Concept for the Guarantee of the Integrity of Bolted Flanged Connections in a German Nuclear Power Plant

In nuclear facilities in Germany a systematic treatment of all sealing connections which are opened during the annual shutdowns is performed since several years. Special attention is paid to a design which meets specifications of the bolted flange connections (BFC’s). Apart from the use of suitable and certified materials this includes also the calculation of the required torques in accordance to the present rules. For the calculation procedure the nuclear code KTA 3211.2 (draft 2003) is applied which allows a tightness proof of the BFC, besides a stress analysis. For this calculation, experimentally achieved gasket characteristics according to DIN 28090-1 are required, which are either supplied by the gasket manufacturers or determined in the amtec test laboratory. The geometry and material data of each BFC are stored in a special data base. In addition, the data of the operating state as well as the design and test loading cases are included in the data base, so that all inputs for a later calculation are available. The results of the calculation which must be checked and approved by an expert third-party are stored in the flange data base, too (assembly state settings of each flange connection). On this base individual flange data sheets can be provided to the flange fitter teams that include all necessary information for assembly of each BFC (bolts, nuts, gasket, geometry and material specifications, lubricant, etc.).