The purpose of this appendix is to provide guidance in determining when a change to a nuclear power plant PRA is PRA maintenance and when it is a PRA upgrade, and when peer review is advisable. PRA maintenance and PRA upgrade are defined in Section 2 of the Standard for Probabilistic Risk Assessment for Nuclear Power Plant Applications, ASME RA-Sb-2005. Within the context of Section 5, PRA Configuration Control, para 5.4 requires such a determination and further requires that a PRA upgrade be peer reviewed pursuant to the requirements of Section 6. There is no requirement for PRA maintenance to be peer reviewed.