A-Sa_Erra_2009.pdf

ERRATAtoASME/ANS RA-Sa2009Standard for Level 1/Large Early Release FrequencyProbabilistic Risk Assessment for Nuclear PowerPlant ApplicationsOn page 2,insert the following two paragraphs at the end of 1-1.3.3:It is intended that by meeting all the SRs under a given HLR,a PRA will meet that HLR.Thetechnical requirements section of each respective section of this Standard also specifies the requireddocumentation to facilitate PRA applications,upgrades,and peer review.The SRs specify what to do rather than how to do it,and,in that sense,specific methods for satisfyingthe requirements are not prescribed.Nevertheless,certain established methods were contemplatedduringthedevelopmentoftheserequirements.Alternativemethodsandapproachestotherequirementsof this Standard may be used if they provide results that are equivalent or superior to the methodsusually used and they meet the HLRs and SRs presented in this Standard.The use of any particularmethod for meeting an SR shall be documented and shall be subject to review by the peer reviewprocess described in Section 1-6.On page 25,insert the following two paragraphs at the end of 1-3.6.2:For risk-informed applications,the terms“relevance”or“significance”can be evaluated from differ-ent perspectives.“Relevance”is related to the applicability of a hazard group.“Significance”ofsequences,contributors,cutsets,etc.can be measured either by their contribution to a specific hazardgroup(e.g.,fires within the plant)or by their contribution to the overall plant risk.When performinga baseline PRA using this Standard,addressing“significance”requires an assessment and characteriza-tion of the relative contribution of risk contributors within a given hazard group.For example,asupporting requirement in Part 4 of this Standard that identifies an action to be performed for“signifi-cant”fire zones is assessed within the context of the other fire risk contributors only(i.e.,within theFire PRA itself).However,when performing a risk-informed application,it is often more appropriateto evaluate“significance”across all relevant hazard groups.When the risk-informed application isimplemented,it is necessary to determine whether it would alter baseline assumptions or plant condi-tions such that“significance”within a hazard group is now altered or more uncertain.The evaluationof“significance”at this level may or may not require further analysis within a hazard group.In meeting the requirements of this Standard,those supporting requirements associated withassessing or identifying levels of significance are first performed for the baseline PRA models that areusedtoquantifyaverageannualestimatesofriskfromallhazardgroups.Withregardtotheapplicationsprocess of this Standard(Section 1-3),the assessment or identification of significance(Box 12 of Fig.1.3.1-1)is to be evaluated first across all risk contributors within the context of the change(s)beingproposedbytherisk-informedapplication,andthenwithineachhazardgrouptodetermineifadditionalanalysis is necessary.THE AMERICAN SOCIETY OF MECHANICAL ENGINEERSThree Park Avenue,New York,NY 10016-5990A1531EApril 2009Copyrighted material licensed to Stanford University by Thomson Scientific(),downloaded on Oct-05-2010 by Stanford University User.No further reproduction or distribution is permitted.Uncontrolled when printed.