16.2 - Severe Accident Analysis (RRC-B) - EDF Hinkley Point

SUB-CHAPTER : 16.2PRE-CONSTRUCTION SAFETY REPORTCHAPTER 16: RISK REDUCTION AND SEVEREACCIDENT ANALYSESPAGE : 58 / 295Document ID.No.UKEPR-0002-162 Issue 04SECTION 16.2.2.1 - TABLE 13Relevant scenarios for H 2 risk [Ref]Mode of ReleaseRelevant H 2 Release forRepresentative SenariosRelevant H 2 Release forBounding In-vessel Passive orActive Reflooding ScenariosBreak release only 1SB(LOCA) 5 cm (20 cm²) cold legfast secondary cooldown2. Local risk dynamic pressureSB(LOCA) 7.5 cm (46 cm²)pressuriser leak fast secondarycooldownHigher H 2 stratification than 1Other SB(LOCA) with differentbreak locations (as hot legSB(LOCA))SB(LOCA) fast secondarycooldown if no disk rupture ofpressuriser relief tank duringreflooding (< 19 bar) boundedwith 1).PDS release(pumpscompartments 2and 3)LOOP bounded by LOOP with reflood 4. LOOP with reflood 4 MHSIInerted containment (nocombustion)Highest H 2 release (100 kg)Influence thermal loads dueto H 2 recombinationMixed release:break andpressuriser3. SB(LOCA) 5 cm (20 cm²) cold legwith secondary partial cooldownSignificant burnable H 2 release.Limited time window between invessel H 2 production and ex-vesselH 2 production5. SB(LOCA) 5 cm (20 cm²)cold leg partial secondarycooldown delayeddepressurisationHighest amount of burnableH 2 with significant steamcontentInfluences pressuredynamic loads and thermalloads on metallic liner6. SB(LOCA) 5 cm (20 cm²)cold leg fast secondarycooldown (reflooding 4MHSI highest H 2 productionwith lowest steam content