Decommissioning and Reutilization of the Musashi Reactor
Tomio Tanzawa, Nobukazu Iijima, Norikazu Horiuchi, Tadashi Yoshida, Tetsuo Matsumoto,
Naoto Hagura and Ryouhei Kamiya
Musashi Institute of Technology
MI-TECH 1
4th WORLD TRIGA USERS CONFERENCE September 8 to 10, 2008
CONTENTS
1. Outline of the Musashi Reactor2. Planning of Decommissioning3. Progress of the Decommissioning
and Issues Remained4. Reutilization of the Installations for
Musashi Reactor Simulator5. Department of Nuclear Safety
Engineering Newly Established
MI-TECH 2
Key Notes on Research Reactors in Japan
●
Many Research Reactors with Long Term Operation
What are Ageing Issues ?
Keep Operation or Decommissioning ?
●
New Regulations
Introduction of Periodic Safety Review in 2004.
Establishment of Decommissioning Stage Regulation in 2005.
MI-TECH 3
Research Reactors in Japan (15 Reactors In Operation)FacilityName
Operator Power(kW)
Type First Criticality
HTTR JAERI(JAEA) 30,000 High temp. gas cooled 1998
JMTR JAERI(JAEA) 50,000 Tank(material test) 1968
JRR-3M JAERI(JAEA) 20,000 Pool 1990
JRR-4 JAERI(JAEA) 3,500 Pool 1965
NSRR JAERI(JAEA) 300 TRIGA ACPR 1975
FCA JAERI(JAEA) 2 CA(fast reactor) 1967
TCA JAERI(JAEA) 0.2 CA(light water reactor) 1962
STACY JAERI(JAEA) 0.2 CA(homogeneous) 1995
TRACY JAERI(JAEA) 10 CA(pulsing) 1995
JOYO JNC(JAEA) 140,000 Fast reactor 1977
YAYOI Tokyo Univ. 2 Tank 1971
KUR Kyoto Univ. 5,000 Tank 1964
KUCA Kyoto Univ. 0.1 CA 1974
UTR-KINKI Kinki Univ. 0.001 Argonaut 1961
NCA Toshiba Corp. 0.2 CA(light water reactor) 19634
Research Reactors in Japan (Decommissioned and under Decommissioning)
FacilityName
Operator Power(kW)
Type Decommissioning Start Completion
AHCF JAERI(JAEA) 0.01 CA(homogeneous) 1967 1979
JRR-1 JAERI(JAEA) 50 Water boiler 1969 2003
SCA Sumitomo Corp. 0.1 CA 1970 1971
MCF Mitsubishi Corp. 0.2 CA 1973 1974
OCF Hitachi Corp. 0.1 CA 1974 2003
JPDR JAERI(JAEA) 90,000 Prototype of BWR 1982 2002
JMTR-C JAERI(JAEA) 0.1 CA(for JMTR) 1995 2003
HTR Hitachi Corp. 100 Pool 1975 －
Mutsu JAERI 36,000 PWR 1992 －
JRR-2 JAERI(JAEA) 10,000 Tank 1997 －
VHTRC JAERI(JAEA) 0.01 CA 2000 －
TTR Toshiba Corp. 100 Pool 2001 －
DCA JNC(JAEA) 1 CA 2002 －
Rikkyo Rikkyo Univ. 100 TRIGA Mark Ⅱ 2002 －
Musashi Musashi Inst. 100 TRIGA Mark Ⅱ 2004 － 5
The Musashi ReactorTRIGA-Ⅱ(Training, Research and Isotope
Production Reactor designed by General Atomic)
• Max. Thermal Output : 100kW
• Moderator : Zirconium-Hydride
• Coolant : Light Water
• Reflector : Graphite
• Fuel Element : 20% Enriched Uranium Zirconium Hydride Alloy, Stainless Steel or Aluminum Cladding
• Control Rod : Boron-Carbide MI-TECH 6
Vertical Cross-sectional View of Reactor
ConcreteConcrete
Spent Fuel Spent Fuel Storage PoolStorage Pool
Core
Reactor Tank
Irradiation Irradiation RoomRoom
MI-TECH 7
Core and Reflector
Fuel Elements
Reflector
Reactor Tank
Neutron Detectors
Control Rods
Pneumatic Tube
Experimental Tube
MI-TECH 8
Fuel Element of Musashi Reactor (TRIGA-Ⅱ)
Fuel ：20%Enriched UraniumZirconium Hydride
Cladding：Stainless Steel orAluminum
Dimension ：SS-Clad Al-Clad
Length ~75cm ~72cmDiameter ~38mm ~37mm
Fuel Diameter ~36mm ~36mmFuel Length ~38cm ~36cm
MI-TECHFuel Element (unit:mm) 9
History of the Musashi Reactor
Oct., 1959 : Permission for Establishment by Competent Authority
Jan., 1963 : First Criticality
July., 1976 : Addition of Medical Use to Reactor Operation
Mar., 1985 : Change Core from Al Clad Fuel Elements to SS Clad
Dec., 1989 : Small Leakage of Water from the Reactor Tank
Shutdown Reactor Operation
Investigation of Leakage Causes and Planning of Repair
Discussion of “ Restart or Decommissioning”
May, 2003 : Decision of Decommissioning
Jan., 2004 : Submit Decommissioning Plan to Competent Authority MI-TECH 10
General Flow of Decommissioning
(1)Basic Senario
(2)Planning and Submission of Initial Plan to Competent Authority
(3)Implementation
①Detail Plan for Decommissioning Work
②Review and Update the Initial Plan
(4) Completion
MI-TECH 11
Planning
Regulatory Requirements for Completion of Decommissioning
(1) Removal All of the Spent Fuels from the Site
(2) Appropriate Disposal of Radioactive Waste
Key Factors or Conditions for Implementing Decommissioning
(1) USDOE’s Foreign Reactor Spent Nuclear Fuel Acceptance Program
(2) Radioactive Wastes are Low or Very Low Level, and Large Part of Wastes might be ‘Clearance Material’
(3) Under Site Selection for Undertaking Plan of the Waste Disposal Facility for Research Reactor
(4) Under Development of “Clearance Criteria” for Waste from Research Reactor (established in December, 2005)
MI-TECH12
Basic Scenario of Decommissioning
(1) Time period of the decommissioning would be long term.
(2) So, the activities would be carried out in a series of discrete operations(i.e., “phased decommissioning”).
During first phase, (3) most high priority activity would be delivering the
spent nuclear fuels to USDOE, and(4) nuclear installations for the reactor operation would
be released from regulatory control and would be being stored inside the reactor housing facility for long time period.
(5) Dismantling the reactor tank and concrete shielding would be started on condition that the undertaking of the waste disposal facility would be established. 13
Perm anent Shutdow nStorage of Radioactive D isposal ofEquipm ents inside Facility Radioactive W aste
Fuel Transportaition
(In O peration) (Facility w ithout Reactor C ore) (No Radioactive W aste)
Fuels C ore
［Rem oval from C ore Tank］ ［Store inside Facility］Disposal Site
USD O E
Phase 1 Phase 2 Phase 3
General Plan and Image of the Musashi Reactor Decommissioning
14
Decommissioning Plan of the Musashi Reactor and Its Progress
Year
Item
Phase 1 Phase 2 Phase
3
Status of Facility Decision of Decommissioning
Submit Initial Plan to Competent Authority
Permanent Stop Reactor
Shut Down Operational Function
Spent Nuclear Fuel Preparation of Packaging
Transportation Shipping Fuels to USDOE
Pre-shipment Preparation
Dismantling and Storage of Radioactive
Waste Management Waste inside the Facility
; Actual Dismantling Installation and
; Planned Disposal of Radioactive Waste
Future20042003 2005 2006 2007～
15
Permanent Shutdown of Reactor
Cover over the Reactor TankMI-Tech
Seal Seal
Appearance of the Reactor Tank
Top of the Reactor Tank
16
Stop Operational Function of Reactor Control and Instrumentation System
・Control Rod
・Control Rod Drive Mechanism
・Neutron Detector
・Others
・Remove and Store inside Facility
・Open Power Supply
・Disconnect Cable
Disconnected Cables inside ConsoleMI-Tech17
Stop Operational Function of Water Cooling System
・Pipe of Primary Coolant
・Circulation Pump of Coolant
・Close Pipe
・Open Power Supply for Circulation Pump
Pipe Circulation Pump
MI-Tech
純化装置
熱交換器
電気伝導度計
圧力計
圧力計
ろ過器
流量計
流量計
流量計
温度計
温度計
圧力計
圧力計排水ピットへ
原子炉タンクル
タンク出口閉止弁
閉止蓋
タンク入口閉止弁
循環ポンプ
循環ポンプ
温度計
温度計
2-10
2-132-4
2-5
2-11
2-1
2-2
2-72-6
1-1
1-5
1-7
1-8
1-31-2
1-4
1-6
電気伝導度計
18
Radiation Measurements of Installations
MI-Tech
All of the Installations Removed
Surface Radiation Level
Over 0.1μSv/h
Store in Container
Record and Label
Store in Area withRadiation Shielding
Radiation Monitoring
Label
Max. 20mSv/h
19
Work Flow of Spent Nuclear Fuel Delivery from Preparations of Casks to Transportation of Packages
Design & Fabrication of Fuel Baskets
Accept of Cask Body to the Reactor Room
Install the Baskets to Cask Body
Design & Fabrication of Fuel & Cask Handling Equipments
Inspection of Casks
Loading & Inspection of Fuels
Inspection of Packages
Inland Transportation to Port Oversea Transportation
USA Inland Transportation to USDOE Laboratory
MI-Tech20
Transportation Cask (JMS-87Y-18.5T)
Shock Absorber
Diameter;1.9m
Height;2m
Fuel BasketCask Body
Weight;20tonMaterial;SSNo. of Fuels;80
MI-Tech21
Fabrication of Fuel Baskets
MI-Tech
Fabrication was startedin April, 2005
Completed in October, 2005
Inspections;Dimension,Material,
Ultra Sonic,etc
Fuel Baskets
22
Acceptance of Empty Cask into Reactor Room
MI-Tech23
Loading and Inspection of Fuels
Fuel Storage Cask
・Outer Surface Appearance・Confirmation of Fuel ID・Weight Measurement
Fuel Inspections
Transportation CaskNeutron Measurement
Fuel Storage Cask, Transportation Cask and Fuel Handling Equipment
MI-Tech
Fuel Handling Console and Monitoring TV24
Inspection of Packages
MI-Tech
Smear Test Radiation Survey Temperature Measurement
Pressure Test Leak Test Lifting Test
25
Store Installations Stopped Their Operational Function and Maintain Following Facilities Inside the Site
o Gaseous, Liquid and Solid Waste Disposal Facilities,
o Radiation Measurement and Control Facility,
o Reactor Housing Facility
MI-TECH
Phase 2
26
Issues Remained
o It may take long term to complete decommissioning, still under site selection for undertaking plan of the waste disposal facility for research reactor.
o Safe guard regulation is not terminated. It may be issue to be discussed that “zero inventory facility” under decommissioning can be released from safe guard of nuclear material.
MI-TECH 27
Framework of the Musashi Reactor Simulator
Operation Console
Personal Computer
DIO Card
DIOInterface
Simulated Core
Control Rod
Drive
Fuel Element Identification
Neutron Counting
Reactor Operation Data Neutron Transport Calculation
MI-TECH 28
Reutilization of Installation for Education
29
Realistic Simulation of the Musashi Reactor
Control Rod Drive
Simulated Fuels and Core
30
N ：
Number of Neutrons ∝
Reactor Powerkeff ：
Effective Neutron Multiplication Factor
β：
Effectine Delayed Neutron Fraction = 0.008
ι：
Neutron Life Time = 0.0008
λi：Decay Constant （i:1～6）
Ci ：
Precursor （i:1～6）
Reactor Kinetic EquationReactor Kinetic Equation
∑+−−
= iieff CN
lk
dtdN λ
β 1)1(
iiii CN
ldtdC λβ
−=• Control Rod Worth• Temperature Effect• Core Composition
31
Control Rod WorthControl Rod Worth
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 20 40 60 80 100
Control Rod Position [%]
Rea
ctiv
ity[$
] SAFETY
SHIM
REG
32
)( 00 θθρρ −−= DT
)( wGNWdtd θθθ
−−⋅=
：Coolant Temperature25℃
：Initial Core Temperature25℃
wθ
0θ
D：Reactivity Coefficient of Temperature
0.785￠/℃
Reactivity Effect associated with TemperatureReactivity Effect associated with Temperature
33
Reactivity Change due to Substitution of Fuel Element by Water Element
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
B4 C7 D11 E15 F19
Reac
tivi
ty [
$]
Experiment
MCNP4C ENDF/B-VI
βeff：0.008
B4C7D11E15F19
燃料
グラファイト
水
FuelGraphiteWater
Location of Fuel Element 34
New Department of Nuclear Safety Engineering
Faculty of Engineering
Until 2007
Mechanical Eng.
Electric & Electronic Eng.
Energy Science Eng.
Graduate School
Energy Science and Nuclear Engineering
Atomic Energy Research Laboratory
From 2008
Mechanical Eng.
Electric & Electronic Eng.
Energy Science Eng.
Nuclear Safety Eng. Nuclear Safety Eng.35
エネ
ルギ
ー
政策
Design and Operation
Nuclear Fuel Cycle
Application of Radioactivity
Environment
Inspection and DiagnosticApplication
Atomic Energy Policy
Nuclear Safety Regulation
International Energy Policy
Nuclear Risk Management
Nuclear Experiment and TrainingJAEA
Utility and Plant Maker
Atomic Energy Research Laboratory
Nuclear Engineering
Three Courses and Collaboration
Maintenance
36
Engineers and Researcher for Nuclear Energy and Radiation Utilization
Professional Education
Knowledge of Nuclear Technology, Safety, Experience and Training
Bases of Nuclear Engineering
Bases for Engineering and Ethics
First
Second
Third
Fourth
■Curriculum
37
Concluding Remarks-Phased decommissioning was selected for the Musashi Reactor starting with permanent shutdown of the reactor in 2004.
-The first phase was finished with completion of spent nuclear transportation.
-Issues remains for the completion of the decommissioning.
-Remained installations such as control drive mechanism, operation console will be reutilized for education.
MI-TECH38
4th WORLD TRIGA USERS CONFERENCE September 8 to 10, 2008
Decommissioning and Reutilization of the Musashi Reactor
Tomio Tanzawa, Nobukazu Iijima, Norikazu Horiuchi, Tadashi Yoshida,
Tetsuo Matsumoto, Naoto Hagura and Ryouhei Kamiya
Musashi Institute of Technology
The Musashi Institute of Technology Research Reactor (the Musashi Reactor) is a TRIGA-Ⅱ
with maximum thermal power of 100kW. The decommissioning was decided in May, 2003. The
reactor facility is now under decommissioning. The phased decommissioning was selected. Phase 1
consists of permanent shutdown of the reactor and stopping the operational functions, and
transportation of the spent nuclear fuels. After completion of the transportation, the reactor facility
is characterized as the storage of low level radioactive materials. This is phase 2. Activities of
phase 1 were completed and the facility is now under phase 2. Activities of phase 3 consist of
dismantling the reactor tank and the shielding, and delivering the radioactive waste to a waste
disposal facility. The phase 3 will be started on condition that the undertaking of the waste disposal
for research reactors will be established. On the other hand, reutilization of the facility has
being studied, and “realistic” reactor simulator was turned out by utilizing the reactor
installations such as control rod drive and operation console.
1. Introduction
The Musashi Reactor is a TRIGA-Ⅱ, tank-type research reactor, as shown in
Table 1. The Atomic Energy Research Laboratory of the Musashi Institute of
Technology had operated the reactor for education, training and research since first
critical, January 30, 1963. Reactor operation was shut down due to small leakage of
water from the reactor tank on December 21,1989. After shutdown, investigation of the
causes, making plan of repair and discussions on restart or decommissioning had been
done. Finally, decision of decommissioning was made in May, 2003. The
decommissioning initial plan was submitted to the competent authority in January,
2004. Activities of the decommissioning were started in April, 2004. Under
decommissioning as the reactor facility is, the laboratory is playing important roles on
education, training and research for nuclear engineering as ever. The installations
decommissioned such as control rod drive and operation console can be reutilized as
1
4th WORLD TRIGA USERS CONFERENCE September 8 to 10, 2008
educational and training installations.
2. Decommissioning Plan and Its progress
2.1 Basic Scenario of Decommissioning
Regulatory requirements for completion of decommissioning are ;
(1) Removal all of the spent nuclear fuels from the site,
(2) Appropriate disposal of radioactive waste.
Key conditions as follows were taken into considerations for planning the
decommissioning of the reactor ;
(1) USDOE’s Foreign Research Reactor Spent Nuclear Fuel Acceptance Program,
(2) Radioactive wastes are low or very low level, and large part of waste might be
“Clearance Material”,
(3) Under site selection for undertaking plan of the waste disposal facility,
(4) Under development of “Clearance Criteria” for waste from research reactor
(established in December, 2005)
For removal of the spent nuclear fuel, it was only path to deliver them to
USDOE based on the USDOE’s program.
Regarding the disposal of radioactive waste, it would be appropriate to deliver
them to the low level radioactive waste disposal facility outside the site of the reactor.
It may take more ten years to establish the facility.
Considering aboves, basic scenario of decommissioning was made. Its points are
as followings ;
(1) Time period of the decommissioning would be long term,
(2) So, the activities would be carried out in a series of discrete operations(i.e.,
“phased decommissioning”),
(3) During first phase, most high priority activity would be delivering the spent
nuclear fuels to USDOE,
(4) Nuclear installations for the reactor operation would be released from regulatory
control and would be being stored inside the reactor housing facility for long time
period,
(5) Dismantling the reactor tank and concrete shielding would be started on condition
that the undertaking of the waste disposal facility would be established.
2
4th WORLD TRIGA USERS CONFERENCE September 8 to 10, 2008
2.2 General Plan of Decommissioning and its Progress
Figure 1 and Figure 2 show the general plan of the decommissioning. Figure 2
also shows its progress. The decommissioning will be carried out at three phases.
Phase 1 consists of permanent shutdown of the reactor and stopping the operational
functions, and transportation of the spent fuels. After completion of fuel transportation
work, the reactor facility is characterized of the facility without reactor core and the
storage of low level radioactive material. This is phase 2. The amount of concrete
shielding was estimated more than 80% of the total amount of waste. The reactor tank
and the shielding will be maintained as they are, during phase 2. Phase 3, in future, will
be started with dismantling the concrete. Delivering the radioactive waste to the waste
disposal facility will be done in one continuous activity following the dismantling.
The activities of the decommissioning was started in April, 2005 and the phase 1
was completed. The reactor had been stopped since December 21,1989. The fuels were
removed from the core and stored in the spent fuel storage, and the core components
were also removed from the core, in order to investigate the causes of the small
leakage of reactor tank water. The decommissioning was started with this status. First
actions of the decommissioning was covering over the reactor tank with steel plate and
setting seal onto the plate at the top of the reactor tank, and removal of the control
drive mechanism as permanent shutdown. Following that, operational functions of the
systems such as the instrumentation, reactor control, cooling, and emergency power
supply, were stopped. The systems for the reactor operation were released from the
regulatory control.
The Reactor had 80 stainless steel-clad fuel elements and 65 aluminum-clad fuel
elements. These fuels had enough reactivities because of low burnup. As a
consequence, transportation of the spent nuclear fuels was first experience for the
Musashi Reactor. Therefore, preparation works for the spent fuel transportation needed
two and half years. These were (1)preparation of packaging including design of cask,
safety analyses of packaging, application of package design to competent authorities
and manufacturing cask, (2)communication with USDOE for delivering the fuels,
(3)planning of transportation, preparation of manuals for transportation, fuel and cask
handling related works, (4)design and manufacturing the equipments for fuel loading
into the cask and fuel inspections. The loading the spent fuels into the casks were done
June through July, 2006 and the transportation was finished in October, 2006. With this
3
4th WORLD TRIGA USERS CONFERENCE September 8 to 10, 2008
finish, the activities of phase 1 were completed.
During phase 1, following nuclear installations were being maintained to retain
their capability ;
(1) Fuel storage and fuel handling tools,
(2) Gaseous, liquid, and solid waste disposal systems,
(3) Radiation measurement and control systems,
(4) Reactor housing.
Now, the fuel storage and fuel handling tools were released from the regulatory control.
And, (2), (3) and (4) will be being maintained during phase 2.
3. Musashi Reactor Simulator
3.1 Framework of Simulator
Figure 3 shows the framework of the Musashi Reactor Simulator. The operation
console and the control rod drive are the installations decommissioned. Simulated fuel
elements and grid plate compose the simulated musashi reactor core. Type of the fuel
element and its location in the core are identified through electric circuits. Core
characteristics are reproduced on a personal computer using the actual operation data
of the Musashi Reactor and neutron transport calculations with the monte carlo
methods. Operation of control rod, core characteristics, core configuration and
instrumentation data are mutually linked and controlled by a interface.
3.2 Core Simulation
Photo 1 shows the core of the simulator. The core consists of simulated fuel
elements, upper grid plate with 91 holes, lower grid with fuel holders and control rod
drive. Fuel elements including fuel, reflector, void and others were manufactured from
transparent vinyl chloride. These are equipped with electrical resistance so as to
identify their existence, type and location in the core through the holders at the bottom.
3.3 Simulation Software
Software which calculate core thermal power and reactor period were prepared
based on a time-dependent diffusion equation. The actual operation data of the
Musashi Reactor such as core excess reactivity, control rod worth, reactivity effect of
fuel temperature were incorporated into the software. In simulated experiences of
4
4th WORLD TRIGA USERS CONFERENCE September 8 to 10, 2008
critical approach and reactivity effect of fuel, reflector and void elements, the actual
operation data base were not sufficient. Neutron transport calculations using the
monte carlo method of MCNP code were done to provide the core location dependent
reactivity effect of each element. These results were also incorporated into the
software.
3.4 Simulator Operation
The functions essential to the operation of the reactor are reutilized. These are
meters, recorders, switches, dropping control rods (scram), and interlock used in
operating the reactor. Consequently, one can experience very realistic TRIGA reactor
operation through control rod operation and monitoring console panels.
4. Concluding remarks
Considering the status of undertaking plan of the waste disposal facility for the
low level radioactive waste from research reactors, the phased decommissioning was
selected for the Musashi Reactor. First phase of the decommissioning activities
including the actions of permanent shutdown and delivering the spent nuclear fuels to
USDOE was completed. Installations such as the control rod drive and the operation
console decommissioned were reutilized and the realistic Musashi Reactor simulator
was turned out. The simulator will be improved by introducing new software program.
Table 1 General Specifications of the Musashi Reactor
TRIGA-Ⅱ(Training, Research and Isotope Production
Reactor Designed by General Atomic)
-Maximum Thermal Output : 100kW
-Moderator : Zirconium-Hydride
-Coolant : Light Water
-Reflector : Graphite
-Fuel Element : 20% Enriched Uranium Zirconium
Hydride Alloy, Stainless Steel or Aluminum Cladding
-Control Rod : Boron-Carbide
Perm anent Shutdow nStorage of Radioactive Disposal ofEquipm ents inside Facility Radioactive W aste
Fuel Transportaition
(In O peration) (Facility w ithout Reactor C ore) (No Radioactive W aste)
Fuels C ore
［Rem oval from C ore Tank］ ［Store inside Facility］Disposal Site
USD O E
Figure 1 G eneral Plan of D ecom m issioning
Phase 1 Phase 2 Phase 3
5
4 USERS CONFERENCE ber 8 to 10, 2008
6
th WORLD TRIGA Septem
Year Item
Phase 1 Phase 2 Phase 3Status of Facility Decision of Decommissioning
Submit Initial Plan to Competent Authority
Permanent Stop ReactorShut Down Operational Function
Spent Nuclear Fuel Preparation of PackagingTransportation Shipping Fuels to USDOE
Pre-shipment Preparation
Dismantling and Storage of RadioactiveWaste Management Waste inside the Facility
; Actual Dismantling Installation and; Planned Disposal of Radioactive Waste
Figure 2 The G eneral Plan of D ecom m issioning and Its Progress
Future20042003 2005 2006 2007～
Operation Console Control Rod Drive
Interface Personal
Computer
Neutron Counting
Rod Identification Simulated Core
Reactor Operation Data Neutron Transport Calculation
Upper Grid
Fuel Elements
Control Rod Drive
Figure 3 Framework of the Musashi Reactor Simulator
Photo 1
Simulated Core
Lower Grid with Holders
Recommended
