平成２６年度

教育訓練講習A

Safe handling Ⅱ
Actual radiation generator
handling
生命資源研究・支援センター
RI実験分野島崎 達也
1Radiation generator(Accelerator)

3-1

Type and characteristic of Radiation generator◼

Electrostatic accelerator(1) Cockcroft–Walton accelerator(2) Van de Graaff accelerator(3) Transformer type accelerator◼

Radio-frequency accelerator(4) Cyclotron(5) Synchrocyclotron(6) Synchrotron(7) Betatron(8) linear accelerator(9) Microtron(10) Plasma generator

Range of subject to the law１）A device that generates radiation by accelerating charged particles such aselectrons and protons using an electric or magnetic field (those with anenergy of 1 MeV or more).
２）A 1 cm dose equivalent rate exceeding 0.6 μSv/h．（at 10cm distance fromthe surface of device）
3

Accelerator used in medicine
Linac
リニアック

Cyclotron
サイクロトロン

type
種類

Linear accelerator
直線加速器

Cyclicaccelerator
円形加速器

accelerating
加速粒子
particleelectron
電子

proton陽子

purpose目的

radiotherapy
放射線治療

PETPET核種生成
nuclide generation

Cyclotron
Succeeded in accelerating
proton 9MeV with Units 1and 2 and RIKEN 60-inch
cyclotron.
Abandoned in Tokyo Bay
by the U.S. military in 1945
Unit 3 (1953) Electromagnet：Saved in Japan Radioisotope Association (Komagome, Bunkyo-ku)

Small AVF cyclotron for selfshielding PET（CYPRIS-HM12S）
Proton １２MeVDeuteron ６MeV
Weight 60t
5

3-2

Number of radiation generators permitted touse (by type and institution)
Institution
Total Ratio(%)

Medical

Education

Research

Privatesector

Other

1,133
74.1

64
4.2

152
9.9

141
9.2

38
2.5

139
8

4
3

23
25

37
3

31

Generator
TotalRatio(%)

Cyclotron
Synchrotron
Synchrocyclotron
Linear accelerator(Linac)
Betatron
Van de Graaff acceleratorCockcroft–Walton accelerator
Transformer type accelerator
Microtron
Plasma generator

1,52810020640－
1,144
337721691

13.5
2.6－
74.9
0.2
2.4
4.7
1.0
0.6
0.1－
982－
－
－
4－
23
1
1416－

－
3－

－

－
45
2
222482
1（出典：「放射線利用統計」，2012）

－
60
1328－
34－

－－－－－－

6

Cancer therapy by external irradiation〇Linac：Radiation therapy equipment using X-ray and electron beams
Novalis, CyberKnife：Special linac device for X-ray stereotactic radiotherapy〇Cobalt irradiation device: Radiation therapy equipment using γ-ray(less used in Japan)
GammaKnife：Cobalt device by γ-ray stereotactic irradiation

Medical accelerator：Cyclotron, Synchrotron
・Heavy ion beam cancer treatment device: Heavy ion beam (HIMAC: Carbon ion)・Proton beam / heavy particle beam combined treatment device: (Hyogo Ion Beam MedicalCenter)
・Heavy ion beam cancer treatment device: Heavy ion beam （ Gunma University Heavy Ion
Medical Center)
・Heavy ion beam cancer treatment device: Heavy ion beam (SAGA Heavy ion MedicalAccerelator in Toshu)

Boron Neutron Capture Therapy Equipment (Medical Reactor): Research Stage
・Kyoto University Reactor (KUR): Thermal neutron beam . Utilization of nuclear
reaction 10B(n,α)7Li.
・Japan Atomic Energy Agency Research Reactor (JRR4): Thermal Neutron Ray8

Pinpoint irradiation by particle beam therapy
X-ray and gamma ray therapy

Particle therapy

Cyberknife
Gamma knife

Relativedose

Heavy ion radiotherapy device
Proton therapy device

Relative
dose
Distance

Bragg curve

Distance

9What kind of tumor is heavy ion beam effective for?
Diseases that were intractable withconventional treatments ;Skull base tumor
Head and neck adenocarcinoma,
Adenoid cystic carcinoma,
Malignant melanoma, sarcoma
Bone and soft tissue sarcoma
Rectal cancer postoperative recurrence
Pancreatic cancer
Kidney cancer ... etc.

Diseases that can be treated more safely
and in a shorter period of time thanconventional treatments ;Prostate cancer
Lung cancer (stages I-II)
Liver cancer
Head and neck squamous epithelial
cancerMetastatic lung tumor (single)
Metastatic liver tumor (single)

Diseases that are difficult to adapt
Wide range: hematological tumors, extensive metastatic tumors(Other treatments have been established: breast cancer, cervical cancer)

10

Heavy ion radiotherapy facility（HIMAT）
SAGA Heavy ion medical accelerator in Tosu．Toshu city, Saga Pref.

11

Synchrotron radiation facility（Domestic）

RIKEN HARIMA BRANCH
SPring-8 (Super Photon ｒing-8、Energy Maximum ８ GeV)

SPring-8

SACLA(X-ray free electron laser wavelength 63 pm )Interaction between synchrotron radiation (X-ray) and matter
Recoil electron(Compton scattering)
MatterScattering → the crystal structure
・Elastic scattering (Tomson scattering)・Inelastic scattering (Compton scattering, Raman scattering)Interaction

Transmission→ Local structure，Chemical bond state

Scattering cross section of C

Fluorescence (characteristic) X-ray→Elemental analysis
Heat・Photoelectric effect・Tomson scattering
・Compton scattering
・Electron-pair creation

Photoelectron, Auger electron→ Local structure，Chemical bond stateVarious scientific fields pioneered by synchrotron radiation
Crystal structure
analysisElectron density
distribution
CrystalProteinphase transition
Constructive－
Electronic －Magnetic －Dielectric －Chemically bound －Bioscience/materialscienceelectron
spectroscopic
analysismagneticscatteringPhotoelectron
spectrometry
Compton scattering
Photoelectron
microscope

inelastic
scattering

Mossbauer
resonanceelemental
analysischemicalbonding state

X-ray
florescenceanalysis

microbeam/ micro spectroscopy

Geoscience

Electronmagnetic
devicePhysics/
Chemistry

Environment/ Energy
scienceSafe handling of Radiation generator

Radiation generated by radiation
generator◼ Primary radiation• Accelerated electrons, protons and heavily charged particles◼ Secondary radiation• X-rays from bremsstrahlung

Beware of unexpectedradiation• neutron ray◼ Induced radioactivity• Radionuclides are generated by the nuclear reaction
between the components of the accelerator particle
beam passage and the primary and secondary radiation.
(activated)

3-3-1◼ Primary radiation

Most of the radiation is generated in operation of theaccelerator. Therefore, if the accelerator is stopped, theradiation will be greatly reduced.
◼ Induced radioactivity（ Activated ）When the beam is irradiated with a target or the like(shutter, slit, etc.), the irradiated substance is activated.
The radiation emitted from it remains even if theaccelerator is stopped (residual radioactivity).
Almost no radioactive material is produced in facilities that use
electron accelerators with maximum energies less than 6.0 MeV(or Ion accelerator with maximum energy per nucleon less than 2.5 MeV).
20

3-3-2◼ Secondary radiation

When the beam (primary radiation) hits the target, thenuclear reaction generates secondary radiation suchas radiation and braking X-rays. If the beam is notproperly controlled, the beam may hit an unexpected
place to generate secondary radiation, or the part hit
by the beam may be activated.
◼ Neutron ray

Among the secondary radiation, neutrons aretroublesome. Surrounding substances including air
are activated by the neutron capture reaction. Inaddition, it easily changes its direction due to elastic
scattering with the atomic nucleus, and may come out
21through the gap of the shield.

3-3-3◼ Slit beam

The beamline is usually equipped with shutters andslits to stop and throttle the beam. However, if they
are incomplete, the beam may leak through thesurrounding gaps. Since the beam is thin, it is difficult
for the detector to catch it.
Please note that the GM tube type survey meterinterferes with the measurement due tothe counting drop and suffocation phenomenon.
◼ Sky shine

When radiation is radiated toward the sky, it isscattered by the air and part of it returns to the ground(Sky shine). Insufficient ceiling shielding will causeradiation to fall outside the controlled area.
22

Safety management system◼ Automatically display equipment•

A device that automatically displays that "accelerator isin operation"◼ Interlock•

It is a control that can be operated only when theentrance door of the use room is "closed".

◼ Entry / exit management•Carry a measuring instrument with an alarm when entering theroom•

Know the emergency release switch, escape exit, etc.

3-4-2

Automatically display equipment◼ The radiation generator is obliged toindicate that the generator is inoperation by a display device such as alamp during operation.

24

3-4-2Interlock◼ An interlock is a mechanism that prevents

the generator from operating if theconditions required for safe operation are
not met. When all the conditions aresatisfied, the generator can be operated.
Due to the installation of the interlock, the accelerator
will stop if any one of them becomes abnormal.
In addition, the interlock must not be released
intentionally under any circumstances.
25

Example of accelerator interlock system
Closing switch ofentrance

Closing switch ofequipment hatch

Outside roommonitor

Accelerator
control board
Emergency stopswitch

Accelerator access door

Outdoor monitor（出典：「放射線・アイソトープを取扱う前に」，2012）26

3-4-1

Entry / exit management system◼ By introducing an entry / exit management system, theopening and closing of doors is controlled so that entry
during accelerator operation can be prohibited.
◼ By sharing the key of the accelerator control panel andthe key of the door, there is an advantage that theaccelerator will not be operated unless the person whoopened the accelerator main body room or thelaboratory brings the key.
◼ With this system, the number of people in the room

can be constantly grasped, and the exposure ofworkers due to the operation of the generator can beprevented.
27

Standardization of keys for shielddoors and control board

key boxControl board
key switch
Shield door
Accelerator
control board（出典：「放射線・アイソトープを取扱う前に」，2012）28

3-4-3Radiation monitoring system◼ Since the amount of radiation increases in the main

body room and laboratory while the accelerator is inoperation, γ-ray and neutron monitors are installedoutside the shielding wall to constantly check forradiation leaks.
◼ When radiation amount (rate)is exceeded thethreshold, an alarm sounds and measures such as
stopping the accelerator operation are taken.
◼ Even after the end of operation, the radiation dose
does not drop immediately because the beam duct,target, slit, and air are also activated in the main bodyroom and laboratory.
Only after the dose has dropped below
the threshold can you enter the room.

29

3-5-1For safe use (entrance / exit)◼ A person who conducts an irradiation experimentor develops a device in a laboratory or a main
body of a radiation generator must be registeredas a radiation worker at the place of business.
◼ When you actually enter or leave the room, youmust follow the prescribed procedure.
◼ Even if you are trapped in a room, you can open
the shield door from the inside, so you can open
it without hassle.
◼ Notify the control room by intercom. If it isunlikely that the operation will start in time, press
the emergency stop button.
30

3-5-2（Records）◼ Records are indispensable for finding the causeof any trouble.
◼ When entering or leaving the controlled area,

be sure to read the ID card and sign the registerbook.
◼ Clarify who is responsible for the operation andrecord the operation so that the person involvedin the operation can understand it.
31

Radiation protection

1-2

Three principles of external
exposure protection
Inverse of (Dose)=(Distance)^2

ShieldTimeDistance(Dose)=(Dose rate on workplace)×(Time)

Dose rate

Dose

Distance from radioactive material (m)Dose rateTime(h)（出典：原子力図面集2005年）

Concrete thickness(cm)

33

1-6

Five principles of internal exposure
protection（3D・2C）◼ Dilute（Dilution by addition of solvent or carrier, etc.）◼ Disperse（Ventilation, dilution of radioactive effluent, etc.）◼ Decontaminate（Use of hood, decontamination, etc.）◼ Contain（Storage in a container, use of a glove box）
◼ Concentrate（RI concentration separation, storage of34
radioactivity, etc. ）Radiation type and penetrating
Absorb: α ray
α ray move at 1/10 of light speed

β rayγ(X) ray

β ray move at 1/2 of light speed

neutron ray
γ ray move at light speed

α ray（α particle）
β ray（electron）
γ ray
X ray（electromagnetic waves）
Neutron ray（neutron）

A paper

1mm thickness ofaluminum
10mm thickness ofacryl

1.5cm
thickness of
Lead

Water orconcrete（出典：原子力図面集2005年、原子力防災基礎用語集 ）35

2-13-4Tool for shielding γ (X) rays

◼ Lead is mainly used as a shielding material. Leadblocks having a thickness of 5 cm, a height of 10cm, and a width of about 20 cm are commerciallyavailable, and a plurality of these blocks are often
used side by side or stacked.(Be careful of gaps,
earthquake resistance, and load capacity.)◼ In addition to lead, concrete blocks and iron plates
can also be used, but they have a lower shielding
effect than lead and take up a lot of space. Inaddition, there is a lead glass partition, which isuseful for visual observation of the radioactive
source.
◼ Tungsten and molybdenum are used to shield lowenergy gamma rays and X-rays. Flexible sheetshaped shields are commercially available.
36

X-ray, gamma ray shieldingmaterial （Lead block）
Do not crush the corners!

（出典：（株）千代田テクノルＨＰ ）37

2-13-5Tools for shielding neutron rays
◼ Polyethylene blocks and paraffin blocks

are commercially available.
◼ Paraffin blocks containing boron, which
has a high ability to absorb thermal
neutrons, are also used.

38

1-5-4

Shielding material due to difference in neutron energy
EnergyReaction

Shielding material

Substances with large
Inelastic
A few MeV
atomic numbers such as
scattering
iron and lead are effective
Paraffin and water
Hundreds ofElastic scattering containing a lot ofkeV or lesshydrogen are effective
When
Absorb neutrons Boron and lithium areeffective as absorbent
decelerated to using capturematerials
about 0.1eV
reaction (n, γ)63
107
Li(n, a) H,B(n, a) Li

Usually, in the case of a small shielding container, iron is often used on
the inside, then polyethylene having a thickness of about 10 cm, and ironor lead on the outside. Boron and cadmium is often contained in39
polyethylene.

Neutron shielding material(special polyethylene block for neutronshielding)（出典：（株）千代田テクノルＨＰ ）40

4-13-1

Handling of radioactive substances◼ When irradiating neutrons with an accelerator, be

careful not to irradiate excessive neutrons. Dueto its strong radioactivity, it may not be possible
to handle it directly by hand.
◼ Irradiated samples are doubly enclosed inpolyethylene bags to prevent contamination.
When the irradiation time is lengthened, it isadvisable to wrap the inner bag with paper or use
a polypropylene bag instead of the polyethylene
bag in order to prevent the polyethylene bag frombeing welded by heat.
41

4-13-2

Characteristics of radioactivesubstances◼ It is too large to fit in a waste container.

◼ Mostly incombustible◼ There are places where the surface dose

equivalent rate is locally high.
◼ The material itself is activated and there isalmost no surface contamination.
42

GM tube type / scintillation type survey meter

The time constant is basically set short (3 seconds) for contamination
inspection and long (30 seconds) for dose rate measurement, but it isusually measured in 10 seconds. (Never set the time constant to 30
seconds and do not perform contamination inspection or radiation
source loss survey.)（出典：（株）アロカＨＰ ）43

Accidents and countermeasures

Occurrence of radioactive material leakage accident at accelerator
experimental facility J-PARC in Tokai Village, Ibaraki PrefectureRadioactive material leak occurred (noon on the 23rd)
Alarm indicating abnormality
Judging that the alarm is malfunctioning,
continue the experiment
Increased radiation dose and surface contamination(10 times) on the afternoon of the 23ｔｈ
Release radioactive substances to the outdoors(short half-life, ventilation twice)
It was the evening of the 24th that the staff noticed theradioactive material leak by data analysis (report to thenational and local governments 33 hours after the accident).

【Place】Ｊ−ＰＡＲＣ Nuclear particle physics
experimental facility【Time】 Around noon on the 23th May【Cause】 Occurrence of internal exposuredue to scattering of radioactive substances(Au, Hg) into the air due to abnormal proton
beam output【Investigation】
Measured 49 out of 55 people who may be
exposed (measurement subjects who werein the facility at that time)・Exposed: 30 (including 2 women)
・Exposure dose: 0.1-1.7 mSv(193Hg inhalation intake: 1.6 x 106 Bq)【 Impact on health 】 Judgment at thisstage:"It is very unlikely that it will affect yourhealth"（2013/05/27までのデータより）

Safety management system is important!
Example) A worker was exposed during the installation adjustment of
the linac by the manufacturer. The cause was that the radiation test
was conducted without noticing that the worker was behind the ceiling.
Estimated exposure dose of 200 mSv or less (National Center forChild Health and Development, 2001/12/21)◼ The direct cause is lack of contact /Worker
Ceiling board

confirmation◼ No interlock◼ No entry / exit managementCarry a measuring instrumentwith an alarm
出典 ： 文部科学省原子力安全課 緊急被ばく医療 REM net

To prevent unexpected accidents
Humanerror

Unknown
event
MechanicalfailureUntil 50 years ago

SpillovereffectHumanerror

Unknown
event
MechanicalfailureCurrent
The damage is great
because it is automated.

引用 ： 『ヒューマンエラーを防ぐ知恵 ― ミスはなくなるか―』 ISBN 978-4-7598-1304-3, 化学同人

There is not always one cause
Jun, 2000

electric parts factory

Three workers who had been conducting non-destructive inspection byunlocking the interlock of the soft X-ray equipment were locallyexposed to the right hand (40-60 Gy). Radiation burns◼ There is no risk of exposure because of

having safety device.
◼ No need to appoint a authorized chief

X-ray inspection engineer.

Prevention of situations that impair
the safety of people around us◼ Learn from past radiation accidents and establish

safety management technology◼ Easy to deal with after an accident, but very difficult to
detect hidden dangers• Labor shortage, busy (overwork)• Veteran transfer, retirement• Trouble caused by new equipment, technology and procedures• During maintenance• Unsafe behavior / rule violation◼ Actions that differ from safety procedures

can cause serious accidents