Cleaning up residential areas after a nuclear accident – Accident scenario Michael Ammann, STUK

Imagine a serious accident at the Loviisa NPP … A fire in the electrical cabinet of reactor 1 Core cooling fails Containment is isolated Site emergency is declared 5-km zone is evacuated according to emergency plans

Precautionary evacuation of the 5-km zone

Some hours later Core is heating up General emergency declared Vessel breaches at high pressure Large amounts of hydrogen and carbon monoxide have been produced Risk of uncontrollable hydrogen combustion Precautionary evacuation

Loviisa is evacuated

Second day Hydrogen combustion occurs and the containment fails 80 % of noble gases and 1 % of iodine and caesium were released, presumably

Imagine now a week later Radiological situation has been monitored and modelled Deposition is known to some extent Received and future doses have been estimated

The dose from the 1 st week Cloud, inhalation, 7 days ground exposure Effective, normal living, adults

It was raining Wet deposition of 137 Cs

137 Cs deposition

131 I deposition

Measured and predicted dose- rates

Key nuclides … as percentages of the total effective dose after 70 years

Data aggregation Let us use the contour bands of the 137 Cs deposition map for data aggregation

Zone 0 - Characteristics

Zone 1 - Characteristics

Zone 2 - Characteristics

Zone 3 - Characteristics

Zone 1 – Relocation of different duration

Zone 1 – Clean-up actions

Strategies Zone 1Zone 2Zone 3 1Relocate 1 week Cut grass 2Relocate 3 weeks Cut grass 3Relocate 1 year Cut grass Hosing roofs and walls Sweeping pavement Cut grass 4 Hosing roofs Cut grass Hosing roofs 5Cut grass Hosing roofs Cut grass 6 Hosing roofs and walls Sweeping pavement Cut grass

Consequence table