Overview of Horonobe URL project1

Nuclear Fuel Cycle & Disposal of nuclear waste in Japan©NUMO

TRU: TRans-Uranic waste
HLW: High-Level radioactive Waste
2What is vitrified Waste?
Vitrification

Vitrified Waste in canister• Material: borosilicate glass• Melting temperature: 1,100~1,200oC• Height: 134cm• Diameter: 43cm
• Weight: 500kg• Radioactivity: about 1.5x1016Bq/can.
• Initial surface dose: 1,500Sv/h
Vitrified waste in a
19 cm thick metal
container (after 50yrs of cooling)

Storage for cooling(30-50 years)

１ｍConcrete wall
Thickness:
approx. 0.8 m

Radiation levels
that can workwithout radiation
control in law.

Spent fuels of about 30t are discharged by operation of a 1GWe power plant for a year,
and about 30 canisters are produced by reprocessing those spent fuels.
Currently, HLW equivalent to 26,000 vitrified wastes have accumulated in Japan.
3

Framework for HLW Disposal in Japan & Role of JAEA©NUMOJAEA has responsibility for R&D for both implementation and regulation to ensure the reliability ofgeological disposal technology and safety assessment methodology.
In 1994, Atomic Energy Commission recommended. “URLs should be constructed at several places.”
JAEA started two “generic” URL projects at Mizunami URL in 1996 and Horonobe URL in 2001.
4

Two generic URLs in JapanThe two URLs are subjected to representative rock and groundwater environments in Japan.
URLs are used for only geoscientific research and/or R & D of geological disposal technology, and are not a
candidate site for geological disposal. It is forbidden to bring in or use any radioactive materials.

Mizunami URL ProjectHoronobe URL Project(Sedimentary rocks, saline water)(Crystalline rocks, fresh water)
Suttu town
Kamoenai village
Granitic rocks
Crystalline schist
Basaltic rocks
Rhyolitic rocks
Gabbroic rocks
Limestone
Pre-Tertiary sedimentary rocks
Neogene volcanic rocks
Neogene sedimentary rocks
Quaternary volcanic and sedimentary rocks

Fracture
Grain

Groundwater

Groundwater

R&D related to geoscience➢Site investigation methods for granite➢Facility construction and operation (eg.
countermeasure for groundwater inflow)➢Modeling technologies for solute transport etc.

R&D related to geoscience and disposaltechnology➢ Engineering technologies➢ Safety assessment methods➢ Promote public’s understandingetc.
5Mizunami URL project

2029

2025

Apr 2023

2020

2015

2010

2005

2000

History of URLs
As the land lease from the local
government expired in Jan., alltunnels have already been
backfilled and are now in theenvironmental monitoring phase.

Phase I
Phase II
Phase III
Backfilling

Monitoring phase
Horonobe URL project

Phase I

Phase II

In 2020, the extension of theURL project until 2029 wasapproved by the municipality.

Phase III
Excavation to 500 m depth(Apr 2023 to Mar 2026)

Phase I: Surface-based investigation
Phase II: Construction (investigation during tunnel excavation)
Phase III: Operation (investigation in subsurface facilities)

6

Outline of the Horonobe site
Horonobe URL
Central Horonobe
SapporoHokkaido

Tokyo

Horonobe URL
0Wakkanai 

500 kmReindeer Farm

 Central Horonobe

The URL is constructed in Neogene sedimentary rocks of the coastal area.
The area is characterized by relatively soft sedimentary rocks, porous media, and saline
groundwater.
7

Policy for social concerns on the Horonobe URL Project
JAEA promised with Hokkaido Prefecture and Horonobe Town（2000） that;✓ JAEA never brings nor uses any radioactive wastes in the area for theproject during and after the project.
✓ JAEA never lends nor transfers the URL facilities to the implementing
organization (Nuclear Waste Management Organization of Japan: NUMO)
for the final disposal of HLW.

✓ JAEA closes the facilities on the ground and refill the underground facility
after completion of the project.
✓ JAEA never introduces a permanent disposal site nor an interim storage
for radioactive waste in Horonobe.

✓ JAEA openly discloses information related to the project.
✓ The Horonobe site will be open to academic research and education.

8Phased R&D at Horonobe URL

Survey geology andgeological structure

Estimate mechanicalstrength, groundwater flow,
water chemistry
Deterministically set geological structure Statistically set geological structure
Large fault

Small fault

Layout design of the facility,
estimate the amount ofwater inflow and quality
Ventilation Shaft
West Access East Access
Shaft
Shaft

Koetoi Formation
BoundaryModelling

140 m

Anticline
Water-conducting zone

250 m

Possibly waterconducting zone
350 m

Wakkanai Formation
500 m

Omagari Fault

Shafts / galleries excavated⚫ Neogene argillaceous marine sedimentary rocks (Koetoi and Wakkanai Formations)⚫ Soft rock and saline groundwater with dissolved methane gas⚫ Several hundreds meter far from Omagari Fault at ground surface

9

Specificity and generality of the Horonobe site

The age of the bedrock is younger than that of overseas, but the chemicalcomposition of groundwater and the strength of the bedrock are similar.

10Investigation and facility design
Horonobe URL

Hydraulicconductivity
1.000E-05

透水係数

Yuchi F.
Koetoi F.
Omagari F.
Wakkanai F.
Masuporo F.

Phase I: Surface-based investigation
Develop a geological model and plan thefacility design and research• Three shafts up to a depth of over 350m
and a gallery with 140, 250, and 350m
depths avoiding water conduction zones.
• The ventilation shaft and two main shafts
were designed for safety control.
Phase II: Investigation during the facility
construction
Verify the model constructed in Phase I andunderstanding the Excavation Damage Zone /Excavation disturbed Zone(m/s)

Ventilation Shaft
West Access
East Access
Shaft
Shaft

Koetoi Formation
140 mAnticline
Water-conducting zone250 m

Possibly waterconducting zone
350 m

Wakkanai Formation
500 m

Phase III: Investigation in the undergroundfacility
Currently, various tests are being conducted
mainly in the 350m gallery.
The shaft and gallery will be extended to500m by FY 2025.

Omagari Fault

Shafts / galleries excavated

3D geological model in the vicinity of Horonobe URL

11

Geological features at 350 and 500m depths
350m gallery⚫Mixing of young shallow
water and fossil seawater
Faults are hydraulically⚫Advection-dominant via
connected by numerous
fault network
dilational fractures
along the faults.

Geological section
The Wakkanai Formation is mechanicallydivided into two domain; the shallow domain
preferable to tensile failure (DI<2) and thedeep domain suitable to shear failure (DI>2).
Ductility Index (DI)= Effective mean stress /Tensile strength

Isotopic signatureof groundwater

Faults are hydraulicallyless connected by a few
dilational fractures
along the faults.

500m gallery to be built in the future⚫Fossil seawater older than 1 Ma⚫Hydraulically closed due to the limited fault
connectivity12R & D activities in the galleries350m gallery➢ Solute transport in the area where fractures are connected
over hundreds meters (severe geological feature case).
➢ Engineered barrier system (EBS) emplacement/retrieval➢ Excavation Damage Zone (EDZ) sealing experiment➢ Dismantling the full-scale EBS➢ Water-tight plug and backfilling test
➢ Evaluation of an initial environments if repository maintained
for retrievability

Occurrence of faults at 350 m level

500m gallery to bebuilt in the future➢ Solute transport in regions where small-scale faults exist, butwith limited hydraulic connectivity and relatively closed
migration paths (preferable geological feature case).
➢ Demonstrate the construction technology of a repository
tunnel for sedimentary rocks under higher rock stress➢ Differences in geological characteristics and engineeringknow-how can be compared between two depths.

Optimisation of a systematic combination of technologies
towards EBS emplacement
Occurrence of fault at 500 m level

Galleries currently under design13Research on engineered barrier system
350m gallery

T-H-M simulation
Overpack
corrosion test
Occurrence of faults at 350 m level

Full-scale Engineered Barrier System (EBS) test

Excavation Damage Zone (EDZ)
identification and sealing test

Dismantling

Solute transport tests involving
colloids/organics and microbe

14

Status of the facility construction
Shaft Excavation Status
East Access Shaft ： 380.0 m
Ventilation Shaft ： 380.0 m
West Access Shaft： 365.0 m
Gallery Excavation Status
GL -140 m Gallery ： 186.1 m
GL -250 m Gallery ： 190.6 m
GL -350 m Gallery ： 757.1 m
GL -500 m Gallery will be constructedby FY 2025

West Access Shaft(2014.3.26)

East Access Shaft

Niche No.4
(East Loop Gallery of the depth of 350 m)
Full-scale Engineered Barrier System Experiment(2015.1.13)

Gallery of the depth of 350 m(2014.3.26)

Video of the excavation: https://www.youtube.com/watch?v=cS8C_UMaXMY(2023.6.15)

15

Safety measure for groundwater inflow and methane
Safety measure for a large amount of spring water① Based on the agreement with the fishermen's cooperative association①・Remove boron and the ammonia
・Maximum drainage is limited to 750 m3 per day

②

③
坑道

② Groundwater inflow restraint by the grouting

Drift④③・Pre-grouting：Grouting before excavation
・Post-grouting：Grouting after excavation②①破砕帯

Safety measure for the rise of the methane gas content

fracture zone

① Ventilation of the URF: Sending ground fresh air to underground forcibly② Stratified management by the methane content
・Watching the methane gas content by a large number of sensors for 24 hours
・Use of non-explosive machines

Safety measure standard

methane gascontent（Vol%）
≧0.25
≧ 0.5
≧ 1.0
≧ 1.5*

Correspondence measures
Prohibition of the firearms use work
Patrol light lighting
Worker evacuation
Power supply interception* Measures based on the labor security hygiene rule16

Promoting better understanding of geological disposal
1. Public experience of the site
Horonobe URL, about 13,200 people experienced
the real underground and 124,000 visited theexhibition hall until 2022.
2. Hosting young researchers under the Internship
Scheme for Students and the International Fellowship
Scheme for Sabbatical Leave Researchers totransfer the experiential knowledge.
3. Use the digital tools: Access log analysis andsequential updating of web pages, more YouTube
videos, Twitters
4. Publication of a series of articles in local PRmagazines
5. Science Cafe for local residents
6. Delivery lessons at primary schools to universities

17Experience of geophysical survey• Experience of the geophysical survey (Seismic tomography).
• Technology to investigate inside rock without destruction.
• Generate very small artificial seismic (vibration) andmeasure the propagation time of it in the rock.
What you do is:
Hit the tunnel wall by hammer and special machineand observe the generated signals.

Seismic wave measurement using boreholes.

Experience of groundwater investigation• Experience of the groundwater sampling.
➢ How to collect and measure to get the reliable chemical
data of deep-groundwater?

Ventilation
shaft
West
shaft

Eastshaft

Study site
140m gallery

What you do is:• Measure the physico-chemical parameters ofgroundwater• Analyze concentration of Iron species➢ What happens over time?

250m gallery

350m gallery

Layout of Horonobe URL

Groundwater sampling andmeasurement at the gallery

Analyzing at Laboratory