Generic safety issue 106. Piping and the use of highly combustible gases in vital areas

General Design Criterion 3, Fire Protection, in Appendix A to 10CFR Part 50 states that Structures, systems and components important to safety shall be designed and located to minimize, consistent with other safety requirements, the probability and effects of fires and explosions. With respect to this criterion, it is noted that combustible gases such as hydrogen, propane, acetylene, and methane are used during normal operation of nuclear power plants as well as in plant laboratories. All of these gases should be considered with respect to their onsite storage requirements as well as their distribution and use in plant buildings. Hydrogen is the most prevalent combustible gas used in nuclear power plants and is of principal interest. The safety issue represented by hydrogen, propane, acetylene, methane, and other combustible gases is identified as Generic Safety Issue (GSI) 106, Piping and the Use of Highly Combustible Gases in Vital Areas. It was identified in NUREG-0705 and is related to GSI 136 which is concerned with the new uses of large quantities of hydrogen and oxygen in BWRs for the HWC system. The staff approval of EPRI topical report NP-5283-SR-A in July 1987 was the resolution of GSI 136. This EPRI report provides guidance for the design, construction, and operation of permanent hydrogen systems for the hydrogen water chemistry applications. In the acceptance letter, the staff referred to recent potentially hazardous events involving hydrogen supplies for generator cooling and the volume control tank for PWRs and suggested that EPRI modify the report to include guidance for these applications. This modification was not made