ML063620486
| ML063620486 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 01/23/2007 |
| From: | Case M J NRC/NRR/ADRA/DPR |
| To: | Pederson C D Division of Reactor Safety III |
| sep; hdc1; jaf2 | |
| References | |
| TAC MD1181, TAC MD1182 | |
| Download: ML063620486 (8) | |
Text
January 23, 2007MEMORANDUM TO:Cynthia D. Pederson, DirectorDivision of Reactor Safety Region IIIFROM:Michael J. Case, Director /RA/Division of Policy and RulemakingOffice of Nuclear Reactor Regulation
SUBJECT:
FINAL RESPONSE TO QUAD CITIES NUCLEAR POWER STATION -TASK INTERFACE AGREEMENT (TIA) 2006-002 RE: THE REPLACEMENT OF REACTOR RELIEF VALVES WITH VALVES NOT QUALIFIED IN ACCORDANCE WITH SECTION 50.49 OF TITLE 10 OF THE CODE OF FEDERAL REGULATIONS (10 CFR)(TAC NOS. MD1181 AND MD1182)On April 10, 2006, the Region III Division of Reactor Safety requested assistance from theOffice of Nuclear Reactor Regulation (NRR) to determine if the replacement of Category I Target Rock Power Operated Relief Valves (PORVs) with Category II Electromatic Relief Valves (ERVs) was acceptable under the requirements of 10 CFR 50.49. Specifically, Region III requested that NRR provide answers to the following questions:1.Can a licensee ever, without NRC [U.S. Nuclear Regulatory Commission]approval, replace equipment already qualified in accordance with the requirements of 10 CFR 50.49, with equipment not qualified in accordance with 10 CFR 50.49 as long as the licensee has sound reasons?2.Did Quad Cities Nuclear Power Station have sufficient "sound reasons to thecontrary" to justify the replacement of the PORVs with ERVs, and are they in violation of 10 CFR 50.49?The NRR staff's assessment is documented in the enclosed safety evaluation.
Docket Nos: 50-254 and 50-265
Enclosure:
As statedCONTACT:Sean E. Peters, NRR/DPRHolly D. Cruz, NRR/DPR301-415-1842301-415-1053 January 23, 2007MEMORANDUM TO:Cynthia D. Pederson, DirectorDivision of Reactor Safety Region IIIFROM:Michael J. Case, Director /RA/Division of Policy and RulemakingOffice of Nuclear Reactor Regulation
SUBJECT:
FINAL RESPONSE TO QUAD CITIES NUCLEAR POWER STATION -TASK INTERFACE AGREEMENT (TIA) 2006-002 RE: THE REPLACEMENT OF REACTOR RELIEF VALVES WITH VALVES NOT QUALIFIED IN ACCORDANCE WITH SECTION 50.49 OF TITLE 10 OF THE CODE OF FEDERAL REGULATIONS (10 CFR)(TAC NOS. MD1181 AND MD1182)On April 10, 2006, the Region III Division of Reactor Safety requested assistance from theOffice of Nuclear Reactor Regulation (NRR) to determine if the replacement of Category I Target Rock Power Operated Relief Valves (PORVs) with Category II Electromatic Relief Valves (ERVs) was acceptable under the requirements of 10 CFR 50.49. Specifically, Region III requested that NRR provide answers to the following questions:1.Can a licensee ever, without NRC [U.S. Nuclear Regulatory Commission]approval, replace equipment already qualified in accordance with the requirements of 10 CFR 50.49, with equipment not qualified in accordance with 10 CFR 50.49 as long as the licensee has sound reasons?2.Did Quad Cities Nuclear Power Station have sufficient "sound reasons to thecontrary" to justify the replacement of the PORVs with ERVs, and are they in violation of 10 CFR 50.49?The NRR staff's assessment is documented in the enclosed safety evaluation.
Docket Nos: 50-254 and 50-265
Enclosure:
As statedCONTACT:Sean E. Peters, NRR/DPRHolly D. Cruz, NRR/DPR301-415-1842301-415-1053DISTRIBUTION:RidsNrrAdroMMcConnellPUBLICKCorpRidsNrrPMHCruz PSPB Reading FileTKoshy RidsNrrDprGWilson RidsNrrDprPspbPHiland RidsNrrLADBaxleyRidsRgn1MailCenter RidsAcrsAcnwMailCenterRidsRgn2MailCenter RidsNrrPMSPetersRidsRgn3MailCenter RidsOgcMailCenter RidsRgn4MailCenterADAMS ACCESSION NO: ML063620486*No significant changes to the SE.OFFICEPSPB/PMPSPB/PMPSPB/LAOGC/NLO*EEEB/BC*PSPB/BCDPR/DNAMEHCruzSPetersDBaxleyDRothGWilsonSRosenbergMCaseDATE1/09/0712/20/0601/11 /0711/01/0611/02/0601/11 /0701/ /07OFFICIAL RECORD COPY ENCLOSURESAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATIONADEQUACY OF REPLACEMENT OF REACTOR RELIEF VALVES WITH VALVES NOTQUALIFIED IN ACCORDANCE WITH SECTION 50.49 OF TITLE 10 OF THE CODE OF FEDERAL REGULATIONS (10 CFR) AT QUAD CITIES NUCLEAR POWER STATION, UNIT 2TASK INTERFACE AGREEMENT (TIA) 2006-00
21.0 INTRODUCTION
In February 2004, Exelon Generation Company, LLC, the licensee for Quad Cities NuclearPower Station (QCNPS), Unit 2, approved and replaced the QCNPS, Unit 2, reactor pressure vessel (RPV) relief valves. More specifically, the licensee replaced the Target Rock Power Operated Relief Valves (PORVs), which are qualified as Category I in accordance with the environmental qualification (EQ) requirements of 10 CFR 50.49, with Dresser Electromatic Relief Valves (ERVs), which are qualified as Category II EQ components. The inspectors viewed this replacement as a potential violation of the requirements of 10 CFR 50.49, "Environmental qualification of electric equipment important to safety for nuclear power plants,"
Section (l), which requires that "Replacement equipment must be qualified in accordance with the provisions of this section unless there are sound reasons to the contrary."2.0 BACKGROUNDThe Dresser ERVs had been a part of the original design for the QCNPS, Unit 2, RPV reliefvalves prior to being replaced with Target Rock PORVs in 1995. The licensee completed this replacement in accordance with 10 CFR 50.49 such that the replacement valves were upgraded consistent with the EQ Category I criteria in NUREG-0588, "Interim Staff Position on Environmental Qualification of Safety-Related Electric Equipment." After several years of operation, the licensee decided to replace the Category I Target Rock PORVs due to operational performance issues. The new replacement valves are the same type of valves as in the original design, Category II, Dresser ERVs. The licensee justified replacing the Category I Target Rock PORVs with the Category II Dresser ERVs by performing a "sound reason to the contrary" evaluation (Section (l) of 10 CFR 50.49 requires that replacement equipment be qualified in accordance with the provisions of 10 CFR 50.49 unless there are sound reasons to the contrary).The inspectors questioned whether this reversion to the original design was allowable under10 CFR 50.49. Specifically, since the PORVs were already established as part of both the design and licensing basis for the plant, the inspection team questioned if it was allowable under 10 CFR 50.49 and whether the licensee's "sound reasons to the contrary" wereapplicable in replacing an EQ component with one that has lesser demonstrated capability.3.0 EVALUATIONBy this TIA, Region III requested answers to the following questions:1.Can a licensee ever, without NRC [U.S. Nuclear Regulatory Commission]approval, replace equipment already qualified in accordance with the requirements of 10 CFR 50.49, with equipment not qualified in accordance with 10 CFR 50.49 as long as the licensee has sound reasons?The purpose of 10 CFR 50.49(l) is to address the replacement of Category I components andthe upgrade of Category II components, not the opposite. The statements of consideration for 10 CFR 50.49 "Environmental qualification of electrical equipment important to safety for nuclear power plants" clearly state this position in The Federal Register, 48 FR 2729.In [memorandum and order] CLI-80-21, the Commission stated that unless there weresound reasons to the contrary, replacement parts should be qualified to the standardsset forth in Category I of NUREG-0588 or IEEE 323-1974. The Commission reaffirms that position in this rulemaking. Such qualification constitutes compliance with the provisions of paragraph 50.49(l). The Commission's position is designed to promote thepolicy of upgrading the environmental qualification and reliability of installed electricequipment. [emphasis added]In memorandum and order CLI-80-21, the Commission recognized that the componentsqualified under the old program ("Guidelines for Evaluating Environmental Qualification of Class IE Electrical Equipment in Operating Reactors," November 1979, Division of Operating Reactors (DOR) Guidelines) did not go through a rigorous testing process for qualification and that some components qualified as Category II failed when tested against the criteria in NUREG-0588. In order to gradually improve safety and reduce the impact on licensees, the Commission accepted the existing qualifications for the life of those Category II components.
When the final rule was issued on replacement equipment, the intent was to replace those safety-related components with enhanced qualified components to improve safety and reliability. At no point was it considered that Category II components could replace Category I components. The NRC staff believes that this action would reduce the quality of components and was never the intent of the regulation. Regulatory Guide (RG) 1.89, "Environmental Qualification of Certain Electric EquipmentImportant to Safety for Nuclear Power Plants," Section C.6, states: "Replacement electric equipment installed subsequent to February 22, 1983, must be qualified in accordance with the provisions of § 50.49 unless there are sound reasons to the contrary. The NRC staff considers the following to be sound reasons for the use of replacement equipment previously qualified in accordance with the DOR Guidelines or NUREG-0588 in lieu of upgrading." [emphasis added] The reasons listed include:- Items that are routinely replaced as part of normal equipment maintenance,- Items that are part of a qualified assembly,
- Items used as replacement that were part of the utility's stock prior to February 22, 1983, - Replacement equipment qualified in accordance with the provisions of 10 CFR 50.49 does not exist,
- Replacement equipment qualified in accordance with the provisions of 10 CFR 50.49 is not available to meet installation and operation schedules but may be used only until upgraded equipment be obtained and an outage of sufficient duration is available for replacement,
- Replacement equipment qualified in accordance with the provisions of 10 CFR 50.49 would require significant plant modifications to accommodate its use, and
- The use of replacement equipment qualified in accordance with the provisions of 10 CFR 50.49 has a significant probability of creating human factor problems.
The provision to replace the Category II components with like Category II components instead of upgrading was to allow licensees a short duration of time to deplete the existing spare supply. It was never the intent of RG 1.89 to outline sound reasons to the contrary for replacement of Category I components with non-like-for-like (e.g., Category II) components.Sound reasons to the contrary are misapplied in this context. Based on the above, the NRCstaff finds that replacement of a Category I component with a non-like-for-like (i.e., Category II) component needs prior review and approval of the NRC before initiating such a replacement. 2.Did Quad Cities Nuclear Power Station have sufficient "sound reasons to thecontrary" to justify the replacement of the PORVs with ERVs, and are they in violation of 10 CFR 50.49?As stated above, the licensee did not upgrade the components when changing from aCategory I to a Category II component. It was never the intent of RG 1.89 to outline sound reasons for replacement of Category I components with non-like-for-like (e.g., Category II) components. Therefore, the stated sound reasons to the contrary are inapplicable. The licensee also appears to base its actions on the nonexistence of qualified equipment andthe significant plant modifications needed to accommodate the use pursuant to RG 1.89, Section C.6. In the licensee's report, "EQ review/evaluation for Reverting to Dresser ERV's For Unit 2," the licensee cites two sound reasons stated in RG 1.89 for replacement of equipment not qualified to the standards of 10 CFR 50.49 and how it applies to QCNPS, Unit 2.Section C.6.d: "Replacement equipment qualified in accordance with theprovisions of Section 50.49 does not exist."With the exception of the Target Rock valves now in use only at Quad CitiesUnit 2, and which continue to experience operational difficultie s, ... there are noexisting valves qualified to Category I that would be a direct replacement. Section C.6.f: "Replacement equipment qualified in accordance withSection 50.49 would require significant plant modifications to accommodate its use."... Exelon examined several potential replacements and found each would entailsignificant plant modifications. Direct acting valves by various manufacturers are utilized by the newest GE [General Electric] BWRs [boiling water reactors] for this application. Being direct acting versus pilot operated, the valve actuator is required to develop sufficient force to overcome the full force seen by the valve disk. This requires an air operator that is very large in size, weight, and air consumption. Consequently, ... these valves would require significant plantmodifications (e.g., seismic evaluation/support upgrades, pneumatic system and crane upgrades, piping modifications) to accommodate their use.The NRC staff does not agree with the licensee's first sound reason that replacementequipment qualified as Category I does not exist. It is the NRC staff's understanding that the licensee currently has one Target Rock valve in use and that Target Rock valves are widely used in the nuclear power industry. Additionally, a smaller sized valve is already qualified as Category I for use at light-water reactor nuclear power plants.In response to an NRC staff request, the licensee referenced its EQ review/evaluation, January 23, 2007, (Agencywide Document Access Management System (ADAMS) Accession No. ML070230294) for reverting to Dresser ERVs for RPV relief valves. In its EQ review/evaluation, the licensee cited two Category I replacement options: (1) Target Rock and (2) Dikkers and Crosby valves. Therefore, there is at least one other replacement equipment option qualified in accordance with the provisions of 10 CFR 50.49. Based on this information, the NRC staff does not find the licensee's rationale to be sound.The NRC staff also does not agree with the licensee's report that discounts Target Rock valvesas a possible Category I replacement option and concludes that Target Rock valves are unsuitable for use at QCNPS, Unit 2. The licensee did cite five different attempts to improve maintenance and operation of the Target Rock PORV. The licensee stated that the design limitations surrounding the valve's tolerance to pilot leakage and the inability to differentiate pilot leakage from main seat leakage, make the valve subject to increased levels of risk to valve performance, and plant safety. In a December 17, 1999, memorandum titled 'Closeout of Generic Safety Issue B-55,"Improved Reliability of Target Rock Safety Relief Valves,"' the NRC staff documented its findings relative to Generic Safety Issue B-55 and evaluated the activities by the industry to improve the reliability of Target Rock safety relief valves (SRVs). According to the report, Target Rock SRVs were installed in 22 BWRs at that time. The report states that there have been several occurrences of improper operation both in spuriously opening and blowing down the reactor coolant and in opening at pressures significantly above the technical specification requirements. However, the report found that no further improvements to the three-stage Target Rock SRVs were necessary at that time. Each of the following had shown that the installed three-stage SRVs have acceptableperformance: Operating history, improved maintenance activity, increased simmer margins, and a reduced number of challenges. In conclusion, the NRC staff found that the BWR Owners Group and the individual licensees had significantly improved the performance of Target RockSRVs, as demonstrated by plant specific operational experience and test data. The inadvertent actuation problems which had existed with the three-stage Target Rock SRVs have been corrected. In summary to the report, the NRC staff found that there had been significant improvements to the performance of the three-stage and two-stage Target Rock SRVs and proposed no new requirements as a result of this issue.With respect to the licensee's second sound reason, the NRC staff also does not agree thatSection C.6.f of RG 1.89 is valid for QCNPS, Unit 2, for the reason stated above and as identified in the licensee's EQ review/evaluation report. The licensee summarized all three available design options for replacement of the Target Rock PORVs:
!The Dresser ERVs utilize a solenoid operator provided by GE. GE has notprovided these parts to any US utilities to EQ standards greater than DOR.
!The Target Rock 2 or 3 stage valves utilize air operators. Target Rock 67Ffamily valves has evolved with the most recent 7567F models being offered to Category I standards. Earlier 7367F and 7467F were available only to DOR guidelines.
!For the direct acting valves, with Dikkers and Crosby being the most common,the pneumatic requirements are substantially greater than those of the pilot operated valves. Crosby Valves (in use at other Exelon sites) are offered to Category I standards.The licensee considered the first option the most feasible since the ERV offers the greatesttolerance to pilot valve leakage, as well as the greatest ease to differentiate pilot leakage from main seat leakage and the minimal costs for replacement even though it is not qualified for Category I. The licensee did not consider the second option feasible (the Target Rock valves) because thenew vertical outlet of the valve would require reconfiguration of the downcomer piping. The NRC staff finds that the reconfiguration of the downcomer piping is not a significant plant modification per Section C.6.f. in RG 1.89. The licensee further noted that the sensitivity of Target Rock valves to pilot leakage and the replacement cost would be greater than the ERV option. As stated above and in the NRC staff closeout memorandum for Generic Safety Issue B-55, the NRC staff finds the Target Rock valves an option worth pursuing further even with the sensitivity to pilot leakage. The licensee identified the third option as not feasible because a detailed evaluation would berequired to determine if the valve would fit and allow routine maintenance within the MARK I containment. The licensee further noted that the replacement cost would be greater than the ERV option. The NRC staff does not agree that a detailed evaluation and replacement cost of the valves are "significant plant modifications". Even though the licensee stated that utilizing these valves would require significant plant modifications that would include seismic evaluations/support upgrades, pneumatic system and crane upgrades, as well as piping modifications, a detailed evaluation was not conducted to validate these reasons. In the NRC staff closeout memorandum for Generic Safety Issue B-55, the NRC staff noted thatmost of the later constructed BWRs (BWR/5s and BWR/6s) do not utilize Target Rock SRVs.
These plants utilize spring-actuated SRVs manufactured by Crosby or Dikkers. Although these valves are large in size, there is a significant amount of operating data available for these spring-actuated SRVs which indicates that they are not experiencing the opening or closing problems as found with the Target Rock SRVs. The Dikkers and Crosby valves have a reliable operating history. The NRC staff understands the possible issues associated with the large size of these valves; however, with no licensee evaluation to support the licensee's statements, the NRC staff does not find the reasoning to be sound.The NRC staff has determined that the reasons stated by the licensee are not supported andthat the licensee does not meet 10 CFR 50.49(a) and (l) for environmental qualification of electric equipment important to safety for nuclear power plants. The provisions of 10 CFR 50.49(a) are to be adhered to once a component has been upgraded from Category II to Category I. 4.0 PRECEDENTThe NRC staff researched previous actions to determine if there was a precedent for thelicensees' request for relief to change EQ components from Category I to Category II. Nocases were found where such a change was made.
5.0 CONCLUSION
The NRC staff concludes that the replacement of the Category I Target Rock PORVs withCategory II Dresser ERVs does not meet the requirements of 10 CFR 50.49.Principal Contributors: K. Corp M. McConnellDate: January 23, 2007