Strategy of WCCB-TBM Testing in ITER

Transcription

1 Third IAEA DEMO Programme Workshop 13 May 2015 Hefei, China Strategy of WCCB-TBM Testing in ITER JAEA Blanket technology group Hisashi Tanigawa, T. Hirose, Y. Kawamura and M. Enoeda

2 Outline DEMO blankets developed in Japan WCCB (Water Cooled Ceramic Breeder) TBM and demonstration tests in ITER Issues in Blanket development and relationship with TBM testing Actions to solve the issues Summary 2/18

3 DEMO concepts developed in Japan Japan has been developing the DEMO concepts with water-cooled ceramic breeder blankets. SlimCS (JAEA) SSTR (JAERI) DEMO-CREST (CRIEPI) 3/18

4 Why is water selected as coolant? BOP study in DEMO2001 Fusion power: 2.3 GW, Total power: 2.91 GW Heat removal in Blanket: 2.42 GW (83%) Heat removal in Divertor: 0.49 GW (17%) BOP study in the present DEMO He with Brayton Cycle He with combined cycle supercriticalwater Water with PWR conditions power generation efficiency 22.1% 35.3% 41.4% ~30% Coolant conditions in 220, out 500 in 250, out 500 in 280, out 500 in 290, out 325 Steam turbine in 130, 25 MPa 15.5 MPa out 470 Water-cooling is selected with considerations that; maximum allowable temperature of RAFM is about 550, early realization of electric power is important. 4/18

5 Major specification of blanket in Japan Pebble bed of tritium breeder (Li2TiO3, Li4SiO4, Li2O) Pebble bed of neutron multiplier (Be or Be12Ti) With minor difference in breeder or multiplier materials and coolant conditions. Box structure of RAFM steel as container Pebbles of breeder and multiplier materials are packed in layeredconfiguration Cooling water Container and inner structures (RAFM F82H) 5/18

6 WCCB TBM demonstrates functions required for DEMO blanket in ITER condition With TBM corresponding to DEMO blanket configuration, demonstration of tritium production and electric power extraction RAFM(F82H) WCCB TBM V.V. Power generator Water loop Pebble bed (Be) TCWS Vault Pebble bed (Li2TiO3) Purge gas loop TES Plasma side ITER Cross Section Tritium building Japan is in a position to - act as a Port Master and a TBM Leader to test the WCCB TBM, - participate as a Partner in HCPB/HCCB and LiPb-based TBMs. 6/18

7 Issues for blanket development and relationship with TBM testing Issue Purpose Outcomes from TBM (inc. ITER) TBR evaluation with high accuracy To show ensuring TBR in DEMO A unique environment for integrated demonstration EM loads To show structural soundness in DEMO Demonstration + practical plasma conditions Irradiation effects in materials To show structural/functional soundness in DEMO Very limited demonstration (low fluence) In-box LOCA To show structural soundness in DEMO Direct demonstration will be difficult Remote handling To show compatibility in DEMO Partial demonstration (different requirements are expected in DEMO) Decay heat (LOCA) To show structural/functional soundness in DEMO Direct demonstration will be difficult 7/18

8 Issues for blanket development and relationship with TBM testing Issue Purpose Outcomes from TBM (inc. ITER) TBR evaluation with high accuracy EM loads Irradiation effects in materials In-box LOCA Remote handling Decay heat (LOCA) To show ensuring TBR in DEMO To show structural soundness in DEMO To show structural/functional soundness in DEMO A unique environment for integrated demonstration Demonstration + practical plasma conditions New knowledge To through show TBM testing Very is limited only demonstration achievement of practical DT plasma structural/functional conditions (loads (low fluence) on TBM). soundness in DEMO DEMO blanket concept has to be well developed before TBM To show structural Direct demonstration will be testing. soundness in DEMO difficult For demonstrations to show DEMO relevancy, developments To show compatibility Partial demonstration of models and design schemes before or in parallel to TBM in DEMO (different requirements are testing are important. expected in DEMO) Following to the limitation of TBM testing, additional tests to TBM are also necessary. Direct demonstration will be difficult 8/18

9 Actions to irradiation effect in materials In ITER, total fluence is 0.3 MWa/m2 for 20 years. In DEMO, expected neutron wall loads range 1 3 MW/m2. For 3 years operation fluence will be 3 9 MWa/m2, times higher than all period of ITER operation. Actions before TBM testing Elemental understandings of material properties based on irradiation data Development of design scheme treating irradiation effects Actions in parallel to TBM testing Irradiation data using fusion nuclear source (He effect) Sophistication of irradiation data, understandings of material properties (including simulation techniques) and design schemes. 9/18

10 Actions to irradiation effect in materials In ITER, total fluence is 0.3 MWa/m2 for 20 years. In DEMO, expected neutron wall loads range 1 3 MW/m2. For 3 years operation fluence will be 3 9 MWa/m2, times higher than all period of ITER operation. Actions before TBM testing Elemental understandings of material properties based on environments irradiation data before DEMO. Development of design scheme treating irradiation effects There is no real-scale experimental fusion Developments and sophistications of modeling and design scheme are important. Actions in parallel to TBM testing Irradiation data using fusion nuclear source (He effect) Sophistication of irradiation data, understandings of material properties (including simulation techniques) and design schemes. 10/18

11 In-box LOCA leading to inner pressure loading to container structure Break of the coolant pipe in blanket leads to ingress of high temperature and pressure water/vapor into the container and increase of inner pressure to the container. SRD for TBM WCCB TBM Event title: In-TBM LOCA Main requirements: TBMs structure able to withstand the coolant pressure Increase thickness of container structure Decrease in TBR For TBM testing, demonstration of accurate prediction capability in TBR is important to extrapolate the design schemes to DEMO. Modification of container configuration might be necessary for DEMO. 11/18

12 Consideration of pressure relief equipment Blanket 1 Water 15.5 MPa Pressure relief 1. Coolant pipe break 2. Container break 3. Ingress of water/vapor and pebbles into VV 3 2 VV If it is acceptable in view of plant safety, container break has to be avoided for investment protection. Partial water pressure will load to the container due to flow resistance of water/vapor through pebble beds. Two aspects are being studied to find compatible conditions; decrease pressure load to container by pressure relief, improve pressure resistance of container by configuration change. 12/18

13 Actions to in-box LOCA Actions before TBM testing Development of guideline to secure plant safety defining safety requirement of blanket Development of DEMO blanket design treating in-box LOCA Design of pressure relief system Thermal-hydraulic studies of water/vapor in pebble beds (analyses and experiments) Development of thermal-hydraulic analysis code Actions in parallel to TBM testing Functional demonstration of pressure relief system Development of cooling system compatible with the pressure relief system 13/18

14 Actions to Be/water chemical reaction Reduction of chemical potential Developments of new neutron multiplier materials such as Be12Ti (chemical reaction rate is lower than Be). Improvement of accuracy in numerical analysis Modified thermal-hydraulic calculation code that can treat the chemical reaction in pebble bed are being developed. Safety analysis for WCCB-TBM shows in-box LOCA will not lead to a runaway reaction. Water/vapor ingress has two aspects; production of hydrogen and reaction heat, and increase of heat transfer capability (with expansion of heat transfer area). In DEMO expected situation might be different from TBM, and balance of two effects has to be evaluated under reasonable initiating events in view of safety. 14/18

15 Actions to TBR prediction with high accuracy TBR prediction requires integrated understandings of nuclear, thermal and chemical behaviour for tritium in blanket system. No margin in TBR design results in necessity of demonstration in TBM with high accuracy. In addition, to understand tritium behaviour in TBM is more difficult than in DEMO. TBM is located in limited area of vessel (equatorial port) Information of irradiated neutron into TBM will be limited. Transient behaviour of tritium has to be evaluated due to pulsed operation of ITER. Actions before TBM testing Establishment of modeling and analysis methods related to TBR prediction 15/18

16 In-situ measurement for TBM testing and corresponding modeling & analyses TBM shield Bio shield Cooling & power generation Tritium Extraction TBM Neutron spectra Temperature Port cell Tritium concentration Tritium building Tritium concentration and chemical state TCWS vault Tritium in water Water temp. Nuclear analyses Tritium production Nuclear heating Thermo-mechanical & Thermo-hydraulic analyses Temperature in pebble bed Tritium analyses Concentration Chemical state Permeation to water or atmosphere Agreement between measurements and analyses results shows feasibility of design scheme. 16/18

17 Difficulty related transient response in TBM Temperature distribution in TBM after 400s Transient response of temperatures in TBM After 1000s temperatures reach stable. For 400s pulsed operation, temperatures of breeding materials are transient. Tritium behaviour is also transient. Later period in ITER, pseudo stable experiments are planned by repeatable pulsed operation. 17/18

18 Summary Japan is in a position to develop DEMO reactor with water-cooled blanket as a first option, and to act as a Port Master and a TBM Leader to test the WCCB TBM. For TBM testing, demonstration of accurate prediction in TBR is important to extrapolate the design schemes to DEMO. Evaluation of tritium behaviour in TBM system is difficult due to ITER environment (for example, pulsed operation). With consideration of circumstances, TBM testing has limitation due to ITER environment, There is no real-scale experimental fusion environments before DEMO, developments and sophistications of modeling and design scheme are important. 18/18