How to Behave in Case of NPP accident? General Rules

Currently, there is no accident at ZNPP. We will inform you if an event happens at ZNPP. The purpose of this message is to inform our readers on possible scenarios for the progression of events and actions in case they occur.

In preparation of this message, data on the current condition (configuration) of ZNPP units available at SSTC NRS were used.

Since 2011, upgrades aimed at sever accident prevention and/or management have been implemented at ZNPP units. Such upgrades include mobile diesel generators and mobile pump units necessary to ensure the makeup of steam generators, spent fuel pools and spray ponds. The use of these systems is intended to prevent severe accidents or significantly increase the time for personnel to take actions to mitigate accident consequences. It should be pointed out that ZNPP units have been shut down for the last nine months (part of the power units was shut down after ZNPP site occupation and the rest – last autumn).

Currently, one of ZNPP power units is in hot shutdown, four are in cold shutdown and one is in refueling outage. In both hot shutdown and cold shutdown, the control rods are inserted into the core, concentration of boric acid in the reactor and primary circuit will not allow the chain reaction to be maintained (shutdown concentration), and high pressure and temperature in the primary circuit are ensured by operation of reactor coolant pumps and not by the chain reaction in nuclear fuel. In other words, under all listed operating states, the power units do not generate electricity and do not contain radioactive iodine (I-131).

First of all, note that all potential options for development of events at ZNPP can take place according to two scenarios:

• intact-containment accident (containment);
• open-containment accident (or containment failure/damage).

Scenario 1 – intact-containment accident (containment)

Each ZNPP reactor is arranged inside the containment. The containment is made of reinforced concrete (walls are about 1 meter thick). It can withstand a pressure of at least 5 atmospheres (water pressure at a depth of 50 meters) and a temperature of at least 150°C. The main purpose of the containment is to confine radioactive materials and radioactive decay products inside and prevent them from being released into the environment.

The SSTC NRS assessed the radiation consequences of a “power unit blackout” accident at ZNPP site. This accident is identical to a loss-of-spray-pond accident (for example, due to the loss of spray pond). It is most unfavorable for the progression of the loss-of-coolant accident accompanied with the loss of coolant used to remove the heat from the core fuel and spent fuel pool.

During the analysis, it was considered that a power unit is under shutdown (hot shutdown) for the last 9 months (the shortest shutdown time for all ZNPP units) for meteorological conditions as of 3 p.m. of 16 June 2023.

The simulation of a hypothetical severe core damage accident with total loss of power at one ZNPP unit (with undamaged/intact containment) demonstrates that radiation consequences of the accident will be limited mainly by the boundaries of the control area (2.5 km around ZNPP). And this will mostly concern ZNPP personnel.

In this case, it is necessary to limit people stay outdoors within the control area.

Iodine prophylaxis is not required.

Scenario 2 – open-containment accident (or containment failure/damage)

Currently, in the event of open-containment accident scenario, there is no need to use iodine pills or solutions. Unreasonable use of potassium iodide pills threatens your health. Ingestion of Iodine, Betadine or Lugol solutions can cause serious burns of mucous membrane and poisoning.

In case of open (damaged)-containment accident, the radiation consequences will have a wider geography and will be worse. The contamination area will depend on separate scenario and meteorological conditions. In the event of such an accident, we will inform you additionally on the level of releases, situation at emergency power unit and predicted contamination zone.

In the event of NPP radiation accident, the reliable notification on the accident will be ensured. After alarm, it is necessary to switch on the radio, TV or Internet immediately and listen to the message. Trust only the verified information provided by official authorities, such as the State Emergency Service of Ukraine, SNRIU, SSTC NRS, Ukrainian Hydrometeorogical Center, local authorities, military administrations and police.

The first step to take is to put on a respirator or a cotton-gauze dressing. If there are none, cover your nose and mouth with a towel, handkerchief or scarf.

You should stay indoors or find the nearest shelter or basement immediately if you are outside. Radioactive material settles from the outside of the building, so it is necessary to stay as far as possible from the walls and roof. If you came from the outdoors, remove the top clothing and place it to plastic bag or airtight container. This can remove up to 90% of radioactive contamination and reduce the time you are exposed to radiation.

Close and block all windows, doors and ventilation openings in the room and do not approach them unless necessary; turn off the air conditioners and heaters.

Only bottled water and food in sealed containers (cans, bottles, boxes) or food from the fridge or freezer is safe for consumption. It is possible to use the food from garden, vegetable garden or from the outside and tap water after official notification that it is safe.

It is important to follow the rules of personal hygiene. Wipe food containers, tables and utensils with a damp cloth or clean towel. Do not forget about your pets, wipe their bowls and rugs. Put used cloth in hermetically sealed bag or plastic box.

And finally, listen further notifications of the State Emergency Service of Ukraine, SNRIU, SSTC NRS, Ukrainian Hydrometeorogical Center, army, police or local authorities. They will notify you on further actions, evacuation and safety rules.

How to prepare for a hypothetical radiation accident?

First of all, make sure you have a storage battery-powered radio. It can turn out that it will be the only way of communication in case of emergency. Store bottled water and food for at last a few days. Prepare emergency bag. And of course, keep calm and don’t panic!

And remember, currently there is no scenario of accident at ZNPP that would require iodine prophylaxis! Follow our updates, we will keep you informed.