Assesment of Radiation Characteristics of Operating Storage for Solid Radwaste at the Ignalina NPP

The Ignalina NPP is the main source of radwaste in Lithuania. The total radwaste generation rate is about 2100 m3 per year (spent nuclear fuel is not taken into account) under normal operation conditions of the Ignalina NPP. Solid radioactive waste forms about 1100-1200 m3 of the total radwaste generation rate per year. Concrete buildings 155, 155/1, 157 and 157/1 at the Ignalina NPP site are designed for the interim storage of solid radioactive waste. The Lithuanian Atomic Energy Safety Inspectorate which licenses the operation of the 1st unit of the Ignalina NPP specifies that a particular safety analysis must be performed for the existing radioactive waste storage facilities of the Ignalina NPP. This paper presents a radiation shielding analysis of the 157/1 building which is in operation. The French computer code MERCURE-5.3 was used for this purpose. The calculated equivalent dose rates were compared with the measured values. Besides, according to the waste generation rate and loading scenario, a prognosis of the equivalent dose rate when all sections of the building are filled up was done. Equivalent dose rate calculations showed that till 1995 the measured activity of radioactive waste was overestimated and the activity data starting from 1995, when the activity determination methodology was changed, are more reliable. (author)