ML20090K772
| ML20090K772 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 03/13/1992 |
| From: | Shelton D CENTERIOR ENERGY |
| To: | |
| Shared Package | |
| ML20090K767 | List: |
| References | |
| NUDOCS 9203190292 | |
| Download: ML20090K772 (8) | |
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Docket Number 50-366 -l License Number NPF-3 !
Serial Number 2026 l Enclosure !
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APPLICATION FOE AMENDMENT ;
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FACILITY OPERATING LICENSE NPF-3 ;
DAVIS-BESSE NUCLEAR POVER STATION UNIT NUMBER 1 i
Attached are requested changes to the Davis-Besse Nuclear Power ,
Station, Unit Number 1 Facility Operating License Number NPF-3. Alse included is the Safety Assessment and Significant flazards ,
consideration, and the Environmental Assessment.
The proposed changes (submitted under cover letter Serial Number 2026) concern Appendix A, Technical Specification 3/4.4.11, Reactor Coolant System - ;
Reactor Coolant System Vents i Appendix A, Technical Specification Bases 6.9.2 Reporting Requirements .
- Special Reports By: /\ A D. C. Shelton
-Vice President, Nuclear- .;
Sworn and Subscribed before me this 13th day of March , 1992 b Nr/nr) Y ll6L Notsty PuM ic, State of Ohlo
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EVEtVNLOPESS NOTidir0JA STMEOF0HIO - i 14 CommaaEq;osMy 28,1994 ;
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PDR- ADOCK 00000346 P -PDR -;
Docket Number 50-346-License Number NPF-3 '
Serial Number 2026-Enclosure-Page 2 The following information is provided to support issuance of the requested changes to1 Davis-Besse Nuclear-Power Station, Unit Number 1 Operating License Number NPF-3, Appendix A. Technical Specification (TS) 3.4.11 Reactor Coolant System - Reactor Coolant System Vents, and TS'6.9.2, Reporting Requirements - Special Reports, i A. Time Required to Implement: This change is to be implemented within 7 days af ter NRC issuance of the License Amendmer.t.
D. Reason for Change (License Amendment Request Number 92-0004,
- Revision 0)
The Reactor Coolant System (RCS) High Poin' vent System provides vents on each of the two hot legs and on th_ pressurizer to vent stear and noncondensible gases to aid in refilling the RCS and promote natural circulation flow for core _ cooling. The High Point Vent System was installed in accordance with the requirements o' NUREC-0737, Item 1131.1 and 10CFR50.44, Standards for combustibic gas control system in light-vater-cooled power reactors". The requirement.to vent the reactor vessel' upper head was met by installation oi a Continuous Vent Line (CVL) system.- 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. The purpose of the'CVL is to allov any noncondensible gases-or steam which may collect in the reactor vessel upper head regioa, ,
_during accident _ conditions, to vent to the hot leg high point of SG 1-2. The gasea can then be removed via thL high point vents, and the-steam can be condensed.
Technical Specification.3.4.11 currently requires that three reacto coolant-system vent paths shall be operable a.) Reactor 1 Coo's* System Locp 1 vith vent path through valves RC 4608A and RC l 4 6'%u , b. ) Reactor Crolnnt System Loop.2 vith vent path through valves RC-4610A and R 4610B;.and c.)- Pressurizer with vent path through either valves RC 11 and RC 2A (PORV), or valves RC 239A and KC 200. Technical Specification Action 3.4.ll.a currently states
-"Vith one of the above vent paths-inoperable, cestore the
-inoperable-vent path to OPERABLE status'vithin 30 days, or, be in HOT STAND 8Y vithin six hours and in HOT 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 proposed change.to TS-3.4.11 veuld revise the 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 inoperable and cannot be restored to operable statut 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 L Specification 6.9.2 within the next 30 days outlining the action taken, the cause of inoperability, and the plans and schedule for o restoring the vent path to an operable status. A plant shutdown-
.vould continue to.be required in the event the pressurizer vent-L path is inoperable for longer than 30 days. Current Actions b, c, J and d would be unchanged-with the exception that they would be redesignated as-Actions c, d, and e, respectively,
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Docket' Number 50-346-License Number NPP-3 Serial Number 2026 Enclosure Page-3 Technical Specification 6 9,2 summarizes the Special Reports requited to be submitted to the NRC. The above described proposed change to TS 3.4.11 would add a nov Special Report requirement, which vould require a new item entry to TS 6.9.2. This is an administrative change.
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 folluving an event in which natural circulation was lost due to noncondensible gas collection. As stated it. USAR Section 5.5.10.2, redundancy of one RCS Loop vent path is provided by the other RCS Loop vent path. However, design basis events do not generate sufficient noncondensible gases to block natural circulation. The RCS vent paths are, accordingly, not required to function to mitigate a Design Basis accident. Since the RCS Loop vent path's only safety function is to act as part of the RCS
-pressure boundary, the inability to open the valves or to vent the RCS via these flovpaths will have no adverse effect on safety, therefore the present TS requirement to shutdown the plant with only one of the two RCS Loop vent paths inoperable is overly >
conservative.
The Continuous Vent Line serves to transport steam-and noncondensible gases to the inlet plenum ul Steam Generator 1-2 and to improve flow 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 rmall break LOCA. However, the DBNPS small break LOCA analyces have taken credit for reflux cooling (coupled heat transfer from the RCS to the-SG secondary side) to keep the reactor cooled. Consequently, there is no specific need to be able to remove the steam or noncondensible gases transported from the reactor vessel upper head to the RCS loop high point by the CVL.
Therefore, removal of the requirement to shutdown the. plant if a RCS Loop vent path becomes inoperable has no effect on safety.
The proposed change vill reduce the potential for unduly requiring cooldown and heakup 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 L
inoperable RCS vent path to be deferred to a refueiing outage when the' radiation dose rate associated with the repair can be better l planned and scheduled in order to minimize individual and occupational. doses in accordance with th- As Lov As Reasonably Achievable-(ALARA) Program C. Safety Assessment and Significant Hazards Consideration: See Attachment!1.
D. Environmental Assessment: See Attachment 2.
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' Docket Number 50-346' License Number NPF-3 Serial Number 2016
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Attachment 1 4 _Page 1 SAFETY ASSESSMENT AND SIGNIFICANT' HAZARDS CONSVDERATION FOR LICFNSE 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 Not* 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, Apper. dix 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 flow for core cooling.- The High Point Vent System was 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 power reactors". The requi.rement i3 vent the reactor vessel upper head was met by installation of a Cont.nuous Vent Line (CVL) system. As described in USAP'Section 5.5.t4,-the CVL consists of a pipe attached to the reactor v-enel head which terminates at a connection near the top of Steam Generator-(SG) 1-2. There are no valves.assuciated with-the CVL.- The purpose of the CVL is to allow any noncondensible 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 steamLean be condensed.
Technical' Sp cification 3.4.11 currently requires that three' reactor l coolant-system vent paths shall_be operable: a.) keactor Coolant System Loop 1 with 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-vith 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 inoperable, restore the inoperable vent path to OPERABLE-status within 30 days, or, be.in HOT-STANDBY-vithin six hours at6 in HOT 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-proposed change to TS 3.4.11 vould revise the 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 inoperable and cannot be restored to OPERABLE status within 30 days. Under this scenario, in lieu of'a plant shutdown, a Special Report would be prepared and_ submitted to the NRC pursuant to Specification 6.9.2 vith.in _ the next 30 days outlindng the action taken, the cause of
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Docket Nember.50-346-License Number NPF-3 Serial Nuinber. 2026 Attachment 1
. Page 2 inopctability, and the plans and schedule for restoring the vent path to an-OPERABLE status. A plant shutdown voeld continue to be-required in the event the pressurizer vent path is inoperable for longer than 30 days.- Current Actions b, c, and d would be unchanged with the exception that they vould be redesignated as Acti_ons c, d, and e, '
respectively.
Technical Specification 6.9.2 summarit:es 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 voald require a new item entry to TS 6.9.2. This is an administrative change.
A similarly worded license amendment was approved by the NRC and issued en May 8, 1989 for the Florida Power Corporation Cryctal River Unit 3 Nuclear Generating Plant (Docket No. 50-302, Amendment No. 112 to License No. DPR-72)._ -t SYSTEMS, COMPONENTS, AND ACTIVITIES AFFECTED:
Reactor Coolant System !!igh Point Vents Reactor Vessel Continuous Vent Line SAFETY FUNCTIONS OF THE AFFECTED SYSTEMS, COMPONENTS AND ACTIVITIES:
The kCS Loop vent paths and the CVL do not have an assigned safety function except to form a part of the RCS 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 l
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 l
Inadequate Core Cooling and Reactor Head P t,-NUREG-0737 Items II.F.2 l
.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 L '
L noncondensible gases (NCGs) to the high-point vents-following a LOCA.
Piping of the CVL provides a direct flow path for gases _or steam 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 i_noperable 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 hsis events do not generate l
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Docket Number 50-346 ,
License Number NPP-3 Serial Number 2026 Attachment'l'
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- i sufficient noncondensible 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 safety function is to act as part of the RCS pressure boundary, the inability to open the valves or to vent the RCS via these flovpaths vill have no effect on safety, therefore the present TS requirement to shutdown the plant with only one of the two RCS Loop vent paths inopetable is overly conservative.
The Continuous Vent Line serves to transport steam and noncondensible gases to the inlet plenum of Steam Generator 1-2 and to improve flow in the reactor vessel upper head region during natural circulation cooldown. 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. Ilovever, 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. 1543 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 transported from the reactor vessel upper head to the RCS loop high point by the CVL. Ticrefore, removal of the requirement to shutdown the plant if a RCS Loop vent path becomes inoperable has no effect.on safety.
The proposed change vill reduce the potential for unduly requiring cooldown end 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 schejuled in order to minimize individual and occupational doses in accordance with the As
. Low As Reasonably Achievable (ALARA) Program.
Tlie proposed r.hange vill not alter source ter ns, containment isolation requirements,-or increase projected or allowable values for radiological releases. Therefore, the radiological consequences of-this proposed change vill not adversely affect 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.ano has no adverse effect on safety.
SICNIFICANT HAZARDS CONSIDERATION:
'The'NRC has provided standards in 10CFR50.92(c) for determining whether a significant' hazard 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 vould: (1) Not involve a significant increase in the probability or consequences of an accident previously evaluated; (2)
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Docket Number 50-346-License Number NPF-3 Serial Number 2026 Attachment 1
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Not create the possibility of a new or dif ferent kind of accident f rw; any attident previously evaluated; or (3) Not involve a significant reduction in a margin of safety. Toledo F.dison has reviewed the proposed change and determined that a significant hazards consideration does not exist because Operation of the Davis-Besse Nuclear Power Station, Unit Number 1, in accordance with these changes vould la. Not involve a significant increase in the' probability of an accident previously evaluated because no Updated Safety Analysis Report accident initiators are affected by the proposed changes.
The proposed change to Technical Specification (TS) 3.4.11 removes the requirement to shutdown in the event that either the Reactor Coolant System (RCS) Loop 1 or the RCS Loop 2 vent paths is inoperable for longer than 30 days. Removal of the requirement to shutdown has no bearing 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. .
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Ib. Not involve a significant increase in the radiological consequences of an accident previously evaluated because no dCCident Conditions or assumptions are affected by the proposed changes.- Removal of the-requirerent to shutdown does not alter the source term, containment isolation, or allovable releases.
The proposed changes, therefore, vill not increase the radiological consequences nf 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 create the_ possibility of a new kind of accident from any accident previously evaluated because no new typec of failures or
- accident initiators are introduced by the proposed chaages.
The proposed change to TS 6.9.2 is administrative only and-has no effect on the possibility of a new kind of accident previously evaluated, i
2 b .- Not create the possibility of a different kind of accident from any accident previously 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 and has no l adverse ef fect on .the possibility of a dif ferent kind' of accident L from'any accident previously evaluated.
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Docket: Number 50-346
-License Number NPF-3
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- 3. Ilo t involve a1significant 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 shutdown the plant vill not. adversely affect the margin of safety. The administrative change to TS 6.9.2 vill not adversely af fe e t 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 concerns a proposed change to the Technical Specifications that must be reviewed by the Nuclear Regulatory Commission, this License Amendment Request does not constitute an unreviewed safe *y question.
ATTACilHENT:
Attached are the_ proposed marked-up changes to the Operating License.
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