ML20126D889

Application for Amend to License NPF-3,revising TS 3/4.6.4.3,Containment Hydrogen Dilution Sys & Associated TS Bases 3/4.6.4,Combustible Gas Control,To Add an Addl Action Statement to Apply When Both Sys Inoperable

ML20126D889
Person / Time
Site:	Davis Besse
Issue date:	12/21/1992
From:	Shelton D CENTERIOR ENERGY
To:
Shared Package
ML20126D861	List: ML20126D858 ML20126D889 ML20126D898
References
NUDOCS 9212280204
Download: ML20126D889 (6)

Text

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i Docket-Numbar 50-346 i

Liesnse Numb 3rLNPF-3 Serial Number 2071 p=

Enclosure Page 1 i.

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APPLICATION FOR AMENDMENT i

TO j

. FACILITY OPERATING LICENSE NUMBER NPF-3 l

DAVIS-BESSE NUCLEAR POVER STATION f

UNIT NUMBER 1 I

l Attached are the requested' changes to the Davis-Besse' Nuclear Power 4'

Station, Unit. Number.1 Facility Operating License Number NPF-3.,

Als o..

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. included is the Safety Assessment and Significant Hazards l

Consideration.

4 The proposed changes (submitted under cover letter Serial Number 2071) concerns a

Appendix A, Technical Specification Section 3/4.6.4.3, containment Hydrogen Dilution System f

. Appendix A, Technical Specification Bases 3/4.6.4, Combustible Gas L

Control i

By:

D. C.-Shelton-Vice President - Nuclear--

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Sworn and Subscribed before me this' 21st day of December. :

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/A/Sll9A -

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i NotaryP/11c,BtateofOhio 1l' CW L WOOD, f!atary PutJ'c

2:e ciOhio MyCommidon EgitesJuly1.1996 i

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9212280204-921221 PDR ADOCK 05000346 P-PDR

Docket Numbar 50-346 Licensa Number NPF-3 Serial Number 2071 Enclosure Page 2 The following information is provided to support issuance of the requested changes to the Davis-Besse Nuclear Power Station. Unit Number 1 Operating License Number NPF-3, Appendix A, Technical Specification (TS) 3/4.6.4.3, Containment Hydrogen Dilution System, and its associated Bases.

A.

Time Required to Implement: This change is to be implemented 4

within 90 days after the NRC issuance of the License Amendment.

B.

Reason for Change (License Amendment Request Number 92-0009):

The addition of the Action statement to the Technical Specifications to allov both containment hydrogen dilution systems to be inoperable for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> vill avoid a potential unwarranted entry into TS 3.0.3 and subsequent plant shutdown.

C.

Safety Assessment and Significant Hazards Consideration See Attachment.

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Docket Number 50-346

. License Number NPF-3:

Serial Number 2071 Attachment Page 1 l

SAFETY ASSESSMENT AND SIGNIFICANT. HAZARDS CONSIDERATION

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l TITLE:

Addition of an-Action Statement to Technical Specification (TS) 3/4.6.4.3, Containment Hydrogen Dilution System., Addressing Two-i Inoperable Containment Hydrogen Dilution Systems; and Related Change to Bases 3/4.6.4, Combustible Gas Control, Adding a Discussion of the j

llydrogen Recombination System.

DESCRIPTION:

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The purpose of the proposed changes is to modify-the Davis-Besse l'

Nuclear Power Station (DBNPS) Operating License NPF-3, Appendix A TS 3/4.6.4.3 (Containment Hydrogen Dilution (CHD) System) and its

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associated Bases.

l The. proposed change-to TS 3/4.6.4.3 vill add an additional Action 1

statement which vill state: "With both containment hydrogen. dilution l

systems inoperable, restore at least one dilution system 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 J

hours." This vill provide a reasonable time period under-most circumstances to-restore at least one containment hydrogen dilution system to operable status, and therefore, avoid putting the plant through an unwarranted shutdown.

A proposed change to TS-Bases 3/4.6.4 clarifies that the-Containment Hydrogen Purge System Filter Unit functions in conjunction with the CHD System.

An additional proposed change to TS Bases 3/4.6.4 vill add a paragraph l

vhich vill states "As a backup to the CHD System and the Containment Hydrogen Purge System, the capability to install an external hydrogen

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recombination system has been provided." This vill provide a description of the alternative means of contro111ng' hydrogen

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concentration.

I SYSTEMS, COMPONENTS,-AND ACTIVITIES AFFECTED:

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Combustible Gas Control System (Including Hydrogen Recombination l

System)

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

The Combustible Gas Control System is described in the DBNPS Updated Safety Analysis Report (USAR)-Subsection 6.2.5, combustible Gas Control in Containment Vessel. The Combustible Gas Control System is designed to control the concentration of hydrogen which may be released vithin the Containment Vessel' atmosphere following a-Loss of Coolant. Accident-(LOCA). The system is composed of the Containment Hydrogen Dilution (containment atmosphere dilution) System and the Hydrogen Purge System.

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Docket Number 50-346.

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License Numbar NPF-3 i

Serial Number 2071 Attachment Page 2

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The Containment Hydrogen Dilution System is designed to add air to the-l Containment Vessel to effectively maintain hydrogen concentrations within acceptable limits.

i The Hydrogen Purge System is designed to release air from the Containment Vessel atmosphere through High Efficiency. Particulate. Air 3

(HEPA) filters and charcoal filters to the station vent.

The Hydrogen l

Purge System operates in conjunction with the Containment Hydrogen i

Dilution System. The Hydrogen Purge System is addressed by TS l

3/4.6.4.4 which provides for a 30-day allowed outage time.

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Post-accident hydrogen mixing is adequately accomplished by natural l

convective currents along with the turbulence created by-the combined action of the containment spray and the containment air cooler fans.

l As a backup to the Containment Hydrogen Dilution System and the Hydrogen Purge System,.the capability to install an external hydrogen l

recombination system has been provided at DBNPS in accordance with l~

10 CFR 50.44, Section(c)(3)(li).

Following a LOCA, hydrogen gas may accumulate within the Containment j

Vessel from various sources. If a sufficient amount of hydrogen.is generated, it may react with oxygen present in the Containment Vessel

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atmosphere at rates rapid enough to lead to high temperatures and significant overpressurization of the Containment Vessel..As stated in AEC Safety Guide Number 7, the lover flammability limit for hydrogen in i

air saturated with water vapor at room temperature and atmospheric j

pressure is assumed to be four volume percent.

i The Combustible Gas Control System components are designed to be operated as necessary to maintain the maximum. hydrogen concentration in i

the Containment Vessel at or below-three volume percent following a l

LOCA. The limit of three volume percent was chosen to reflect a reasonable margin to alleviate problems such as nonhomogeneous mixing, etc.

Using the conservative assumptions of AEC Safety Guide Number 7, j

a concentration of three volume percent is reached at approximately 21 i

days after the LOCA.

L The Containment Hydrogen Dilution (CHD) System consists of two full L.

capacity, redundant, rotary, positive displacement type blowers to supply air to the containment. The CHD system controls the hydrogen concentration by-the addition of air to the Containment Vessel.

resulting in a pressurization of the containment and suppression of the hydrogen volume fraction.

The Hydrogen Recombination System functions as a means of reducing any i

hydrogen concentration in the Containment Building.

The air containing.

hydrogen is pumped from containment-through the recombiner.

The' air is l

heated electrically within the recombiner-until recombination occurs-i between the hydrogen and oxygen to form vater vapor. The hydrogen free effluent is then returned to containment. The installed system includes piping, manual remote operated valves, and electrical hookups L

for the self-contained Hydrogen Recombiner that would-be brought on-site if the need should arise.

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Docket Number 50-346 License Number NPF-3 Serial Number 2071 Attachment Page 3 EFFECTS ON SAFETY:

The proposed change to TS 3/4.6.4.3 adding an additional Action statement allowing both containment hydrogen dilution-systems to be inoperable for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, is acceptable because, as noted above, the lover flammability limit is assumed to be four volume percent (hydrogen). As shown in USAR Figure 6.2-50, Post-LOCA Hydrogen Percent By Volume, and reiterated in Section 6.2.5, Combustible Gas Control l

Systems, of the NRC Safety Evaluation Report for the Operating License J

(NUREG-0136, December 1976), this concentration vould not be reached until approximately 37 days following a postulated LOCA. This provides ample time to either restore at least one containment hydrogen dilution system to functionality (depending on the location and nature of the cause for inoperability), or to install the external hydrogen recombination system, in the highly unlikely event that a LOCA occurs during the 72-hour allovable outage time allotted by the proposed nev Action statement. Therefore, it is concluded that this proposed change has no adverse effect on plant safety.

The proposed changes to TS Bases 3/4.6.4 provide additional clarifying information, and have no adverse effect on plant safety.

SIGNIFICANT_ HAZARDS CONSIDERATION:

The Nuclear Regulatory Commission has provided standards in 10 CFR 50.92(c) for determining whether a significant hazard exists due to a proposed amendment to an Operating License for a facility.

A proposed amendment to an Operating License for a facility involves no i

significant hazards consideration if operation of the facility in accordance with the proposed changes would (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 operation of the Davis-Besse Nuclear Power Station, Unit Number 1, in accordance 1

with these changes vould la. Not involve a significant increase in the probability of an accident previously evaluated because no Updated Safety Analysis Report (USAR) accident initiators are affected by the proposed changes. The proposed change to TS 3/4.6.4.3 adding an additional Action statement allowing both containment hydrogen dilution J

systems to be inoperable for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> has no bearing on the probability of an accident previously evaluated. The proposed changes to TS Bases 3/4.6.4 provide additional clarifying inf rmation regarding the containment Hydrogen Purge System Filter Unit and the Hydrogen Recombiner System, and have no adverse effect on the probability of experiencing an accident previously evaluated.

Docket.Numbar 50-346 License Number NPF-3 Serial Number 2071 Attachment Page 4 J

lb. Not involve a significant increase in the consequences of an accident previously evaluated because the proposed changes do not invalidate accident conditions or assumptions used in evaluating the radiological consequences of any accident. The proposed change to TS 3/4.6.4.3 adding an additional Action statement allowing both containment hydrogen dilution systems to be inoperable for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> does not alter the source term, containment isolation, or allovable releases, and therefore vill not increase the radiological consequences of a previously evaluated accident. The proposed changes to TS Bases 3/4.6.4 provide additional clarifying information regarding the Containment Hydrogen Purge System Filter Unit and the Hydrogen Recombiner System, and have no adverse effect on the consequences of an accideat previously evaluated.

2a. Not create the possibility of a new kind of accident from any i

1 accident previously evaluated because no ne / types of failures or accident initiators are introduced by the ;roposed changes.

2b. 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.

3.

Not involve a significant reduction in the margin of safety.

The proposed change to TS 3/4.6.4.3 adding an additional Action statement allowing both containment hydrogen dilution systems to be inoperable for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> will not have an adverse effect on the margin of safety because as shown in USAR Figure 6.2-50, Post-LOCA Hydrogen Percent by Volume, the lover flammability limit of four volume percent hydrogen vould not be reached until approximately 37 days following a postulated Loss of Coolant Accident (LOCA). The hydrogen concentration control function can be established in the event of a LOCA via the hydrogen recombination system within this timeframe. All accident analyses will remain valid. The proposed changes to TS Bases 3/4.6.4 provides additional clarifying information and have no adverse impact on 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 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 are the proposed marked-up changes to the Operating License.

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