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

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 1st week

• Cloud, inhalation, 7 days ground exposure

• Effective, normal living, adults

It was raining

Wet deposition of 137Cs

137Cs deposition

131I deposition

Measured and predicted dose-rates

Key nuclides

• … as percentages of the total effective dose after 70 years

7 days 14 days 30 days 1 year 70 yearsI-131 1 % 2 % 3 % 3 % 3 %Cs-134 1 % 2 % 3 % 21 % 42 %Cs-137 0 % 0 % 1 % 9 % 55 %Total 2 % 4 % 6 % 33 % 100 %

Data aggregation

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

Zone 0 - CharacteristicsNumber of people 18Number of houses 3Avg. Cs-137 deposition (kBq/m2) 16278Avg. Cs-134 deposition (kBq/m2) 16239Avg. I-131 deposition (kBq/m2) 154895Avg. dose in first week (mSv) 43Avg. dose-rate in coming week (uSv/h) 84Avg. dose in coming month (mSv) 46Avg. dose in next 50 years (mSv) 3356Coll. dose in next 50 years (manSv) 57Number of add. cancer deaths 3

Zone 1 - CharacteristicsNumber of people 3031Number of houses 699Avg. Cs-137 deposition (kBq/m2) 2653Avg. Cs-134 deposition (kBq/m2) 2646Avg. I-131 deposition (kBq/m2) 23170Avg. dose in first week (mSv) 4Avg. dose-rate in coming week (uSv/h) 17Avg. dose in coming month (mSv) 8Avg. dose in next 50 years (mSv) 380Coll. dose in next 50 years (manSv) 1123Number of add. cancer deaths 56

Zone 2 - CharacteristicsNumber of people 5152Number of houses 2166Avg. Cs-137 deposition (kBq/m2) 385Avg. Cs-134 deposition (kBq/m2) 384Avg. I-131 deposition (kBq/m2) 3603Avg. dose in first week (mSv) 1Avg. dose-rate in coming week (uSv/h) 4Avg. dose in coming month (mSv) 2Avg. dose in next 50 years (mSv) 81Coll. dose in next 50 years (manSv) 405Number of add. cancer deaths 20

Zone 3 - CharacteristicsNumber of people 12920Number of houses 4132Avg. Cs-137 deposition (kBq/m2) 20Avg. Cs-134 deposition (kBq/m2) 20Avg. I-131 deposition (kBq/m2) 372Avg. dose in first week (mSv) 0Avg. dose-rate in coming week (uSv/h) 0Avg. dose in coming month (mSv) 0Avg. dose in next 50 years (mSv) 7Coll. dose in next 50 years (manSv) 87Number of add. cancer deaths 4

Zone 1 – Relocation of different duration

Day7 to 14

Day7 to 30

Day7 to 90

Day7 to 182

Day7 to 365

Per-manent

Averted dose per caput (mSv)

3 8 22 41 70 380

Averted coll. dose (manSv)

8 23 65 120 208 1123

Averted number of cancer deaths

0 1 3 6 10 56

Costs (1000 euro) 1533 4355 14939 31166 63446 3218158

Zone 1 – Clean-up actionsHosingpavem.

Hosingroofs

Hosingwalls

Sweep.pavem.

Cuttinggrass

Pruningtrees

Averted dose per caput (mSv) 15 15 22 18 65 7Averted coll. dose (manSv) 46 46 65 55 194 21

Averted number of cancer deaths 2 2 3 3 10 1Costs (1000 euro) 34 105 36 2 66 1726Coll. dose to workers (manSv) 0 0 0 0 0 2Decontaminated area (10,000 m2) 12 9 13 12 79 79Waste (1000 kg) 0 0 0 24 5 16Work (man-days a 8 hours) 121 377 128 5 158 7918

StrategiesZone 1 Zone 2 Zone 3

1 Relocate 1 week

Cut grass

Cut grass

2 Relocate 3 weeks

Cut grass

Cut grass

3 Relocate 1 year

Cut grass

Hosing roofs and walls

Sweeping pavement

Cut grass

4 Cut grass

Hosing roofs

Cut grass

Hosing roofs

5 Cut grass

Hosing roofs

Cut grass

6 Cut grass

Hosing roofs and walls

Sweeping pavement

Cut grass

Consequence table

Strategy Averted coll. dose

(manSv)

Averted number of

cancer deaths

Costs (1000 euro)

Coll. dose to

workers (manSv)

1 271 14 1802 02 286 14 4624 03 635 32 63857 0.14 325 16 715 0.25 308 15 374 0.16 428 21 411 0.1