Safety Methodology Implementation in the Conceptual Design Phase of a Fusion Reactor

Transcription

1 Safety Methodology Implementation in the Conceptual Design Phase of a Fusion Reactor Lina Rodríguez-Rodrigo Joëlle Uzan-Elbez 1

2 Safety Methodology Implementation in the Conceptual Design Phase of a Fusion Reactor For an experimental reactor could have been the question that the fathers of the ITER safety approach asked themselves. Answers are in a 1995 FED publication, NSSR and GSSR 2

3 Safety Methodology Implementation in the Conceptual Design Phase of a Fusion Reactor Why coming back to the same question for future fusion reactor? ITER will be a reference Today environment: Non safety educated fusion community Non fusion educated safety community Safety-fusion educated community should integrate improve, organise safety in the design of future reactors introducing an appropiate quality assurance framework to be appliedin thewholeexistingfusioncommunity Provide scientific and technicat elements for informing the society? How? A conclusion for this meeting 3

4 Safety background in the Fusion Community Fusion Machines JET MW fusion power 1997 DTE1 16 MW fusion power Safety case UK requirements and standards followed Dismantling included in UKAEA decommissoning TFTR years DT campaign 11.5 MW Fusion power PSAR FSAR approved in 1978 USDOE approved in 1992 for DT operation Dismantling and safe disposal 2002 (in time and cost) 4

5 Safety background in the Fusion Community Safety background in the Fusion Community Fusion Machines 5

6 Safety background in the Fusion Community Tritium laboratories Active Gas Handling System at JET Tritium Laboratory Karlsruhe Tritium Process Laboratory at Naka Tritium Systems Test Assembly at Los Alamos (TSTA) Tritium Laboratory at Valduc Inertial fusion Methodology for IFE safety and environment assessment HYLIFE-II SOMBRERO 2005 INTERNATIONAL FUSION RESEARCH COUNCIL report 7% of the article tackles safety for future fusion reactors Normal operation <1% of the naturally occurring dose rate Most severe internal accident about annual natural radiation 1µSv Waste 6

7 Fission background for fusion reactor conceptual design Already implemented in previous mentioned installations and in ITER Slight differences Definition of safety functions fission Control of the nuclear process in the reactor core Removal of heat from the core Confinement of the radioactive materials. fusion Up to now limited potential of a fusion power increase Removal of the heat from the FW and VV activated material Confinement of the radioactive materials 7

8 Safety objectives Risk Source term Energies Tritium AP ACP Mass Activity Physical state Location Doses to the workers Effluent Releases Safety functions Confinement of radioactive products 1st barrier 2nd barrier Dynamic confinement Safety objectives Limitation of exposure for workers and environment Residual power evacuation Radioprotection Worker s Doses evaluation ALARA zoning Safety objectives Safety objectives Passive means Maximum values Means for satisfying Safety functions + Illustration on the representative situations: operation, maintenance, incidents, design basis accidents 8

9 RISK evaluation 1 Frequency RISK evaluation Safety margin Curve of damage limit Curve of characteristic risk 0 Damage 9

10 Principals of Damage mitigation Protection by barriers Compensating Defence Depth means for risk Lines of defence Passive safety Use of system Reduction of consequences to the Public, workers environement in normal, incidental en accidental situations 10

11 Reduction of the frequency of the damage Redundancy Compensating means for risk Diversity Geographical separation Unique failure criteria Avoid common mode failure Lowering probability of occurence of events 11

12 Ensure reliable, stable and easily manageable operation. Prime goal the prevention of accidents. Appropriate application of the Defence-In-Depth principle: several levels of protection and multiple barriers to prevent releases of radioactive materials to ensure that failures or combinations of failures that might lead to Compensating means for risk Design Principals significant radiological consequences are of very low probability. Incorporated Technologies proven or qualified by experience or testing or both The systematic consideration of the man machine interface and human factors shall be included in all stages of design and in the associated development of operational requirements. The exposure to radiation of site personnel and releases of radioactive materials to the environment shall be made by design As Low As Reasonably Achievable (ALARA). A comprehensive safety assessment and independent verification shall be carried out to confirm that the design will fulfil the safety objectives and requirements before the operating organization completes its submission to the regulatory body. IAEA Safety series nº

13 Design Systems Equipments Buildings... Modification Prime goal the prevention of accidents Scenarios Transients Accidents Analysis of the events Models, codes, experiments, (Damage, frequency) NO OK? YES Safety functions Safety Objectives Implementation in the Design 13

14 Design Systems Equipments Buildings... Modification Prime goal the prevention of accidents Scenarios Transients Accidents Analysis of the events Models, codes, experiments, (Damage, frequency) NO OK? YES Optimisation Safety functions Safety Objectives Cost/Benefit NO OK? YES Implementation in the Design 14

15 Safety function confinement several levels of protection and multiple barriers 15

16 Safety function Decay heat removal Approaches to safety, environment and regulatory approval for ITER Fusion Engineering and Design 27 (1995)

17 ORE and releases of radioactive materials to the environment by design As Low As Reasonably Achievable (ALARA). Design Systems RH-Equipments Buildings Sheldings Modification Maintenance Effective Doses calculation Collective doses NO OK? YES Optimisation Cost/Benefit Safety functions Safety Objectives ALARA NO OK? YES Implementation in the Design 17

18 ORE and releases of radioactive materials to the environment by design As Low As Reasonably Achievable (ALARA). Design Systems Flow-rate Buildings Modification NO Normal operation Ventilation-fire risk OK? YES Optimisation Cost/Benefit Safety functions Safety Objectives Reduction of releases ALARA NO OK? YES Implementation in the Design 18

19 Tools for safety in the conceptual design phase for future reactors Classical methods would be complemented by probabilistic assessment using support of forthcoming improved FMEA databases and associated computer tools 19

20 Application to future power plants Reactor containement Not only a fusion device Nuclear buildings Interfaces Integration in the design 20

21 Schematic of a fusion power plant Stack Power supply Ventilation detritiation System Fuelling facility Hot cells-radwaste Control system Reactor building Auxilliary systems T Fuelling facility 21

22 Schematic of a fusion power plant Stack Power supply Ventilation detritiation System Fuelling facility Hot cells-radwaste Control system Reactor building Auxilliary systems T Fuelling facility 22

23 IMPACT on the DESIGN As already done for ITER or IFMIF generic approach + consideration of internal hazards that are not regulation depending Fire Explosion Flooding 23