JNFL Sub-Surface Disposal Plan and Safety Strategy for Relatively Higher LLW Kazuyuki KATO Japan Nuclear Fuel Limited (JNFL) Technical Meeting on the Disposal of ILW September 9-13, 2013 Vienna, IAEA

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

3 Classification of Radioactive Waste Disposal

4 Disposal Concepts for Radioactive Waste in Japan 300m < Sub-surface disposal with engineered barrier (Relatively higher LLW) (L1) Near-surface disposal with engineered barrier (Relatively lower LLW) (L2) Near-surface disposal without engineered barrier (Trench disposal) (VLLW) (L3) Geological disposal (High-level radioactive waste) Geological disposal (LLW highly contaminated TRU) 50m < < 50m K. KATO, FEPC, Intermediate Depth Disposal of Radioactive Waste: The Safety Basis and its Realization - International Workshop, Korea, 8-12 December, 2008 JNFL(In operation) Category 1 Category 2 ILW in IAEA’s classification

5 VLLWRelatively lower LLWRelatively higher LLW (L3)(L2)(L1) Disposal DepthNear-surface: < 50mSub-surface: 50m < Engineered Barrier System (EBS) without EBSwith EBS with High Performance EBS TrenchConcrete pit Active control period~50 years~ years Upper Bounds of Concentration (Bq/ton-waste) C-14-1E+111E+16 Cl-36--1E+13 Co-601E+101E+15- Ni-63-1E+13- Sr-901E+071E+13- Tc-99-1E+091E+14 I E+12 Cs-1371E+081E+14- alpha-1E+101E+11 Upper Bounds of Radioactive Concentration for Burial of Low-Level Radioactive Solid Waste (in Japanese), NSC, May Upper Bounds of Concentration for each LLW Disposal Concept

6 Basic Concept of Sub-Surface Disposal

7 Regulatory Requirement for Disposal Depth 0m 20m 40m Foundation of ordinary house Foundation of high rise building and its basement subway Water pipe sewerage underground multipurpose duct Foundation of motorway and train overpass Example of sub-surface disposal concept Sufficient depth against normal use of underground (ex m). Tunnel type Silo type LLW for sub- surface disposal 0 m 20 m 40 m Foundation of ordinary house Foundation of High-rise building And basement Subway Water pipe Sewerage underground multipurpose duct Example of sub-surface disposal concept Sufficient depth against normal use of underground (ex m). Example of sub-surface disposal concept Sufficient depth to avoid normal use of underground (e.g m). Tunnel type Silo type LLW for Sub - surface disposal The depth of sub-surface disposal is defined over 50m in law

8 (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 Concept of Sub-Surface Disposal

9 Target Waste and Facility Design Activity

10 Nuclear Power Plant Reprocessing Plant MOX Fuel Fabrication Plant Recovered Uranium /Plutonium Spent Fuel Uranium Fuel MOX Fuel Low-level waste High-level waste High-level waste Low-level waste ・ Concrete pit Disposal(L2) ・ Trench Disposal (L3) Concentrate d liquid waste Incombustibles Inflammabl es Incombustibility thing Metallic piping, Plastic material Channel box (CB) Burnable poison (BP) － BWR －－ PWR － Control Rod (Reactor core internal etc.) Sub-surface Disposal (L1) （ Note ） CB/BP are generated from not only the power stations but also a reprocessing plant. Ion exchange resin ・ Geological Disposal （ vitrified waste, hull, end-piece ） Target Waste for Sub-Surface Disposal Uranium Enrichment Plant /Fuel Fabrication Plant Control Rod

11 Time after generation [y] Operational waste from power station (activated metal) 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) [Bq/ton] Radioactive concentration Ni-63 C-14 Ni-59 Zr-93 Ni-63 C-14 Ni-59 Zr-93 Example of the Waste Inventory for Sub- Surface Disposal

Objectives of Site Investigation in Rokkasho 2) Groundwater -Hydraulic characteristics -Geochemical characteristics 3) Rock mechanics Stability of cavern Permeable zone 1) Geology -Geological structure -Properties of faults/fractures stream Approx.100m marsh 12

Exploratory drift (for accessing) 6. ５ m 7 m Entranc e 16 ｍ 18 ｍ Test cavern Test Cavern and Exploratory Drifts 13

14 The difference of EBS performance T. Shimizu, The Fourth Annual RadWaste Summit, September 7-10, 2010, Las Vegas, Nevada Hydraulic Conductivity Kw [m/s] Effective Diffusion Coefficient De [m 2 /s] Near-surface disposal(in operation) Sub-surface disposal

15 Engineered Barrier System of Sub-Surface Disposal Bentonite Mortar Reinforced concrete pit Backfill (soil, concrete) Liner concrete Waste packages Host Rock (sedimentary rock) Mortar fill (Low permeability layer) (Low diffusivity layer) approx. 18 ｍ

16 Structure of sub-surface disposal facility Disposal Facility Cross sectionDisposal Facility Profile Approx. 18 ｍ Approx. 13 ｍ Approx. 12 ｍ Approx. 14 ｍ Support / Secondary Lining Low permeability layer Filler Waste packages Concrete pit Low diffusivity layer Backfill material K. KATO, FEPC (2008)

17 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) Lid Additional shield Waste Main body of the waste package Handling guide Structure of the Waste Package (conceptual view)

18 Safety Strategy For Sub-Surface Disposal

19 L1 waste (sub-surface disposal) Vitrified HLW (geological disposal) Change of potential risk of radioactive wastes (relative risk to the initial risk of vitrified HLW) (reference from NSC document (modified)) L2 waste (near surface disposal) (“pit disposal”) Potential risk (effect) per unit mass (relative risk) Time (year) Safety Issues and Time-Frame for L1 waste Institutional Control until significant decay Consideration for very long-term safety Multi-barrier System for slow migration

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

21 Safety strategy Multiple countermeasures may be necessary for a certain radionuclide in different cases. C-14 Cl-36, I-129 key RN : C-14, Cl-36, Ni-59, Tc-99, Zr-93, Nb-94, I-129, alpha.. Ni-59,Nb-94,alpha

22 Key Issues for multi-barrier system of Sub-Surface Disposal Key nuclides in groundwater scenario are C-14 and Cl- 36. 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.

23 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.

24 How to select disposal concept for ILW? After a very long time, only long lived wastes exist Geological Disposal From intermediate to shallow depth of facility is feasible # 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. Depth? State of barriers? Required Depth [m]=Erosion Rate [m/y] X Enough decay time [y]

Conceptual logic for disposal option 25 NBEB Activity Geological Disposal Intermediate Depth Disposal Surface Disposal (Concrete Pit) Surface Disposal (Trench) > NB EB ≒ NB EB > NB Sorption Sorption, Permeability, Diffusion Travel time Travel time, Separation Travel time, Isolation, Reducing Sorption, Permeability, Diffusion Travel time

26 Required scenario & target dose Scenario category Sub-scenariosTarget dose per RMEI 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 10~100 mSv/yr Human intrusion Borehole scenarios Tunnel excavation scenarios A large-scale land use scenario Residents: 1~10 mSv/yr Intruder: 10~100 mSv RMEI : Reasonably Maximally Exposed Individual BASIC GUIDE NSC Japan, August 2010 A new regulatory framework is under discussion among regulatory authorities in response to the Fukushima Daiichi NPP accident.

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

28 Thank you for your attention! END