Nucl. Tracks Radiat. Meas., Vol. 19, Nos 1-4, pp. 899-902, 1991 Int. J. Radiat. Appl. Instrum., Part D Printed in Great Britain

0735-245X/91 $3.00 + .00 Pergamon Press pk

Radiation Chemistry Research at JAERI. Present and Future Possibilities

Miyuki HAGIWARA

Takasaki Radiation Chemistry Research Establishment Japan Atomic Energy Research Institute

1233, Watanuki, Takasaki, Gunma 370-12, Japan

ABSTRACT

The Takasaki Radiation Chemistry Research Estabishment(TRCRE) of Japan Atomic Energy Research Institute(JAERl) was founded in 1963 as the center for Research and Development of radiation chemistry in Japan. Using its large facilities for irradiation of gamma rays from Cobalt 60 source and electron beams from accelerators, the TRCRE has been contributed to R&D on technology for industrial application of radiation chemistry. In 1987, the TRCRE started the construction of the ion beam irradiation facilities to promote a new project "Advanced Radiation Technology Study using Ion Beams (ART project)". The ART project is intcnded to push forwarded with R&D on materials for space and nuclear fusion reactors, biotechnology and new functional materials using ion beams. Two ion accelerators (AVF cyclotron and Tandem type accelerator) are now under construction to be operational in summer of 1991, and other two accelerators (van de Graaff accelerator and ion beam implanter) are further scheduled to be installed in 1993.

In this report, the present R&D activities using gamma rays and electron beams are first summarized, and the future program using ion beams is described.

KEYWORDS: Ion beam, AVF cyclotron, Radiation chemistry, Materials for space use, Nuclear fusion reactor, Biotechnology, New functional materials

P r e s e n t Fac i l i t i e s and A c t i v i t i e s

Irradiation Facilities

The TRCRE has four gamma ray irradiation facilities, i.e., three for high intensity and one for low intensity irradiation (total storage capacity for Co-60 = 2,400kCi), and it has three electron accelerators (max. energy = 0.3, 2 and 3 MeV).

R&D Activities

"Synthesis and modification of polymers" Application of radiation to synthesis and modification of polymers is one of advanced

fields of the industrial radiation processing. The TRCRE is presently promoting the R&D's on the following subjects.

(1) Synthesis of adsorbents for collecting uranium from sea water Now fibrous adsorbent for collecting uranium from sea water has been developed by

radiation grafting. This adsorbent contains functional groups which can make bonds with uranium.

(2) Immobilization technique of biofunctional componen Immobilization of biofunctional components such as enzyme, antibody, microbial cell,

tissue cell and drug in polymer matrix, has been studied by moans of radiation polymerization of vinyl monomers at low temperature.

(3) Radiation vulcanization of natural rubber latex Natural rubber latex is -vulcanized by gamma rays in the presence of various

additives to seek suitable compounds to reduce radiation dose and to improve properties of goods from the irradiated latex.

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(4) Electron beam (EB) curing of coatings EB curing process has been studied to meet increasing attention in various industries

such as paints, printing inks, magnetic medias and adhesives.

"Other Radiation Application" (1) Application to environmental conservation

Removal of sulfur dioxide(SO2) and nitrogen oxides(NOx) by electron beam irradiation has been studied. Radiation disinfection of dewatered sludge has also been studied. The irradiated sludge is tempested for the use as fertilizer.

(2) Studies of radiation effects on materials for space and nuclear power development Radiation effects on semiconductor devices, such as transistors, solar cells and LSI's

have been studied. Studies have also been made on radiation resistance of fiber reinforced plasties(FRP) and polymer materials for their use in space and nuclear fusion reactor .

Fu tu r e Poss ib i l i t i e s wi th the Use o f Ion B e a m s

R&D Plan

Ion beams cause ionization and excitation of high density in matters, displacement of atoms and nuclear reactions, creation of novel materials by being implanted within the substance. Their excellent controllability makes it possible to cause above mentioned actions in a small specified region. As shown in Table I, the ART project is intended to push forwarded with R&D on materials for space and nuclear fusion r e a c t o r s , biotechnology and new functional materials using ion beams.

Tab le 1. Resea rch P rogram in the A R T Projec t

Materials for Space Environment *Space radiation resistance of semiconductor devices and sensors *Space environment endurance of construction materials for satellites

Materials for Nuclear Fusion Reactor *Radiation damage mechanism of the first wall and breeder blanket materials *Radiation resistant organic composite materials

Biotechnology *Environment tolerant gene resources *Radiation chemistry of biomaterials *Bionics materials *New labeled compounds

New Functional Materials *Creation and modification of novel materials *Novel analysis technology

"R&D on materials for space and nuclear fusion reactor" R&D efforts on materials for space use are directed to research on the mechanism of

aged deterioration (total dose effect) by protons and electrons which constitute the main component of the space radiation. Studies are undertaken simultaneously on the single event effect due to heavy ions that causes malfunction in semiconductor devices in artificial satellites. Organic materials arc also studied to evaluate their durability under simulated space environments. Application of ion beams to R&D on materials for nuclear fusion reactor is intended to simulate the degradation of structural and tritium breeder materials due to radiation under the reactor environment, especially high energy neutrons. Displacement of constituent atoms, and formation of gas bubbles of helium and hydrogen causes the degradation. Simulation by ion beams for the degradation is conducted with a triple-beam in which ion beams of three different kinds such as a heavy ion (iron, nickel or oxygen depending on selected test materials), helium

JAERI RADIATION CHEMISTRY RESEARCH 901

and hydrogen are applied simultaneously. The degradation of organic composites for insulation of superconducting magnet is also studied by the application of proton beams.

"R&D on biotechnology and functional materials" In the studies of biotechnology, focused ion beams are used to give radiation effects

to a specified micro region in a cell. This technology would serve to study functions of organs in the irradiated areas in relation to radiation susceptibility of the cell. Studies on the ion beam induced mutation is intended to create novel gene resources which have never been developed with gamma rays and electron beams. The manufacture of short- l ife r ad io i so topes and synthes is of new labeled compounds are put forward simultaneously for medical, agricultural and environment science studies. In the studies on functional mater ia ls , various ion assisted technologies such as implanta t ion , deposition, sputtering and so on are applied, especially for surface modification. In parallel to these studies, the analysis technique is developed to follow material changes during the ion beam treatment.

Accelerator Facilities

In order to promote the above-mentioned research plan, the ion beams covering wide ranges of energy, current and mass number are necessary. Types and capacities of four accelerators are listed in Table 2.

Table 2. Ion Accelerators to be Installed at TRCRE

Accelerator Ion Energy

(MeV)

AVF Cyclotron p 5- 90 d 5 -55 Ar 100-700 X¢ 310-620

M a x i m u m Characteristics of beam Current Utilization (e~A)

40 Micro beam( 10tt m); 40 Pulsed beam( 2ns); 5 Irradiation to large area; 0. I high energy neutron

3 MVTandem p 0.8- 6 5 Micro beam( 2ttm); Electrostatic Ni 0.8-15 5 Combined use with other Accelerator Au 0.8- 9 10 accelerators

3 MV p 0.4- 3 300 Micro beam( 0.1t.tm); Van de Graaff He 0.3- 3 300 Combined use with other Accelerator e 0.3- 3 100 accelerators; electron beam

400 kV Ion He 0,025-0.4 50 Various heavy ions; Implanter Ni 0.025-0.4 30 Combined use with other

Au 0.025-0.4 30 accelerators

The cyclotron is equipped with a ECR heavy ion source to ensure effective acceleration of heavy ions up to Xe. The tandem accelerator is equipped with a heavy ion microbeam (ca. 2~tm) system for studies on the single event effect in semiconductor devices, biotechnology and others. The van de Graaff accelerator is characterized by being equipped with a system for submicron beam (ca. 0.1- 0.2~tm) of MeV grade. The ion implanter is equipped with a 400keV analytical scanning electron microscope which enables observation of surface phenomena under irradiation.

Characteristics of the beam utilization at the JAERI's facilities are: microbeam (0.1 - I0 ttm), pulsed beam (2ns), vertical beam, irradiation to large area (10xl0, 5x5 and

2 x 2 c m 2) by beam scanning, simultaneous irradiation with different kinds of ion beams (dual- or triple beam irradiation), irradiation with high energy neutron (by p-Be reaction) and so on.

The Photograph shows the expected view of facility buildings and location of accelerators. The facility buildings are composed of three buildings; (1) cyclotron(floor area; 8 ,100m2) , (2) m u l t i p l e - b e a m (4,000m 2) and (3) ion beam research building (4 ,700m2) . Of these buildings, (1), a part of (2), and (3) are scheduled to be completed in 1990 (fiscal year), The main body of the cye!otron had been assembled in a factory,

902 M. HAGIWARA

and tests for its performance such as RF power, beam output current for ECR ion source were successufully completed at the end of 1989. The 3MV tandem accelerator is now under cons t ruc t ion in a factory. The two accelerators descr ibed above are to be operational in 1991. The construct ion of the van de Graaff accelerator and the ion implanter will be started in 1992, and operational in 1993.

BEAM NETWORK OF THE ION BEAM IRRADIATION FACILITY "TIARA "~

~) AVF Cyclotron (~) 3MV Tandem Accelerator (~) Switching Magnet (~) Ion Implanter ~) Light Ion Room (~ 3MV Van de Graaff Accelerator ~) Heavy Ion Room (~) Target Room

The JAERI 's facilities will be operated as a user's facility which is accessible for users out of JAERI in Japan as well as overseas.