Safety-related Residual Heat Removal Chains of German Technology Pressure Water Reactors (Light and Heavy Water)

摘要

Introduction The Nuclear Power Plants (NPPs) with Pressure Water Reactor for enriched fuel (PLWR, Pressurized Light Water Reactor) and for natural uranium (PHWR, Pressurized Heavy Water Reactor), developed in Germany, are largely identical in their basic design. However, there is a striking difference in the scope of the main reactor systems. While in PLWR these only consist of Reactor and Reactor Coolant System including Pressurizer and Pressurizer Relief Tank, in PHWR the Moderator System is added. In power operation of a PLWR, the entire thermal reactor power is transferred to the water/steam cycle via the Steam Generators. In PHWR, on the other hand, part of the power has to be removed - at a lower temperature level - from the moderator, which is spatially separated from the main reactor coolant within the Reactor Pressure Vessel, but is kept at the same pressure via function-related compensating openings. This portion of power is used to preheat the feed water before it enters the Steam Generators. The Moderator System installed for this purpose can also be used in a second function as the inner link in the Residual Heat Removal Chain (RHRC) for cooling the Reactor after it has been switched off. In PLWR the analog system is operated exclusively for the removal of residual heat from the Reactor and, if necessary, the Fuel Pool. In the following, the development steps of the RI-IRC of both NPP lines are shown and the main differences between both NPP-types in this regard are explained by comparing the most recently erected plants, DWR 1300 MW (KONVOI) and Atucha 2.