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5MeV electron beam facilities in Japan
Radiat. Phys. Chem. Vol. 52, Nos I 6, pp. 475 477, 1998
Pergamon
Plh S0969-806X(98)00178-9
5MeV Electron
Beam Facilities
© 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain o969-8o6x/98 si9.oo + o.oo
in J a p a n
K. Mizusawa, M. Kashiwagi, Y. Hoshi Nissin-High Voltage Co.~Ltd., Kyoto, Japan
ABSTRACT There are 3 facilities with 5MeV electron beam processing machines in Japan and another one is planned to s t a r t operation in 1 9 9 8 . 2 of them are installed by Nissin-High Voltage and the other are by Sumitomo Heavy/Radiation Dynamics. In this report are introduced 2 facilities which we have installed and are operating satisfactorily. The first one was: installed at Radia Industry for irradiation services and. the second one for in-house use in a factory of a pharmaceutical plastic container manufacturer, Shinko Chemical. And the second one is available for contract irradiation. The machine in Radia Industry has a comprehensive conveyor system with a turn-over equipment to shoot from the top and the.. bottom of materials with e-beam and X-ray, and has been successfully operated for m a n y years. The machine in Shinko Chemical is equipped with a unique conveyor system w i t h two conveyor lines under the beam window and the motion of the lines are opposite e a c h other. T h i s conveyor system also has a turn-over equipment like other machines but the: directio n of turning-over is designed to give the irradiated material s more uni form dose.
KEYWORDS electron: electron beam: e-beam: EB: X-ray: irradiation: service facility: sterilization.
INT R O D U C TION Since 195 7 we have been involved in the electron beam business and have supplied more than 2 3 0 units in Japan, Asia, Europe and North America. The range of the e-beam machines is from low energy (200keV) to high energy (5MeV) and the output power of the largest one is 6 4 0 k W . The application fields of those e-beam machines are expanding from conventional wires and tires to flue gas treatment and sterilization of medical devices recently. We have supplied 1 unit of 6 4 0 k W and manufacturing 2 units of 6 0 0 k W machines for flue gas treatment ,and 2 units of 5MeV 1 5 0 k W machines for sterilization of medical devices. This paper introduces features of the facilities with 5MeV machines supplied for sterilization purposes.
5MeV EB MACHINE The first 5MeV 1 5 0 k W machine was supplied at Radia Industry in Takasaki, 1 0 0 k m north-west of Tokyo in 1 9 9 1 . Radia Industry is a irradiation service company having 2 units of Co-60 and a 5MeV e-beam. The 5MeV EB machine is equipped with a X-ray converter to have more penetration for thicker materials. The second machine was installed at a factory of Shinko Chemical near city of Kanazawa. The Headquarters of Shinko Chemical is in Kanazawa and their products are plastic container for pharmaceutical and sanitary liquids. The machine installed in Shinko Chemical is for irradiating their own products and also available for fig.1 5MeV EB machine contract irradiation.
475
476
K. Mizusawa et al.
The major improvements in the second machine are 1)the power conversion efficiency and 2)the motorgenerator system for the filament power supply. 1)The power conversion system To improve the power conversion efficiency we used a new thyristor 3kHz power supply for the main power and were able to improve it to as high as 73-75% which we believe is the best power conversion efficiency among machines with energy around 5MeV. 2)The motor-generator system for the filament power supply The motor-generator system for the first machine was column-supported configuration and for the second machine was self-supported configuration. With the self-supported configuration driving insulation rod is separated from the Cockcroft-Walton high voltage generator column t h a t allows the system free from movement of the generator. We assume this improvement gives a long term stability to the system.
CONVEYOR
SYSTEM
The conveyor system at Radia is 120cm in width and has a turn-over equipment outside the X-ray shielding. The conveyor is basically made of stainless steel and materials being irradiated are conveyed on the 1.2m wide stainless steel pallets into the irradiation zone.(fig.3) The materials to be irradiated from the top and the bottom are first irradiated from the top and come out to be turned over and then go into the irradiation zone again to be irradiated from the bottom side. The advantage with this system is t h a t they can see the operation of turning-over directly. Since the machine has X-ray irradiation capability the speed of the conveyor can be adjusted to fit for it so t h a t they will be able to take variety of requests from the customers'. The system view is shown in fig. 9. t.;;• k[?,,
"
fig.2 System view at Radia Industry
The factory of Shinko Chemical was newly built for the 5MeV irradiation facility in 1 9 9 5 and was disclosed recently. The installation and testing of machine was finished in September, 1 9 9 5 and the validation was co .mpleted at the end of the year. They irradiate their products which are plastic containers for pharmaceutical products packed in card board boxes. They carry out comprehensive quality control using radiation dose reader, chemical dose indicator and biological tests to provide excellent quality assurance. Basically, it is the in-house machine but while they do not irradiate their product the machine is available for customers who want to have their materials to be irradiated. The conveyor has two lines under the irradiation window as shown in fig.3.(top of the next page) The direction of motion of the 2 lines are opposite to each other. On the forward line the boxes are irradiated from the top then the boxes are turned-over at the t u r w o v e r equipment and irradiated from the bottom on the backward line.
10th International Meeting on Radiation Processing
477
II ///lJ: fig.3 Irradiation zone at Shinko Chemical. The turn-over equipment is located inside the X-ray shielding (rigA) and designed to turn-over boxes adequately so t h a t the boxes receive more uniform (smaller max/rain ratio) dose. Fig.5 shows the first irradiation on the forward conveyor line and the second irradiation on the backward line to achieve more uniform irradiation.
\
/
!
I1\\\\
r i g a Turn-over equipment at Shinko Chemical
fig.5 Direction of the first and second irradiation
Inside the X-ray shielding there are features to keep the irradiated materials clean. The ceiling is covered with stainless steel plates to free from dust drop. The wall and the ceiling are heated to avoid moisture dewing during r a i n y season and warm and humid days. Irradiation zone is covered by sta'inless steel chamber and exhausted to keep ozone produced by electron inside the cover, And the whole conveyor area inside the X-ray shielding is supplied with fresh air. Accordingly the facility is kept suitably d e a n for treatment of medical
goods. OPE RATIO
N
The machine at Radia has been operated 6 years and the one at Shinko Chemical has been 1 and a half, the machines did not have any maj or failures but some minor problems occurred with the conveyor system. The conveyor at Shinko Chemical is a system with complex con~ol and those problems were with control as the initial problems which have cleared after a few months of operation. The running cost of the facility depends mostly on the amortization of the investment and the cost of human power including overhead charge. The portion of utility cost and maintenance cost are rather small since power efficiency of our 5MeV 1 5 0 k W machine is over 70% and the machine operates with good stability and reliability. Another big factor for the running cost is running hours. In order to reduce the running cost the machine has to be operated as long as possible to reduce the portion of amortization and secondly squeeze the human cost as much as possible. Our machines runs long time and requires less people which are suitable to pursue tho se two objectives. ACKNOWLEDGEMENT Finally, we would like to express our sincere appreciation to persons in charge at Radia Industry and Shinko Chemical for providing us of information to make this paper comprehensive and also would like to extend appreciation for taking care of our 5MeV machines at everyday operation.
Pergamon
Plh S0969-806X(98)00178-9
5MeV Electron
Beam Facilities
© 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain o969-8o6x/98 si9.oo + o.oo
in J a p a n
K. Mizusawa, M. Kashiwagi, Y. Hoshi Nissin-High Voltage Co.~Ltd., Kyoto, Japan
ABSTRACT There are 3 facilities with 5MeV electron beam processing machines in Japan and another one is planned to s t a r t operation in 1 9 9 8 . 2 of them are installed by Nissin-High Voltage and the other are by Sumitomo Heavy/Radiation Dynamics. In this report are introduced 2 facilities which we have installed and are operating satisfactorily. The first one was: installed at Radia Industry for irradiation services and. the second one for in-house use in a factory of a pharmaceutical plastic container manufacturer, Shinko Chemical. And the second one is available for contract irradiation. The machine in Radia Industry has a comprehensive conveyor system with a turn-over equipment to shoot from the top and the.. bottom of materials with e-beam and X-ray, and has been successfully operated for m a n y years. The machine in Shinko Chemical is equipped with a unique conveyor system w i t h two conveyor lines under the beam window and the motion of the lines are opposite e a c h other. T h i s conveyor system also has a turn-over equipment like other machines but the: directio n of turning-over is designed to give the irradiated material s more uni form dose.
KEYWORDS electron: electron beam: e-beam: EB: X-ray: irradiation: service facility: sterilization.
INT R O D U C TION Since 195 7 we have been involved in the electron beam business and have supplied more than 2 3 0 units in Japan, Asia, Europe and North America. The range of the e-beam machines is from low energy (200keV) to high energy (5MeV) and the output power of the largest one is 6 4 0 k W . The application fields of those e-beam machines are expanding from conventional wires and tires to flue gas treatment and sterilization of medical devices recently. We have supplied 1 unit of 6 4 0 k W and manufacturing 2 units of 6 0 0 k W machines for flue gas treatment ,and 2 units of 5MeV 1 5 0 k W machines for sterilization of medical devices. This paper introduces features of the facilities with 5MeV machines supplied for sterilization purposes.
5MeV EB MACHINE The first 5MeV 1 5 0 k W machine was supplied at Radia Industry in Takasaki, 1 0 0 k m north-west of Tokyo in 1 9 9 1 . Radia Industry is a irradiation service company having 2 units of Co-60 and a 5MeV e-beam. The 5MeV EB machine is equipped with a X-ray converter to have more penetration for thicker materials. The second machine was installed at a factory of Shinko Chemical near city of Kanazawa. The Headquarters of Shinko Chemical is in Kanazawa and their products are plastic container for pharmaceutical and sanitary liquids. The machine installed in Shinko Chemical is for irradiating their own products and also available for fig.1 5MeV EB machine contract irradiation.
475
476
K. Mizusawa et al.
The major improvements in the second machine are 1)the power conversion efficiency and 2)the motorgenerator system for the filament power supply. 1)The power conversion system To improve the power conversion efficiency we used a new thyristor 3kHz power supply for the main power and were able to improve it to as high as 73-75% which we believe is the best power conversion efficiency among machines with energy around 5MeV. 2)The motor-generator system for the filament power supply The motor-generator system for the first machine was column-supported configuration and for the second machine was self-supported configuration. With the self-supported configuration driving insulation rod is separated from the Cockcroft-Walton high voltage generator column t h a t allows the system free from movement of the generator. We assume this improvement gives a long term stability to the system.
CONVEYOR
SYSTEM
The conveyor system at Radia is 120cm in width and has a turn-over equipment outside the X-ray shielding. The conveyor is basically made of stainless steel and materials being irradiated are conveyed on the 1.2m wide stainless steel pallets into the irradiation zone.(fig.3) The materials to be irradiated from the top and the bottom are first irradiated from the top and come out to be turned over and then go into the irradiation zone again to be irradiated from the bottom side. The advantage with this system is t h a t they can see the operation of turning-over directly. Since the machine has X-ray irradiation capability the speed of the conveyor can be adjusted to fit for it so t h a t they will be able to take variety of requests from the customers'. The system view is shown in fig. 9. t.;;• k[?,,
"
fig.2 System view at Radia Industry
The factory of Shinko Chemical was newly built for the 5MeV irradiation facility in 1 9 9 5 and was disclosed recently. The installation and testing of machine was finished in September, 1 9 9 5 and the validation was co .mpleted at the end of the year. They irradiate their products which are plastic containers for pharmaceutical products packed in card board boxes. They carry out comprehensive quality control using radiation dose reader, chemical dose indicator and biological tests to provide excellent quality assurance. Basically, it is the in-house machine but while they do not irradiate their product the machine is available for customers who want to have their materials to be irradiated. The conveyor has two lines under the irradiation window as shown in fig.3.(top of the next page) The direction of motion of the 2 lines are opposite to each other. On the forward line the boxes are irradiated from the top then the boxes are turned-over at the t u r w o v e r equipment and irradiated from the bottom on the backward line.
10th International Meeting on Radiation Processing
477
II ///lJ: fig.3 Irradiation zone at Shinko Chemical. The turn-over equipment is located inside the X-ray shielding (rigA) and designed to turn-over boxes adequately so t h a t the boxes receive more uniform (smaller max/rain ratio) dose. Fig.5 shows the first irradiation on the forward conveyor line and the second irradiation on the backward line to achieve more uniform irradiation.
\
/
!
I1\\\\
r i g a Turn-over equipment at Shinko Chemical
fig.5 Direction of the first and second irradiation
Inside the X-ray shielding there are features to keep the irradiated materials clean. The ceiling is covered with stainless steel plates to free from dust drop. The wall and the ceiling are heated to avoid moisture dewing during r a i n y season and warm and humid days. Irradiation zone is covered by sta'inless steel chamber and exhausted to keep ozone produced by electron inside the cover, And the whole conveyor area inside the X-ray shielding is supplied with fresh air. Accordingly the facility is kept suitably d e a n for treatment of medical
goods. OPE RATIO
N
The machine at Radia has been operated 6 years and the one at Shinko Chemical has been 1 and a half, the machines did not have any maj or failures but some minor problems occurred with the conveyor system. The conveyor at Shinko Chemical is a system with complex con~ol and those problems were with control as the initial problems which have cleared after a few months of operation. The running cost of the facility depends mostly on the amortization of the investment and the cost of human power including overhead charge. The portion of utility cost and maintenance cost are rather small since power efficiency of our 5MeV 1 5 0 k W machine is over 70% and the machine operates with good stability and reliability. Another big factor for the running cost is running hours. In order to reduce the running cost the machine has to be operated as long as possible to reduce the portion of amortization and secondly squeeze the human cost as much as possible. Our machines runs long time and requires less people which are suitable to pursue tho se two objectives. ACKNOWLEDGEMENT Finally, we would like to express our sincere appreciation to persons in charge at Radia Industry and Shinko Chemical for providing us of information to make this paper comprehensive and also would like to extend appreciation for taking care of our 5MeV machines at everyday operation.