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Conceptual layout design of CFETR Hot Cell Facility
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Conceptual layout design of CFETR Hot Cell Facility Zheng Gong a,b,∗ , Minzhong Qi b , Yong Cheng b , Yuntao Song a,b a b
University of Science and Technology of China, Hefei 230026, China Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China
h i g h l i g h t s • • • •
This article proposed a conceptual layout design for CFETR. The design principles are to support efficient maintenance to ensure the realization of high duty time. The preliminary maintenance process and logistics are described in detail. Life cycle management, maneuverability, risk and safety are in the consideration of design.
a r t i c l e
i n f o
Article history: Received 8 December 2014 Received in revised form 10 May 2015 Accepted 18 June 2015 Available online xxx Keywords: CFETR Maintenance Hot Cell Layout Conceptual design
a b s t r a c t CFETR (China Fusion Engineering Test Reactor) is new generation of Tokomak device beyond EAST in China. An overview of hot cell layout design for CFETR has been proposed by ASIPP&USTC. Hot Cell, as major auxiliary facility, not only plays a pivotal role in supporting maintenance to meet the requirements of high duty time 0.3–0.5 but also supports installation and decommissioning. Almost all of the Tokomak devices are lateral handling internal components like ITER and JET, but CFETR maintain the blanket module from 4 vertical ports, which is quite a big challenge for the hot cell layout design. The activated in-vessel components and several diagnosis instruments will be repaired and refurbished in the Hot Cell Facility, so the appropriate layout is very important to the Hot Cell Facility to ensure the high duty time, it is divided into different parts equipped with a variety of RH equipment and diagnosis devices based on the functional requirements. The layout of the Hot Cell Facility should make maintenance process more efficient and reliable, and easy to service and rescue when a sudden events taking place, that is the capital importance issue considered in design. © 2015 Elsevier B.V. All rights reserved.
1. General CFETR (China Fusion Engineering Test Reactor) is next generation fusion experimental facility in China which is beyond the EAST and intervening between ITER and Fusion DEMO. The mainly purpose of CFETR is to test the related fusion technology and engineering in fusion power plant, especially long pulse or steadystate operation with envisioned duty cycle time at the range of 0.3–0.5 and exploring option for DEMO blanket & divertor with easy changeable in-vessel components by remote handling equipment [1–4] (Fig. 1). As the lynchpin of the maintenance system, Hot Cell plays an important role in the campaign to guarantee the high duty time implementation. Many technical, economic, safety, managerial,
logistic, organizational, legislative issues and other factors should be taken into account when planning maintenance activities such as remove, transport, inspection, repair, renewal, disassembly and refurbishment for the in-vessel components in the host to make the high duty time requirement of CFETR. Furthermore, layout’s good and bad of design will directly influence the whole function of maintenance. The CFETR maintenance system consists of Hot Cell Facility (HCF), Radwaste Treatment Facility (RTF) and Control & Access Facility (CAF) three main sub-systems which are located to southeast side of the CFETR Tokomak Building. In this paper, one layout design version of the Hot Cell Facility is established under the consideration of maintenance process combined with the components life cycle management and the efficient maintenance strategy. 2. Maintenance methodology
∗ Corresponding author. E-mail addresses: [email protected] (Z. Gong), [email protected] (M. Qi), [email protected] (Y. Cheng), [email protected] (Y. Song).
The realization of the high duty time is based on the reliability of host device, equipment and all in-vessel components, as a
http://dx.doi.org/10.1016/j.fusengdes.2015.06.088 0920-3796/© 2015 Elsevier B.V. All rights reserved.
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From the dissection above, several maintenance strategy issues are taken in to the design requirements: • Maintenance based on the functions protection. • Each component of host is to maintain in their own cell or unit, maintenance area without crossing and overlapping for increasing the availability of CFETR host. • Replacement and repairs implement in parallel. • Replacement of reparation with change, preparing enough parts for turnover. • Routing maintenance based on the process sequence, saving the intermediate costing. • The travel distances minimizes during the transfer of the in-vessel components from/to the tokomak building and HCF. 3. Maintenance process in Hot Cell
Fig. 1. Section view of CFETR host [1].
consequence, RCM (Reliability-centered maintenance) is introduced as the main maintenance methodology of CFETR to ensure the mission and goal of the maintenance. RCM is an international general maintenance method, which is currently used in the aircraft and some other larger and complex equipment maintenance. For fusion device maintenance, one of the potential function of RCM is to determine the preventive maintenance requirements and also provide the system engineering approach to optimize the maintenance process and support to design the related maintenance equipment and system. In order to meet the requirement of high duty time, the most important issue in the consideration of the layout design for HCF is how to make the maintenance process as efficient as possible to improve the availability, it can be expressed as: A=
Uptime Uptime + Downtime
The availability of a year, for example, the denominator of the formula about 8760 h, the inherent availability from the perspective of design must meet the following formula: Ainherent =
MTTF MTTF + MTTR
MTTF: Mean Time To Fail MTTR: Mean Time To Replace From the formula, if the average failure time (MTBF, mean time between failure) interval or the average time (MTTF, mean time to fail) before failure is greater than MTTR (MTTR, mean time to repair) and the average recovery time (MTTR, mean time to replace), the availability will be higher. Similarly, if the mean time to repair or mean time to recovery is very small, the availability will be higher too. If reliability decline decrescendo, we need to improve the maintainability, such as reducing MTTR can achieve the same availability. Usually, for certain availability, reliability growth, the maintainability is not so important. So we can make a balance between reliability and maintainability, to achieve the same availability, but the two constraints must be synchronous improvement. If no human negligence occurred in system operation, the Ainherent is the biggest one we can get to support the high duty time.
Sequence and operation of maintenance for each components and equipment have been studied and generated by CFETR China National Integration Design Group. Each maintenance process will involve several main processes and specific technological dispose located at cubicle rooms in each sub-cell and unit inside Hot Cell Facility. 3.1. The overall of maintenance In order to study the arrangement of hot cell layout, the design team draw up a preliminary maintenance process. The overall maintenance framework including several sections: 1. Removal and transport: the removal of In-vessel components from the host will be implemented by dedicated RH tools and transshipped by TB (Tokomak Building) cask to docking station after preliminary cleaning, transferred by intermediate cask to the respective maintenance area. 2. Maintenance: after enter the sub maintenance cell or units, the in-vessel components firstly will be placed in buffer storage area or the decay heat removal room, waiting to enter the next disassembly cubicle room, then the dismantling parts will be deep decontaminated and shipped by internal mover to next room, finally repaired and refurbished on the complex maintenance stand to check, inspection, discard and renew some parts of invessel components. All the new parts in spares room are standby for supporting maintenance, the failure parts storage area is also reserved in each sub-cell. 3. Post processing: all the activated and discarded parts will be specially disposed before decommissioning such as beryllium separation, tritium removal, and encapsulation for storage shipping and deep burial, these special process are all carried out in the radwaste facility. Based on the maintenance process, a simplified maintenance workflow has been established shown as Fig. 2. 3.2. Maintenance process in sub-cell 3.2.1. For in-vessel components After removing out of the vacuum vessel, the in-vessel components (IVC) will be preliminary cleaned in docking station and be packaged and kept in the decay heat removal room using HAVC (Heating, Ventilation Air Condition) to carry out decay heat removal process for a long time, the coolant is gas not water which is the coolant for decay heat in fission, due to the restrictions tritium water [5–7]. After that the transporter will remove it out of the decay heat removal room and deliver IVC into the sub maintenance cell to start maintenance process in sub cell: firstly, removing
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Fig. 2. Maintenance flow chart.
Fig. 3. Maintenance process in sub cell.
radioactive dust from the surface of IVC then dismantling and opening the seal for decontamination. After completion of the corresponding pretreatment process to reduced radioactive effluent in the maintenance area, the IVC will be maintained on the dedicated maintenance stand to do the inspection, repair and refurbishment, all the stands are covered with cladding structure for residual tritium in material. New spares and components will be delivered into the sub-cell, the radwaste will be shipped into RTF with preliminary package as shown in Fig. 3. 3.2.2. For remote handling system The activation of remote handling (RH) system is unlike the IVC which is irradiated by 14 MeV neutron. During remote
handling process in removing the IVC out of the Tokomak machine, the remote handling system is contaminated with large amounts of radioactive dust in vacuum vessel. It is just short-term exposure to the activated IVC, the activation of remote handling system is more weak than IVC, so the main radiation from RH mainly comes from the dust. Whether the remote handing system need to remove the decay heat is still in the study, so current maintenance temporarily don’t consider the influence of the decay heat process, as shown in Fig. 3: firstly, cleaning and removing radioactive dust, then dismantling and opening the seal for decontamination. After entering repair room, remote handling system will be inspection and replacement of failure, damage and loss parts on dedicated stand. After a series of maintenance process, refurbished remote
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Z. Gong et al. / Fusion Engineering and Design xxx (2015) xxx–xxx Table 1 Radiation partition [8,9].
Fig. 4. Radiation partition for IVC maintenance sub-cell.
handing system are stored in the buffer area, waiting for the next maintenance cycle of use. Another point is also worth noting, remote handling system after decay heat removal and refurbishment whether can be continue to use is also still in discussion and research. 3.3. Radiation partition in Hot Cell Several task force have carried out the radiation and tritium protection research [8–12]. The radiation partition is shown in Table 1 with the principle of ALARA to ensure the safe of maintenance process and personnel safety. All the maintenance process in Hot Cell should to take the whole-process management to reduce the influence of the materials activation and residual tritium, so based on the function requirements, the radiation partition in sub-cell is developed with maintenance process, shown in Figs. 4 and 5. 4. Maintenance channel distribution The structure of CFETR is dissimilar like the common tokomak as JET, ITER which handling channel are lateral, for increasing the maintenance efficiency, and 4 vertical channels are used to
installation and removal of the blanket module. The host also has 8 horizontal ports and 8 bottom (lower) ports for the plasma heating apparatus, diagnostic plugs and divertor cassette to remote handling, shown as Fig. 6. Based on the distribution of maintained components, design team arrange each maintenance sub-cells and units located close to the maintenance channel as far as possible. Hence, the first floor serves for components work through the bottom port like divertor, divertor RH tools and cryopumps. Port plugs and ports plugs RH tools are placed on the second floor, for the blanket maintenance, there is a duplex space between first floor and second floor, on account of the huge size of the bunch blanket module and maintenance equipment with three layer coated. 5. Maintenance item and objectives The CFETR Hot Cell Facility and systems are designed to receive and process objects which have been activated due to exposure to the 14 MeV neutrons from the plasma and some toxic substances such as beryllium. Its main objectives as below: • In-vessel components maintenance • Throughput of operation requirements
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Fig. 5. Radiation partition for RH maintenance sub-cell.
Fig. 7. Interfaces between TB and HCF. Fig. 6. Maintenance channels and components distribution.
• • • • • • •
Several remote handling system maintenance Radwaste treatment and storage Port plug maintenance Ancillary equipment unit maintenance Ancillary services support Rescue system support Experiment and test support
6. General description of Hot Cell CFETR Hot Cell is a rectangular reinforced concrete building which is composed of 4 floors with nearly 200 m long and 150 m wide. The layout of CFETR Hot Cell Facility was developed in conjunction with series of important maintenance issues and highly integrated with many important subsystems. The presented layout are established according to the requirement of the special craft, each sub-cells linked by the intermediate cask corridor including two elevators are positioned to provide minimum transfer distance. Each sub-cell has 3 passageway connected to the corridor, for components, spares and radwaste to get in and out of the maintenance area.
7. Interfaces between TB and HCF Due to the different blanket removal scheme not via the horizontal port as ITER and JET but pulling the whole bunch blanket module through the vertical port out of CFETR host [1] and comprehensive consideration of maneuverability and potential risk to enter dock also in the vertical direction, as Fig. 7. For the divertor and port plugs, they will be removed by teleoperation device and transferred across the tokomak building in TB Cask. After the cask sealing connection with the docking station, the internal transfer device will pass them into docking area in each floor. 8. Layout of CFETR HCF 8.1. 1st Floor Lay Out During the maintenance period divertor cassette removed from the host by the divertor remote handling system CMM and CTM tools [4], it will be conveyed into docking station by TB Cask and then cleaned by preliminary clean station with dry ice blasting to dispel radioactive particles, later through an air lock chamber transferred by the intermediate cask into the divertor maintenance cell to complete rest of the maintenance process.
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Fig. 10. The layout of hot cell 3rd floor. Fig. 8. The layout of hot cell 1st floor.
Fig. 9. The layout of hot cell 2nd floor.
The divertor and RH maintenance cells are next to the cask cell located in the opposite direction of blanket cell and docking & delivery station. Along the corridor, there are 3 openings in each sub-cells reserved for the logistics of maintained components, spares and discarded radwasted, as Fig. 8. 1st floor includes: • • • • •
Blanket maintenance cell Divertor maintenance cell Intermedia cask cell Docking station and preliminary clean station Delivery station and inspection station
8.2. 2nd Floor Lay Out The main mission of second floor is to support maintenance for port plugs such as plasma heating and diagnostic equipment. Due to embezzlement (reserve space) of Blanket maintenance cell, the second floor only have half side. Similar with Floor 1, port plugs RH cell, diagnosis port plugs and NBI maintenance cell are located along half side of Hot Cell Facility, as Fig. 9. 2nd floor includes: • • • • • •
Port Plug RH maintenance cell Port Plug maintenance cell NBI maintenance cell Intermedia cask cell Docking station and preliminary clean station Delivery station and inspection station
8.3. 3rd Floor Lay Out Different from the first two floors, there is no immediate docking & delivery station link to the tokomak building on the 3rd floor, all the transportation rely on the elevators in the corridor, as a consequence, it provides service for low workload sub systems such as rescue robot system, blanket RH tools and ancillary equipment, and also reserves a buffer storage area which can be the extension in future. The maintenance process in Hot Cell is quite complex, the rescue robot is necessary to perform emergency rescue, and can reach anywhere in HCF, but it is not commonly used system, therefore, it is arranged on this floor next to the blanket RH cell. Via bottom channel in blanket RH cell, the blanket RH tools can entering blanket docking & delivery station using the same access like blanket module, as Fig. 10. 3rd floor includes: • • • • • •
Blanket RH maintenance cell Rescue robot cell Buffer storage area Intermedia cask cell Docking station and preliminary clean station Delivery station and inspection station
8.4. 4th Floor Lay Out Due to the task of HCF, which need to deal with a large number of radiation and residual tritium components, and the tritium has a strong penetration and diffusion. The extreme environment makes the Hot Cell need to have a set of filtering and ventilation, and all these devices will also be contaminated by radioactive dust and tritium, so that all these sub-system should be arrange in the HCF. The complexity maintenance process requires other related auxiliary systems supporting such as carbon dioxide blasting, climate protection welding and laser or gas cutting. So, the 4th floor is divided into different areas and equipped with a variety of ancillary equipment and support system, as Fig. 11. 4th floor includes: • • • • • • • • • • •
Fire suppression and extinguishing system High/low power RF line Electrical supply Tooling support system Control systems Gas station (nitrogen etc.) Helium distribution & circulation system Gas treatment station Detritiation system Demineralized water supply Fire water protection system
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incorporated with dimension and layout optimization of the Hot Cell. References
Fig. 11. The layout of hot cell 4th floor.
9. Conclusions The existing CFETR hot cell layout and the preliminary maintenance workflow has been established to satisfy function recovery and envisioned high duty time requirements combined with comprehensive consideration of process, safety, logistics and some other important issues. The more detail of maintenance process, dedicated equipment and special procedures are based on the CFETR host components related R&D in further
[1] Y.X. Wan, Mission of CFETR, in: ITER Training Forum & Second Workshop on MFE Development Strategy, Hefei, 2012, 6. [2] S.T. Wu, Y.T. Song, Status of the concept design of CFETR Tokomak machine, in: The 2nd Workshop on MFE Development Strategy in China, Hefei, USTC, 30 May–1 June, 2012. [3] Y.T. Song, S.T. Wu, Concept design of CFETR Tokomak machine, in: IEEE 25th Symposium on Fusion Engineering, June 9, 2013, San Francisco, USA, 2013. [4] Y.T. Song, S.T. Wu, Concept design on RH maintenance of CFETR Tokomak reactor, Fusion Eng. Des. 89 (2014) 9. [5] P. Klenov, R. Gouttebroze, Decay heat calculation for Port Plug, Divertor and Blanket Module, in: ITER Organization Cadarache, IDM ITER UID NPHAMT v1.0, 2014. [6] D. Tsuru, Y. Neyatani, Study on decay heat removal of compact ITER, Fusion Eng. Des. 58–59 (2014) 985–989. [7] H.W. Bartels, E. Cheng, Decay heat removal in the ITER outline design, Fusion Eng. Des. 31 (1996) 203–219. [8] Y.C. Wu, X.L. Wang, Radiation protection and safety RAMI analysis summary for CFETR, in: The 11th general design of magnetic confinement fusion (preparatory) expand work conference, Hefei, 2015, 12.5-6. [9] Q. Zeng, G. Song, Radiation protection and safety consideration for CFETR, in: International Thermonu-clear Experimental Reactor ITER Training Forum and Second Workshop on MFE Development Strategy, May 30–June 1, Hefei, 2012. [10] Ministry of Environmental Protection of the People’s Republic of China, GB6249-2011, Regulations for Environmental Radiation Protection of Nuclear Power Plant, 2011. [11] Y. Wan, Design and strategy for CFETR, in: 25th Symposium on Fusion Engineering, San Francisco, 2013. [12] H. Wang, Preliminary considerations of D-T fuel recycling and tritium safety system for CFETR, in: 25th Symposium on Fusion Engineering, San Francisco, 2013.
Please cite this article in press as: Z. Gong, et al., Conceptual layout design of CFETR Hot Cell Facility, Fusion Eng. Des. (2015), http://dx.doi.org/10.1016/j.fusengdes.2015.06.088
ARTICLE IN PRESS
FUSION-8107; No. of Pages 7
Fusion Engineering and Design xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Conceptual layout design of CFETR Hot Cell Facility Zheng Gong a,b,∗ , Minzhong Qi b , Yong Cheng b , Yuntao Song a,b a b
University of Science and Technology of China, Hefei 230026, China Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China
h i g h l i g h t s • • • •
This article proposed a conceptual layout design for CFETR. The design principles are to support efficient maintenance to ensure the realization of high duty time. The preliminary maintenance process and logistics are described in detail. Life cycle management, maneuverability, risk and safety are in the consideration of design.
a r t i c l e
i n f o
Article history: Received 8 December 2014 Received in revised form 10 May 2015 Accepted 18 June 2015 Available online xxx Keywords: CFETR Maintenance Hot Cell Layout Conceptual design
a b s t r a c t CFETR (China Fusion Engineering Test Reactor) is new generation of Tokomak device beyond EAST in China. An overview of hot cell layout design for CFETR has been proposed by ASIPP&USTC. Hot Cell, as major auxiliary facility, not only plays a pivotal role in supporting maintenance to meet the requirements of high duty time 0.3–0.5 but also supports installation and decommissioning. Almost all of the Tokomak devices are lateral handling internal components like ITER and JET, but CFETR maintain the blanket module from 4 vertical ports, which is quite a big challenge for the hot cell layout design. The activated in-vessel components and several diagnosis instruments will be repaired and refurbished in the Hot Cell Facility, so the appropriate layout is very important to the Hot Cell Facility to ensure the high duty time, it is divided into different parts equipped with a variety of RH equipment and diagnosis devices based on the functional requirements. The layout of the Hot Cell Facility should make maintenance process more efficient and reliable, and easy to service and rescue when a sudden events taking place, that is the capital importance issue considered in design. © 2015 Elsevier B.V. All rights reserved.
1. General CFETR (China Fusion Engineering Test Reactor) is next generation fusion experimental facility in China which is beyond the EAST and intervening between ITER and Fusion DEMO. The mainly purpose of CFETR is to test the related fusion technology and engineering in fusion power plant, especially long pulse or steadystate operation with envisioned duty cycle time at the range of 0.3–0.5 and exploring option for DEMO blanket & divertor with easy changeable in-vessel components by remote handling equipment [1–4] (Fig. 1). As the lynchpin of the maintenance system, Hot Cell plays an important role in the campaign to guarantee the high duty time implementation. Many technical, economic, safety, managerial,
logistic, organizational, legislative issues and other factors should be taken into account when planning maintenance activities such as remove, transport, inspection, repair, renewal, disassembly and refurbishment for the in-vessel components in the host to make the high duty time requirement of CFETR. Furthermore, layout’s good and bad of design will directly influence the whole function of maintenance. The CFETR maintenance system consists of Hot Cell Facility (HCF), Radwaste Treatment Facility (RTF) and Control & Access Facility (CAF) three main sub-systems which are located to southeast side of the CFETR Tokomak Building. In this paper, one layout design version of the Hot Cell Facility is established under the consideration of maintenance process combined with the components life cycle management and the efficient maintenance strategy. 2. Maintenance methodology
∗ Corresponding author. E-mail addresses: [email protected] (Z. Gong), [email protected] (M. Qi), [email protected] (Y. Cheng), [email protected] (Y. Song).
The realization of the high duty time is based on the reliability of host device, equipment and all in-vessel components, as a
http://dx.doi.org/10.1016/j.fusengdes.2015.06.088 0920-3796/© 2015 Elsevier B.V. All rights reserved.
Please cite this article in press as: Z. Gong, et al., Conceptual layout design of CFETR Hot Cell Facility, Fusion Eng. Des. (2015), http://dx.doi.org/10.1016/j.fusengdes.2015.06.088
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From the dissection above, several maintenance strategy issues are taken in to the design requirements: • Maintenance based on the functions protection. • Each component of host is to maintain in their own cell or unit, maintenance area without crossing and overlapping for increasing the availability of CFETR host. • Replacement and repairs implement in parallel. • Replacement of reparation with change, preparing enough parts for turnover. • Routing maintenance based on the process sequence, saving the intermediate costing. • The travel distances minimizes during the transfer of the in-vessel components from/to the tokomak building and HCF. 3. Maintenance process in Hot Cell
Fig. 1. Section view of CFETR host [1].
consequence, RCM (Reliability-centered maintenance) is introduced as the main maintenance methodology of CFETR to ensure the mission and goal of the maintenance. RCM is an international general maintenance method, which is currently used in the aircraft and some other larger and complex equipment maintenance. For fusion device maintenance, one of the potential function of RCM is to determine the preventive maintenance requirements and also provide the system engineering approach to optimize the maintenance process and support to design the related maintenance equipment and system. In order to meet the requirement of high duty time, the most important issue in the consideration of the layout design for HCF is how to make the maintenance process as efficient as possible to improve the availability, it can be expressed as: A=
Uptime Uptime + Downtime
The availability of a year, for example, the denominator of the formula about 8760 h, the inherent availability from the perspective of design must meet the following formula: Ainherent =
MTTF MTTF + MTTR
MTTF: Mean Time To Fail MTTR: Mean Time To Replace From the formula, if the average failure time (MTBF, mean time between failure) interval or the average time (MTTF, mean time to fail) before failure is greater than MTTR (MTTR, mean time to repair) and the average recovery time (MTTR, mean time to replace), the availability will be higher. Similarly, if the mean time to repair or mean time to recovery is very small, the availability will be higher too. If reliability decline decrescendo, we need to improve the maintainability, such as reducing MTTR can achieve the same availability. Usually, for certain availability, reliability growth, the maintainability is not so important. So we can make a balance between reliability and maintainability, to achieve the same availability, but the two constraints must be synchronous improvement. If no human negligence occurred in system operation, the Ainherent is the biggest one we can get to support the high duty time.
Sequence and operation of maintenance for each components and equipment have been studied and generated by CFETR China National Integration Design Group. Each maintenance process will involve several main processes and specific technological dispose located at cubicle rooms in each sub-cell and unit inside Hot Cell Facility. 3.1. The overall of maintenance In order to study the arrangement of hot cell layout, the design team draw up a preliminary maintenance process. The overall maintenance framework including several sections: 1. Removal and transport: the removal of In-vessel components from the host will be implemented by dedicated RH tools and transshipped by TB (Tokomak Building) cask to docking station after preliminary cleaning, transferred by intermediate cask to the respective maintenance area. 2. Maintenance: after enter the sub maintenance cell or units, the in-vessel components firstly will be placed in buffer storage area or the decay heat removal room, waiting to enter the next disassembly cubicle room, then the dismantling parts will be deep decontaminated and shipped by internal mover to next room, finally repaired and refurbished on the complex maintenance stand to check, inspection, discard and renew some parts of invessel components. All the new parts in spares room are standby for supporting maintenance, the failure parts storage area is also reserved in each sub-cell. 3. Post processing: all the activated and discarded parts will be specially disposed before decommissioning such as beryllium separation, tritium removal, and encapsulation for storage shipping and deep burial, these special process are all carried out in the radwaste facility. Based on the maintenance process, a simplified maintenance workflow has been established shown as Fig. 2. 3.2. Maintenance process in sub-cell 3.2.1. For in-vessel components After removing out of the vacuum vessel, the in-vessel components (IVC) will be preliminary cleaned in docking station and be packaged and kept in the decay heat removal room using HAVC (Heating, Ventilation Air Condition) to carry out decay heat removal process for a long time, the coolant is gas not water which is the coolant for decay heat in fission, due to the restrictions tritium water [5–7]. After that the transporter will remove it out of the decay heat removal room and deliver IVC into the sub maintenance cell to start maintenance process in sub cell: firstly, removing
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Fig. 2. Maintenance flow chart.
Fig. 3. Maintenance process in sub cell.
radioactive dust from the surface of IVC then dismantling and opening the seal for decontamination. After completion of the corresponding pretreatment process to reduced radioactive effluent in the maintenance area, the IVC will be maintained on the dedicated maintenance stand to do the inspection, repair and refurbishment, all the stands are covered with cladding structure for residual tritium in material. New spares and components will be delivered into the sub-cell, the radwaste will be shipped into RTF with preliminary package as shown in Fig. 3. 3.2.2. For remote handling system The activation of remote handling (RH) system is unlike the IVC which is irradiated by 14 MeV neutron. During remote
handling process in removing the IVC out of the Tokomak machine, the remote handling system is contaminated with large amounts of radioactive dust in vacuum vessel. It is just short-term exposure to the activated IVC, the activation of remote handling system is more weak than IVC, so the main radiation from RH mainly comes from the dust. Whether the remote handing system need to remove the decay heat is still in the study, so current maintenance temporarily don’t consider the influence of the decay heat process, as shown in Fig. 3: firstly, cleaning and removing radioactive dust, then dismantling and opening the seal for decontamination. After entering repair room, remote handling system will be inspection and replacement of failure, damage and loss parts on dedicated stand. After a series of maintenance process, refurbished remote
Please cite this article in press as: Z. Gong, et al., Conceptual layout design of CFETR Hot Cell Facility, Fusion Eng. Des. (2015), http://dx.doi.org/10.1016/j.fusengdes.2015.06.088
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Z. Gong et al. / Fusion Engineering and Design xxx (2015) xxx–xxx Table 1 Radiation partition [8,9].
Fig. 4. Radiation partition for IVC maintenance sub-cell.
handing system are stored in the buffer area, waiting for the next maintenance cycle of use. Another point is also worth noting, remote handling system after decay heat removal and refurbishment whether can be continue to use is also still in discussion and research. 3.3. Radiation partition in Hot Cell Several task force have carried out the radiation and tritium protection research [8–12]. The radiation partition is shown in Table 1 with the principle of ALARA to ensure the safe of maintenance process and personnel safety. All the maintenance process in Hot Cell should to take the whole-process management to reduce the influence of the materials activation and residual tritium, so based on the function requirements, the radiation partition in sub-cell is developed with maintenance process, shown in Figs. 4 and 5. 4. Maintenance channel distribution The structure of CFETR is dissimilar like the common tokomak as JET, ITER which handling channel are lateral, for increasing the maintenance efficiency, and 4 vertical channels are used to
installation and removal of the blanket module. The host also has 8 horizontal ports and 8 bottom (lower) ports for the plasma heating apparatus, diagnostic plugs and divertor cassette to remote handling, shown as Fig. 6. Based on the distribution of maintained components, design team arrange each maintenance sub-cells and units located close to the maintenance channel as far as possible. Hence, the first floor serves for components work through the bottom port like divertor, divertor RH tools and cryopumps. Port plugs and ports plugs RH tools are placed on the second floor, for the blanket maintenance, there is a duplex space between first floor and second floor, on account of the huge size of the bunch blanket module and maintenance equipment with three layer coated. 5. Maintenance item and objectives The CFETR Hot Cell Facility and systems are designed to receive and process objects which have been activated due to exposure to the 14 MeV neutrons from the plasma and some toxic substances such as beryllium. Its main objectives as below: • In-vessel components maintenance • Throughput of operation requirements
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Fig. 5. Radiation partition for RH maintenance sub-cell.
Fig. 7. Interfaces between TB and HCF. Fig. 6. Maintenance channels and components distribution.
• • • • • • •
Several remote handling system maintenance Radwaste treatment and storage Port plug maintenance Ancillary equipment unit maintenance Ancillary services support Rescue system support Experiment and test support
6. General description of Hot Cell CFETR Hot Cell is a rectangular reinforced concrete building which is composed of 4 floors with nearly 200 m long and 150 m wide. The layout of CFETR Hot Cell Facility was developed in conjunction with series of important maintenance issues and highly integrated with many important subsystems. The presented layout are established according to the requirement of the special craft, each sub-cells linked by the intermediate cask corridor including two elevators are positioned to provide minimum transfer distance. Each sub-cell has 3 passageway connected to the corridor, for components, spares and radwaste to get in and out of the maintenance area.
7. Interfaces between TB and HCF Due to the different blanket removal scheme not via the horizontal port as ITER and JET but pulling the whole bunch blanket module through the vertical port out of CFETR host [1] and comprehensive consideration of maneuverability and potential risk to enter dock also in the vertical direction, as Fig. 7. For the divertor and port plugs, they will be removed by teleoperation device and transferred across the tokomak building in TB Cask. After the cask sealing connection with the docking station, the internal transfer device will pass them into docking area in each floor. 8. Layout of CFETR HCF 8.1. 1st Floor Lay Out During the maintenance period divertor cassette removed from the host by the divertor remote handling system CMM and CTM tools [4], it will be conveyed into docking station by TB Cask and then cleaned by preliminary clean station with dry ice blasting to dispel radioactive particles, later through an air lock chamber transferred by the intermediate cask into the divertor maintenance cell to complete rest of the maintenance process.
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Fig. 10. The layout of hot cell 3rd floor. Fig. 8. The layout of hot cell 1st floor.
Fig. 9. The layout of hot cell 2nd floor.
The divertor and RH maintenance cells are next to the cask cell located in the opposite direction of blanket cell and docking & delivery station. Along the corridor, there are 3 openings in each sub-cells reserved for the logistics of maintained components, spares and discarded radwasted, as Fig. 8. 1st floor includes: • • • • •
Blanket maintenance cell Divertor maintenance cell Intermedia cask cell Docking station and preliminary clean station Delivery station and inspection station
8.2. 2nd Floor Lay Out The main mission of second floor is to support maintenance for port plugs such as plasma heating and diagnostic equipment. Due to embezzlement (reserve space) of Blanket maintenance cell, the second floor only have half side. Similar with Floor 1, port plugs RH cell, diagnosis port plugs and NBI maintenance cell are located along half side of Hot Cell Facility, as Fig. 9. 2nd floor includes: • • • • • •
Port Plug RH maintenance cell Port Plug maintenance cell NBI maintenance cell Intermedia cask cell Docking station and preliminary clean station Delivery station and inspection station
8.3. 3rd Floor Lay Out Different from the first two floors, there is no immediate docking & delivery station link to the tokomak building on the 3rd floor, all the transportation rely on the elevators in the corridor, as a consequence, it provides service for low workload sub systems such as rescue robot system, blanket RH tools and ancillary equipment, and also reserves a buffer storage area which can be the extension in future. The maintenance process in Hot Cell is quite complex, the rescue robot is necessary to perform emergency rescue, and can reach anywhere in HCF, but it is not commonly used system, therefore, it is arranged on this floor next to the blanket RH cell. Via bottom channel in blanket RH cell, the blanket RH tools can entering blanket docking & delivery station using the same access like blanket module, as Fig. 10. 3rd floor includes: • • • • • •
Blanket RH maintenance cell Rescue robot cell Buffer storage area Intermedia cask cell Docking station and preliminary clean station Delivery station and inspection station
8.4. 4th Floor Lay Out Due to the task of HCF, which need to deal with a large number of radiation and residual tritium components, and the tritium has a strong penetration and diffusion. The extreme environment makes the Hot Cell need to have a set of filtering and ventilation, and all these devices will also be contaminated by radioactive dust and tritium, so that all these sub-system should be arrange in the HCF. The complexity maintenance process requires other related auxiliary systems supporting such as carbon dioxide blasting, climate protection welding and laser or gas cutting. So, the 4th floor is divided into different areas and equipped with a variety of ancillary equipment and support system, as Fig. 11. 4th floor includes: • • • • • • • • • • •
Fire suppression and extinguishing system High/low power RF line Electrical supply Tooling support system Control systems Gas station (nitrogen etc.) Helium distribution & circulation system Gas treatment station Detritiation system Demineralized water supply Fire water protection system
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incorporated with dimension and layout optimization of the Hot Cell. References
Fig. 11. The layout of hot cell 4th floor.
9. Conclusions The existing CFETR hot cell layout and the preliminary maintenance workflow has been established to satisfy function recovery and envisioned high duty time requirements combined with comprehensive consideration of process, safety, logistics and some other important issues. The more detail of maintenance process, dedicated equipment and special procedures are based on the CFETR host components related R&D in further
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