From 1982-1984, it became clear that the pool storage in Building No. 5 was in such a poor condition following an accident in February 1982 that it was no longer possible to use it for storage.
Around 3,000 m3 of radioactive cooling water leaked out in the accident. It was decided to construct three concrete tanks for dry storage of the spent nuclear fuel. The spent fuel was transferred from run down temporary storage solutions to the new storage tanks. The present concrete tanks have now been in use for more than 18 years and are 100% filled.
Three 1,000-cubic meter tanks designed for storing and reprocessing high activity liquid waste were rebuilt into dry storage tanks for spent nuclear fuel from Building No. 5. The tanks were given the numbers 2-A, 2-B and 3-A.
The first of these tanks, 3-A, was taken into use in June 1983. The tank was used to store 900 assemblies with spent nuclear fuel. The 2-A and 2-B tanks were consequently taken into operation in 1985-1986, and are designed to store 1,200 assemblies with spent nuclear fuel each. In keeping with a decision of the Northern Fleet Technical Department, spent fuel in tanks was to be stored in dry cells specifically designed to hold assemblies with spent nuclear fuel. The dry cells were constructed using 250mm-270 mm diameter pipes, and the space between the pipes was filled with concrete.
The 3-A tank was soon filled to capacity with spent fuel unloaded from the rundown storage facility in Building No.5. After loading of assemblies with spent nuclear fuel assemblies, the 3-A tank was covered by lead sheets and resin (See drawing). The 2-A and 2-B tanks were used as a working part of the storage until 1999. A part of the fuel was reloaded from the rundown storage to the 2-A and 2-B tanks in 1984. Fuel from both active and retired submarines is stored in these two tanks also.
Each cell of the 2-A and 2-B tanks was closed with a metal lid (See picture) and metal plates on top of it (See picture). The construction was designed to prevent rain and snow from coming inside the cells and assemblies; however, snow and rain still penetrated inside the cells and casks during loading and unloading of the assemblies. Low temperatures caused the water to freeze, and this in turn led to the development of cracks in the external cladding of the assemblies. Although a full examination of the assemblies has never been carried, out, it is believed that most of them are damaged. It is difficult to specify the exact number of damaged assemblies., but according to different data returns, there are about 300 of them. Bellona Foundation researchers estimate that at least 40%-50% of total number of assemblies are is damaged.
From a perspective of radiation safety, the process of loading and unloading of the 2-A and 2-B tanks is unsafe. In an attempt to stop the spread of radioactive gases and dust around the whole area of the base covering clothes and skin of the working personnel, an upgraded ventilation installation for the concrete tanks was built. In the 2-A and 2-B concrete tanks a lid was installed at a height of about 2.5 metres and a building to contain the ventilation system was constructed. The lid of each tank was made of metal plates tightly set together, and was placed on metal posts. The ventilators were intended to push the air between the lid and the casks with spent nuclear fuel to the filters and then to the outside, but the lid construction and ventilation system did not perform as intended. Consequently, during its operation many parts of the system broke down and required reparation.
The concrete tanks for dry storage do not meet present nuclear safety requirements (PBYa 06-00-88). Both the storage area and the construction constitute a potential threat to the environment and population living in the immediate area. In the event of an accident, the storage lacks any design to d to minimise or tackle the consequences. Finally, the concrete storage is situated on the slope of the hill 350 metres from the water line. In case of an accident there would be a high probability for runoff from the storage and into the sea.