Practical Radiation Control at KEK
Takenori SUZUKI
Radiation Science Center
J-PARC Project DivisionHigh Energy Accelerator Research Organization (KEK)Contents
Scope of this talkRadiation Control(1) Exposure control
KEK, Government(2)Controlled area
Activation of beam line
12GeV-PS and the Utilizing Facilities
Extraction beam line
EP1, Neutrino Beam Line, Target Station
500MeV Beam Transport Line
Another speaker will give more information:
Professor Satoh
Maintenance scenario
Professor Kawakubo Practical maintenance experience
Radio-activities and radiation exposure from the maintenanceRadiation Source at KEK (Proton)•Proton Accelerators
45MeV Linear Acc.

∼ 30µA

500MeV Synchrotron ∼ 6−10µA(3 −5kW)
12GeV Synchrotron∼ 0.3 −0.7µA (∼3 −8kW)

168h/w,2186h/3m (5000∼ ６０００h/y)• Experimental Hall (168h/w,2186h/3m (4500h/y))
12 GeV Protons ∼ 0.58µA(∼7kW)
North Counter Hall (EP1 and Neutrino Beam Line)
East Counter Hall (EP2 Beam Line)
500 MeV Protons ∼ 10µA(∼5kW)

Radiation Source at KEK (Electron)
Electron and Positron Accelerators
Linear Accelerators 10GeV 0.625µA
PF-AR Synchrotron

8GeV 0.25A

PF Synchrotron

3GeV 0.6 A

KEKB Synchrotron 10GeV 1A
5GeV 1A
168h/w,2186h/3m ( ６０００∼7 ０００h/y)Japanese Radiation Exposure Control

KEK Radiation Exposure Control

KEK Working Level of Exposure Control

Design Value for Radiation ShieldingArea
Site Boundary

KEK DesignValue＜50μSv/yGeneral Area

＜0.2μSv/hWarning Area

＜1.5μSv/h

General Radiation
Controlled＜20μSv/hRestricted Radiation
Controlled Area

<100mSv/h

Forbidden Radiation
Controlled Area

>100mSv/h

Law＜250μSv/3m＞ 1.3mSv/3m(2.6μSv/h)＜1mSv/w

Ground Water activation
10μSv/y at site boundary from drinking water

Radiation Controlled Area determined by Dose Rate (KEK)

Forbidden>100mSv/h

20μSv/h<Restricted <100mSv/h
1.5μSv/h <General <20μSv/h
0.2μSv/h<Warning <1.5μSv/h
Free on Site ≤0.2μSv/h
Site Boundary<50μSv/y

PublicRadiation Controlled Areas

Radiation Control (Principle)
Daily Radiation Control(1) Radiation Dose
(2) Access Control(3) Radioactive Material Control(4) Exposure Control
Control Scheme is different
during operation,
during maintenance after operation

Radiation Control (operation)

During Operation
High energy neutrons (1〜100MeV) in the experimental area.
Access to the beam line is strictly controlled by interlock system.
Radiation controlled area, experimental hall,
are monitored continuously to watch the radiation level.
Radiation workers and experimentalists, who enter radiation
controlled area, are recorded automatically by card system.

Radiation Control (maintenance)
After stopping operation,
Maintenance inside beam line must be restricted.
Procedure to start maintenance inside beam line:
1) measure radiation dose along beam line,2) write proposal for maintenance
who, where, when, how3) if the maintenance is at a high radiation place,
permission from radiation officer,
a person in charge of the facility,
plan to proceed the maintenance to avoid high exposure,shielding, individual working time,
many people to distribute exposure,
key person must be away from radiation work tillnecessary.
4) Every one must carry an alarm dosimeter,
The responsible person must control and organize.

Radiation Controlled Section

Induced Radio-activities and Radiation Field

12 GeV PS Ring and Related Facilities
Extraction Septum Magnets
3×1012pps (5.7kW) for EP1 Fast Extraction
1×1012pps (1.9kW) for EP1 Slow Extraction
Counter Hall
T5 and T6 Target (PT6cm)
1×1012pps
Neutrino Target station
Neutrino Production Target(AL65cm) 3×1012pps

500 MeV Utilizing Facility
Neutron and Meson Laboratory (NML)
Beam Transport Line
P4 Line for slow muon Production

PS-MR(12GeV), North Counter Hall (NCH), East Counter Hall (ECH)

12GeV-ECH (sec. 2)
12GeV-NCH(sec. 2)
PS-MR(Sec. 1)PS-Linac (sec. 1)
PS-BS (sec. 1)

500MeV-NML (sec. 3)

PS-MR Dose Rate 01/05/00

100mSv/h
EP1:12GeV
10mSv/h
1mSv/hInjection
500MeVEP2 12GeVEP1 and EP2 Extraction Line 25/12/’02

EP1 Extraction(25/12/’02)

EP2 Extraction(25/12/’02)

EP1 and EP2 Extraction Line 14/01/’03
3 weeks cooling

EP1EP2North Counter Hall and EP1 Beam Line
North Counter Hall
(K5 and K6 Experimental Area)
EP1 Beam Line, Neutrino Beam Line
EP1-A,Experiment Utilizing Primary Proton Beam
12GeV; 0.16nA (1.0×109 pps)
EP1-B, 1) Production of Secondary Particles, π, K
Target T5(PT6cm): K5 Exp. Area
Target T6(PT6cm): K6 Exp. Area
2) Transmit Proton Beam to Neutrino Target
StationNeutrino-TS
AL target 65cm 2cm diameter
12GeV;Max 0.576µA (3.6×1012 pps,6.9kW)

SM4: AL and PT Target Irradiation
with 12GeV Protons
12GeV Protons 1.0(3.0)E+12 P/sfor 30 days irradiation on PT(AL) (MARS calculation)

Dose Rate (mSv/h)

105
Na-24

410Na-22

103
102
1

10

AL-65cm
PT-6cm100
10-1
10-2 -4 -3 -2 -1 0 1 2 3 4 5 6
10 10 10 10 10 10 10 10 10 10 10Time (hours)

NML Line (500MeV) Beam Intensity
Neutron and Meson Science Laboratory,
NML Beam Line
500MeV, MAX:9.6µA (6.0×1013 pps)
Neutron Experimental Hall
Production Target W with Ta clad 2.9cm × 4
Meson Experimental Hall
Meson No.1 Laboratory
Meson No.2 Laboratory (P-4 Beam Line)Summary (Dose rate)

Dose rate created by induced activities
Dose Rate (mSv/h)
12GeV-PS
extraction
septum magnets

Beam LossMax

Average

400W
580W

30-40
80
1510
10~20
1~5Target (EP1) in 12GeV-PS Related Facilities
PT (6cm)
960W
1000
Near Target
50~1008h cooling3w cooling3 d cooling

Working Level for Exposure Control at KEK
KEK Working Level of Exposure Control

Close Contact
0.5 mSv/d30 minutes/d at 1mSv/h
3 minutes/d at 10mSv/h
Planning maintenance1 ∼ a few hours

1 mSv/w
7 mSv/y

2 days/w
7 weeks/y