Introduction The decommissioning of the nuclear facilities is the final stage of their life cycle. It is one of the most complicated processes, which needs thoroughly preparation and shall be handled with particular care.
Decommissioning of a nuclear facility consists of implementation of legal, organisational and technical measures to manage the nuclear facility, when the decision for shutdown is adopted and the facility do not operate for the main purpose.
The first unit of Ignalina NPP has been finally stopped on 31st of December 2004. The second unit was finally stopped on 31st of December 2009.
The Ignalina NPP exceeds the other NPPs in many countries by size and extent of decommissioning works, therefore, it is important, that the decommissioning:
shall be implemented safely from radiation protection point of view;
shall be safe for workers, population and environment;
the huge amount of radioactive waste shall be respectively managed and safely disposed.
Safe decommissioning operations of Ignalina NPP in terms of radiation protection are important and shall ensure no risks to population or environment either now or in many years to come. One of the most important aspect of safety ensuring – protection of workers and members of general public against possible harmful ionizing radiation impact. Thus the main role performs the successful implementation of the basic principles of radiation protection:
exposure optimization (ALARA);
dose restriction.
Documents related to projects on decommissioning of Ignalina NPP were evaluated and agreed in 2009, namely: Technical Design and Preliminary Safety Analysis Report on Facilities for Management and Storage of Solid Radioactive Waste (agreed in 2009); Technological Design of Dismantling and Decontamination of Facilities of Building No. 117/1 of Ignalina NPP; Environmental Impact Assessment Report of the planned economic activity “Ignalina NPP Unit 2 Decommissioning Project for the Final Shutdown and Defueling Phase”; Environmental Impact Assessment Report, Technical Design of Repository of Very Low Radioactive Waste, and other documents related to Ignalina NPP decommissioning.
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 and water, in 2009 was approximately 0,15 μSv, that makes about 0,1% 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 about 33 man Sv.
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.
Aiming for longterm protection main attention shall be attracted to such questions:
minimization of radioactive wastes volumes (decontamination process, waste compacting, incineration);
detailed radiological, chemical, physical evaluation of packages after final waste treatment.
The part of Radiation Protection Centre in Decommissioning of Ignalina NPP According the
Law on Radiation Protection, the
Law on Nuclear Energy, the Radiation Protection Centre:
Exercises state radiation protection supervision and control at the NF;
Takes part in issuing licencies for decommissionig of the NF.
