ML20043D566

Application for Amend to License NPF-3,revising Tech Specs 3/4.6.4.1,combustible Gas Control - Hydrogen Analyzers. Proposed Change Consistent W/Generic Ltr 83-37,dtd 831101, NUREG-0737 Tech Specs & Item II.F.1.6

ML20043D566
Person / Time
Site:	Davis Besse
Issue date:	05/31/1990
From:	Shelton D TOLEDO EDISON CO.
To:
Shared Package
ML20043D561	List: ML20043D560 ML20043D566 ML20043D567
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-2.F.1, TASK-TM 1781, GL-83-37, NUDOCS 9006080237
Download: ML20043D566 (7)

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Docket Nu ber 50-346

~ i Lic'_nst Nu;ber NPF-3

. serial Number 1781~

Enclosure 'I n Page l' i APPLICATION FOR AMENDMENT TO FACILITY OPERATING LICENSE NUMBER NPF-3 DAVIS-BESSE NUCLEAR POVER STATION UNIT NUMBER 1 l

Attached is the requested change to the Davis-Besse Nuclear Power Station, i Unit Number 1 Facility' Operating License Number NPF-3. Also included are-the Safety Assessment and Significant Hazards Consideration.

The proposed change (submitted under cover letter Serial Number 1781) concerns:

Technical Specifications Section 3/4.6.4.1, Combustible Gas Control - Hydrogen Analyzers. -

By: A- #

D. 'C. Shelton, Vice Pres'itleht Nuclear l Sworn and Subscribed before me this 31st day of May, 1990.

(6[(M Notiry Put/lic,' State of Ohio EVELYNLDRESS NOTARYPUBUO, STATE OF0H10

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, Dockht Nu:ber 50-346 Lic0nse Nurbcr NPF-3

. serial' Number 1781 Enclosure  !

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The following information is provided to support issuance of the requested change to the Davis-Besse Nuclear Power Station, Unit Number 1 Operating License Number NPF-3, Appendix A, Technical Specifications, Section 3/4.6.4.1.

I A. Time Required to Implement: This change is to be implemented within 45 days after the NRC issuance of the License Amendment.

I B. Reason for Change (License Amendment Request Number 90-0008):

The addition of the Action statement to the Technical f,pecifications to allov both hydrogen analyzers to be inoperable for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> vill allow the plant to operate within the guidelines set forth in Generic Letter Number 83-37. In addition, an unnecessary entry into TS 3.0.3 and subsequent shutdown of the plant may be avoided in the event of inoperability of both hydrogen analyzers.

C. Safety Assessment and Significant Hazards Consideration: See Attachment 1 i

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.:  :* Dock 3t Nu2ber 50-346 Lic:nse Nu;b3r NPF-3

. Serial Number 1781 I Attachment 1

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SAFETY ASSESSMENT AND SIGNIFICANT HAZARDS CONSIDERATION FOR LICENSE AMENDMENT REQUEST NUMBER 90-0008 l 1

1 TITLE:

' Addition of Ar Action Statement to Technical Specificatien 3/4.6.4.1, Hydrogen Analyzers, Addressing Two Inoperable Analyzers 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) 3.6.4.1 (Hydrogen Analyzers). The proposed change vill add an additional Action statement which will state: "Vith both hydrogen analyzers inoperable, restore at least one analyzer to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at least HOT STANDBY vithin the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />." Presently, if both hydrogen analyzers were to become inoperable, TS 3.0.3 vould be entered which requires action to be initiated within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to place the unit in a Mode in which the Specificatio.7 does not apply, i.e., MODE 3 (HOT STANDBY). The proposed change is consistent with the Nuclear Regulatory Conmission's guidance (Generic Letter 83-37, dated November 1, 1983, NUREG-0737 Technical Spetifications, item II.F.1.6) for the Action statement which allows both ana1>rers to be inoperable for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

SYSTEMS, COMPONENTS, AND ACTIVITIES AFFECTED:

Hydrogen Analyzers (no hardware changes) i Initiation of Combustible Gas Control System (no hardware changes)

SAFETY FUNCTIONS OF THE AFFECTED SYSTEMS, COMPONENTS, AND ACTIVITIES:

The function of the hydrogen analyzers (discussed in USAR. Subsections 6.2.5.4, 7.13.3.4 and 9.3.2) is to provide the control room with indication of Containment Vessel hydrogen concentrations following a Loss of Coolant Accident (LOCA). The two redundant gas analyzer systems are external to the Containment Vessel and draw samples from four points within.the Containment Vessel.

The hydrogen analyzers are designed to monitor the Containment Vessel atmosphere for a zero to 10% range under both positive and negative ambient pressure. Indicators are located in the main control room and on the front panels of the cubicles which house the analyzers. The safety function of the l

I hydrogen analyzers is to provide the Control Room with indication of the hydrogen concentration in the Containment Vessel following a LOCA. Based on the hydrogen concentration, the Reactor Operator can initiate the Combustible j, Gas Control System to ensure that the concentration does not exceed the e

conservative value of three volume percent thereby ensuring that the post LOCA hydrogen concentration remains below the flammability limit.

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, . Dock 3t Nu2bsr 50-346 Licants Nu bar NPF-3 Serial Number 1781 Attachment 1 Page 2 Following a LOCA, hydrogen gas may accumulate within the Containment Vessel from various sources. If a sufficient amount of hydrogen is generated, it may

. react with oxygen present in the Containment Vessel atmosphere at rates rapid enough to lead to high temperatures and significant overpressurization of the Containment Vessel. The lover flemmability limit for hydrogen in air saturated with water vapor at room temperature and atmospheric pressure is assumed by the Updated Safety Analysis Report (USAR) to be four volume percent. The NRC Safety Evaluation Report for the Operating License (NUREG-0103, December 1976) cites in Section 6.2.5 that analysis of hydrogen generation following a LOCA is consistent with Regulatory Guide, 1.7, Control of Combustible Gas concentrations, and indicates that the concentration in the Containment Vessel vould not reach four volume percent until approximately 37 days after that accident. Using conservative assumptions of Atomic Energy Commission (AEC) Safety Guide Number 7, the USAR assumes a concentration of three percent is reached at approximately 21 days after a LOCA. The three percent concentration in 21 days assumes no operator action was taken to initiate the hydrogen dilution system.

Immediate assessment of Containment Vessel hydrogen concentration is not assumed and is automatically precluded by the Safety Features Actuation System (SFAS) which initiates post LOCA to prevent or limit fission products released '

to the outside environment. An SFAS initiation by high containment radiation, high containment pressure, or low reactor coolant pressure results in closure of the following containment air sampling valves: CV5011A, CV5011B, CV50110, CV5011D, CV5010A, CV5010B, CV50100 and CV5010D. These valves are located on the sample lines from which the hydrogen analyzers draw their air sample.

The RPS, SFAS, SFRCS or SG Tube Rupture procedure, Specific Rule number 4, Hiscellaneous Post Accident Action, allows the Reactor Operator, if there is a need to sample, to override SFAS and open the containment air sampling valves.

Therefore, if an SFAS level 1 actuation has occurred following a LOCA, the Reactor Operator cannot immediately determine the Containment Vessel hydrogen concentration because the air sample lines are isolated. At a later time when the Reactor Operator has determined that there is a need to sample, the valves can be opened per Specific Rule number 4. The ability of the Reactor Operator to monitor the Containment vessel hydrogen concentration following a LOCA is potentially affected by the proposed change.which allows both hydrogen analyzers to be inoperable for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

The use of the Combustible Gas control system, which requires knowledge of the containment hydrogen concentration, vill not be affected by this change. The i

Combustible Gas Control System is designed to control the concentration of l- hydrogen which may be released into the Containment Vessel atmosphere following a LOCA. The system was originally comprised of the Containment Hydrogen Dilution System, the Hydrogen Purge System, and the Containment Recirculation System. The Containment Recirculation System is no longer required to provide adequate mixing because the natural convective currents along with the turbulence created by the combined action of the containment spray and fan coolers vill provide sufficient containment mixing.

l Accordingly, the Containment Recirculation System was removed from the l Technical Specifications by Amendment Number 66 (Log Number 1437, dated l

January 20, 1984). As a backup to the Containment Hydrogen Dilution System l

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Dockot Nu:bar 50-346 Lic nsa Nu b r NPF-3 5erial Number 1781 Attachment 1 Page 3 and the Hydrogen Purge System, Davis-Besse has the capability to install an external hydrogen recombination system. The Combustible Gas Control System components are designed to be operated as necessary to maintain the maximum i hydrogen concentration in the containment Vessel at or below three volume l percent following a LOCA. The limit of three volume percent was determined to i reflect a reasonable margin to alleviate problems such as nonhomogeneous  !

mixing. The ability of the Reactor Operator to make an assessment of the  !

hydrogen concentration in the containment Vessel following a LOCA and, based  !

on that assessment, initiate the Combustible Gas Control System, is not  ;

affected by the proposed change.  !

EFFECTS ON SAFETY  !

The proposed change vill allov both hydrogen analyzers to be inoperable for a '

period of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. If, during this timeframe, a LOCA vere to occur, the i containment hydrogen concentration could be determined using the Post Accident j Sampling System (PASS) which is required by TS 6.8.4. The PASS '

containment air portion has the capability to obtain samples from containment air via the containment radiation monitoring system. The PASS containment air l portion is located in the fuel handling area in the Auxiliary Building. The containment air is recirculated back to the containment through this system  :

using a blower. The samples are obtained through a septum using a syringe. j Based on the concentrations determined by analysis of the PASS samples, the  !'

Reactor Operator can then initiate, if necessary, the Combustible Gas Control Systems to maintain a concentration less than three volume percent. l The ability to obtain containment air samples via the PASS and determine the I hydrogen concentration addresses the safety issue of the Reactor Operator not being able to determine the hydrogen concentration as necessary to take corrective action in a timely manner. In addition to being able to determine the hydrogen concentration via the PASS, it is important to address the fact t that the hydrogen concentration in the Containment Vessel vill not rapidly increase to the lover flammability limit of four volume percent. A concentration of three volume percent takes approximately 21 days atter the LOCA. This gradual increase allows additional time for corrective actions to take place or sampling to occur.

Technical Specification 3/4.6.4.1, Hydrogen Analyzers, is applicable in Modes 1 and 2 and requires two independent containment hydrogen monitors to be

!- operable, or with one hydrogen analyzer inoperable, to restore the inoperable-l analyzer to operable status within 30 days or be in at least hot standby within the next six hours. Under the present Technical Specification, in the event that both analyzers are inoperable, TS 3.0.3 must be entered requiring initiation of plant shutdown within one hour. The imposition of a shutdown transient solely for this purpose is undesirable from an equipment cycling

1. standpoint and is not consistent with NRC guidance regarding the loss of both '

hydrogen-analyzers. The Nuclear Regulatory Commission (NRC) guidance (Generic Letter Number 83-37, NUREG-0737 Technical Specification, item II.F.1.6? states that with both hydrogen monitors inoperable, restore at least one monitor to L operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at least hot standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.

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. Dock 2t Nu2bsr 50-346' 4 Lic:nso Nu:ber NPF-3

~' Serial N a ..' 1781 Attachment i .

Page 4 Toledo Edison letter Serial Number 1661, dated August 21, 1989 to the NRC I,

proposed an amendment to TS 3/4.6.4.l'to transfer the channel check surveillance requirement from the Post-Accident Instrumentation TS 3/4.3.3.6. '

The change proposed by letter Serial Number 1661 is not affected by this proposed change regarding both hydrogen analyzers being inoperable at the same  ;

time.  !

Based on the above, it is determined that the proposed change to allow both hydrogen analyzers to be inoperable for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> has no effect on safety.

There exists an alternative method to obtain and analyze containment air samples for hydrogen, and utilizing these results, the Reactor Operator can initiate corrective action in a timely manner.

SIGNIFICANT HAZARDS CONSIDERATION: ,

The Nuclear Regulatory Commission 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 consideration 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) Not create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) Not involve a significant reduction in a margin of safety. -Toledo Edison has reviewed the proposed change and determined that a significant hazards consideration does not exist because o 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 accident initiators or assumptions are affected. No. hardware changes are being made and no testing is being degraded. Capability to determine Containment Vessel atmosphere hydrogen concentrations, as provided by the PASS following a LOCA, and the available time to take action prior to reaching the hydrogen flammability limit result in no significant increase in the probability of an accident previously evaluated.

Ib. Not involve a significant increase in the consequences of an-accident previously evaluated'because no accident conditions or assumptions are affected. No hardware changes are being made and no testing is being degraded. Capability to determine containment Vessel atmosphere hydrogen concentrations, as provided by the PASS following a LOCA, and the available time to take action prior to reaching the hydrogen flammability limit-result in no radiological consequences being affected.

2a. Not create the possibility of a new kind of accident from any accident previously evaluated because no accident initiators are created. No changes in hardware are being made. Capability to determine Containment Vessel atmosphere hydrogen concentrations, is provided by the PASS following a LOCA.

. Docket Number $0-346 Licen:a Nomber NPF-3 Serial Number 1781 Attachment 1  :

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2b. Not create the possibility of a different kind c, accident from any accident previously evaluated because no hardware changes or changes in equipment operation are being made. On matters related to nuclear safety-  ;

no new accidents are created and no new malfunctions are involved. i

3. Not involve a significant reduction in a margin of safety because an evaluation in the USAR has analyzed a Loss of Coolant Accident (LOCA) to determine the amount of time, approximately 21 days, for the containment Vessel atmosphere to reach three volume percent hydrogen concentration.

If both hydrogen analyzers were inoperable and a LOCA occurred, there ,

exists an alternative means, the PASS, to obtain a Containment Vessel air sample, which can be analyzed for hydrogen. Based on the results of the analysis, the Reactor Operator can take the appropriate action necessary to maintain the hydrogen concentration at or below three volume percent '

in the necessary time frame as outlined in the USAR.

CONCLUSION:

On the basis of above, Toledo Edison has determined that the License Amendment Request does not involve a significant harards consideration.

As this 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 safety question.

ATTACHMENT:

Attached is the proposed marked-up change to the Operating License.

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