Improved Testability Provisions for Boiling Water Reactors

Safety Systems (Emergency Core Cooling and Reactor trip) circuits at Peach Bottom were provided with complete, overlapping zone, on-line testability. This was accomplished by adding to and greatly expanding the coverage of the manufacturer installed test plugs. The general philosophy is that with proper insertion of test plugs, full logic initiation can be tested including valve operation and pump starts. No jumpers or lifted leads are required and injection into the core is defeated during test. These provisions simplified the testing program for Technical Specification (Tech Spec) requirements and eased licensing considerations. Although applied to a BWR, the principles outlined are applicable to any system or plant using digital inputs.