The quick boron supply system (QBSS), being developed as an additional reactor trip system, comprises a system of 4 special loops bypassing the main coolant pumps. Each loop consists of a hydroaccumulator containing concentrated boron acid solution and pipelines with quick-acting valves that do not require electric power for their opening. These valves are opened when the reactor fails to scram. When this occurs concentrated boron solution is pressed out of the hydro-accumulators into the primary loops and further into the reactor. Tn case of a station blackout the boron solution delivery occurs in the period of reactor coolant pump (RCP) coast-down.

The RCPs have a large flywheel inertia which provides the possibility of ejecting all boron concentrate from the QBSS hydro-accumulators. The amount and concentration of the boron solution are chosen to provide a certain equivalency from the viewpoint of reactivity inserted by this system and by the solid absorber scram. Tn fact, this system, being a part of the primary coolant circulation system increases the ‘inherent’ safety of the reactor design.

FIG. XIII-1. Containment and the systems of WWER-1000/392 that used passive principles. (I — reactor; 2 — steam generator; 3 — steam path; 4 — condensate path; 5 — inlet circular header; 6 — PHRS heat exchanger; 7 — PHRS slide valve; 8 — PHRS draught tube; 9 — PHRS exit header ; 10 — deflector; 11 — quick boron supply system; 12 — HA-2; 13 — HA-1; 14 — filtering unit; 15 — tube of passive filtering system; 16 — steam header; 17 — valve).