approx. 18ｍ
15
Structure of sub-surface disposal facility
Backfill material
Approx. 13ｍ
Low permeability layer
Low diffusivity layer
Concrete pit
Filler
Approx. 18ｍ
Disposal Facility Cross section
K. KATO, FEPC (2008)
Approx. 14ｍ
Approx. 12ｍ
Approx. 18ｍ
Waste packages
Support /
Secondary Lining
Disposal Facility Profile
16
Structure of the Waste Package
(conceptual view)
蓋
Lid
Additional
shield
追加遮へい体
Waste
廃棄物
Handling把持ガイ
guide ド
Main body of本体
the waste package
Size : 1.6m L ×1.6m W ×1.6m H (some are 1.2m H)
Material : Carbon Steel (SM400 etc.)
Weight : approx. 28 ton (Max, including inner shield, waste)
17
Safety Strategy
For Sub-Surface Disposal
18
Safety Issues and Time-Frame for L1 waste
Potential risk (effect) per
unit mass
(relative risk)
Vitrified HLW
1
Institutional Control
until significant decay
Multi-barrier System for
slow migration
単 -1
位 10
重 -2
量 10
当 -3
た 10
り -4
の 10
潜 -5
在 10
的 -6
影 10
響 -7
10
（
相 -8
対 10
値 -9
10
）
10-10
1
(geological disposal)
高レベル放射性廃棄物
Consideration for very
long-term safety
余裕深度処分
L1 waste
(sub-surface disposal)
対象廃棄物
L2 waste
コンクリートピット処分
(near surface disposal)
対象廃棄物
(“pit disposal”)
10
102
103
104
105
106
経過時間[年]
Time (year)
放射性廃棄物の潜在的影響の経時変化の比較
Change of potential
risk of radioactive wastes
（
高ﾚﾍﾞ
ﾙ
放射性廃棄物（
ｶﾞﾗｽof
固化体)の1年目を
(relative risk to
the initial risk
vitrified HLW)1とした相対値）
(出典：
原子力安全委員会資料より(一部編集）
）
(reference from NSC document (modified))
19
Key Issues on Safety Assessment of Sub-Surface Disposal
(Intermediate Depth Disposal)
1. Peak dose rate of ground water scenario must be lowered
below regulatory limit by multi-barrier system.
2. Sufficient inaccessibility to the biosphere for a long time
3. Even if separation to the biosphere would be lost after very
long time, public should be protected safely from the risk of
radiation exposure.
Concerning 1 and 2,
Future geological environment could be estimated with enough
accuracy, and would be stable for long time. Accordingly, for this time
frame, the separation to biosphere would be sufficient and the key
scenario would be the migration in underground water. For this
evaluation, degradation of engineered barriers should be considered
appropriately.
Concerning 3,
For this time frame, functions of engineered barriers could not be
expected, the effects according with the decrease of depth, such as
increase of water flow velocity, should be considered appropriately.
20
Safety strategy
key RN : C-14, Cl-36, Ni-59,
Tc-99, Zr-93, Nb-94, I-129,
alpha ..
C-14
Cl-36, I-129
Ni-59,Nb-94,alpha
Multiple countermeasures may be necessary
for a certain radionuclide in different cases.
21
Key Issues for multi-barrier system of
Sub-Surface Disposal
Key nuclides in groundwater scenario are C-14 and Cl36. Because of its long half-life, only the retardation
function by the natural barrier may not be sufficient.
In the intermediate depth,
 Reducing condition of groundwater may not be expected
 Groundwater velocity is generally slower than that of near
surface/shallow disposal facility, but groundwater velocity is faster
than that of geological disposal facility.
Both low permeability and low diffusivity would be
expected for a long time to assure high retardation
performance.
The design of engineered barriers should be considered
appropriately the site characteristics and waste
characteristics.
22
How deep is safe enough?
Even after very long time, effect of the radioactivity is not
negligible. Even if separation to biosphere would be lost,
safety of public should be assured.
 If the site characteristics shows uplift tendency, the
disposal facility should be initially located at appropriate
depth to keep sufficient separation for a long time
considering uplift and erosion.
 Based on expected time that the disposal facility would
have exposed, the volume and concentration of
radioactive waste to be disposed should be limited to
assure the safety of public.
23
How to select disposal concept for ILW?
Activity
content
After a very long time, only
long lived wastes exist
Depth?
State of barriers?
HLW
high level waste
(deep geologic disposal)
Geological Disposal
ILW
intermediate level waste
(intermediate depth disposal)
From intermediate to shallow
depth of facility is feasible
LLW
low level waste
(near surface disposal)
VSLW
very short lived
waste
(decay storage)
# Depth and facility design decrease
the risk of human intrusion
# Considering uplift/erosion and
activity of long-lived nuclides, enough
time is required before the facility
exposure.
VLLW
very low level waste
(landfill disposal)
EW
exempt waste
(exemption / clearance)
half-life
Required Depth [m]=Erosion Rate [m/y] X Enough decay time [y]
24
Conceptual logic for disposal option
Activity
Geological
Disposal
NB
>
Travel time,
Isolation, Reducing
NB
Travel time,
Separation
Surface
Disposal
(Concrete Pit)
Surface Disposal
(Trench)
NB
Travel time
≒
>
Intermediate Depth
Disposal
EB
Sorption, Permeability,
Diffusion
EB
Sorption, Permeability,
Diffusion
EB
Sorption
NB
Travel time
25
Required scenario & target dose
BASIC GUIDE
Scenario
category
Sub-scenarios
Target dose per RMEI
RMEI : Reasonably Maximally Exposed Individual
Natural process
Likely
scenarios
Groundwater scenario
Gas migration scenario
Land use scenario
0.01 mSv/yr
Less-likely
scenarios
Groundwater scenario
Gas migration scenario
Land use scenario
0.3 mSv/yr
Very
unlikely
scenarios
Earthquakes/Fault movement
Volcanic/Igneous activity
Human intrusion
Borehole scenarios
Tunnel excavation scenarios
A large-scale land use scenario
10~100 mSv/yr
Residents: 1~10 mSv/yr
Intruder: 10~100 mSv
A new regulatory framework is under discussion among regulatory
authorities in response to the Fukushima Daiichi NPP accident. NSC Japan, August 2010
26
Conclusion
Relatively higher LLW (ILW) would be disposed at tunnel
type facility of intermediate depth in Japan.
In both design and safety assessment of the facility,
complementary and reasonable performance between
natural barrier and engineered barrier should be
considered.
Sufficiency of initial depth should be evaluated by the
safety assessment when the disposal facility would have
exposed. The volume and concentration of radioactive
waste to be disposed should be limited based on the result
of safety assessment.
Logics to show the safety of ILW disposal should be
clarified.
27
END
Thank you for your attention!
28