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

SUB-CHAPTER : 16.2PRE-CONSTRUCTION SAFETY REPORTCHAPTER 16: RISK REDUCTION AND SEVEREACCIDENT ANALYSESPAGE : 249 / 295Document ID.No.UKEPR-0002-162 Issue 04SECTION 16.2.3 - TABLE 2Radiological Data and Assumptions Used for the Reference Core Melt Scenario- Aerosol depletion in the containment : deposition onlyIodine behaviour:• Starting point: ∼ 97.5 % attached to aerosols,2.5 % elemental iodine0.2 % organic iodine• Later on: Aerosol depletion : Deposition only.Steady state for elemental iodine after 3 hours : 0.2%.Constant level for organic iodine- Containment leak rate:Inner Containment 0.3% vol./day- Leaks collected in Annulus are released to the environment filtered via the stack(aerosol depletion: identical to the long term depletion in the containment)- Ventilation rate: 200 m 3 /h- Filter retention efficiency of 99% for aerosols and all gaseous iodine forms- Emission height: 0 m.- Weather conditions in respect of activity dispersion are assumed to have a conditionalprobability of 95%; i.e. probability that they will be exceeded is 5%.- Dispersion parameters, gamma dose factors, deposition and washout factors as wellas transfer factors from soil to plants are taken from German Accident CalculationBases.- Tissue weighting factors are taken from ICRP Publication 60. The committed doseswere calculated for 50 years. Continuous occupancy at one location was assumed.