âControl technology to keep reactor operation against thermal disturbance ... helium gas temperature fluctuation is within 10 oC at SG outlet. Simulation test on ...
Current Status of Research and Development on System Integration Technology for Connection between HTGR and Hydrogen Production System at JAEA
Hirofumi Ohashi, Yoshitomo Inaba, Tetsuo Nishihara, Tetsuaki Takeda, Koji Hayashi and Yoshiyuki Inagaki Japan Atomic Energy Agency, Japan
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Contents Concept of the HTGR hydrogen production system R&D items on the system integration technology 9 Control technology to keep reactor operation against thermal disturbance caused by the hydrogen production system 9 Estimation
of tritium permeation from reactor to hydrogen
9 Countermeasure
against explosion of combustible gas
9 Development of a high-temperature isolation valve to separate reactor and the hydrogen production system in accidents
Conclusion
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Concept of the HTGR Hydrogen Production System HTGR
Hydrogen Production System Chemical reactor Secondary helium hot gas duct
Reactor Isolation valve Intermediate heat exchanger (IHX) 3
R&D Items on System Integration Technology Blast Explosion Isolation valve
Reactor scram Reactor
Chemical reactor
IHX
Raw material
Tritium Tritium Hydrogen
Primary He gas
Secondary He gas
Hydrogen Process gas
9 Control technology to keep reactor operation against thermal disturbance caused by the hydrogen production system 9 Estimation of tritium permeation from reactor to hydrogen 9 Countermeasure against explosion of combustible gas 9 Development of a high-temperature isolation valve to separate reactor and the hydrogen production system in accidents
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Control Technology (1/3) Objective Development of the control technology to keep reactor operation against thermal disturbance caused by the hydrogen production system.
Approach JAEA proposed to use a steam generator (SG) as the thermal absorber which is installed downstream the chemical reactor in the secondary helium gas loop. In the HTTR hydrogen production system, target value of the mitigation for the helium gas temperature fluctuation is within 10 oC at SG outlet.
Reactor
Simulation test on the loss of chemical reaction was carried out using a mock-up test facility
IHX
SG
Chemical reactor Raw material Hydrogen
Primary He gas
Secondary He gas
Process gas 5
Control Technology (2/3) Simulation test on loss of chemical reaction ¾ Mock-up test facility LN2 tank
9 With electrical heater instead of IHX of HTTR
Nitrogen feed line
LNG tank Natural gas feed line Steam feed line Water tank
Radiator
Flare stack
600oC 450oC
Chemical Reactor (Steam reformer)
650oC
Steam generator Helium gas circulation loop
880oC
CH4+H2O Æ3H2+CO
4MPa Hot gas duct
9 Helium gas temperature and pressure at the chemical reactor inlet (880oC, 4MPa) are same as those of the HTTR hydrogen production system. 9 Steam reforming of methane is used instead of the IS process.
Circulator Electric heater Chemical reactor
Flare stack
Steam generator
Steam generator (SG)
Helium gas circulator
Electric heater
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Control Technology (3/3) Simulation test on loss of chemical reaction ¾ Procedure The supply of the raw gas for the hydrogen production, methane, was suspended during the normal operation.
¾ Experimental result
Hydrogen Radiator
Raw gas
Feed water
Helium gas temperature [oC]
1000
Chemical reactor
Chemical reactor inlet SG
800 Chemical reactor outlet
600
Loss of chemical reaction
SG inlet
400 200 -1
Nitrogen Natural
SG outlet
0
1
2
Helium gas （840oC, 4MPa）
3
4
Circulation Radiator
5
6
Elapsed time [h]
The fluctuation of the helium gas temperature could be mitigated at SG outlet within the target range of 10 oC.
Chemical reactor
SG Helium7gas （840oC, 4MPa）
Estimation of Tritium Permeation (1/2) Objective To investigate the permeability on the material of the IHX tubes, Hastelloy XR.
Apparatus Hydrogen and deuterium are used instead of tritium Pre-Heater (1kW)
Hastelloy XR (Test Pipe) Measurement Pipe (Hastelloy X)
Measurment System -Temperature -Pressure -Flow Rate
Automatic Control System
Heating System Main Heater (6kW) Exhaust System
Measurment System -Hydrogen Cooling System Flow Control
Flow Control Molecular Sieve Gas Supply System H2/He,D2/Ar,etc.
Vacuum System
Molecular Sieve Gas Purge System Ar, He,etc.
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Estimation of Tritium Permeation (2/2) Experimental result Permeability : Kp = F0 exp(-E0 / RT) Temperature [oC] Hydrogen deuterium
570 ∼ 820 670 ∼ 820
Partial pressure of H2 [Pa]
E0 [kJ/mol]
F0 [cm3(NTP)/(cm⋅s⋅Pa0.5)]
1.06×102 ∼ 3.95×103
67.2 ± 1.2
(1.0 ± 0.2)×10-4
9.89×102 ∼ 4.04×103
76.6 ± 0.5
(2.5 ± 0.3)×10-4
The basic data on the permeability of hydrogen and deuterium has been obtained for the Hastelloy XR tube.
Next research items 9 To investigate the permeability on the heat transfer tube material of the chemical reactor in IS process, SiC. 9 To estimate the tritium concentration in the IS process and the produced hydrogen.
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Countermeasure against Explosion (1/2) Principal countermeasures against explosion of combustible gas 9 Take a distance between the reactor and the hydrogen production system enough to mitigate the overpressure within an allowable range. 9 Protect blast with barriers such as wall, bank and so on. 9 Limit the leak amount of combustible gas.
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Countermeasure against Explosion (2/2) Limit the leak amount of combustible gas ¾ Design of coaxial pipe of combustible gas Manhole
Filled with nitrogen gas
Combustible gas
Support Outer pipe Inner pipe
Next research item A conceptual design using a wall and/or a bank is under way from the viewpoint of mitigation of blast 11
Development of High-Temperature Isolation Valve (1/4) Objective Development of an isolation valve for the high-temperature condition around 900oC.
High-temperature Isolation Valve (HTIV)
Technical issues ¾ Prevention of the valve seat from thermal deformation An angle valve with an inner thermal insulator was selected. ¾ Development a new coating metal for the valve seat surface A new coating metal was developed based on the Stellite alloy that is used for valves at around 500 oC. ¾ Selection of a valve seat structure having a high sealing performance A flat type valve seat was selected. ¾ Confirmation of the seal performance and structural integrity A component test was carried out using 1/2 scale model of HTIV.
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Development of High-Temperature Isolation Valve (2/4) 1/2 scale model of HTIV
Actuator
Rod Body (HastelloyX) Seat (HastelloyX) Coating metal (Stellite No.6 + 30wt%-Cr3C2)
Electric heater
Thermal insulator (Glass wool) Casing (Carbon steel)
Nominal Size Bore
HTIV
1/2 scale model
22 B
16 B
200 mm
100 mm 350 oC
Design Temp. (Casing) Design pressure
5.0 MPa
4.5 MPa 13
Development of High-Temperature Isolation Valve (3/4) Component test ¾ Apparatus
Actuator
Ar gas supply system
To He gas detector
Electric heater
Exhaust Electric heater 1/2 scale model of HTIV
Cooling water Thermal insulator He gas supply system
¾ Experimental condition and procedure (1) (2) (3)
Helium gas was supplied to the 1/2 scale model of HTIV and increased up to 4.0MPa and heated up to 900oC. Valve seat was closed and helium gas at the upstream of the closed valve seat was exhausted. The pressure difference across the valve seat was set to 4.1MPa. The electric heater was shut off and the helium gas leak rate through the closed valve 14 seat was measured from 900oC to 200oC by the helium gas detector.
Development of High-Temperature Isolation Valve (4/4) Component test Leak rate of helium gas (cm3/s)
¾ Experimental result 10 4.4 cm3/s ： Target value
1 10-1 10-2 10-3 10-4 0
200
400
600
800
1000
Temperature of valve seat (oC) The current technology can be applied to the HTTR hydrogen production system, however, the lapping of the valve seat is necessary after closing at a high temperature.
Next research item The improvement of the durability of the valve seat
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Conclusion (1/2) The system integration technology has been developed for connection of the hydrogen production system to HTGR. The following conclusions were obtained. The control technology to keep reactor operation against thermal disturbance caused by the hydrogen production system 9 JAEA proposed to use SG as the thermal absorber, which is installed downstream the chemical reactor in the secondary helium gas loop, to mitigate temperature fluctuation of secondary helium gas. By the simulation test with the mock-up test facility, it was confirmed that SG could be used as the thermal absorber.
Tritium permeation from reactor to hydrogen 9 The permeability on Hastelloy XR which is the heat transfer tube material of IHX was obtained. 9 Next research item is to investigate the permeability on the heat transfer tube material of the chemical reactor in IS process, SiC, and to estimate the 16 tritium concentration in the IS process and the produced hydrogen.
Conclusion (2/2) Countermeasure against explosion of combustible gas 9 The coaxial pipe of combustible gas was designed from the viewpoint of protection of the leakage aiming at arrangement of the hydrogen production system closed by the reactor. 9 A conceptual design using a wall and/or a bank is under way from the viewpoint of the mitigation of the blast.
Development of the high-temperature isolation valve to isolate reactor and hydrogen production systems in accidents 9 The new material for the coating of the valve seat surface was developed and the seal performance of the valve was confirmed to satisfy the design target with the 1/2 scale model of the high-temperature isolation valve. 9 The improvement of the durability of the valve seat is the next target for the development. 17
Acknowledgement
The present study is the results of “Development of Nuclear Heat Utilization Technology“ in fiscal year from 1997 to 2001, 2003 and 2004 entrusted by Ministry of Education, Culture, Sports, Science and Technology (MEXT) to Japan Atomic Energy Research Institute (JAERI) succeeded by into Japan Atomic Energy Agency (JAEA). The authors are indebted to Dr. S. Shiozawa and Dr. M. Ogawa for their useful advice and discussion in this research.
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Control Technology Simulation test on loss of chemical reaction
60
Steam
40 20
Nitrogen Methane
0 140 120 100
1000
Chemical reactor inlet 800
Chemical reactor outlet
600
SG inlet 400
SG outlet 200 6 5 4 3 2 1 0 -1
Pressure in SG [MPa]
Hydrogen production rate [m3/h] Flow rate [g/s]
80
He temperature [oC]
¾ Experimental result
80 60 40 20 0 -1
-0.5
0
0.5
Elapsed time [h]
1
0
1
2
3
4
5
6
Elapsed time [h]
20
