Transcript PowerPoint プレゼンテーション

IAEA-CN-178/08-03
Demonstration Test Program for
Long–term Dry Storage of PWR Spent Fuel
2 June 2010
M. Yamamoto,
The Japan Atomic Power Company
The Kansai Electric Power Co., Inc.
Kyusyu Electric Power Co., Inc.
Mitsubishi Heavy Industries, Ltd.
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Contents
1. Introduction
2. Demonstration Test Program





Test Overview and Process
Fuel Assemblies for Test
Outline of Test Container
Verification Method of Fuel Integrity
Confirmation during Storage Tests
3. Designing of Test Container


Current Knowledge and Experience
Simulated Environment of Actual Casks
4. Summary
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1. Introduction
 Mutsu interim spent fuel storage facility in Japan is preparing for the
maximum 50-year storage of spent fuel in dry metal casks for both
transportation and storage.
 To reduce risk of radiation exposure to workers and waste materials, the
facility has no hot cells, and the spent fuel will be confirmed for their
integrity indirectly by monitoring casks during storage and
transported after the storage without opening the cask lid.
Lots of demonstrations &
experiences in overseas
Lots of fuel cladding
integrity investigations
in Japan
Dry storage experiences
of BWR fuel in Japan
Long-term storage test for “fuel integrity” in domestic research facility
to accumulate knowledge and experience on long-term integrity
of PWR spent fuel during dry storage.
To make assurance doubly sure on safety of transportation after storage.
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2. Demonstration Test Program (1/5)
Test Overview and Process
Time Schedule of Demonstration Test of PWR Fuel Storage
Fiscal year
Planning
& Designing
Manufacture
& Preparation
Storage test
& Inspection
2009
2010
2011
2012
2013 2023 2033 2043 - - –2022 –2032 –2042 –2052
Planning
Designing
Safety analysis
Licensing
Manufacturing of test container
Thermal test
(55GWd/t fuel)
(48GWd/t fuel)
Preparation & Fuel inspection
Loading to container
48GWd/t type fuel test
55 GWd/t type fuel test
Gas sampling
---
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2. Demonstration Test Program (2/5)
Fuel Assemblies for Test
 Up to two spent fuel assemblies (Type 48GWd/t and 55GWd/t ) will be
stored.
 48GWd/t : Some of the fuel rods were used for PIE tests, and now it is
stored in the pool of the hot laboratory in Tokaimura (NDC).
 55GWd/t : a proper spent fuel will be prepared in the future.
Fuel assemblies Assumed for Tests
Type 17×17 48GWd/t Fuel
Assembly
Type 17×17 55GWd/t
Fuel Assembly
Burn-up (MWd/t)
42,800 (past record)
≤55,000 (assumption)
Cooling period
19 years
(as of October, 2012)
>10 years
(as of October, 2022)
Cladding material
Zircalloy–4
MDA or ZIRLO
Remarks
15 empty fuel rods*
Non
*Fuel rods used in PIE are never used for long-term storage tests.
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2. Demonstration Test Program (3/5)
Outline of Test Container
Lid
Outline
item
Components
- Lid
(Steel, Resin,
Double metal
gasket)
- Body
(Steel, insulator,
Resin)
- Basket
(Steel, Boron-Al)
- Outer thermal
insulator
Size
- Height :
Approx. 5.2m
- Outer diameter
Approx. 2.2m
Contents
Max. 2 PWR
spent fuel
assemblies
Cover gas
Helium (negative
pressure)
Outer thermal
insulator*
Inner thermal
insulator
Mid-body
Cross section
Inner container
PWR spent
fuel assemblies
Neutron shield
Basket spacer
(Boron-Al)
Basket
(Stainless steel)
Trunnion
*Note: Outer thermal insulator installed at loading only 48GWd/t F/A is
removed when 55GWd/t fuel assembly is added.
Description
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2. Demonstration Test Program (4/5)
Verification Method of Fuel Integrity
Loading to test
[ 48GWd/t fuel assembly] container*
Start of Storage Test
Inspection of fuel
before storage test
under Dry Condition
– Visual inspection
of fuel assembly
10 years
[ 55GWd/t fuel assembly] Loading to test
container*
Inspection of fuel
before storage test
– Visual inspection
of fuel assembly
* The following inspections of
sampled cover gas are to be
carried out at the start of storage
test after fuel loading;
– Kr-85 radioactivity analysis
– Gas composition analysis
Analysis and monitoring
during storage test
– Kr-85 radioactivity analysis
– Gas composition analysis
– Monitoring of surface temperature of
test container
– Monitoring of containment boundary
pressure of test container
End of Test
Flow Diagram of
Test Program
Increase of Kr-85 level
Suspension of Test
Inspection of fuel
Investigation of cause
after storage test
– Visual inspection of fuel assembly
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2. Demonstration Test Program (5/5)
Confirmation during Storage Tests
Sampling of cover gas in test container
- Confirm detection of fuel leakage
- Induction of cover gas into sampling pod
- Scheduling every 5 years
- Radioactive gas (Kr-85) analysis with a Ge detector
- Gas components analysis with a mass spectrometer
Temperature monitoring
- Estimate temperature history of fuel rods
- Installation of thermocouples on the outer surface in the middle area.
- Calculation of the fuel rods temperature with a previously-verified
assessment tool by thermal performance tests.
Pressure monitoring
- Confirm maintenance of containment of the test container
- Monitoring of helium gas pressure at the lid boundary.
- Installation of pressure gauges to a buffer tank leading to gap of double
metal gaskets.
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3. Designing of Test Container (1/4)
Current Knowledge and Experience
Evaluation of Degradation Events
Conditions to
be considered
Thermal
degradation
Chemical
degradation
Radiation
degradation
Mechanical
degradation
Actual Conditions of
Stored Cask
Around 230°C
(Gradually decrease
with decrease in
decay heat)
Test Conditions
(target)
Around 230°C
(Gradually decrease
with decrease in
decay heat)
Negligible oxidation/hydrogen
absorption during storage (inert gas
atmosphere) compared to that
during in-core irradiation
He gas atmosphere
Moisture:
10% or less
He gas atmosphere
Moisture:
10% or less
Negligible neutron irradiation
influence during storage
Saturation of mechanical strength
due to neutron irradiation at
relatively low burn-up (around
5GWd/t)
Maintenance of integrity under
normal test conditions of transport
(free drop) (Acceleration :20 to 45G)
Burn-up of stored
fuel:
Maximum 47GWd/t
Burn-up of contained
fuel:
5GWd/t or more
During storage:
static position
During earthquakes:
Acceleration of 1G
During storage:
static position
During earthquakes:
Acceleration of 1G
Technical Evidence
No embitterment due to hydride
reorientation, failure due to creep
strain, recovery of irradiation
hardening, or stress corrosion crack
under 100MPa or less
circumferential stress at 275°C
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3. Designing of Test Container (2/4)
Simulated Environment of Actual Casks
Chemical degradation
 The test container is filled with helium gas having negative pressure as
with actual dry cask cavity.
 Vacuum drying operation is carried out before backfilling of helium gas.
 Amount of moisture is confirmed.
Radiation degradation
 Mechanical strength of cladding tubes shows saturation and ductility
shows slow deterioration at low burn-up (around 5GWd/t).
 Test fuel Burn-up is 42.8GWd/t. (Irradiation dose is 1021 to 1022n/cm2)
Mechanical degradation
 The test container is statically positioned in a vertical direction.
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3. Designing of Test Container (3/4)
Simulated Environment of Actual Casks --- Temperature
Thermal degradation
 The maximum temperature of fuel cladding tubes during the storage test is
set as around 230°C regarding to design value of actual casks.
 Gradual decrease of fuel temperature is simulated considering to the
condition of actual casks.
Maximum
temperature 1
(°C)
230
210
3
55GWd/t fuel assembly
2
48GWd/t fuel assembly
0
10
Schematic drawing of Max.
Temperature transition
Test Time （year）
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3. Designing of Test Container (4/4)
Simulated Environment of Actual Casks --- Temperature
Heat load and max. temperature of cladding at initial test conditions
Beginning of test
Addition of 55GWd/t fuel assembly
Loaded fuel
assemblies
48GWd/t
(cooling for 19 years)
48GWd/t (cooling for 29 years) &
55GWd/t (cooling for 10 years) .
Heat Load
547 W
1472 W (455+1017 W)
Initial max.
temperature of fuel
cladding
Approx. 250°C
(at 48GWd/t fuel
assembly)
Approx. 230°C
(at 55GWd/t fuel assembly)
 Thermal analyses were
conducted for estimation of max.
temperature of fuel claddings
covered with He gas.
 The obtained temperatures will
meet the aimed temperature
around 230°C or more.
Thermal Analyses of Test Container (during loading of 48&55GWd/t fuel assemblies)
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4. Summary
 Some Japanese utilities are planning to conduct a long-term storage
test for up to 60 years by placing PWR fuel assemblies in a test
container simulating temperature and internal gas of actual casks to
accumulate knowledge and experience on long-term integrity of
PWR spent fuel assemblies during dry storage.
 The storage test plans such as test methods and inspection items,
and container design have been prepared. In the future, safety
analyses, licensing and manufacturing of the test container are to be
done, and the storage test of 48GWd/t fuel assembly will start in
fiscal 2012.
 Thermal design of the test container is important. Its temperature is
controlled with thermal insulators and heat-transfer performance is
confirmed by heat transfer tests at the completion of the container.
 Others ----- Japan Nuclear Energy Safety Organization (JNES) plans to
participate in this test from a regulator’s standpoint. We will discuss its
details in the future.
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Supplemental OHP
Confirmation of containment
Wireless
Web data
logger
P1
V6
Inert gas
inlet / outlet
T1
V7
P2
V8
Server
PC
T2
Controlled area
V9
V10
V5
Buffer tank
V4
Non–controlled area
V3
V2
V1
Lid part
Schematic Drawing of
Pressure Monitoring
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