Principal semiproducts for pressure vessels are forged rings and plates. Plates are subsequently hot-stamped to the form of spherical or elliptical dishes for bottoms and covers.

Rings for integral RPVs will be about 4m long. 6-7m of outer diameter and 250 — 300 mm thick. flange-rings will be shorter with the wall thicknes about 500 mm — There is not such need of complicated thick-walled nozzle rings as at PVR pressure vessel. Plates for dishes will have to have diametres about 10m. It is not excluded to make the part by welding.

Existing procedures of heat — treatment of forgings for quality Cquenchlng. tempering) give high certainty in reaching homogenous structure and mechanical properties even in very thick valIs.

Velding

Vessels are welded from individual rings and dishes by circumferential welds. Automated submerged-arc welding to a narrow gap is generally applied. A promissing method could be electron beam technique which is applicable to large material thicknesses and allows the performance of high-quality welds in short time spans.

The simultaneous heating by gas flame or by electricity is applied during the welding.

The number of circumferential velds in an integral RPV will be 4-8.

The necessary welding equipment consists of a welding automat, rotating positioners of an appropriate loading capacity and of a heating device (electric heaters or gas torch). Monitoring and registration of welding parametres is required.

Cladding

Cladding is performed by automated submerged-arc method by using strip or wire (multiple wire) electrodes: plasma technique is a pespective method.

Following i-equlrements have to be fulfilled when cladding1 •

— the cladded surface must be clean. vithout impurities and sulphur Inclusions which is assured by piercing ingots by the mandrel which removes the central part of the ingot containing segregates, or by using hollow ingots.

— proper laying of individual beads and their mutual overlapping,

— an optimized heat input which is important for the depth and properties of the heat-affected zone under the cladding

All the measures are aimed at eliminating the formation of underclad cracks.

The cladding equipment consists of positioners (rotating ones for cylindrlc rotating ones for spherical eliptical and heating device.