Introduction
The decommissionig of the nuclear facilities in the world is the final stage of their lifetime. It is one of the most complicated processes to be handled with particular care. The detailed preparation for the decommissioning and responsible implementation of are essential. Decommissioning of a nuclear facility consist of implementation of legal, organisational and technical measures to manage the nuclear facility when the decision for shutdown is adopted.
The first unit of Ignalina NPP has been finally stopped on 31st of December 2004, the second unit is scheduled to be shutdown at the end 2009. The size and extent of decommissioning works at Ignalina NPP will be much vaster than that of many other NPP’s in many countries, therefore, it is important, that the decommissioning:
- would be implemented safely (from radiation protection point of view);
- would be safe for workers, population and environment;
- will generate the high quantities of radioactive waste.
Therefore, it is essential to manage and dispose radioactive waste safely.
One of the main targets for ensuring safety – protection of humans (workers and members of population) against harmful ionizing radiation. Thus it is very important to implement the basic principles of radiation protection:
• exposure optimization (ALARA);
• dose restriction.
Radiation protection of general public
According to the Hygiene Standard HN 87:2002 “Radiation Protection in nuclear facilities” 87 point – The annual dose constraint applied for the members of public during designing, construction, operation (during normal operation and anticipated operational occurrences) and decommissioning of NF is 0,2 mSv. Annual effective dose for critical group members of general public, conditioned by Ignalina AE radionuclides emitted into air, in 2007 was approximately 1,37 μSv, that makes about 0,7 % of annual dose constraint and this is approximately a thousand times less than dose conditioned by natural exposure.
Prediction of Occupational Exposure
It is preliminary estimated, that the decommissioning will cause collective dose of the workers of about 33 man Sv. To compare, collective dose of the INPP workers and outside workers was 2,57 man Sv, average individual – 0,7 mSv in 2007.
Exposure dose of the workers received during decommissioning can be compared with the dose received during large outages of the reactors.
Prediction of Occupational Exposure
It is preliminary estimated, that decommissioning will cause collective dose of the workers of about 33 man Sv. To compare, in 2004 collective dose of the INPP workers and outside workers was 6.825 man Sv.
Exposure dose of the workers received during decommissioning can be compared with the dose received during large outages of the reactors.
Occupational radiation protection
Measures taken to reducing the occupational exposure:
- remote tools,
- mobile monitors,
- ventilation systems,
- new technologies,
- works in contaminated areas will be performed in such way, that no other areas will be contaminated (area will be hermetically closed, the pressure in that area will be lower than the outside area),
- special equipment for the removal of the radiactive waste, contaminated air and liquids from the contaminated areas will be installed.
Environment monitoring
Environment monitoring programme describes:
- monitoring of the athmospheric and liquid disposals,
- monitoring of the water quality in Druksiai lake,
- monitoring of concentration of the radionuclides in the air, water, precipitation, soil, fish, mushrooms, leaves, sludge.
- monitoring of the radionuclides and chemical composition of Ignalina NPP drain water,
- monitoring of the dose and dose rate in the sanitary (3 km) and supervised (30 km) areas.
The role of Radiation Protection Centre durring Decommissioning
According the
Law on Radiation Protection, the
Law on Nuclear Energy, the Radiation Protection Centre:
1. Exercises state radiation protection supervision and control at the NF;
2. Takes part in issuing licencies for decommissionig of the NF.
Ignalina programme project “Support to activities of the Radiation Protection centre related with radiation protection in decommissioning of the Ignalina Nuclear Power Plant” has been started in 2007. The main purpose of the project – to strengthen the capabilities of the authorized institution on radiation protection of the Lithuanian Republic – Radiation protection center (RPC) – the competence of the RPC in questions related to radiation protection as regards decommissioning of Ignalina NPP. More information about the Project (link).
In 2007 more attention was paid for decommission projects of Ignalina NPP, to assess and coordinate projects related documents. Environmental impact assessment (EIA) reports “Interim storage facility for RBMK spent nuclear fuel assemblies from Ignalina NPP units 1 and 2” and “Ignalina NPP new solid radioactive waste management and storage facilities” of Ignalina NPP nuclear power plant proposed economic activity were assessed and coordinated, from the radiation protection viewpoint, assessment of other documents in process – technical projects, protection analysis report and other documents (for example, information prepared for Europe Commission according to Europe Union Commission Recommendations 1999/829/Euratom on the application of Article 37 of the Euratom Treaty).
