J. KRALOVEC

Skoda Nuclear Machinery Plzen,

Plzen, Czech Republic

Abstract

Integral water-cooled reactors are typical with eliminating large-diameter primary pipes and placing primary components, і.e. steam generators and pressurlzers in reactor vessels. This arrangement leads to reactor pressure vessels of large dimensions: diameters. heights and thick walls’and subsequently to great weights. Thus, even medium power units have pressure vessels which are on the very limit of present manufacturing capabi1 іties. Principal manufacturing and inspection operations as well as pertinent equipment are concerned: welding, cladding, heat treatment. machining. shop-handling. non-destructive testing, hydraulic pressure tests etc.

The transport of such a large and heavy component makes a problem which effects its design as well as the selection of the plant site. Railway, road and ship are possible ways of transport. each of them having its advantages and limitations.

Specific features and limits of the manufacture and transport of large pressure vessels are discussed in the paper.

INTRODUCTION

Though the Czech Republic at present time does not intend to develop and construct integral reactors, a contribution on problems of manufacturing and transportation of large pressure vessels which is based on the experience from the manufacture of VVER reactors can be inspiring. In addition to that. the situation in the Czech Republic can be representative to other countries which could potentially utilize integral reactors. The situation is typical with following features:

— inland position.

— complicated terrain.

— geological situation limiting the choice of construction sites.

— lack of water transport ways.

— complicated network of railways and roads having limited transporting profiles as well as limited bearing capacities.

In addition to that, heavy machinery factories which are qualified to produce nuclear components are located out of the direct reach of water-transport.

Integral water-cooled reactors are typical by the elimination of large — diameter primary components i. e. steam generators and pressurizers in reactor vessels. This arrangement leads to reactor pressure vessels of large dimensions: dimeters, heights and thick walls and subsequently to great weights. Thus, even medium-size power reactors have pressure vessels vhich are on the limit of present manufacturing capabilities.

There are 424 reactors in operation in the world, from which are 239 PVRs. 89 BVRs. 2 PHVRs (with a pressure wessel). Under construction there are 48 PVRs and 6 BWRs. for which pressure vessels have been mostly manufactured. Totally. 384 RPVs have been manufactured.

Not ice

Materials will be used which have for PVRs and properties of which are uniformity of chemical composition technological properties. even for very and extremely heavy forgings.

Following materials should be considered:

Ni-Мо-Сг type: SA 508 C1.2. 22NiMoCr37. SQV2A.

Mn-Mo-Cr type: SA 508 C1.3. 16MND5. SA 533 Gr. B.

Cr-Mo< N і)type; 15Ch2MFA,15Ch2MNFA.

and corresponding Japan steels. eventually improved mod і f і cat і ons-

The technology of casting extremely large ingots Cup to 600t) from these steels have been mastered by leading firms assuring the required homogen іty of chemical composition and high purlty.