Because the activity and mass of radioactive equipment of the integral reactors considered are substantially lower than those ones of conventional NPP reactors, this influences irradiation doses.

According to calculations personnel irradiation dose during VPBER-600 and AST-500 unit decommissioning is 2.5-3.5 man. Sv taking account of plant-level systems).

The radiological effect on the inhabitants during decommissioning was evaluated proceeding from the amount of radioactive product releases which can enter the atmosphere. The result obtained was that during AST-500 equipment and reactor vessel disassembly the reactivity release to the atmosphere including cleaning in wet scrubbers and aerosol filters gives the value ~3 mCi for Co 60, that is -20% of the specified limit.

6. COMPARISON OF DECOMMISSIONING CONDITIONS FOR INTEGRAL AND

VVER-TYPE REACTORS

The advantages of integral reactor decommissioning emerge when comparing decommissioning conditions for VPBER-600 and VVER-440 "Lovisa" (Fig.9).

The concept of "immediate" dismounting in 2 years following termination of preparatory work is suggested both for "Lovisa” and VPBER-600 reactors. The main problem of NPP "Lovisa" decommissioning is the handling of the hot reactor vessel which must be broken up in hot chambers by remotely controlled equipment and be removed in large thick-walled casks to stores or the reactor vessel and equipment must be removed and disposed off as a whole. One should note that special manipulators and other expensive facilities are not required for breaking up the VPBER-600 reactor vessel.

Comparison results show that in spite of higher power a more prolonged operation period and shorter hold-up time following shutdown, safety characteristics (activity value, radwaste amount, irradiation doses) during VPBER-600 reactor decommissioning are tens and hundreds times smaller than those for VVER-440 reactor.

7. CONCLUSION

So, the structural features of AST and VPBER reactors (including the integral layout of their main primary equipment and location of a leaktighr reactor in an additional guard vessel) ultimately simplify the technologically difficult, radiologically dangerous and expensive decommissioning of PWR (VVER)-type NPP reduce the amount of radwaste and the costs and make integral reactor decommissioning safe for both personnel and inhabitants.

[1] Dimensions were taken from available literature. Heights and weights of vessels were determined approximately after subtracting the ones of covers.

[2] Dimensions and weights have been determined from Г21. 13].[4] by approximation after subtracting covers.

From the comparison of pressure vessels of PVRs. BVRs and those of integral reactors it follows, that diameters and lengths of last ones are comparable with those of BVRs. Due to the higher operating pressure which is equal to operating pressure of PVRs. walls of integral reactor vessels are more thick (in the range of 250 — 300 mm) and their weights exceed the weight of the to date heaviest RPV of ATUCHA 2 (975 t).