The suitability of the old and operating mines in Finland for the storage and final disposal of the different kinds of nuclear wastes was analysed. Due to several unfavorable factors related to either the design or stability of the free spaces, the geological conditions, or the environmental activities, the possibilities of using existing mines instead of conctructing special new waste repositories proved very small.

AIM AND SCOPE OF THE STUDY

The study aims at evaluating the possibilities of using existing mines and corresponding underground facilities for temporary storage and final disposal of nuclear wastes. These possibilities are compared with the.alternative plans, i.e. the underground repositories that.should be.constructed especially for nuclear wastes. The scope of the study included any kind of nuclear wastes as divided into three groups. The waste groups and their estimated amounts from the four existing finish nuclear power plant units, which arecalculated to operate approximately 30 years, are as follows:

  1. .high-level waste (mainly spent fuel)2100 t,

  2. low- and medium-level wastes comprising various vet materials like ion exchange resins, filtration wastes and, evaporator concentrates and mixed solid particles like filters, scrap, and large metal components(after treatment) 17000 m3

  3. mere solid low-level waste (after treatment) 6000 m3

Three main questions were raised which the study endeavours to elucidate:

  1. Are there such underground facilities (and where) which could (at least partly) be easily transformed into safe repositories for the different kinds of nuclear waste?

  2. Can the present mining activities in some mine offer a reasonable opportunity for constructing a deep repository especially for the mentioned types of wastes in the vicinity?

  3. Is there any other way of exploiting the existing facilities considering the disposal of nuclear wastes?

In order to answer these questions, a concise principal examination of all kinds of rock openings existing in Finland was done. According to it, all the underground facilities that have been constructed for some constant activity near the earth''s surface (transport, water conveyance, defence, power generation, industry, etc.) could be excluded. Their aim and use are in a clear disagreement with nuclear waste disposal. Whereas the utilization of deeper mines - especially the already abandoned ones - can be taken into consideration. In principle the underground mine caverns are solely a byproduct of ore mining and their existence has no independent purpose what so ever.

The examination of the required possibilities afforded by the mines was carried out in two stages. Firstly, a preliminary inventory of all mine spaces existing in Finland was carried out at the Geological Survey of Finland. This inventory included both operating mines and Old, abandoned ones, divided into deep (over 400 m in depth) and shallow ones. There were altogether 9 deep mines and 72 shallow mines of which adequate information could be acquired for a critical evaluation. Seven of the deep mines and 26 of the shallow ones were still in operation (by 1978).

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