JNFL Sub-Surface Disposal Plan and Safety Strategy for Relatively Higher LLW

Kazuyuki KATOJapan Nuclear Fuel Limited

(JNFL)

Technical Meeting on the Disposal of ILWSeptember 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)

Cat

egor

y 1

Cat

egor

y 2

ILW in IAEA’s classification

                               

5

VLLW Relatively lower LLW Relatively higher LLW

(L3) (L2) (L1)

Disposal Depth Near-surface: < 50m Sub-surface: 50m <

Engineered BarrierSystem (EBS)

without EBS with EBS with High Performance EBSTrench Concrete pit

Active control period ~50 years ~300-400 years

Upper Bound

s of Concentratio

n(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

Cs-137 1E+08 1E+14 -

alpha - 1E+10 1E+11

Upper Bounds of Radioactive Concentration for Burial of Low-Level Radioactive Solid Waste (in Japanese), NSC, May 2007.

Upper Bounds of Concentration for each LLW Disposal Concept

                               

6

Basic Concept of Sub-Surface Disposal

                               

7

Regulatory Requirement for Disposal Depth

0m

20 m

40 m

Foundation of

ordinary house

Foundation of high

rise building and

its basementsubway

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. 50 -100m).

Tunnel type

Silo type

LLW for sub -

surface disposal

0m

20m

40m

Foundation of ordinary house

Foundation ofHigh-rise buildingAnd basementSubwayWater

pipe

Sewerageunderground multipurpose duct

Example of sub -surface disposal concept

Sufficient depth against normal use of

underground (ex. 50 -100m).

Example of sub-surface disposal concept

Sufficient depth to avoid normal use of underground (e.g. 50-100m).

Tunnel typeSilo type

LLW forSub-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

NuclearPower Plant

ReprocessingPlant

MOX Fuel Fabrication Plant

Recovered Uranium/PlutoniumSpent FuelUranium Fuel

MOX 　 Fuel

Low-level wasteLow-level waste High-levelwasteHigh-levelwaste Low-level wasteLow-level waste

・ Concrete pit Disposal(L2)・ Trench Disposal (L3)

Concentrated liquid waste

Incombustibles

Inflammables

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.

Ionexchangeresin

・ 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] 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]

[Bq/ton]

Ra

dio

act

ive

co

nce

ntr

atio

n

Ra

dio

act

ive

co

nce

ntr

atio

n

Ni-63

C-14

Ni-59

Zr-93

Ni-63

C-14

Ni-59Zr-93

Example of the Waste Inventory for Sub-Surface Disposal

                               

Objectives of Site Investigation in Rokkasho 沼経路－沼産物摂取

沢経路－沢水飲用

沢水飲用畜産物摂取

沢水灌漑農耕

ベントナイト

廃棄物

施設浸入水

沢および沼

溶出率

（黒鉛・放射化物）

廃棄体層（均一混合）

移流・分散

GL-100m

拡散

コンクリート（バリア機能無視）低拡散バリア

拡散

クラック

クラック

ヘアークラック

9割：沼に直接移行1割：沢 を経由して

沼に移行

沢

一部

大半

1次元移流分散

沼経路－沼産物摂取

沢経路－沢水飲用

沢水飲用畜産物摂取

沢水灌漑農耕

ベントナイト

廃棄物

施設浸入水

沢および沼

溶出率

（黒鉛・放射化物）

廃棄体層（均一混合）

移流・分散

GL-100m

拡散

コンクリート（バリア機能無視）低拡散バリア

拡散

クラック

クラック

ヘアークラック

9割：沼に直接移行1割：沢 を経由して

沼に移行

沢

一部

大半

1次元移流分散地下水の浸入

② 地下水調査 ・地下水の流れる速さ ・地下水の流れる方向

③ 地盤調査 空洞の安定性確認

地下水の流れ

高透水層（地下水が流れやすい箇所）

① 地質調査 断層、割目の有無確認

沼100m程度

沢

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

Entrance

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

10-15 10-10 10-510-15

10-10

10-5

Hydraulic Conductivity Kw [m/s]

Effe

ctiv

e D

iffus

ion

Coe

ffici

ent

De

[m2 /

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 section Disposal Facility Profile

Approx. 18 ｍ

Appro

x.

18

ｍ

Approx. 13 ｍ

Appro

x.

12

ｍApprox. 14 ｍ

Support 　 / Secondary Lining

Low permeability layer

Filler

Waste packages

Concrete pit

Low diffusivity layer

Backfill material

K. KATO, FEPC (2008)

                               

17

把持ガイド

廃棄物

追加遮へい体

蓋

本体

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

[ ]経過時間 年

単位重量当たりの潜在的影響（

相対値）

103 104 105 10610210110- 10

10- 9

10- 8

10- 7

10- 6

10- 5

10- 4

10- 3

10- 2

10- 1

1

放射性廃棄物の潜在的影響の経時変化の比較) 1 1（高ﾚﾍ ﾙ゙放射性廃棄物（ｶ ﾗ゙ｽ固化体 の 年目を とした相対値）

( (出典：原子力安全委員会資料より一部編集））

高レベル放射性廃棄物

余裕深度処分対象廃棄物

コンクリートピット処分対象廃棄物

[ ]経過時間 年

単位重量当たりの潜在的影響（

相対値）

103 104 105 10610210110- 10

10- 9

10- 8

10- 7

10- 6

10- 5

10- 4

10- 3

10- 2

10- 1

1

放射性廃棄物の潜在的影響の経時変化の比較) 1 1（高ﾚﾍ ﾙ゙放射性廃棄物（ｶ ﾗ゙ｽ固化体 の 年目を とした相対値）

( (出典：原子力安全委員会資料より一部編集））

高レベル放射性廃棄物

余裕深度処分対象廃棄物

コンクリートピット処分対象廃棄物

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

Applicable to only limited period⇒ Depending on facility design / siting

Judgement of necessity of additional barriers

What kind of composition is necessary?Depending on facility design⇒

Siting / Composition of barriers

Avoidance by siting

option

option

option

Underground disposal (Isolation and Shielding to the biosphere are expected) 地中処分( 地中処分という概念自体が生活環境に対する離隔の確保としゃへい )に期待したもの

postclosureperiod

Naturalprocess

Groundwatermigration

Relatively short-lived

Concentration/containment

preventing groundwater contact with waste packages

Retardation

Retardation by NBS

Retardation by EBS

Relatively long-lived

Dilution /dispersion Spatial dilusion

Dilusion by water

Dispersion of source

Temporal dilusion

Restricting inventory / concentration

Gas migration

Relative movement by uplift/erosion

Relatively short-lived

Relatively long-lived

Very unlikely natural processHuge Earthquakes/fault movement

Volcanic/igneous activities

human intrusion

operational period

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

half-life

Activity content

VSLW very short lived

waste (decay storage)

HLW high level waste

(deep geologic disposal)

ILW intermediate level waste

(intermediate depth disposal)

LLW low level waste

(near surface disposal)

VLLW very low level waste

(landfill disposal)

EW exempt waste

(exemption / clearance)

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

NB EBActivity

GeologicalDisposal

Intermediate DepthDisposal

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-scenarios Target dose per RMEI

Natural process

Likely scenarios

Groundwater scenarioGas migration scenarioLand use scenario

0.01 mSv/yr

Less-likely scenarios

Groundwater scenarioGas migration scenarioLand use scenario

0.3 mSv/yr

Very unlikely scenarios

Earthquakes/Fault movementVolcanic/Igneous activity

10~100 mSv/yr

Human intrusionBorehole scenariosTunnel excavation scenariosA large-scale land use scenario

Residents: 1~10 mSv/yrIntruder: 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