ML071170254
| ML071170254 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 04/12/2007 |
| From: | Davant G Entergy Operations |
| To: | Bhalchandra Vaidya NRC/NRR/ADRO/DORL/LPLIV |
| Vaidya B, NRR/DORL/LP4, 415-3308 | |
| Shared Package | |
| ML071170244 | List: |
| References | |
| Code Case N-716, GG-ISI-002, TAC MD3044 | |
| Download: ML071170254 (12) | |
Text
DRAFT RESPONSES TO GG-ISI-002 RAI SET #1 REQUEST FOR ADDITIONAL INFORMATION RISK-INFORMED INSERVICE INSPECTION RELIEF REQUEST ENTERGY OPERATIONS, INC.
GRAND GULF NUCLEAR STATION DOCKET NO. 50-416
- 1) Entergy, requests authorization to implement a risk-informed inservice inspection (ISI) program based on American Society of Mechanical Engineers Boiler and Pressure Vessel Code Case N-716 (N-716). There appears to be, however, some differences between the methodology in N-716 and the method applied by Entergy as described in the submittal.
a) Table 3 in N-716 discusses high, medium, and low failure potential and pairs these potentials with degradation categories large brake, small leak, and none respectively. It does not appear that this table was used in the submittal. Was this table used in the submittal? If not, what was used in lieu of Table 3?
Response - The information contained in Table 3 of N-716 was used in the GGNS application and submittal. The information is identified in Table 3.4-1 and Table 5 of the submittal. The information is contained in the column identified as Failure Potential. This column is further divided into two sub-columns (i.e. DMs and Rank).
The Failure Potential Rank for HSS locations is then assigned as high, medium or low depending upon potential susceptibly to the various types of degradation. [Note:
LSS locations were conservatively assumed to be a rank of medium (i.e. Assume Medium). See response to question 3b.
b) Section 5(c) in N-716 case does not appear to provide a with probability of detection (POD) and without POD option in the calculation but the submittal includes one set of estimates for with POD and another w/o POD in Table 3.4-1. Please clarify how the with POD and w/o POD columns in Table 3.4-1 are consistent section 5(c) in N-716.
Response - It is true that N-716 does not discuss the two options presented above. The GGNS submittal contained both options in order to be consistent with previous RI-ISI submittals which contained both options. These two sets of analyses are typically conducted to provide a sensitivity of the delta risk evaluation with respect to assumptions on POD.
c) The estimates in the w/o POD column in Table 3.4-1 seem to all include a standard POD of 0.5. Is this correct? If not, please provide some examples using the conditional core damage probability (CCDP) values from page 11 of 28 to produce the entries in Table 3.4-1.
Response - That is correct. The w/o POD column applies a POD of 0.5 for both the Section XI program and the N-716 program. Thus, there is no extra credit assumed for an N-716 inspection as compared to Section XI inspection as to inspection effectiveness (e.g. due to larger inspection volumes in the N-716 program).
d) Section 7 in N-716, Program Updates, includes several steps that make up a program update. Page 14 of 28 in your submittal states that, [u]pon approval of the RIS_B Program, procedures that comply with the guidelines described in Electric Power 1 of 12
DRAFT Research Institute (EPRI) TR-112657 (EPRI Topical) will be prepared to implement and monitor the program. Please identify the Sections in the EPRI Topical that describe the update program that Exelon intends to implement. Please describe and compare the update program that Exelon intends to implement against the characteristics of such a program as described in Section 7 of N-716.
Response - The wording in the GGNS submittal was based on previous RI-ISI submittals. While the intent of both updating processes (EPRI TR-112657 and N-716) is the same, Entergy will meet the wording of N-716.
- 2) The relationship between N-716's guideline that, any piping segment whose contribution to core damage frequency (CDF) is greater than 1E-6/year is a high safety significant (HSS) segment, and the EPRI Topical guidelines for safety significant categorization is unclear.
For example, a low consequence segment in the EPRI Topical methodology has a CCDP less than 1E-6, an identical numerical value but a different metric than the 1E-6/year guideline in N-716. Page 3-8 in the EPRI Topical provides an explanation that the CCDP and conditional large early release probability (CLERP) ranges were selected, to guarantee that all pipe locations ranked in the low consequence category do not have a potential CDF impact higher than 1E-8 per year or a potential large early release frequency (LERF) impact higher than 1E-9 per year. Inspection of Table 3.1 in your submittal also indicates that there are no entries in the CDF > 1E-6" column indicating that no segments in the Grand Gulf flooding probabilistic risk assessment (PRA) exceeded this guideline.
a) The N-716 code case section 2(5) does not include a LERF guideline analogous to the CDF guideline, and Table 3-1 in your submittal includes a column for CDF but not for LERF. Please explain why a LERF guideline is not included as a guideline in parallel with CDF.
Response - N-716 provides five criteria for determining the classification of welds. The CDF guideline for PRA internal flood segments was added to provide additional margin, as applicable, to the initial scope of high safety significant welds (i.e. a belts and suspenders approach). As discussed in the whitepaper, N-716 is based upon lessons learned from a large number of risk-informed applications (e.g. RI-ISI, RI-BER). With respect to defining the scope (e.g. HSS vs. LSS), these insights include both the impact on CDF and LERF (e.g. RI-BER insights). In the whitepaper, eight plants (4 BWRs, 4 PWRs) were compared to the N-716 criteria and N-716 was shown to provide for more inspections than traditional RI-ISI approaches even when the criterion of section 2(5) is not used.
Additionally, as a final step, N-716 requires an assessment of the impact on plant risk which includes both CDF and LERF. This change in risk assessment includes so-called risk category 6 and 7 locations, which are not required to be included in the EPRI RI-ISI delta risk assessment. Risk acceptance criteria for these metrics, are consistent with other RI-ISI applications and meet Reg. Guide 1.174 criteria.
b) Please provide a discussion justifying the guideline value for CDF selected in section 2(5) in N-716 (i.e., 1E-6/year).
Response - N-716 provides five criteria for determining the classification of welds. The CDF guideline was added to provide additional margin, as applicable, to the initial scope of high safety significant welds (i.e. a belts and suspenders approach). As discussed in the whitepaper, N-716 is based upon lessons learned from a large 2 of 12
DRAFT number of risk-informed applications (e.g. RI-ISI, RI-BER). In the whitepaper, eight plants (4 BWRs, 4 PWRs) were compared to the N-716 criteria and N-716 was shown to provide for more inspections than traditional RI-ISI approaches even when the criterion of section 2(5) is not used.
Section 2(5) of N-716 provides an additional criterion that can only potentially increase the scope of high safety significant locations (i.e. will only increase the number of inspections). Consistent with EPRI TR-112657 (Section 3.3.2), the value of 1E-6 (CDF) was chosen as a value that is suitably small and is consistent with the decision criteria for acceptable changes in CDF found in Reg. Guide 1.174. Further, the guideline value is consistent with the philosophy found in EPRI TR-105396 (PSA Applications Guide). Allocating resources (e.g. NDE) on components below this guideline value (e.g. section 4.2.2) will provide negligible risk benefit while expending unnecessary worker dose and radwaste.
Finally, the assessment of the impact on plant risk (Section 5 of N-716) due to implementing N-716 provides an additional level of assurance that the overall impact on plant risk (CDF and LERF) will be acceptably low. Risk acceptance criteria for these metrics, are consistent with other RI-ISI applications and meet Reg. Guide 1.174 criteria. This change in risk assessment also includes so-called risk category 6 and 7 locations, which are not required to be included in the EPRI RI-ISI delta risk assessment.
c) Please provide a list of all the piping segments that were compared to the >1E-6/year criteria along with the CDF and LERF estimates, the pipe failure frequency, and the CCDP and conditional large early release probability for each segment.
Response - The scope of piping reviewed against this criterion consisted of Class 2 piping not classified as HSS (e.g. BER), Class 3 and non nuclear safety piping. The GGNS internal flooding study was used to conduct this comparison. The GGNS internal flooding study was performed in a step by step manner with an initial qualitative screening to identify the significant flood events and a quantitative analysis to determine the contribution to core damage for the most significant flood scenarios.
As opposed to a segment by segment evaluation, the GGNS internal flooding study was performed by defining flood zones, identification of their contents (e.g. important equipment), identification of potential flood sources, identification of flood propagation pathways, a qualitative screening analysis and a quantitative analysis of potentially important flood scenarios.
With respect to flood frequency, only the largest flood initiator per system in each flood zone was considered, if the frequency and consequence of the larger flood initiator were approximately of the same magnitude as those of the smaller ones. If the frequency of the smaller flood initiators was higher and their consequences similar to that of the larger initiator, the smaller flood initiator was considered the primary flood source for that particular system. For screening purposes, this is conservative from an internal flooding study perspective. It is also conservative from an N-716 perspective because some of these flooding sources (e.g. tanks) may not be within the N-716 scope (e.g. piping).
An example of the process is described as follows:
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DRAFT A flooding scenario in flood zone A revealed that a Flow Control Valve (FCV) in support of system Z would become submerged. Using the component failure matrix developed for the internal flooding study, this FCV is identified to fail when submerged. The fault tree for system Z is reviewed and it is found that the FCV failure leads to the failure of the in-line pump, which results in system Z unable to deliver flow to its loads. Therefore, the entire Z system is failed due to submergence of the Flow Control Valve. Subsequent to the analysis of the failure of system Z, the dependency matrices were used to determine which other systems would fail (e.g. IA system failure would lead to failure of several mitigating systems, including CRD, Containment Venting, Feedwater, Condensate, PCS and support systems, including CCW, TBCW and PSW).
A listing of all failed mitigating systems for each flooding scenario, as well as available mitigative systems, was compiled for use in the qualitative analysis.
Flood initiation frequency was on the order of 1E-3 to 1E-04 per year per zone. The failure of a single equipment train is on the order of 1E-2, except for some equipment (e.g. RCIC) which can be higher (e.g. 1E-1). Therefore, the approximate likelihood of a flood plus two unrelated, random system failures is 1E-7 to 1E-8 / year. Due to the approximate nature of these estimated values, it is possible that a flood plus two random failures could occur with some significant probability. Thus, any flood scenario for which two or less random failure could produce core damage was analyzed in more detail. Similarly, any flood scenario for which three or more random system failures could produce core damage was screened out. Typically, this screening was done on a zone by zone basis. Thus, individual segments within the zone would have a likelihood of core damage less than that for the entire zone.
Based on the above, two flooding scenarios required detailed quantification. These scenarios involved the plant service water system (CDF = 1.99E-7) and the standby service water system (CDF = 2.26E-8) which after detailed quantitative assessment fall below the criterion of section 2(5) of N-716.
d) Please provide any observations made during any independent reviews of the Grand Gulf flooding PRA or observations from the internal events review that are also applicable to the flooding analysis. Please describe how these observations have been resolved such that there is confidence that segments that have a CDF greater than the guideline value have been identified.
Response - As indicated in the initial submittal, the industry peer review of the GGNS PRA was conducted in August 1997. The facts and observations (F&O) from this review were characterized with regard to level of significance and given scores of A, B, C or D. An F&O with a level of significance of A is one that is extremely important and necessary to address to assure the technical adequacy of the PSA or the quality of the PSA. These should be addressed promptly. An F&O with a level of significance of B is one that is important and necessary to address, but may be deferred until the next PSA update. C F&Os are of marginal importance, but are considered desirable to maintain maximum flexibility in PSA Applications and consistency in the industry. D F&Os are editorial or minor technical items left to the discretion of the utility. As such the important F&Os to PSA technical adequacy and quality are those categorized as A or B. Within the A & B F&Os, only two B F&Os are on the internal flooding analysis.
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DRAFT The first B F&O stated that the dependency table in the internal flooding analysis did not list instrument air as a support system. No changes were necessary to address this comment since instrument air was clearly listed as a support system in various locations in the documentation, including the mitigating systems versus support systems dependency table and the support systems versus support systems table.
The remaining B F&O documented issues associated with a single flooding sequence. The first issue questioned whether there was a thermal hydraulic calculation which supports the use of a single Control Rod Drive (CRD) pump for success following a manual emergency depressurization. This issue was addressed by developing a calculation for CRD success criteria. As a result of the calculation, CRD is now credited only after some other system (such as, RCIC or HPCS) has provided core injection for approximately 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> and two CRD pumps operate. This modeling is incorporated in the modeling used to develop CCDPs for the N-716 analysis. The second issue pointed out that the text description of a sequence indicated that it resulted in core damage while the event tree indicated that the core was OK. The text description was in error and since the event tree was the input into the development of the overall model fault tree, there was no related impact on the PRA results. The remaining issue stated that containment venting is not asked in the sequence; therefore, containment heat removal capability is unknown. That was basically a true statement as it was not necessary to vent the containment in order to determine the outcome of this sequence. Containment failure does not directly lead to failure of operating injection pumps since the most likely failure location is high in the containment and any steam released into the auxiliary building is not expected to impact these pumps which are low in the auxiliary building.
- 3) Section 5(c) in N-716 does not clearly specify what population of welds should be included in the change of risk estimates and what welds may be excluded. The description of the parameters in the equations in Section 5(c) indicates that any weld that was inspected under Section XI or that will be inspected under the RI-ISI program will be included in the change in risk estimate.
a) Is the population of welds that should be included in the N-716 change in risk estimate all welds that were inspected under Section XI and that will be inspected under the RI-ISI program? If not, where in code Case N-716 is the guidance that reduces the population of welds that should be included in the change in risk estimate Response - The population of welds that need to be included in the change in risk assessment includes all welds receiving NDE except for those that receive only a surface examination and are not susceptible to outside diameter attack (e.g.
ECSCC). This population includes so-called risk category 6 and 7 locations, which are not required to be included in the RI-ISI delta risk assessment. [Note: Table 5 of the GGNS submittal list the surface examination requirements prior to GGNS implementation of N663]
It is the intent of the Code Case authors to update N-716 to reflect this requirement (i.e. exclusion of surface only examinations without outside diameter attack) as well as any other relevant feedback from the pilot plant process.
b) If all welds that were or will be inspected are included in the change in risk estimates in Table 4.4-1 in your submittal, how are the CCDP, CLERP, and the failure frequency 5 of 12
DRAFT estimated for LSS welds?
Response - For CCDP/CLERP, values of 1E-4/1E-5 were conservatively used. The rationale for using these values is that the change is risk evaluation process of N-716 is similar to that of the EPRI RI-ISI methodology. As such, the goal is to determine CCDPs/CLERPs threshold values. For example, the threshold values between High and Medium Consequence Categories is 1E-4 (CCDP) / 1E-5 (CLERP) and between Medium and Low Consequence Categories are 1E-6 (CCDP) / 1E-7 (CLERP) from the EPRI RI-ISI Risk Matrix. Using these threshold values streamlines the change in risk evaluation as well as stabilizes the update process. For example, if a CCDP changes from 1E-5 to 3E-5 due to an update, it will still be below the 1E-4 threshold value and the change in risk evaluation would not need to be updated.
The appropriateness of the above values was determined from the internal flooding study. As discussed above, for each flooding zone, a listing of all failed mitigating systems for each flooding scenario, as well as available mitigative systems, was compiled. The available mitigative equipment was used to determine CCDP/CLERP values. The failure of a single equipment train is on the order of 1E-2, except for some equipment (e.g. RCIC) which can be higher (e.g. 1E-1). In most cases there are significant mitigative equipment available (e.g. more than three trains), or no damage at all, which would allow use of CCDP/CLERP values consistent with the Medium / Low threshold value (i.e. 1E-6 / 1E-07). However, CCDP/CLERP values of 1E-4/1E-5 were conservatively used in the change in risk assessment for all LSS piping.
With respect to assigning failure potential for LSS piping, the criteria are defined by Table 3 of the Code Case. That is, those locations identified as susceptible to FAC (or another mechanism and also susceptible to water hammer) are assigned a high failure potential. Those locations susceptible to thermal fatigue, erosion-cavitation, corrosion or stress corrosion cracking are assigned to a medium failure potential and those locations that are identified as not susceptible to degradation are assigned a low failure potential.
In order to streamline the application, a review was conducted to verify that the LSS piping was not susceptible to FAC or water hammer. This review was conducted similar to that done for a traditional RI-ISI application. Thus, the high failure potential category is not applicable to LSS piping. In lieu of conducting a formal degradation mechanism evaluation for all LSS piping (e.g. to determine if thermal fatigue is applicable), these locations were conservatively assigned to the medium failure potential (Assume Medium in Table 3.4-1) for use in the change in risk assessment.
Experience with previous RI-ISI applications shows this to be generally very conservative.
- 4) Page 11 of 28 describes how the CCDP and CLERP of different categories of pipe breaks are estimated in support of the change in risk estimates. For example, bounding values for pipe breaks that result in isolable loss-of-coolant accidents (LOCAs) are derived as the product of the CCDP from unisolable LOCAs and the probability of a motor operated valve failing to close on demand. This type of an evaluation can be very analyst specific and essentially bypasses the PRA peer review process upon which the NRC relies to minimize the staff review of the plant specific PRA for each risk-informed submittal.
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DRAFT a) The submittal states that it used bounding CCDP and CLERP values for pipe breaks that result in a LOCA. What are the current CCDP and CLERP values for the different LOCA sizes in the current Grand Gulf PRA? Was one LOCA size selected for all LOCAs and, if so, why is one size sufficient?
Response - The GGNS PRA models a variety of LOCA sizes. LOCA CCDPs were re-calculated to support the previously completed RI-BER application. These values are provided below. As can be seen, Intermediate LOCA is the bounding event. Also, a CCDP/CLERP value of 0.1 was conservatively assigned to develop a corresponding/bounding CLERP. These values (CCDP=5.4E-4 and CLERP = 5.4E-5 were used in the N-716 change in risk assessment for locations that would result in a LOCA.
Initiator Description CCDP
%A Large LOCA 5.19E-04
%S1 Intermediate LOCA 5.40E-04
%S2 Small LOCA 5.31E-06 b) Please identify events modeled in the Grand Gulf PRA that are similar to the isolable LOCA and potential LOCA events quantified on page 11 of your submittal or further clarify why the Grand Gulf PRA can not be used to develop the required estimates. If applicable events in the PRA can be identified, please provide a description of these events and the bounding CCDP and CLERP values for these types of breaks derived from the PRA.
Response - The GGNS PRA does not explicitly model potential and isolable LOCA events, because such events are subsumed by the LOCA initiators in the PRA. That is, the frequency of a LOCA in this limited piping down stream of the 1st RCPB isolation valve times the probability that the valve fails is a small contributor to the total LOCA frequency. The N-716 methodology must evaluate these segments individually, thus it is necessary to estimate their contribution. This is estimated by taking the LOCA CCDP and multiplying this by the valve failure probability.
c) Please describe how the CCDP and CLERP values for non reactor coolant pressure boundary pipe breaks that occur in standby system piping were developed from the Grand Gulf flooding PRA. What is the relationship between this analysis, and the analysis used to implement the N-716 guideline that any segment with a CDF >
1E-6/year should be categorized high safety significant?
Response - Please see responses to 2(c) and 3(b) above.
d) In the Break Location column in Table 3.4-1 in your submittal, there are some entries labeled Class 2". What characteristics results in a Class 2" designation and how are the CCDPs and CLERPs of these welds developed?
Response - The Class 2 designation in Table 3.4-1 is used to identify those Code Class 2 locations that are not HSS because they do not meet any of the five HSS criterion of section 2(a) of N-716 (e.g. not part of the BER scope). With respect to CCDPs/CLERPs, please see the answer to question 3(b).
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DRAFT
- 5) The fourth bullet on page 11 of 28 in your submittal states that CCDP and CLERP values were determined based on the risk informed break exclusion region (RI-BER) evaluation performed for Grand Gulf. How many welds were being inspected in the RI-BER program and how many will be inspected in the proposed RIS_B program? Please summarize the reasons for any change in the number of welds to be inspected in the BER.
Response - Currently there are 24 inspections included within the RI-BER program.
This represents an inspection population that is seven percent of the total BER population. As stated earlier, this program was implemented via the GGNS 10 CFR 50.59 program. Per the requirements of N-716, a minimum of ten percent of the BER population needs to be inspected. For GGNS, this results in a total of 35 inspections. However, N-716 contains an additional requirement that pertains to the BER scope at GGNS. That is, the number of inspections is also weighted towards those locations that are potentially susceptible to degradation versus those locations that do not have a degradation mechanism identified. This requirement increases the number of inspections in the BER portion of this N-716 application to 45 inspections (please see Table 3.3 of the submittal for a breakdown of these locations).
- 6) Note 2 in Table 5 of your submittal explains that the column other in the table was not filled in. Please update Table 5 by filling in the other column. Notes 3 and 4 will provide the needed differentiation between other inspections credited versus not credited in the RIS_B program.
Response - Please see attached the updated table.
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DRAFT Table 5 Inspection Location Selection Comparison Between ASME Section XI Code and Code Case N-716 Code Case N-Safety Significance Failure Potential Section XI Break Code Weld 716 System(1)
Location Category Count Sur High Low DMs Rank Vol/Sur RIS_B Other(2)
Only TASCS, TT, RPV LOCA Medium (Medium) B-F 6 6 0 4(3) 4 (IGSCC)
B-F 1 1 0 0 RPV LOCA TT, (IGSCC) Medium (Medium)
B-J 1 1 0 0 B-F 20 20 0 0 RPV LOCA None (IGSCC) Low (Medium)
B-J 6 6 0 0 B-F 1 1 0 0 RPV LOCA None Low B-J 5 5 0 0 FW LOCA TASCS, TT Medium B-J 60 18 0 9 FW ILOCA TASCS, TT Medium B-J 10 8 2 7 FW BER TASCS, TT Medium C-F-2 10 1 0 3 FW ILOCA TASCS Medium B-J 4 0 4 4 FW LOCA TT Medium B-J 3 2 0 3 FW ILOCA None Low B-J 4 0 1 0 FW BER None Low C-F-2 17 1 0 0 MS LOCA None Low B-J 107 9 4 4 MS ILOCA None Low B-J 64 8 34 0 MS PLOCA None Low B-J 2 0 2 0 MS BER None Low C-F-2 20 2 0 0 SD LOCA None Low B-J 37 0 4 4 9 of 12
DRAFT Table 5 Inspection Location Selection Comparison Between ASME Section XI Code and Code Case N-716 Code Case N-Safety Significance Failure Potential Section XI Break Code Weld 716 System(1)
Location Category Count Sur High Low DMs Rank Vol/Sur RIS_B Other(2)
Only SD ILOCA None Low B-J 4 0 0 0 SP LOCA None Low B-J 5 0 0 1 (4)
RCR LOCA None (IGSCC) Low (Medium) B-J 25 6 0 8 8 RCR LOCA None Low B-J 161 38 4 12 RCR PLOCA None Low B-J 8 0 4 0 CRD Class 2 N/A Assume Medium C-F-2 63 5 0 0 SLC LOCA None Low B-J 5 0 0 4 SLC PLOCA None Low B-J 37 0 4 1 RHR BER TT, CC Medium C-F-2 4 0 0 1 RHR BER TT Medium C-F-2 13 4 0 4 RHR LOCA None Low B-J 24 8 0 7 RHR PLOCA None Low B-J 55 10 0 1 RHR BER None Low C-F-2 18 3 0 0 RHR Class 2 N/A Assume Medium C-F-2 500 32 2 0 LPCS LOCA None Low B-J 7 4 0 3 LPCS PLOCA None Low B-J 25 4 0 1 LPCS Class 2 N/A Assume Medium C-F-2 64 5 0 0 HPCS LOCA TT Medium B-J 4 3 0 2 HPCS LOCA None Low B-J 8 3 1 2 HPCS PLOCA None Low B-J 30 2 0 1 10 of 12
DRAFT Table 5 Inspection Location Selection Comparison Between ASME Section XI Code and Code Case N-716 Code Case N-Safety Significance Failure Potential Section XI Break Code Weld 716 System(1)
Location Category Count Sur High Low DMs Rank Vol/Sur RIS_B Other(2)
Only HPCS Class 2 N/A Assume Medium C-F-2 82 6 0 0 MSLC ILOCA None Low B-J 31 0 1 4 FWLC PLOCA None Low B-J 11 0 0 2 RCIC LOCA None Low B-J 7 0 0 2 RCIC PLOCA None Low B-J 5 0 0 1 RCIC BER None Low C-F-2 12 5 0 0 RCIC Class 2 N/A Assume Medium C-F-2 107 4 0 0 C-F-1 3 3 0 0 CGC Class 2 N/A Assume Medium C-F-2 5 0 0 0 RWCU LOCA None Low B-J 65 11 1 10 RWCU ILOCA None Low B-J 25 8 0 2 B-J 4 0 0 0 C-F-2 22 2 0 0 RWCU BER None Low Class 3 11 0 0 2 Other 1 0 0 0 (5)
RWCU Class 2 None Low B-J 3 0 0 0 RWCU Class 2 N/A Assume Medium C-F-2 2 0 0 0 11 of 12
DRAFT Notes
- 1. Systems are described in Table 3.1.
- 2. The column labeled Other is generally used to identify plant augmented inspection program locations credited per Section 4 of Code Case N-716. Code Case N-716 allows the existing plant augmented inspection program for IGSCC (Categories B through G) to be credited toward the 10% requirement. GGNS selected a 10% sampling without relying on IGSCC Program locations beyond those selected for RIS_B purposes either due to the presence of other damage mechanisms, or where no other damage mechanism is present.
- 3. These four piping welds have been selected for examination per the plant augmented inspection program for IGSCC (Category C) and for RIS_B purposes due to the presence of other damage mechanisms.
- 4. These eight piping welds have been selected for examination per the plant augmented inspection program for IGSCC (Category B) and are being credited for RIS_B purposes.
- 5. Although this piping classifies as Class 2 piping, GGNS conservatively treats it (i.e. NDE) as examination category B-J for inspection purposes.
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