Summary of Safety and Environmental Assessment of ARIES-AT. David Petti Fusion Safety Program, INEEL

Transcription

1 Summary of Safety and Environmental Assessment of ARIES-AT David Petti Fusion Safety Program, INEEL

2 Radiological Release Limits and Key In-Vessel Inventories Release limits to meet 1 Rem no-evacuation dose for 1 km site boundary, average and conservative weather (D & 4 m/s), ground level release Major Inventories Po-210 and Hg-203 in LiPb Tritium in LiPb - very small because of low solubility Tritium in SiC (implantation and co-deposition) Activated W dust in divertor

3 Release Limits and Inventories for ARIES-AT Material Release Limits Inventory Tritium as HTO 150 grams -T avg. weather 540 in SiC 15 grams -T cons. weather < 1 in LiPb 30 g in W 150 g in co-deposited layer (only 180 g is mobilizable in an accident) Po Curies/2.5 Curies 4 ~ 70 Ci/m 3 (no Bi removal) ~40000 Ci (with Bi removal) ~ 2500 Ci (with Bi and Po removal) TBD Hg ,000 Ci /2500 Ci 2000 Ci/m 3 (no cleanup) 1,200,000 Ci (with cleanup) TBD Activated W dust 6 kg/600 g kg Use sum of fractions rule if more than one source is involved in an accidental release

4 Accidents Analyzed for ARIES-AT Failure of double confinement boundary leads to loss of vacuum event (LOVA) In-vessel LOCA of shield leading to bypass of confinement Total loss of all coolant Total loss of flow Ex-vessel loss of LiPb coolant to lower functional area

5 ARIES-AT LOVA Results HVAC isolates in one hour 180 g of tritium and 10 kg of dust is mobilized All but 270 g of dust resettles onto floor of plasma chamber during pressurization Duct is 16 cm in diameter and 10 m long Pressure (MPa) g of tritium and 0.04 g of dust is released Pressure and Flowrates calculated by MELCOR Upper Functional Area Mass Flow Rate (kg/s) Inflow Outflow

6 Results of in-vessel shield LOCA with bypass HT Shield LT Shield/VV Water break from VV impinging on HT shield leading to rapid steam generation, pressurization and failure of SiC Plasma Chamber UFA VV/SHD Cooling System Material Mobilizable Released Inventory LiPb pool at bottom of plasma chamber Tritium 180 g-t 6.7 g-t Dust 10 kg 207 g Po Ci Ci Hg Ci 88.5 Ci

7 ARIES-AT Loss of Cooling and Loss of Flow Loss of flow dominates because of decay heat in LiPb A combination of loss of LiPb flow and loss of water coolant was judged the most severe LOCA/LOFA event Full transient axi-symmetric 2-D finite element model of the tokamak The VV is a heat sink for the blanket during the LOCA/LOFA. Highest temperature occurs in the W- coated SiC divertor plates, reaching 1050 C at 2-3 hours following an accident. The temperature of the SiC components drops quickly to C within several hours. The peak VV temperature occurs at the IB mid-plane, reaching 686 C at 2.4 days following the accident. No need for a separate heat removal system for the ARIES-AT design.

8 ARIES-AT Ex-Vessel LOCA An ex-vessel LOCA into the functional area below the maintenance corridor was analyzed. Curies of Hg Mobilized Stacked Spill pool LFA floor Temperature (C) About 500 Ci of Po-210 and ,000 Ci of Hg-203 are Mobilized available for release Curies of PbPo Stacked

9 Waste Disposal Results for ARIES-AT (assuming Nb and Mo impurity control in ferritic steel components) Fetter Class C NRC Class C Inboard Components FW/B HT Shield Vacuum Vessel Magnet Outboard Components FW/B-I B-II HT Shield Vacuum Vessel Magnet Divertor Components Divertor Plates Manifold, Shield, VV, Magnets << 1 << 1

10 Improvements to be considered in APEX Remove water from vacuum vessel to prevent LiPb/water interaction If Po-210 and Hg can be effectively removed from the LiPb coolant then no spill will have a public safety consequence ARIES-AT design can meet the no-evacuation limit safety even for conservative weather for: LOVA In-vessel LOCA with bypass Loss of all cooling and loss of all flow Ex-vessel LOCA. In the area of waste management, waste is classified by both the volume of the component and hazard. In comparison to previous ARIES designs, the overall waste volume is less because of the compact design. All components can be disposed of as Class C Can this be improved?