Belgian experience in applying the {open_quotes}leak-before-break{close_quotes} concept to the primary loop piping
- Tractebel Energy Engineering, Brussels (Belgium)
The Leak Before Break (LBB) concept allows to eliminate from the design basis the double-ended guillotine break of the primary loop piping, provided it can be demonstrated by a fracture mechanics analysis that a through-wall flaw, of a size giving rise to a leakage still well detectable by the plant leak detection systems, remains stable even under accident conditions (including the Safe Shutdown Earthquake (SSE)). This concept was successfully applied to the primary loop piping of several Belgian Pressurized Water Reactor (PWR) units, operated by the Utility Electrabel. One of the main benefits is to permit justification of supports in the primary loop and justification of the integrity of the reactor pressure vessel and internals in case of a Loss Of Coolant Accident (LOCA) in stretch-out conditions. For two of the Belgian PWR units, the LBB approach also made it possible to reduce the number of large hydraulic snubbers installed on the primary coolant pumps. Last but not least, the LBB concept also facilitates the steam generator replacement operations, by eliminating the need for some pipe whip restraints located close to the steam generator. In addition to the U.S. regulatory requirements, the Belgian safety authorities impose additional requirements which are described in details in a separate paper. An novel aspect of the studies performed in Belgium is the way in which residual loads in the primary loop are taken into account. Such loads may result from displacements imposed to close the primary loop in a steam generator replacement operation, especially when it is performed using the {open_quote}two cuts{close_quotes} technique. The influence of such residual loads on the LBB margins is discussed in details and typical results are presented.
- Research Organization:
- US Nuclear Regulatory Commission (NRC), Washington, DC (United States). Div. of Engineering Technology; Electricite de France (EDF), 69 - Villeurbanne (France); Battelle Memorial Inst., Columbus, OH (United States)
- OSTI ID:
- 489302
- Report Number(s):
- NUREG/CP-0155; CONF-9510432-; ON: TI97004806; TRN: 97:011442
- Resource Relation:
- Conference: Seminar on leak before break in reactor piping and vessels, Lyon (France), 9-11 Oct 1995; Other Information: PBD: Apr 1997; Related Information: Is Part Of Proceedings of the seminar on leak before break in reactor piping and vessels; Faidy, C. [ed.] [Electricite de France, Villeurbanne (France)]; Gilles, P. [ed.] [Framatome, Paris (France)]; PB: 773 p.
- Country of Publication:
- United States
- Language:
- English
Similar Records
Applicability of leak-before-break criteria
Additional requirements for leak-before-break application to primary coolant piping in Belgium