Risk Ranking for B

Pipe and EPRI BPWORKSTM Softw

Chris Burton, FENOCDavid Smith, EPRIIndustry/NRC Meeting on BurSeptember 21, 2010 White F
What is Risk Ranking?

• Risk Ranking is a method to assess the like

and consequence of postulated failures of scomponents

• Result is an importance determination whic

© 2010 Electric Power Research Institute, Inc. All rights reserved.

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appropriate resources to be applied commewith the determined importance

• American Society of Mechanical Engineers 

has developed specific procedures and profor using a Risk Informed approach
Risk Ranking Process

• Risk ranking process for the Buried Piping Integrity 

Initiative needs to meet the intent of the EPRI guid(“Recommendations for an Effective Program to Cthe Degradation of Buried Pipe”)

• Utility responsibility to evaluate the tool and the re

© 2010 Electric Power Research Institute, Inc. All rights reserved.

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• NEI 09-14 guidance will be clarified• Risk ranking software is only one of the tools used 

establish inspection priority

• BPIG venue for comparing experience • INPO evaluations

– Focus area on buried piping programs
Insights for Buried Pipe Risk Ranki

• Widespread, random or low value excavations and 

inspections of buried pipe can damage other buriecommodities and create more consequential haza

• Inspection of pipe underneath or nearby buildings 

safe plant operations and maintenance

• Ins

pections should be chosen 

predicated on overa

© 2010 Electric Power Research Institute, Inc. All rights reserved.

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p p

safety

– Value of Inspection verses Risk of Inspectio

• Low value excavations and inspections can result 

– Inadvertent damage to plant equipment– Impact to safe plant operations and maintenance– Increases in outage durations
Risk Informed Ranking for Class 1 W

• Risk Ranking is recognized in ASME Code Case 

560-2 for selection of ASME Class 1 piping welds examination

– Evaluate probability and consequences of failu

focus on elements in the highest risk group

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– Probability considers relevant degradation 

mechanisms

– Consequence considers break size and operat

mode with highest impact on plant safety
CC N-560-2 Risk Matrix

Table I-8

RISK MATRIX FOR PIPE SEGMENTS

RISK GROUPSHIGH – CAT 1,2 &3MEDIUM – CAT 4 & 5LOW – CAT 6 & 7

CONSEQUENCE CATEGORY

NONE LOW MEDIUM 

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FAILURE POTENTIAL

HIGH CATEGORY 7 CATEGORY 5 CATEGORY 3 

MEDIUM CATEGORY 7 CATEGORY 6 CATEGORY 5 

LOW CATEGORY 7 CATEGORY 7 CATEGORY 6 
Risk Ranking for Buried Pipe

• Philosophy is similar to Code Case N-560-2

– Degradation mechanisms typically different tha

primary piping

– Since most buried pipes do not have a high imp

plant safety, other consequences also consider

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• An important factor is that Risk Ranking is only on

many tools to assist in the inspection planning pro

and does not specifically identify inspection locatio

• Priority for inspection increases when two of more 

tools identify the same location to have a heightenof unacceptable degradation 
Other Tools for the Plant Owner

• Pipe-to-soil potential measurements of the Cathodi

Protection system show a location to be outside NArecommended criteria

• Over-the-Line surveys (e.g., DCVG, ACCA) identify 

that may have significant degradation to the coatin

© 2010 Electric Power Research Institute, Inc. All rights reserved.

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• Plant experiences (internal and external)• Trending of past inspection results• Areas that industry experience has found to be of h

(e.g., locations where the pipe enters or exits the s

• Results of guided wave ultrasonic examinations• Results of ID visual examinations (crawlers, borosc

cases where ID degradation is a significant concer
BPWORKSTM

• BPWORKSTM is one of the tools developed to Risk Ran

Piping segments

– BPWORKSTM developed and supported by EPRI

• Version 1.0 released December 2008• Version 2.0 to be released in November 2010

• Determines Likelihood versus Consequences matrices

© 2010 Electric Power Research Institute, Inc. All rights reserved. 9