ML20091A564
| ML20091A564 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 03/20/1992 |
| From: | Shelton D CENTERIOR ENERGY |
| To: | Murley T Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20091A570 | List: |
| References | |
| 2032, NUDOCS 9203300002 | |
| Download: ML20091A564 (10) | |
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kagg DoneM C. Shonen M N bd VuPW kW imo, OH 4X620001 mm (419)249 2300 Docket Number 50-346 License Number NPT-3 Seital Number 2032 Maich 20, 1992 Dr. Thoman E. Hurley Ditettor Office of Nuclear Reactor Regulation tinited States Nittlear Regulatory Commission one Vhlte Flint Notth 11555 Rockville Pike Rockville, MD 20852 Subjects Request for Temporary Valver of Compliance from Technical Specification 3.4.11 (Reactot Coolant System - Reactor Coolant System Vents)
Dear Di. Mutley:
The purpose of this letter is to requent a temporary valver of '
compliance with Technical Specification (TS) 3.4.11 (Reactor Coolant System - Reactor Coolant System Vents) Action a., to avoid putting the Davis-Besse Nuclear Power Station (DBNPS) through a thermal transient due to shutdown reqitirements (i.e., a cooldown of the pt imary system from approximately $80 degrees F to less than 200 degrees F).
A recent containment entry identified the RCS Loop 2 vent path through valves FC 4610A and RC 4610B as a potential source of increased Reactor Coolant System (RCS) leakage. To minimire RCS leakage, this flow path vas isolated by unlocking and closing upstream manual valve RC 44. The vent path was declared inoperable and the associated TS LCO 3.4.11.a Action statement was entered. This Action statement allovs 30 days to testero the vent path to operable status. Following expiration of the 30 day allowed outage time at 1118 hours0.0129 days <br />0.311 hours <br />0.00185 weeks <br />4.25399e-4 months <br /> nn March 31,-1992, a plant shutdovn vill be required to commence if the vent-path has not been iestored to an operable status.
Toledo Edison estimates that the repair vork on these two valves vould require a duration of 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br /> working at ound-the-clock. Hovever, due to the need to be in Cold Shutdovn (Mode 5) to perform the work and the .
associated Mode change testing requirements, Toledo Edison estimates I that a foiced outage vould have a total duration (breaker to breaker) g appt.oximately 14.8 days.
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Docket Numbet 50-346 License Number NPT-3
' Serial Number 2032 Page 2 Toledo Edison, by letter dated March 13,1992 (Ref et ence Set lal Number 2026), submitted a license amendment application to permanently revise TS 3.4.11. The change proposed by this license amendment application vould revise the TS 3.4.11 Action statement to allow continued operation in the event that either the RCS Loop 1 vent path or the RCS Loop 2 vent path (but not both) is inoperabic and cannot be restored to operable status within 30 days. Under this scenario, in lieu of a plant shutdovn, a Special Report vould be prepared and submitted to the NRC pursuant to Specification 6.9.2 vithin the next 30 days outlining the action taken, the cause of inoperability, and the plans and schedule for restoring the vent path to operable status. Toledo Edison requested that this license amendment application be processed by the NRC on an exigent or emergency basis, in the manner allowed by 10CFRSO.91 (a). A temporary valver of compliance with TS 3.4.11 Action a is requested to allow the plant to continue operating in Mode 1 until this request for a license amendment can be processed.
- 1. Requirements For Vhich Vaiver Is Requested Technical Specification 3.4.11 currently requires that thtee reactor coolant system vent paths shall be operable: a.) Reactor Conlant System Loop 1 vith vent path through valves RC 4608A and RC 4608B b.) Reactor Coolant System Loop 2 vith vent path through valves RC 4610A and RC 4610B and c.) Preosurirer vith vent path through either valves RC 11 and RC 2A (PORV), or valves RC 239A and RC 200. Technica? Specification Action 3.4.11.a currently states "Vith one of the above vent paths inoperable, restore the inoperable vent path to OPERABLE status within 30 days, or, be in HOT STANDBY vithin siv hours and in il0T SHUTMVil within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />."
As noted above, the RCS Loop 2 vent path is currently inoperable due to closure of upstream manual valve RC 44, and the 30 day allowed outage time expires at 1118 hours0.0129 days <br />0.311 hours <br />0.00185 weeks <br />4.25399e-4 months <br /> on March 31, 1992.
- 2. Discussion of Circumstances Surrounding Situation As noted above, a recent containment entry identified the RCS Loc,p 2 vent path through valves RC 4610A and RC 4610B as a potential source of increased RCS leakage. To minimite RCS leakage, this flow path was isolated by unlocking and closing upstream manual valve RC 44. The vent path was declared inoperable and the associated TS LCO 3.4.11.a Action statement was entered. As noted above, the current vording of this Action statement allows 30 days to restore the_ vent path to operable status. Following expiration of the 30 day allowed outage time at 1118 hours0.0129 days <br />0.311 hours <br />0.00185 weeks <br />4.25399e-4 months <br /> on March 31, 1992, a plant shutdown vill be required to commence.
The RCS loop vent ;>ath valves RC 4608A, 4608B, 4610A, and 4610B are solenoid-operated globe valves manufactured by Valcor Engineering Corporation. Those valves are classified as American Society of Mechanical EngPneers (ASHE) Boiler and Pressure Vessel Code Section XI (1986) " Category B" valves - valves for which seat leakage in the closed position is inconsequential for fulfillment of their l
f Docket Number 50-346
. License Number Npp-3
' Serial Number 2032 page 3 function. The valves are stroke tested, however, a valve leak rate test is not required since these valves are classified as Category B. These valves have leaked in the past, however, the leakage could be corrected by cycling the valves, or by allowing the valves to seat themselves over time. A slight leakage from the RCS Loop 2 vent path discharge (one drip every several minutes) vas observed on November 6. 1991, and a Vork Request was initiated. However, since the leak rate was insignificant, the Vork Request was closed, and no significant leakage vas attributed to these valves during plant startup.
As noted in the license amendment application, Toledo Edison plans to attempt to resent the leaking valves (RC 4610A and RC 4610B). A procedure is currently being developed to stroke the valves and to assess leakage. The procedure vill be performed prior to expiration of the 30 day allowed outage time. If the leakage can be corrected, the RCS Loop vent path vill be restored to operable status. In this event, the license amendment request may be processed in_a routine manner rather than as an exigent or emergency request, and the temporary valver of compliance vill not be required.
- 3. Compensatory Actions Toledo Edison vill remain within the Action statement until the RCS Loop 2 vent path is returned to an operable status. This entry vill be tracked to ensure operators are acutely avare of the inoperability of one of the RCS Loop vent paths. The Technical Specifications will continue to require that the plant be in Hot Standby (Hode 3) within the next six hours, if a second_ vent path becomes inoperable and cannot be restored within seventy-tvo hours.
- 4. preliminary Evaluation of Safety Significance and potential Consequences of the proposed Request A Safety Assessment and Significant Hazards Consideration was prepared as part of the license amendment application that was submitted on March 13, 1992, and is included as Attachment 1.
This Safety Assessment and Significant Hazards Consideration is applicable to the requested temporary valver of compliance.
As discussed in the attached Safety Assessment and Significant Hazards Consideration, Toledo Edison has evaluated the appropriateness of a plant shutdovn due to a single inoperable RCS loop vent path and concluded that such a forced shutdovn is unvarranted.
- 5. Justification of Temporary Valver of Compliance Duration As discussed above, this temporary valver of' compliance vill only
-remain in effect until the requested license amendment application can be processed by the NRC. The license amendment application justifies continued plant operation with one inoperable RCS Loop vent path.
Docket Number 50-346 License Number Npr-3
' Serial Number 2032 page 4
- 6. pasis for Conclusion of No Significant Harar ' onside r a t i on A Safety Assessment and Significant Hazards Consideration was prepared as part of the license amendment application that was submitted on March 13, 1992, and is included as Attachmen; 1.
This Safety Assessment and Significant Hazards Consideration is applicable to the requested temporary valver of compliance.
As described in the attached Safety Asse.wment and Significant Hazards Consideration Toledo Edison has determined that a significant harard does not exist.
- 7. Basis for Conclusion of No irreversible Environmental Consequences An Environmental Assessment was prepared as part of the license amendment application that was submitted on March 13, 1992, and is included as Attachment 2. This Environmental Assessment is applicable to the requested temporary valver of compliance.
As described in Attachment 2, Toledo Edison has reviewed the proposed license amendment against the criteria of 10CFR$1.30 for an environmental assessment. The proposed amendment does not involve a significant hazards consideration, does not increase the types or amounts of effluents that may be released offsite, and does not increase individual or cumulative occupational radiation exposures. Accordingly. Toledo Edison finds that the proposed license amendment, if approved by the Nuclear Regulatory Commission, vill have no significant impact on the environment and that no Environmental Impact Statement is required.
- 8. Conclusion The DBNpS has entered TS Action Statement 3.4.11.a due to an inoperable RCS Loop vent path. The 30-day allowed outage time expires at 1118 hours0.0129 days <br />0.311 hours <br />0.00185 weeks <br />4.25399e-4 months <br /> on March 31, 1992. A temporary valver of p compliance is requested to allow continued plant operation while the NRC is processing the previously submitted license amendment application.
If the proposed Technical Specification change is granted, the revised Action statement vould require that a Special Report be prepared and submitted to the NRC pursuant to Specification 6.9.2 vithin the next 30 days. outlining the action taken, the cause of inoperability, and the plans and schedule for restoring the vent path to operable status. This Special Report vould be submitted by April 30, 1992, In order to avoid a potential forced plant shutdown, this temporary valver of compliance is required by 1118 hourr-on March 31, 1992.
- Docket Numhet 50-346 License Number NPF-3 Serial Number 2032 Page 5 In the event this temporary valver of compliance is granted, but the license amendment application is subsequently denied and the RCS Vent path has not been restored to r* operable status, the DBNPS vill be placed in Mode 3 (flot Standby) within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> of notification of denial, and in Mode 4 (flot Shutdovn) within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
The Safety Assessment and Signfilcant liarards Consideration provided to the NRC as part of the license amendment application submitted to the NRC on March 13, 1992 vas reviewed and approved by the DBNPS Station Review Board.
If you have any questions, please contact Mr. Robert V. Schrauder, Manager - Nuclear Licensing, at (419) 249-2366.
Sincerely, H.,L dlm Attachments ,
cci A. B. Davis, Regional Administrator, NRC Region III E. G. Greenman, Regional Division Director for Reactor Projects J. B. Ilopkins, NRC Senior Project Manager V. Levis, DB-1 NRC Senior Resident Inspector J. G. Partlov, NRC/NRR Assistant Director for Projects J. R. Villiams, Chief of Staff, Ohio Emergency Management Agency, State of Ohio (NRC Liaison) dSNRCDocumentControlDesk Utility Radiological Safety Board
Docket Number 50-346 License Number NPF-3 Serial Number 2032 Attachment 1 Page 1 SAFETY ASSESSMENT AND SIGNIPICANT HAZARDS CONSIDERATION FOR LICENSE AMENDMENT REQUEST NUMBER 92-0004 TITLE:
Revision of Technical Specification (TS) 3.4.11 Action Statement for One RCS Vent Path Inoperable, and Revision of TS 6.9.2 to Note the Addition of a Reporting Requirement.
DESCRIPTION:
The purpose for the proposed change is to modify the Davis-Besse Nuclear Power Station (DBNPS) Operating License NPF-3 Appendix A Technical Specification (TS) 3/4.4.11 (Reactor Coolant System - Reactor Coolant System Vents), and TS 6.9.2 (Reporting Requirements - Special.
Reports).
As described in the Davis-Besse Nuclear Power Station (DBNPS) Updated Safety Analysis Report (USAR) Section 5.5.10.2, the Reactor Coolant System (RCS).High Point Vent System provides vents on each of the two hot legs and on the pressurizer to vent steam and noncondensible gases to aid in refilling the RCS and promote natural circulation flov for core cooling. The High Point Vent System vas installed in accordance with the requirements of NUREG-0737 Item II.B.1 and 10CFR50.44,
" Standards for combustible gas control system in light-vater-cooled pover reactors". The requirement to vent the reactor vessel upper head was met by installation of a Continuous Vent Line (CVL) system. As described in USAR Section 5.5.16, the CVL consists of a pipe attached to the reactor vessel head which terminates at a connection near the top of Steam Generator (SG) 1-2. There are no valves associated with the CVL. The purpost of the CVL is to allow any noncondencible gases or steam which may collect in the reactor vessel upper head region, during accident conditions, to vent to the hot leg high point of SG 1-2. The gases can then be removed via the high point vents, and the steam can be condensed.
Technical Specification 3.4.11 currently requires that three reactor coolant system vent paths shall be operable: a.) Reactor Coolant System Loop 1 vith vent path through valves RC 4608A and RC 4608B b.)
Reactor Coolant System Loop 2 vith vent path through valves RC 4610A and RC 4610B and c.) Pressurizer with vent path through either valves RC 11 and RC 2A (PORV), or valves RC 239A and RC 200. Technical Specification Action 3.4.11.a currently states "Vith one of the above vent paths inoperabic, restore the inoperable vent path to OPERABLE status within 30 days, or, be in HOT STANDBY vithin six hours and in HOT SHUTD0VN vithin the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />."
The proposed change to TS 3.4.11 vould revise the Action Statement to allov continued operation in the event that either the RCS Loop 1 vent path or the RCS Loop 2 vent path (but not both) is inoperable and cannot be restored to OPERABLE status within 30 days. Under this scenario, in lieu of a plant shutdown, a Special Report vould be prepared and submitted to the NRC pursuant to Specification 6.9.2 within the next 30 days outlining the action taken, the cause of
Docket Number 50-346 License Number NPF-3 Serial Number 2032 Attachment 1 Page 2 inoperability, and the plans and schedule for restoring the vent path to an OPERABLE status. A plant shutdovn vould continue to be required in the event the pressurizer vent path is inoperable for longer than 30 days. Corrent Actions b, c. and d vould be unchanged with the exception that they vould be redesignated as Actions e, d, and e, respectively.
Technical Specification 6.9.2 summarizes the Special Reports required to be submitted to the NRC. The above described proposed change to TS 3.4.11 vould add a new Special Report requirement, which would require a new item entry to TS 6.9.2. This is an administrative change.
A similarly vorded license amendment was approved by the NRC and issued on May E 1989 for the Florida Power Corporation Crystal River Unit 3 Nut. lear Generating Plant (Docket No. 50-302, Amendment No. 112 to License No. DPR-72).
SYSTEMS, COMPONENTS, AND ACTIVITIES AFFECTED:
Reactor Coolant System High Point Vents Reactor Vessel Continuous Vent Line SAFETY FUNCTIONS OF Tile AFFECTED SYSTEMS, COMPONENTS AND ACTIVITIES:
The RCS Loop vent paths and the CVL do not have an assigned safety function except to form a part of the BCS pressure boundary.
The TS 3.4.11 (Reactor Coolant System - Reactor Coolant System Vents)
Limiting Condition for Operation (LCO) ensures the capability of venting steam or noncondensible gas bubbles from the RCS to maintain or aid in the restoration of natural circulation following a small break loss-of-coolant accident (LOCA).
As stated in the February 14, 1990 " Safety Evaluation by the Office of Nuclear Reactor Regulation Related to Instrumentation for Detection of Inadequate Core Cooling and Reactor Head Vent, NUREG-0737 Items II.F.2 and II.B.1, Toledo Edison Company DBNPS Docket No. 50-346." the CVL is designed to improve the cooling of the reactor vessel upper head (RVUH) during a natural circulation cooldown and also.to transport noncondensible gases (NCGs) to the high-point vents following a LOCA.
Piping of the CVL provides a direct flow path for gases or wteam voids from the reactor head to enter one steam generator above the tube sheet.
EFFECTS ON SAFETY:
The proposed change to TS 3.4.11 vould remove the requirement of a plant shutdown in the event that either the RCS Loop 1 or the RCS Loop 2 vent path is inoperable for longer than 30 days. The RCS vent paths can be used to help restore natural circulation conditions following an event in which natural circulation was lost due to noncondensible gas collection. As stated in USAR Section 5.5.10.2, redundancy of one RCS Loop vent path is provided by the other RCS Loop vent path. However, as described in USAR 6.3.3.1.4, design basis events do not generate
Docket Number 50-346 License Humber NPP-3 Serial Number 2032 Page 3 suffleient nnnrondensible gases to block natural circulation. The RCS vent paths are, accordingly, not required by the USAR to function to mitigate a Design Basis Accident. Since the RCS Loop vent path's only tety function is to act as part of the RCS pressure boundary, the sbility to open the valves or to vent the RCS via these flovpaths 411 have no etfeet on safety, therefore the present TS requirement to shutdown the plant with on1v ane of the two RCS Loop vent paths inoperable is overly conser,- *e.
The Continuous Vent Line serves to transport steam and noncondensible gases to the inlet plenum of Steam Generator 1-2 and to improve flov in the reactor vessel upper head region during natural circulation cooldovn. Relocation of steam and gases to the RCS loop could cause an interruption of natural circulation to RCS Loop 2 during a small break LOCA. Hovever, the DBNPS small break LOCA analyses have taken credit for reflux cooling (coupled heat transfer from the RCS to the SG secondary side) to keep the reactor cooled. Toledo Edison has previously submitted information to the NRC (Serial No. l$43 dated August 23, 1988) regarding the effectiveness of reflux cooling.-
Consequently, there is no specific need to be able to remove the steam or noncondensible gases transpotted from the reactor vessel upper head to the RCS loop high point by the CVL. Therefore, removal of the requirement to shutdovn the plant if a RCS Loop vent path becomes inoperable has no effect an safety.
The proposed change vill reduce the potential for unduly requiring cooldovn and heatup transitions of plant equipment, thus preserving the cycling margin between plant design and actual operating history. The proposed change vill also allow repairs to an inoperable RCS vent path to be deferred to a refueling outage when the radiation dose rate associated with the repair can be better planned and scheduled in order to minimize individual and occupational doses in accordance with the As Lov As Reasonably Achievable (ALARA) Program.
The proposed change vill not alter source terms, containment isolation requirements, or increase projected or allovable values for radiological releases. Therefore, the radiological consequences of this proposed change vill not adversely affeet safety.
Based on the above evaluation, Toledo Edison has concluded that the proposed change to Technical Specification 3.4.11 vill not adversely affect safety.
The proposed change to TS 6.9.2 is administrative only and has no adverse effect on safety.
SIGNIFICANT HAZARDS CONSIDERATION:
The NRC has provided standards in 10CFR50.92(c) for determining whether a significant harard exists due to a proposed amendment to an Operating License for a facility. A proposed. amendment involves no significant hazards if operation of the facility in accordance with the proposed changes voulds (1) Not involve a significant increase in the probability or consequences of an accident previ.osly evaluatedt (2)
Docket Number 50-346 License Number NPP-3 Serial Number 2032 Attachment 1 Page 4 Not crtate the possibility of a new or different ktnd of accident from any accident previously evaluated or (3) Not involve a significant reduction in a margin of safety. Toledo Edison htes reviewed the proposed change and determined that a significant hazards consideration does not exist because operation of the Davis-Befcse Nuclear Pover Station, Unit Number 1, in accordance with these changes vouldi la. Not involve a significant increase in the probability of an accident previously evaluated because no Updated Safety Analysis Report ac cident initiators are af fected by the proposed changes.
The propcsed change to Technical Specification (TS) 3.4.11 removes the requirement to shutdown in the event that either the Reactor Coolant System (PCS) Loop 1 or the RCS Loop 2 vent paths is inoperable fcr longer-than 30 days. Rereval of the requirement to shutdown has no bearirg on experiencing an accident previously evaluated.
The proposed change to TS 6.9.2 is administrative only and has no adverse effect on the probability of experiencing an accident previously evaluated.
Ib. Not involve a significant increase in the radiological-consequences of~an accident previously evaluated because no
', accident conditions or aasumptions are affected by the proposed changes. Removal of the reesirement to shutdown does not alter the source term, contaf 3 ment isolation, or allovable releases.
The proposed changes, .herefore, vill not increase the radiological consequences of a previously evaluated accident.
The proposed change to TS 6.9.2 is administrative only and has no adverse effect on the consequences of an accident previously evaluated.
2a. Not craate the possibility of a new kind of accident from any activent previously evaluated because no nav types of failures or, a ctdent initiators are introduced by the propcsed changes.
The proposed change to TS 6.9.2 is administrative only and has no effect on the possibility cf a new kind of accident previously evaluated.
2b. Not create the possibility of a different kind of accident'from any accident pr2viously evaluated because no different accident initiators or failure mechanisms are introduced-by;the proposed
, changes.
The proposed change to TS 6.9.2 is administrative only an!. has no adverse effect on the possibility'of a different kind of accident from any accident previoucly evaluated.
J
~ 99?thWWF ~k gm Docket Number 50-346 License Number NPF-3 Serial Number 2032 Attach' ment 1 Page 5
- 3. Not involve a significant reduction in the margin of safety. All accident analyses are still valid, so no changes in margins of safety occur. Therefore, removal of the requirement to shutdovn the plant vill not adversely affect the margin of safety. The administrative change to TS 6.9.2 vill -t adversely affect the margin of safety.
CONCLUSION:
On the basis of the above, Toledo Edison has determined that the License Amendment Request does not involve a significant hazards consideration. As the License Amendment Request conce a a proposed change to the Technical Specifications that must be revaeved by the Nuclear Regulatory Commission, this License Amendment Request does not constitute an unrevieved safety question.
ATTACHMENT:
Attached are the proposed marked-up changes to the Operating License, a
t
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