TMI-11-007, Response to Request for Additional Information Concerning Relief Requests Associated with the Fourth Inservice Inspection Interval
| ML110250663 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 01/25/2011 |
| From: | David Helker Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TMI-11-007 | |
| Download: ML110250663 (17) | |
Text
Exelon Nuclear 200 Exelon Way Kennett Square, PA 19348 TMI-11-007 January 25, 2011 www.exeloncorp.com Exelon Nuclear 10 CFR 50.55a U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Three Mile Island Nuclear Station, Unit 1 Renewed Facility Operating License No. DPR-50 NRC Docket No. 50-289
Subject:
Response to Request for Additional Information Concerning Relief Requests Associated with the Fourth Inservice Inspection (lSI) Interval
References:
1)
Letter from P. B. Cowan (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Submittal of Relief Requests Associated with the Fourth Inservice Inspection (lSI) Interval," dated August 10,2010 2)
Letter from P. Bamford (U.S. Nuclear Regulatory Commission) to M. J. Pacilio (Exelon Generation Company, LLC), 'Three Mile Island Nuclear Station, Unit 1 - Request for Additional Information Regarding Fourth Inservice Inspection Interval Relief Requests 14R-02 and 14R-04 (TAC Nos.
ME4519 and ME4521)," dated December 20,2010 In the Reference 1 letter, Exelon Generation Company, LLC (Exelon) submitted relief requests associated with the fourth Inservice Inspection (lSI) interval for Three Mile Island Nuclear Station (TMI), Unit 1. The fourth interval of the TMI, Unit 1 lSI program complies with the 2004 Edition, No Addenda, of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code. The fourth lSI interval will begin on April 20, 2011. In the Reference 2 letter, the U.S. Nuclear Regulatory Commission requested additional information.
Attached is our response to this request.
There are no regulatory commitments in this letter.
Relief Requests Associated with the Fourth Inservice Inspection Interval January 25, 2011 Page 2 If you have any questions concerning this letter, please contact Tom Loomis at (610) 765-5510.
Respectfully, David P. Helker Manager - Licensing Exelon Generation Company, LLC
Attachment:
Response to Request for Additional Information - Relief Requests Associated with the Fourth Ten-Year Interval for Three Mile Island Nuclear Station, Unit 1 cc:
Regional Administrator, Region I, USNRC D. M. Kern, USNRC Senior Resident Inspector, TMI P. J. Bamford, Project Manager [TMI] USNRC
ATTACHMENT Response to Request for Additional Information - Relief Requests Associated with the Fourth Ten-Year Interval for Three Mile Island Nuclear Station, Unit 1
Response to Request for Additional Information - Fourth Interval Relief Requests Page 1 Response to Request for Additional Information Question:
Relief Request 14R-02 "1.
The relief request includes the following paragraph:
The Risk Impact Assessment completed as part of the original baseline [Risk-Informed Inservice Inspection] RISI Program was an implementation/transition check on the initial impact of converting from a traditional [American Society of Mechanical Engineers] ASME Section XI program to the new RISI methodology. For the fourth interval lSI update, there is no transition occurring between two different methodologies, but rather, the currently approved RISI methodology and evaluation will be maintained for the new interval.
The NRC staff does not agree with the implication that, if there is no change in methodology, the change in risk assessment is not part of the living process. Furthermore, the submittal is requesting relief to implement a RISI program instead of an ASME program for the fourth interval, so there is a change from the methodology that would normally be used (Le., without a relief request). Electrical Power Research Institute Topical Report 112657, Revision B-A, which is cited in the application as the evaluation methodology for the RISI program, requires an evaluation of the change in risk (core damage frequency (CDF) and large early release frequency (LERF)) arising from the proposed change in the lSI program. Please provide an estimate of the potential change in risk between the RISI program proposed for implementation in the fourth interval and the ASME Section XI requirements which existed prior to the implementation of the RISI program."
Response
As part of updating the risk-informed Inservice Inspection (RISI) analysis for the fourth Inservice Inspection (lSI) interval, the risk impact assessment was updated to confirm the change in risk was maintained within the acceptance guidelines. The previous methodology of the calculation was not changed, and the change in risk was re-assessed using the latest element selection for the fourth interval RISI program. This risk impact assessment is the comparison of the pre-RISI Section XI program to the RISI program. It has been a part of the Three Mile Island (TMI), Unit 1 RISI living program since initial RISI program implementation and has been maintained for each revision of the TMI, Unit 1 RISI report that has been performed to date.
Based on the fourth interval update of this risk impact assessment, the change in risk for TMI, Unit 1 from the pre-RISI Section XI program to the fourth interval RISI program was 1.15E-07 for core damage frequency (i1CDF) and 6.41 E-09 for large early release frequency (i1LERF). These values are within the1.00E-06 and 1.00E-07 (Regulatory Guide 1.174, Revision 1, "An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis") acceptance criteria for delta-CDF and delta-LERF, respectively. The change in risk analysis was likewise done at a system level, and no system acceptance criteria are exceeded in the current program using the latest RISI element selections, as shown below.
Response to Request for Additional Information - Fourth Interval Relief Requests Page 2 System ilCDF ilLERF Abbrev.
System RISI Acceptance RISI Acceptance BS Reactor Building Spray
-5.14E-12 1.00E-07
-1.47E-12 1.00E-08 CF Core Flood 3.22E-08 1.00E-07 2.14E-09 1.00E-08 DH Decay Heat Removal
-1.59E-09 1.00E-07
-4.24E-10 1.00E-08 EF Emergency Feedwater 3.16E-10 1.00E-07 3.16E-11 1.00E-08 FW Main Feedwater 2.66E-10 1.00E-07 2.65E-11 1.00E-08 HP Hydrogen Purge
<1.0E-11 1 1.00E-07
<5.0E-121 1.00E-08 MS Main Steam
-1.59E-09 1.00E-07
-1.59E-10 1.00E-08 MU Makeup & Purification 5.36E-08 1.00E-07 3.11 E-09 1.00E-08 RC Reactor Coolant 3.20E-08 1.00E-07 1.68E-09 1.00E-08 RR Reactor Building ECW 5.89E-11 1.00E-07 1.18E-11 1.00E-08 1 less than the model truncation limit Question:
"2.
The relief request states:
These portions of the RISI Program have been and will continue to be reevaluated and revised as major revisions of the site Probabilistic Risk Assessment (PRA) occur and modifications to plant configuration are made. The Consequence Evaluation, Degradation Mechanism Assessment, Risk Ranking, Element Selection, and Risk Impact Assessment steps encompass the complete living program process applied under the TMI, Unit 1 RISI Program.
Please provide the date of the last PRA reevaluation and revision that is described above, and a brief description of the results of the reevaluations and revisions undertaken at that date.
Specifically, please provide the baseline CDF and the baseline LERF for the most current PRA. In addition, please explain how any modifications to the plant since the date of the last reevaluation and revision may impact the RISI program."
Response
The RISI program is required to be maintained (and has been maintained) as a living program assessing component and configuration changes and major Probabilistic Risk Assessment (PRA) model revisions throughout the third lSI interval. As part of the fourth interval update process, the consequence and degradation assignments and resultant component risk rankings have been confirmed or updated, element selections have been adjusted, and the risk impact assessment has been revised. The final RISI evaluation for the previous third lSI interval was Revision 2 dated December 2009. This revision of the RISI evaluation incorporated TMI PRA Model 2009 (TM1080),
which is the latest version of the model and is implemented in the initial fourth lSI interval program as discussed on Page 6 of the Relief Request. This model revision has a baseline CDF of 1.2E-05/yr and a baseline LERF of 1.5E-06/yr.
Response to Request for Additional Information - Fourth Interval Relief Requests Page 3 The latest RISI evaluation, Revision 3 dated September 2010, is the current version developed as part of the new fourth interval RISI program. This revision establishes the initial rankings and element selections for the fourth interval and incorporates references to the new interval code of record. The major plant modifications and changes in inspection locations from the initial third interval RISI program (Revision 0 dated October 2002) to the new fourth interval RISI program are summarized in the response to NRC Request 3 below.
Question:
"3.
Are the inspection locations in the RISI program that have been developed for the fourth 10-year interval the same locations as those in the third interval RISI program approved in the NRC staffs November 12, 2003, safety evaluation (ADAMS Accession No. ML032930264)? If not, please summarize the changes to the program and what caused those changes. II
Response
As discussed above in the response to Question 2, the RISI program has been maintained as a living program. During the fourth lSI interval update, risk rankings were validated, element selections were modified as necessary, and the risk impact was recalculated.
The final RISI evaluation of the previous third lSI interval was Revision 2 dated December 2009. The latest evaluation is the current evaluation developed as part of the new fourth interval RISI program (Revision 3 dated September 2010). No updates have been made since then. The changes in inspection locations from the initial third interval program to the new fourth interval program are summarized below.
T bl 1 TMI U 't 1sir S
a e nl e ec Ion ummary Risk Interval 3 Interval 4 Rank Exams Exams Items Affecting Changes (RISI Rev. 0)
(RISI Rev. 3)
High 56 52 Limited Exam Coverage Plant/Component Modifications PRA Model Revisions1 Augmented Alloy 600 Program Medium 141 127 Limited Exam Coverage Plant/Component Modifications PRA Model Revisions1 Augmented Alloy 600 Program Total 197 179 1 Latest incorporated revision is PRA Model 2009 (TM1 080)
Limited Exam Coverage - The welds selected for examfnation were changed in some cases to optimize examination code coverage.
Response to Request for Additional Information - Fourth Interval Relief Requests Page 4 Plant/Component Modifications - As discussed above, the RISI program has been maintained throughout the third lSI interval as a living program. Various minor plant modifications were installed throughout the interval and were evaluated for impact to the RISI program, and when applicable, changes to the RISI scope and element selections were made. Major plant modifications that were incorporated into the RISI program include the Enhanced Once Through Steam Generators (EOTSG) replacement, Feedwater (FW) and Emergency Feedwater (EF) piping associated with the EOTSG replacement including the new ASME Code requirements for smaller Nominal Pipe Size (NPS) EF piping, and various Alloy 600 material mitigation activities.
PRA Model Revisions - The TMI PRA Model applicable to the RISI update was revised in June 2009 and issued as Model 2009 (TM1 080). As the model is updated throughout the interval, impact on the RISI program is assessed and the program is updated as necessary. Some of the major changes to the PRA Model since the original RISI program included:
1.
Addressed Peer Certification "A" and "B" Facts and Observations (F&Os).
2.
Updated initiating event frequencies, component failure rates, unavailability, and common cause factors.
3.
Updated the entire Human Reliability Analysis (HRA) using the EPRI HRA Calculator, and performed a new operator action dependency analysis.
4.
Performed a major update to the Level 2 analysis.
5.
Added common cause failure events for various components and updated the common cause factors to the latest industry data.
6.
Updated generic component failure data based on NUREG/CR-6928 and plant specific data based on recent experience.
7.
Converted the Model from a RISKMAN linked event tree model to a CAFTA single top event fault tree model. During this conversion, each event tree was modified and most of the system logic models were updated.
Augmented Alloy 600 Program - As discussed in the relief request, this program is maintained in addition to the RISI Program and considers requirements such as 10 CFR 50.55a, MRP-139, and other TMI relief requests invoking ASME Section XI, Non-Mandatory Appendix Q.
Question:
"4.
If there are changes in the inspection locations for the TMI-1 fourth 10-year interval RISI program, please provide information for the fourth interval program regarding:
examinations/system/components/degradation mechanisms/class, etc. similar to that provided in Tables 2,3 and 4 of the original submittal of the RISI program for the TMI-1 third 10-year lSI interval dated October 1,2002 (ADAMS Accession No. ML022830211 ).11
Response
A summary of the changes to the inspection locations between the original RISI program implemented in the third lSI interval and the revised program prepared for the fourth lSI interval is contained in the response to Question 3 above. Updated RISI Component and Inspection Summary Tables similar to those provided in the original submittal of the RISI program are included as Enclosure 1 to this response.
Response to Request for Additional Information - Fourth Interval Relief Requests Page 5 Question:
Relief Request 14R-04 "1.
TMI-1 Technical Specification (TS) 4.17.1 (e)(2) provides for an optional functional testing of snubbers in accordance with TMI-1 TS Figure 4.17-1. Please verify that: (1) this plan is equivalent to the 37 or 55 testing sample plan of ASMEIANSI [American National Standards Institute] OM Code Part 4, 1987 Edition with OMa-1988 Addendum (OM-4); and (2) explain whether and how the requirement of additional sampling of at least one-half of the size of the initial sample lot as required by OM-4, Section 3.2.3.2(b), will be met while using TMI-1 TS Figure 4.17-1. If the TS requirements do not meet the OM-4 requirements, please explain how the proposed alternative provides an acceptable level of quality and safety. II
Response
TMI, Unit 1 does not intend to use the TS 4.17.1 (e)(2) testing method during future surveillances. TMI, Unit 1 intends to continue implementation of the TS 4.17.1 (e)(1) testing method during future surveillances. TS 4.17.1 (e) requires that TMI, Unit 1 notify the NRC Regional Administrator prior to implementing a snubber surveillance change to the TS 4.17.1 (e)(2) testing method.
As discussed below, the testing method of TS 4.17(e)(2) is equivalent to OM-4 requirements and provides an adequate level of quality and safety.
The sample plan in TS 4.17.1 (e)(2) (including Figure 4.17-1) uses an accept and reject formula identical to the 37 sampling plan of OM-4 (ASMEIANSI OM Code, Part 4,1987 Edition with OMa-1988 Addendum). The reject line is defined by the formula "C=O.055N+2.007" and the accept line is defined by "C=O.055N-2.007" in both OM-4 Fig. C1 and TS 4.17.1 (e)(2), Figure 4.17-1. An initial random sample of 37 snubbers is chosen and functionally tested.
"C" is the total number of snubbers of a type found not meeting the acceptance requirements of TS 4.17.1 (e)(2). The cumulative number of snubbers of a type tested is denoted by "N". If at any time the point plotted falls in the "Reject" region, all snubbers of that type shall be functionally tested. If at any time the point plotted falls in the "Accept" region, testing of that type of snubber may be terminated.
When the point plotted lies in the "Continue Testing" region, additional snubbers of that type shall be tested until the point falls in the "Accept" region or the "Reject" region, or all the snubbers of that type have been tested.
As shown on Figure 4.17-1, if one (1) snubber fails to meet the acceptance criteria, then an additional sample of 19 snubbers of the failed type is selected in accordance with TS 4.17(e)(2) and will be tested. If a second snubber fails to meet the acceptance criteria then an additional sample of 18 snubbers of the failed type will be tested. This testing continues until the number of failed snubbers falls below the "Accepf' line or all the snubbers of that type have been tested. Thus, the intent of the requirement of additional sampling of at least one-half the size of the initial sample lot as required by OM-4, Paragraph 3.2.3.2(b), will be met while using TS Figure 4.17-1. Therefore, the testing method of TS 4.17(e)(2) is equivalent to OM-4 requirements and provides an adequate level of quality and safety.
Response to Request for Additional Information - Fourth Interval Relief Requests Page 6 Question:
"2.
The requested alternative and TMI-1 TS 4.17 do not address the requirements of OM-4, Section 2.3.4.3, "Examination Failure Mode Groups," and Section 3.2.4.2, 'Test Failure Mode Groups," related to examination and functional testing of snubbers. Please explain how TMI-1 TS 4.17 meets these requirements or provides an acceptable level of quality and safety. II
Response
OM-4, Paragraphs 2.3.4.3 and 3.2.4.2, require unacceptable snubber(s) to be categorized into examination or test failure mode group(s). A failure mode group(s) shall include all unacceptable snubbers that have a given failure mode, and all other snubbers subject to the same failure mode. As discussed in OM-4, the following failure modes shall be used:
(a) design/manufacturing (b) application induced (c) maintenance/repair/installation (d) isolated (e) unexplained OM-4, Paragraph 3.2.5.2(c), permits failure mode groups to be separated for continued testing from the general population of snubbers. However, at least one additional random sample from the general population is required to be tested. Any additional failures within the failure mode group are counted for continued testing only for that failure mode group.
The TMI, Unit 1 TS provides provisions to evaluate the cause of the examination or testing failure as discussed below:
TS 4.17.1 (d) allows snubbers that appear to be inoperable based on visual examination to be determined operable if: 1) the cause for rejection is clearly established and remedied for that snubber and other snubbers that may be generically susceptible, and; 2) the affected snubber is functionally tested in the as-found condition and determined operable per Technical Specification 4.17.1 (f).
Functional TS 4.17.1 (g) requires an engineering evaluation of each functional test failure to determine the cause of the failure. The results of this evaluation are used in selecting additional snubbers which may be subject to the same failure mode for testing in accordance with TS 4.17.1 (e)(1).
If any snubber selected for functional testing either fails to lock up or fails to move, i.e., frozen-in-place, the cause will be evaluated and if caused by manufacturer or design deficiency all snubbers of the same type subject to the same defect shall be functionally tested. This testing requirement shall be independent of the requirements stated in Specification 4.17.1 (e)(1) for snubbers not meeting the functional test acceptance criteria. Thus, for failures due to design/manufacturing, the TS 4.17.1 (g) requirements are essentially the same as those of OM-4, Paragraph 3.2.4.2.
Response to Request for Additional Information - Fourth Interval Relief Requests Page 7 For other failure modes, because TS 4.17.1 does not have specific allowances for failure mode grouping, a more conservative additional testing sample from the overall population can result. For all failure modes, TS 4.17.1 (g) ensures that snubbers subject to the same failure mode are selected for continued testing. TS 4.17.1 requires appropriate evaluation and corrective actions for snubber failures to assure a snubber level of reliability and safety equivalent to OM-4 thus providing an acceptable level of quality and safety.
Question:
"3.
ASME,Section XI, 2004 Edition, Article IWF-5000, Subsections IWF-5200(c) and IWF-5300(c),
clearly state that integral and non-integral attachments for snubbers (including lugs, bolting, pins, and clamps), shall be examined in accordance with the requirements of Subsection IWF.
Please explain whether and how these requirements will be met. If they will not be met, please explain how the proposed alternative provides an acceptable level of quality and safety. II
Response
Examination of snubber integral and non-integral attachments will be performed as required by the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code,Section XI, 2004 Edition, No Addenda, Subsection IWF, as part of the TMI, Unit 1 Inservice Inspection Program. Examination of snubber welded attachments will be performed in accordance with the ASME Code,Section XI, 2004 Edition, No Addenda, Subsections IWB, IWC, and IWD welded attachment examination requirements (e.g., Examination Categories B-K, C-C, and D-A). These examinations ensure compliance with ASME IWF-5200(c) and IWF-5300(c) requirements.
Question:
"4.
TMI-1 TS 4.17.1 (b), footnote "**" states:
The inspection interval for each type of snubber shall not be lengthened more than one step at a time unless a generic problem has been identified and corrected; in that event the inspection interval may be lengthened one step the first time and two steps thereafter if no inoperable snubbers of that type are found.
OM-4, Section 2.3.2.3, "Subsequent Examination Schedule Adjustment, II states that the time to subsequent examination shall not be lengthened more than one increment at a time. Please explain why the inspection intervals described in TMI-1 TS 4.17.1 (b) are acceptable in lieu of the examination schedule requirement noted in OM-4, Section 2.3.2.3."
Response
Per 10 CFR 50.55a(b)(3)(v) the ASME Code for Operation and Maintenance of Nuclear Power Plants, Subsection ISTD ("Preservice and Inservice Examination and Testing of Dynamic Restraints (Snubbers) in Light-Water Reactor Nuclear Power Plants") is an acceptable alternative to Article IWF-5000 of ASME Section XI, which requires compliance with ASME/ANSI OM, Part 4. TS 4.17.1(b),
footnote "**" could in some cases be less conservative than the OM-4, Paragraph 2.3.2.3 requirements but it is more conservative than the Subsection ISTD, Section ISTD-4252 requirements, which is another NRC approved methodology. Therefore, use of TMI, Unit 1 TS 4.17.1 (b) examination scheduling provides an acceptable level of quality and safety.
Response to Request for Additional Information - Fourth Interval Relief Requests Page 8 Figure 1 compares the examination interval reduction requirements for discovery of unacceptable snubbers for the TMI, Unit 1 TS, OM-4, and ISTD code in one examination campaign. TMI, Unit 1 TS 4.17.1 (b) and OM-4 Paragraph 2.3.2.2 are similar in respect to the reduction in time interval between examinations when no failures or one failure are observed and are identical when 3 or more failures are observed. ISTD examination interval reduction is based on the snubber population size and the number of failures and is given in Table ISTD-4252-1. The base ISTD inspection interval is a normal fuel cycle up to 24 months. TMI, Unit 1 currently has approximately 180 snubbers in the Technical Specifications snubber examination and test program. Based upon that population size, ISTD would allow the examination interval be doubled up to a maximum of 48 months if zero or one (1) failure is observed and would require reduction to 2/3rds of the previous interval if more than four (4) failures are observed. As shown in Figure 1, while the TMI, Unit 1 TS examination interval reduction requirements are less conservative than OM-4, they are more conservative than those of ISTD.
Both the TMI, Unit 1 TS and OM-4 can reduce the examination interval from the maximum interval (24 months for TMI, Unit 1 TS and 18 months for OM-4) to as short as one (1) month if eight (8) or more inoperable snubbers are identified during one (1) examination cycle. Per Table ISTD-4252-1, for a population of 180 snubbers, eight (8) inoperable snubbers in a single examination campaign would require the next examination interval be reduced to 16 months (assuming no interpolation per Note 5 of the table). Under ISTD it would take seven (7) consecutive examination cycles of more than four (4) failed snubbers to decrease the examination interval to one (1) month based on the current 24 month examination cycle applied to TMI (assuming no interpolation between Columns Band C in Table ISTD-4252-1). It should also be noted that while Figure 1 shows the ISTD reductions based upon starting with a 24 month inspection interval, if no failures were observed during the previous ISTD examination campaign, the interval per ISTD would have been the maximum allowed of 48 months. Eight (8) failures would have reduced the next inspection interval to 32 months instead of 16 months.
Therefore, TMI, Unit 1 TS 4.17.1 (b) is very conservative when compared to the ISTD requirements for examination interval reduction.
Similarly for examination interval lengthening, while the TS 4.17.1 (b) requirements could in some cases be less conservative than the OM-4, Section 2.3.2.3 requirements, they are more conservative than the Subsection ISTD, Section ISTD-4252 requirements.
Figure 2 shows an assumed situation where one examination campaign identified eight (8) inoperable snubbers, a 24 month exam interval was applicable (18 month for OM-4), a generic problem was corrected, and no inoperable snubbers were identified in subsequent exam intervals.
Both TMI, Unit 1 TS 4.17.1 (b) and OM-4 would require three examinations be completed before the first examination would be required per ISTD. If no failures are observed, the inspection interval would then increase from 16 to 32 months for ISTD. TMI, Unit 1 TS requires three successful visual examination campaigns within a year1s time before returning to 24 month intervals.
This demonstrates that the examination interval lengthening provisions of TMI, Unit 1 TS 4.17.1 (b) are more conservative than the ISTD requirements. Since the ASME OM Code, Subsection ISTD is an approved NRC alternative to ASME Section XI and OM-4 requirements, it can be concluded that the TMI, Unit 1 TS provides an acceptable level of quality and safety for visual examination scheduling.
Response to Request for Additional Information - Fourth Interval Relief Requests Page 9 Figure 1 Comparison of Subsequent Examination Interval Lengths Based on a Previous Exam Interval of 24 Months (18 months for OM-4)
~I 45 40 35 E
30 w
>C IIIz 25 24
~
IJl
~
§ 20
- e 15 10 5
O.
18 o
48 16 12 48 2
24 3
24 4
24 5
16 6
16 7
16 8
16
.OM-488A 0 18TO 04E (Population of 180}]
Figure 2 Change in Subsequent Examination Interval Assuming Previous Examination Interval of 24 months (18 for OM-4), Eight Failures in Current Examination Interval, Then No Subsequent Failures 50 ;-------------------------------
45
~ 40 c
- i1
- ' 35
~.!c
~ 30
.2
'lGc'e 25 24 111w c
Q) 20 i
~
~ 15 oS Q)
~
10 O.
1st Eight Snubber Failures 2nd 3rd 32 4
4th Examination Interval 24 5th 48 24 6th 48 24 7th 48
!lTMI T8 4.17.1 (b) **
.OM-488A o 18TD 04E (Pop. 180)
Response to Request for Additional Information - Fourth Interval Relief Requests Page 10 Question:
"5.
In TMI-1 TS 4.17.1 (e), "Functional Tests", the footnote "*" states:
The four 555,000 Ib reactor coolant pump snubbers are not included. The functional test program for reactor coolant pump snubbers is implemented in accordance with the schedule and other requirements of the snubber testing program.
Please provide details on how the reactor coolant pump snubbers will be tested as compared to the OM-4 requirements."
Response
TMI procedure 1303-9.11 completes reactor coolant pump (RCP) snubber testing in place using a calibrated snubber test device. There are four (4) RCP snubbers installed at TMI, Unit 1. The procedure verifies freedom of motion (snubber break away force and drag force), piston lock-up velocity (activation range), and piston velocity after lockup are acceptable. The testing frequency defined by the test procedure is to perform testing on at least two (2) snubbers at least once every other outage rotating such that the same snubber is not selected in any two (2) consecutive tests unless it failed a previous functional test. If more than one (1) snubber failed functional testing in a prior test cycle, no more than one (1) of the previously failed snubbers may be included in the next test cycle if there are snubbers to be selected which were not tested during the last test cycle. This minimizes long durations between functional tests for anyone RCP snubber.
ASME OM-4 Code requires testing samples of 10 of the snubbers every test cycle. Based upon the representative/random sampling requirements of OM-4 3.2.3.1 (a), the RCP snubbers could be tested as often as one (1) RCP snubber per refueling outage such that it would take four (4) refueling outages to test all four (4) snubbers (assuming no failures). The TMI, Unit 1 approach for RCP snubber testing also results in all four (4) RCP snubbers being tested after four (4) refueling outages (assuming no prior test failures). TMI, Unit 1 procedure 1303-9.11 requires testing all of the remaining untested RCP snubbers should a RCP snubber not meet its functional testing acceptance criteria. The OM-4 10%
Testing Sample Plan additional testing requirements defined in Paragraph 3.2.3.1 (b) would require testing of one (1) additional snubber for each defined failure. As such, the TMI, Unit 1 additional sampling requirements are more conservative than OM-4.
Therefore, the TMI, Unit 1 RCP snubber testing approach provides an equivalent level of operability assurance to the OM-4 Code.
RISI Component and Inspection Summary Tables RISI Component and Inspection Summary Tables Page 1 of 3 Thermal Fatigue Stress Corrosion Cracking Localized Corrosion Flow Sensitive System TASCS TT IGSCC TGSCC ECSCC PWSCC MIC PIT CC E-C FAC BS CF DH X
EF FW X
HP MS X
X MU X
X X
RC 1
X X
X RR NOTES:
1.
Includes systems RC, RCP (Reactor Coolant Pump), RPV (Reactor Pressure Vessel), and PZR (Pressurizer).
2.
This table shows the assessed failure mechanisms for each system. The RISI program addresses the cumulative impact of all mechanisms that were identified in each system.
TASCS - thermal stratification, cycling and striping, TT - thermal transients, IGSCC - intergranular stress corrosion cracking, TGSCC - transgranular stress corrosion cracking, ECSCC - external chloride stress corrosion cracking, PWSCC - primary water stress.corrosion cracking, MIC - microbiologically influenced corrosion, PIT - pitting, CC -
crevice corrosion, E-C - erosion-cavitation, FAC - flow accelerated corrosion RISI Component and Inspection Summary Tables Page 2 of 3 High Risk Medium Risk Low Risk TOTAL System Category 1 Category 2 Category 3 Category 4 Category 5 Category 6 or 7 All Categories BS 111 2
113 CF 15 13 28 DH 4
121 5
265 395 EF 4
198 202 FW 6
99 105 HP 10 10 MS 60 71 79 210 MU 116 653 220 989 RC 1
43 213 256 RR 223 223 TOTAL 66 163 99 1188 5
1010 2531 NOTES:
1.
Includes systems RC, RCP, RPV, and PZR.
2.
This table shows the results of the Risk Categorization. The risk categories are defined in Figure 3-4 of EPRI TR-112657, Revision B-A.
RISI Component and Inspection Summary Tables Page 3 of 3 High Risk Medium Risk Low Risk TOTAL System Category 1 Category 2 Category 3 Category 4 Category 5 Category 6 or 7 All Categories Pre-RISI RISI Pre-RISI RISI Pre-RISI RISI Pre-RISI RISI Pre-RISI RISI Pre-RISI RISI Pre-RISI RISI BS 7
12 7
12 CF 6
2 4
0 10 2
DH 0
1 8
13 0
1 29 0
37 15 EF 1
1 84 0
85 1
HP 0
0 MS 5
15 7
8 15 0
27 23 MU 35 29 137 66 65 0
237 95 RC1 7
7 70 24 77 31 RR 17 0
17 0
TOTAL 5
15 42 37 0
0 236 126 0
1 214 0
497 179 NOTES:
1.
Includes systems RC, RCP, RPV, and PZR.
2.
This table provides a comparison of the RISI element selection to the previous third interval ASME Section XI program based on the 1995 Edition, 1996 Addenda (Pre-RISI).
3.
This table includes the number of welds previously selected for ASME Section XI (Pre-RISI), but excludes the number of welds previously selected for ASME Section XI (Pre-RIS!) that now default to the augmented programs for PWSCC and FAC.