V. S. KUUL. A. V. PICHUGIN, O. B. SAMOILOV

OKB Mechanical Engineering,

Nizhny Novgorod,

Russian Federation

Abstract

World nuclear power rends constantly to decrease the permitted ultimate dose of NPP personnel and population during normal operation and accidents and NPP decommissioning.

1. ISSUES AND HOW TO DECIDE THEM WHEN DECOMMISSIONING NPP

The conditions and radiological safety of reactor decommissioning project are determined by:

1) decommissioning concept ("immediate" or "delayed" dismounting).

2) structure and equipment radioactivity;

3) radioactive waste amount (activity, mass, volume);

4) technology of removable and non-removable equipment;

5) doses of personnel and population.

It is known, when decommissioning NPP with BWR or PWR, that radioactive waste forms an activity of more than 10 MCi. The total mass of waste at NPP decommissioning is several hundreds thousands of tons, and about 1-2% of the waste has high and medium radioactivity, which should be disposed off. The potential danger of radioactivity requires protective measures, eliminating release of radioactive materials into the environment.

Irradiation doses of the personnel involved in NPP decommissioning range from several hundreds to tens of thousands of man. rem depending on the decommissioning strategy adopted.

One of the main problems of NPP decommissioning is handling of hot large equipment. NPP reactors accumulate substantial radioactivity (up to 10 5 Li), which causes high radiation levels from 1 to 10 Sv/hr

Dismounting and disassembly of vessel and structures requires development of special remotely controlled equipment, heavy protective flasks and, hence, large costs or prolonged plant preservation that reduces irradiation doses, potential releases and environment contamination.

But, from the point of view of economic, quick rehabilitation of the site is not evidently advantageous as compared with immediate dismantling.