Modeling of Radiation Fields and Estimation of Doses During Dismantling of RBMK-1500 Reactor Emergency Core Cooling System

There is only one nuclear power plant in Lithuania — Ignalina NPP. The INPP operated two similar units with installed capacity of 1500 MW (each). RBMK-1500 were commissioned in 12/1983 and 08/1987, and the original design lifetime was projected out to 2010 and 2015 respectively. But the first Unit of Ignalina NPP was shutdown December 31, 2004, and second Unit will be closed down in 2009. In relation with this, implementation of new technologies for treatment and conditioning of radioactive waste, construction of the interim dry storage facility for spent nuclear fuel and preparation of the licensing documents for decommissioning of the Unit 1, and some other projects were implemented or are under implementation at Ignalina NPP. Implementation of dismantling activities requires detailed knowledge of the radiological situation at the Unit 1. General Radiological Characterization Program for Ignalina NPP Unit 1 based on NUREG-1575 was prepared in 2005–2006 and approved by Regulatory Bodies. In 2008 development of the dismantling projects at Ignalina NPP Unit 1 has been started. Dismantling project of the emergency core cooling system (Building 117/1) is the first project in this field. Based on the radiological surveys data, detailed modeling of the radiation fields has been performed using “VISIPLAN 3D ALARA Planning tool” computer program (SCK CEN, Belgium). So, in this paper detailed information on radiation fields modelling, proposals for optimization of the radiation doses to the personnel, and emergency core cooling system equipment dismantling is presented.