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Nuclear Safety Cooperation

R2.02/94 All VVER, tightness assessment

  • Closed
All Countries
Benefitting Zone
€ 1,391,670.42
EU Contribution
Contracted in 1995
Technical Assistance to the Commonwealth of Independent States


Type of activity

Design Safety


Services and Supplies

Contracting authority

European Commission

Method of Procurement

(FR2007) Restricted Call for Tender - External Actions


08/01/1996 - 08/02/1998



Project / Budget year
  • WW9406 Nuclear Safety 1994 / 1994
  • WW9306 Nuclear Safety 1996 / 1993


The project aimed to improve the leak tightness of the primary coolant pressure boundary of all VVER (and secondary pressure boundary of the SGs) by designing and testing new sealing systems later to be installed on all bolted flange connections like RPVs, pressurizer, SG collectors and similar bolted flanges in the NPP.
Within this project the necessary technology had to be transferred to Rosenergoatom, and equipment for re-machining the flanges and gasket grooves had to be supplied, as well as some special gaskets. The redesigned flanged connections had to be tested on real size models in an existing test facility in Russia by Rosenergoatom.


The outputs as per TOR have been achieved and approved by the Beneficiary. The same applies to the additional outputs as per Addendum to the Contract. The Beneficiary was provided with new capabilities, hardware and software to be able independently to design and disseminate the results to all VVERs.
The new sealing system was designed based on flexible metal o-rings with an elastic core called Helicoflex.
The solution required a new design and as a consequence a machine for on-site machining the flange joints and grooves. The Beneficiary was provided with tools and new calculation capabilities.