Appendix 5

The Radioactive Material Leak Accident
at the Hadron Experimental Facility ofJ-PARC
June 21, 2013
First External Expert Panel

J-PARC Center
Naohito Saito

Issues with respect to the Accident① Release of radioactive material to theoutside of the radiation controlled area andto the environment outside of the Hadronexperimental hall (HD hall)② Delays in reporting to the relevant
authorities, the local communities and themedia③ Internal radiation exposure on workers who
inhaled contaminated air in the HD hall
④ Failure in timely disclosure of information

What is J-PARC?
• Jointly built and operated by Japan Atomic Energy Agency (JAEA) and HighEnergy Accelerator Research Organization (KEK)• Opened for researchers in the world to study a wide range of research fields
from the origin of the universe to the development of new medicine
Linac(JAEA)

Neutrino
Experimental
Facility(KEK)

HadronExperimental
Facility
(KEK)

3 GeV
Synchrotron(JAEA)
Materials andLife Science
Experimental
Facility (MLF)(JAEA)

50 GeV
Synchrotron(KEK)

3Hadron Experimental Facility
A research facility for elementary particle and nuclear
physics- to investigate the fundamental components of matter- to explore how they interact and constitute matter
Construction began in 2004 and was completed in January
2009. After commissioning, the users experiments started
in January 2010.
Hadron Experimental Hall

Electro Magnet Power
Supply Building

oxygenatom

atomicnucleus

protonquarks

施設外観
MachineBuildingwatermolecule

Hadron Experimental Hall：Power Supply Building

HadronExperimental
Hall

The building is 56 m long, 60 m wide, 16 m roof
height with 6 m deep semibasement structure toaccommodate experimental instruments.
Hadron Experimental Facility:
It consists of the Hadron experimental hall andassociated machine and power supply buildings, etc.

4Outline of the Accident
11:55 on May 23•••••An abnormal proton beam was injected to
the gold target.
The target heated up to a extraordinarily
high temperature.
Radioactive material was released fromthe target.
The radioactive material was leaked into
the HD hall.
→ Workers were exposed to radiation.
The radioactive material was released tothe outside of the radiation controlledarea and to the environment outside of
the HD hall.

6.6 cmgold target5

40 milliseconds600 nanoseconds

to MLF

Fast extraction

Number of protons

Number of protons

J-PARC Accelerators and Beam Extractions
to Hadron Experimental Facility

Slow extraction~ 6 seconds~ 2 seconds

TimeTime

Number of protons

to Neutrino Experimental Facility~ 2 seconds

600 nanoseconds

Time structure of the proton beams

Fast extraction

6Time

Abnormal Beam
• At around 11:55 on May 23, the power supply system of a
special magnet in the 50 GeV Synchrotron malfunctioned.
→ 2x1013 protons were extracted in a very short period of 5
milliseconds, while in normal operation 3x1013 protons should havebeen slowly extracted over 2 seconds.

Abnormal beam
250 times of peakintensity

Malfunction
2 second

Time

Number of protons

Number of protons

Normal beam

1/200 of a secondTime

7

Purpose of the Gold Target•

The target, when bombarded by high-energy protons, produces secondary particles(mesons), which then will be used for research− Radioactive material is produced by nuclear spallation reactions.
− In normal operation the radioactive material stays in the gold target.
− When the proton beam operation is stopped, nuclear spallation reactions stop andno new radioactive material is produced. Radioactive material decays within thetarget.

atomic nucleus
protongold target

pi mesons
K mesons

nuclear spallation
reaction

Gold, unlike uranium, is not a radioactive material.
→ No nuclear chain reaction occurs.
→ However radiations come out from radioactive material produced innuclear spallation reactions induced by the proton beam in the gold target.

8

Target Temperature （Simulation Results）
temperature

2x1013 protons/pulse(5 milliseconds)

goldthermocouples)
3x1013 protons/pulse( 2(2secondsseconds)

copper baseTemperaturerise ( K )cooling waterradial direction (mm)Timebeam axis direction (mm)Hadron Experimental Hall
Apertural areas for secondary
beam transport lines

Presentstatus
circulation
filterExperimental HallFirst bulkhead

Primary beam area

TargetTargetVentilation fans

Status after
proposed（案）
Experimental Hall
Second bulkhead
revisioncirculation
filterPrimary beam area
First bulkhead

ExhauststackfilterTargetmonitoring

monitoring
monitoring

Exhaustventilation

Chronological Sequence of Events
May 23, 2013
• 11:55 Delivery of proton beam from 50 GeV Synchrotron (MR) was halted by Machine Protection System (MPS).
• 12:08 MPS was reset following the regular resetting procedure after discussing with relevant people and delivery of
proton beam for users’ experiments was resumed.
• 13:30 Increase in radiation dose rate of an area monitor in the HD hall was acknowledged. The maximum value of
4 μSv/h is ten-fold of the normal value.
• 15:15 Ventilation fans were turned on. Further decrease in ambient dose rate was acknowledged.
• 17:00 Radiation survey of the HD hall found areas with high dose rate were localized.
• 17:30 Ventilation fans were turned on to reduce airborne radiation dose rate in the HD hall.
• 23:30 Completed evacuation and full-body radiation surveys of all workers in the radiation controlled area. Access tothe HD Facility was restricted.
May 24, 2013
• 10:00 Members on the right held a meeting to discuss the situation. It was not considered this incident to be one for
escalated reporting.
• 17:30 J-PARC Center received inquiry from Nuclear Fuel Engineering Laboratories concerning increased radiationlevels recorded by their monitoring posts• 18:00 Data logs of gamma-ray area monitors on the boundaries of the controlled area of the HD Facility wereexamined. Found increased radiation levels at around15:00 and 17:30 on May 23. Found that the increased
dose rates coincide with the operations of ventilation fans in the HD hall.
• 21:10 Reported to an emergency post of the Nuclear Science Research Institute. Response headquarters wasestablished.
• 22:40 As required by law, the first report to Nuclear Regulation Authority was transmitted by facsimile transmission.
• 22:40 As required under the terms of relevant agreements, the first report was faxed to Ibaraki Prefecture, Tokai
Village and other authorities.
May 25, 2013

• 01:00 Found out that the maximum total exposure dose of the workers in the HD hall was 1.7 mSv.

11

Effects on the Environment 1/2• Evaluations based on
measurements:

1. Increases of the radiation dose rates atmonitoring stations of Nuclear Fuel
Cycle Engineering Laboratories
2. Nuclides and radioactivities found in theairborne sample from the HD hall
3. Direction and velocity of the winds at
the time of release of radioactive
material on May 23• Two kinds of calculation methods
used in estimations:
1. Analytical method based on diffusion
equations for radioactive material
2. The WSPEEDI−II code

half life

radioactivities
(Bq)

43K

22.3 hours

64.0

24Na

15.0 hours

63.5

199mHg42.6 min.

61.0

197Hg

64.9 hours

39.5

76Kr

14.8 hours

32.4

131I

8.02 days

28.6

82Br

35.3 hours

19.5

195mHg41.6 hours

18.4

123I

13.3 hours

17.2

95Nb

35.0 days

9.10

nuclei

total amount353

Radioactive material in the 500 ml airborne sample
collected from the Hadron experimental hall.

12Effects on the Environment 2/2• The released radioactive material distributed within a narrow area of
the west from the HD hall.
• The maximum integrated radiation dose at the site boundary is
estimated to be 0.29 μSv at a location close to the HD hall.
Hadron Experimental Hall
The point shows the maximum
value of radiation dose from thecalculation results.
monitoring posts that observed
momentary increases of radiationdose rate on May 23.
locations where soil samples weretaken on May 26
Nuclear Fuel Cycle Engineering Laboratories• Examination of soil samples from four locations.
→ No radioactive material originating from the accident was detected
at any of these locations.

13

Delays in Reporting and Announcing【May 23】
Our investigation indicates the following:• A part of the gold target was damaged. Radioactive material leaked into
the HD hall and contaminated the floor, etc.
• Workers in the HD hall may were exposed to internal radiation.
← The leaders considered that contaminations were limited to a radiation
controlled area and the exposure dose was below what was expectedin normal operation. Hence they considered that this incident would
not have to be reported as an accident.
【May 24】
Small increases of the dose rates were found at around 15:00 and around17:30 on May 23, in coincidence with the operations of ventilation fans onthat day.
→ The leaders determined that radioactive material had leaked to thearea outside the radiation controlled area and they reported to anemergency post of Nuclear Science Research Institute.
14

Radiation Exposure
Measurement on internal and external radiation exposure
doses of all the persons who entered the radiation controlledarea of the HD Facility after the accident:• Total number of personnel：102• Number of personnel with detectable dose：34
Note: All are registered radiation workers. Individualdoses are in the range of 0.1−1.7 mSv.
• Number of personnel with no detectable dose：66
The remaining two, who were from overseas, had theirwhole body counter measurements at home later, andhave been found to have no detectable dose.
15

Other Facilities
at J-PARC

Materials and Life Science Experimental Facility
Contained in avacuum chamber

・Muon target
Carbon 20 mm thick,
Water cooling

Separated from theexperimental hallMercury
Safety hull
Mercury vessel

Muon targetSafety hull

Mercury vessel

Proton beamcollimators

Protonbeam

Muon beam

Neutron target

Muon target
1st Experimental hall

A class 1 radiation controlled area
A class 2 radiation controlled area
Door way

Radioactive material is contained by:
2nd Experimental hall
• enclosure of target assembly inmultiple layers of containment• negative pressure control

Neutrino Experimental Facility
Fence

Neutrino
Entrance
Control
Bldg.

Primarybeamline

50 GeVsynchrotron

Neutrino
Entrance
Control
Bldg.

Neutrino Utility
Bldg. No. 2
Neutrino
Experimental
Facility

TargetstationDecay volume

Fence
Neutrino
Utility Bldg.
No. 3

Surface level

Target station

class 1
radiation
controlled areaclass 2 radiation
controlled area

Beam dump
Muon monitor

Underground level

TargetTarget
Station
Buildingstation
Negative pressure control

Radioactive material is contained by:• filtered exhaustion ofinterconnection areas• negative pressure control

Figure 2.1 General view of the JPARC facilities Target areaGas-sealed

Helium vessel

Horn-3

Horn-2Horn-1 & target

Accelerator Facility Complex
LinacThe klystrongallery(a class 2radiation
controlled area)

Radioactive material iscontained by:• two-layered containment• filtered exhaustion ofinterconnection areas

The intermediate tunnel(a class 1 radiationcontrolled area)
The accelerator tunnel(a class 1 radiationcontrolled area)

Fire control andair sealing

Exhaust stack

Main tunnel

Sub-tunnel

3 GeV Synchrotron

Electro-magnet
power supply room

Air conditioningroom

Radiation-hot
cooling waterroom

Radiation-hot
machine rooms

Main tunnel

Sub-tunnel

Accelerator Facility Complex
Radioactive material iscontained by:• filtered exhaustion ofinterconnection areas• negative pressure
control

Negative roompressure
EV hallShielding door

Accelerator tunnel

Radiation-hot machineroom

Accelerator tunnel

Hadronbeamline(switch yard)

Connection
tunnelMR Machine Bldg. No.2

EmergencyExit

Negative roompressure

Accelerator tunnel

Emergency Exit

Emergency Exit No.3
Negative roompressure
Accelerator tunnel

Negative roompressure

Connection
tunnelMR Service Bldg. No.2

Power Supply Bldg. No.1

50 GeV Synchrotron

Plans for the Near Future• Continued investigation of facilities and instruments– Target area of the HD Facility– Power supply unit which experienced the malfunction causing
the abnormal beam extractionDetermination of the causes and developmentof preventive measures• Evaluation of the total amount of radioactive material
released from the HD Hall to the environment– Detailed analysis of the air sample which was collected at theHD hall
– Simulation to reproduce the radiation dose rates observed in theHD Facility

Evaluation of the effects on the environment

Appendix 3

June 21, 2013
The First Meeting of External Expert Panel toReview the Radioactive Material Leak Accident
at the Hadron Experimental Facility of J-PARC

External Expert Panel: Viewpoints of Evaluation□ Evaluation of overall response to the accident, including theorganizational framework• Investigation of causes of the accident, analysis of contamination,radiation exposure and environmental impact□ Evaluation of countermeasures• Revalidation of safety management system including developing
preventive measures against recurrence of similar accidents andreview of radiation controlled areas in the J-PARC facilities□ Organization of J-PARC• Relationships between the accident and the organization andoperation of the J-PARC center that is jointly managed by KEK andJAEA□ Efforts to promote the safety culture, etc.

Organization of the External Expert PanelHigh Energy Accelerator
Research Organization(KEK)

Japan Atomic Energy
Agency (JAEA)

External Expert Panel

Validation at the J-PARC on:
・Safety management
・Emergency procedures, etc.

Working Group(all external memberships)

Secretariat
J-PARC Center Investigation Teams(all internal memberships)
Compiling the basic data for the working GroupInvestigation Teams
Team A（accelerators and beam transport）

Team B（target system）

Team C（building and air tightness）

Team D（control and safety）
24

Examination of Timeline of Incidents

1Incident, Action, Judgement, and Reason Incident of abnormal beam
 Damage of the gold target?
 Contamination in the hall
 Release of radioactive material
 Delays in reporting the incident,
suspending accelerator operation, andstopping ventilation fansSummary• Overview of the accident– occurrence, hall contamination, exposure,leakage of radioactive material to the outside of
the radiation controlled area and responses after
the accident• Status of the other facilities• Status of the investigation– hardware aspects (facilities and instruments)– software aspects (safety management system)– the Working Group, secretariat and investigation
teams