ML20133L561

Provides Response to RAI Re Adequacy of Detection & Suppression Systems That Support Use of Low Pressure Systems for Fire Safe Shutdown Per Requirements of 10CFR50,App R,Section III.G.3

ML20133L561
Person / Time
Site:	Vermont Yankee
Issue date:	01/15/1997
From:	Duffy J VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BVY-97-9, NUDOCS 9701220063
Download: ML20133L561 (18)

Text

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l V4Ra&ONT YANKEE

' NUCLEAR POWER CORPORATION H i Ferry Road, Brattleboro, VT 05301-7002 ENGINE R N OFFICE h* 580 MAIN STREET 80LTON. MA 01740 i -- (508) 779-6711 i

January 15,1997 BW 97 United States Nuclear Regulatory Commission.

ATTN: Document Control Desk Washington,'DC 20555

. Referencesi (a) Lloense No. DPR-28 (Docket No. 50-271)

(b) Letter, USNRC to WNPC, NW 96-186, dated December 12,1996 (c) Letter, WNPC to USNRC, BW 96-43, dated April 4,1996

- (d) Letter, WNPC to USNRC, BW 96-67, dated May 21,1996 ,

. (e) Letter, WNPC to USNRC, BW 96-158, dated December 13,1996

Subject:

Response to Request for Additional Information Regarding 10CFR50, L Appendix R Exemptions t

in Reference (b) the NRC requested additional information regarding exemption requests (

submitted by Vermont Yankee in References (c) and (d).' Vermont Yankee provided its ,

response to questions regarding use of the Vemon Tie line in Reference (e). The purpose of 1 this letter is to provide information requested in Reference (b) regarding the adequacy of detection and suppression systems that support the use of low pressure systems for fire safe shutdown strategies per the requirements of 10CFR50, Appendix R, section Ill.G.3.

. We trust that this submittal provides the requested information. However, should you have )

questions or require additional information, please contact this office.  ;

i Sincerely,

. VERMONT YANKEE NUCLEAR POWER CORPORATION James J. Duffy i Licensing Engineer Attachment 1 .

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..USNRC Region 1 Administrator

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< ' USNRC Project Manager- WNPS USNRC Resident Ins'pector- WNPS 9701220063 970115~0, f'A D wm - -

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VERMONr YANKE'E NUCLEAR POWER CORPORATION United States Nuclear Regulatory Commissbn

[ January 15,1997 -

Attachment 1 Page 1 of 13 -

EXECUTIVE

SUMMARY

On May 21,1996, Vermont Yankee requested an exemption from 10CFR50, Appendix R, section lil.G.1.a to allow use of depressurization and low pressure injection fire safe shutdown strategies, in that letter, Vermont Yankee also requested exemption from 10CFR50, Appendix R, section Ill.L.2 to allow short-term core uncovery. Based on further consideration and ,

discussions with NRC staff, Vermont Yankee is responding to the NRC's Request for Additional  ;

i Information [ Reference (b)] by withdrawing its request for exemption from lil.G.1.a and providing information to support our request for exemption from the detection and suppression requirements of 10CFR50, Appendix R, section Ill.G.3. Vermont Yankee's request for exemption from Ill.L.2 remains.

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. Vermont Yankee's fire safe shutdown strategy for Reactor Building Fire Zones RB-1, RB-2, RB- 1 3 and RB-4 includes depressurization for decay heat removal and low pressure injection for reactor inventory makeup until shutdown cooling is initiated. Since depressurization and low pressure injection are considered attemative shutdown strategies, fire detection and a fixed i

suppression system are required in the area, room or zone under consideration (10CFR50, Appendix R, section Ill.G.3). There are detection and suppression in various parts of the fire  ;

zones under consideration. Vermont Yankee plans to enhance the existing fire detection  ;

i capability by installing additional detection in Fire Zones RB-3 and RB-4. However, fire detection and fixed fire suppression will not be provided throughout the Fire Zones RB-1, RB-2, RB-3 and RB-4. Therefore, Vermont Yankee is requesting an exemption from the section i lil.G.3 requirement for detection and fixed suppressian to the extent that these features are j lacking In Reactor Building Fire Zones RB-1, RB-2, RB-3 and RB-4.

In support of this exemption, Vermont Yankee has reviewed the existing fire protection features against existing fire hazards. The factors considered in this review included: combustible loading (fixed and transient), detection and suppression capabilities (automatic and manual),

fire brigade response and administrative controls. Also considered was guidance provided in NRC Generic Letter 86-10, specifically: Enclosure 1, items 5 and 6; and Question / Response 3.1.5 and 3.4.4.

As a result of this review, Vermont Yankee has deterrqined that existing and planned fire protection features provide the capabilities necessary M limit the probability of fire growth and f damage thereby minimizing reliance on attemative shutdown capability. However, should attemative shutdown capability be necessary, Vermont Vankee has demonstrated that this i capability will remain available. Vermont Yankee therefc:re believes that the underlying intent of 10CFR50, Appendix R, section Ill.G.3 is achieved.

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- - United States Nuclear Regulatory Commission

. January 15,1997 Attachment 1 Page 2 of 13

. Response to Request for Additional Information n

j. Question 3.1 The proposed LPIS approach does not appear to satisfy the " hot shutdown" performance criterion of Section Ill.G.1, Ill.G.2, and Ill.G.3 of Appendix R to 10 CFR 50.

Generic Letter 86-10 provides further clarification and staff positions with regard to i defining " alternative" and " redundant" shutdown capabilities. In light of these requirements, it appears the proposed approach is providing an alternative shutdown  :

) capability for the identified fire areas. Please explain why the use of LPIS is not '

identified by WNPC as providing an alternative shutdown capability for Fire Zones RB-1 through RS-4.

l j Resoonse .

The use of depressurization and low pressure injection for fire safe shutdown in Reactor Building Fire Zones RB-1 through RB-4 is considered an altemative shutdown capability.

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Question 3.2 As described above, LPIS appears to be providing an alternative shutdown capability for Fire Zones RB-1 through RB-4. Therefore, please explain why these fire zones have not l been designated as alternative shutdown fire areas.

Response

!~ Fire Zones RB-1 through RB-4 will be designated attemative shutdown fire zones upon ,

approval of this exemption request..

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United States Nuclear Regulatory Commission January 15,1997 Attachment 1 Page 3 of 13 Question 3.3 Provide information which demonstrates that the fire protection features (detection and suppression) provided for the Reactor Building meet Section Ill.G.3 of the regulation, or provide technicaljustification for an exemption from Section lil.G.3 of the regulation where this level of protection is not provided and LPIS is identified as the post-fire safe

- shutdown capability.

80299029 The following provides a discussion of

the fire zones under consideration; safe shutdown t

- capabilities; existing fire protection features; and fire hazards analysis and the adequacy of existing and planned fire protection features.

3.3.1 Fire Zones RB-1. RB-2. RB-3 and RB-4 (see attached figures 1 - 4)

Fire Zones RB-1 and RB-2 are located on the 213ft and 232ft elevations of the Reactor Building and consist of the torus room on the 213ft elevation, the corner rooms (northeast, southeast, and southwest) at the 213ft and 232ft elevations, and the HPCI room in the southwest corner of the 213ft elevation. The torus room has an overall floor 4 area of 13,850ft and is st and east sides of the elevation. The CFZs extend from floor to ceiling in the torus room. The north side of the torus room and the northeast corner room are located in Fire Zone RB-1. The south side of the torus room, the southeast i

and southwest corner rooms, and the HPCI room, are located in Fire Zone RB-2. The north side of the torus room in Fire Zone RB-1 has a slightly smaller floor area than the

! south side in Fire Zone RB-2 due to the location of the CFZs. (Note: the northwest corner room 213ft elevation (fire area RCIC) and the northwest corner room 232ft elevation [ Fire Zone RB1S] do not rely on attemative shutdown capability and therefore are not included in this evaluation.)

i Fire Zones RB-3 and RB-4 are located on the 252ft elevation of the Reactor Building. .

The 252ft elevation has an overall floor area of 20,500ft2 and is separated into north and

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south skies by a combustible free zone (CFZ) on the east side of the elevation and the north wall of the steam tunnel on the west. The north side of the elevation is identified as Fire Zone RB-3 and the south side, including the drywell ante room, the steam tunnel and the railroad airlock, is identified as Fire Zone RB-4. Fire Zone RB-4 is larger than Fire Zone RB-3, due to the location of the CFZ on the east side of the elevation, and since the steam tunnel, ante room, and railroad airlock are part of Fire Zone RB-4.

3.3.2 Safe Shutdown Capabilities Fire Zone RB-1 and Fire Zone RB-2 Fire Zone RB-1 relies on Division SI equipment for fire safe shutdown compliance.

. Decay heat is removed initially with the SRVs relieving to the torus until reactor depressurization is initiated from the Control Room. Core spray is initiated as needed from the Control Room for makeup until Shutdown Cooling operation is initiated. When the reactor pressure reaches 100 psig or less, the Shutdown Cooling decay heat

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4 United States Nuclear Regulatory Commission l January 15,1997 i . Attachment 1 [

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. removal mode of RHR is initiated to take the primary system to cold shutdown. Fire j . Zone RB-2 relies on the same systems for fire safe shutdown, with Division Sil ,

, equipment used for makeup, hot and cold shutdown purposes. .

i l Although Vermont Yankee's analysis credits the use of low pressure safe shutdown

capability throughout Fire Zones RB-1 and RB-2, it is unlikely that redundant high .  ;

, . pressure safe shutdown capability would be challenged by a fire in the corner rooms or  !

j . the HPCI room. A fire on the 213ft and 232ft elevations of northeast or southeast corner l l rooms would not impact high pressure systems since no high pressure equipment or cables are located in these rooms and it is unlikely that the fire would spread into other m rooms areas of the affected fire zone where such equipment and cables are located.

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Similarly, a fire in the southwest comer room or HPCI room on elevation 213ft would not h . impact redundant RCIC equipment, located in a separate fire area (Fire Area RCIC), the

_213ft elevation northwest comer room. Therefore, the separation of, and protection provided for, redundant high pressure systems should preclude the need to rely on depressurization and low pressure injection strategies given a fire in these locations.

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Fire Zone RB-3 Fire Zone RB-3 on the north side of the 252ft elevation is analyzed based on the

- location of Division Si and Division Sil safe shutdown equipment and cables in the zone.

l Division Si safe shutdown cables (RHR, CS) and 2 of 4 SRVs are routed along the west wall of the northwest comer (analysis zone RB-3SI) to Fire Zone RB-4. Division Sil cables (RHR, CS) and 2 of 4 SRVs are routed along the east side of the suppression i area (snalysis zone RB-3Sil) prior to turning east and traveling through the balance of i Fire Zone RB-3 (see figure 4).

!- Redundant Division Si and Division Sil safe shutdown capabilities are separated by a 4 minimum of 18ft, or are protected by a 1-hour rated fire barrier, in the northwest comer, j Detection and multi-level suppression systems are provided in the northwest corner to  !

support the exemption request for less than 20ft of separation between redundant trains  !

of safe shutdown equipment that was approved by NRC in the SER dated 12/1/86. i For a fire occurring in the Division Sll portion of Fire Zone RB-3 (outside the northwest corner, or insido the northwest corner suppression area up to analysis zone RB-3Si

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along the west wall of Fire Zone RB-3), decay heat is removed initially with the SRVs relieving to the torus until reactor depressurization is manually initiated from the Control Room using the 2 SRVs in the Division SI separation area. Core spray is initiated as needed from the Control Room for makeup until the Alternate Shutdown Cooling mode of RHR is initiated. When the reactor pressure reaches 100 psig, the Altemate Shutdown Cooling mode of RHR is initiated to take the primary system to cold shutdown. '

Similarly, for a fire occurring in the Division SI portion of the northwest corner l suppression area. decay heat is removed initially with the SRVs relieving to the torus j until reactor depressurization is manually initiated from the Control Room using the 2 i

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Ei; VERMONT YANXLE NUCLEAR POWER CORPORATION United States Nuclear Regulatory Commission January 15,1997 1

Attachment i

, Page 5 of 13 SRVs routed in the Division Sll portion of the suppression area. Core spray is initiated

as needed from the Control Room for makeup until the Altemate Shutdown Cooling j mode of RHR is initiated.

j_ Fire Zone RB-4 Fire Zone RB-4 is located on the south side of the 252ft elevation. The safe shutdown i compliance strategy is similar to that for a fire occurring in the Division Si portion of Fire i Zone RB-3. ,

" 3.3.3 ' Fire Protection Features ,

) Figures 1,2,3, and 4 depict the arrangement and location of existing fire protection features in Fire Zones RB-1, RB-2, RB-3 and RB-4. Figure 1 depicts the fire protection features in the torus rooms in Fire Zones RB-1 and RB-2 and in the comer rooms at q elevation 213ft. Figure 2 depicts the location of fire detectors at the ceiling of the torus i rooms in Fire Zones RB-1 and RB-2, along with the fire protection features provided in the comers rooms at elevation 232ft. Figure 3 depicts the fire protection features in Fire 4

Zones RB-3 and RB-4 on elevation 252ft. Figure 4 depicts the arrangement of cable trays on elevation 252ft in the northwest comer suppression area of Fire Zone RB-3.

j Smoke detectors are provided at ceiling level of the HPCI room and in both elevations of

the corner rooms, except the southwest corner room which is provided with detection

.only on the 232ft elevation. Smoke and heat detectors are provided at ceiling level of a i

the torus room in Fire Zone RB-1 and Fire Zone RB-2. The torus room smoke detectors are located around the perimeter of the torus ceiling near the cable trays, which are also l located near the ceiling. The heat detectors are located closer in from the perimeter

walls of the torus area above the torus itself.

F Smoke detectors and a multi-level preaction sprinkler system have been provided in Fire i i Zone RB-3 in the northwest comer. Smoke detectors have also been provided on the

. east side of the elevation adjacent to, and inside of, the CFZ that separates Fire Zone

, RB-3 from Fire Zone RB-4. The smoke detectors are provided to detect floor-based or i i cable tray fires in Fire Zone RB-3, and to detect fires spreading up to Fire Zone RB-3 through the open stair from the northeast corner room, before the fire spreads out of i Fire Zone RB-3 to Fire Zone RB-4. Smoke detectors are also provided in the vicinity of the CFZ in Fire Zone RB-4.

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Portable extinguishers and hose stations are located throughout the 213ft and 252ft elevations and are available for use by the fire brigade for manual fire fighting activities.

Vermont Yankee procedure AP be , Plant Fire Prevention and Fire Protection,"

controls activities that could compromise the effectiveness of the plant fire protection

program. The entirety of the Reactor Building is defined as a permanent Fire Control Area (FCA) in AP 0042. A Hot Work Control Permit is required for any hot work activity in any FCA, and a Fire Protection Control Permit is required for the introduction of 1

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7 VERMONT YAN%EE NUCl EAR POWER CORPORATION

. *) ' United' States Nuclear Regulatory Commission ,

i January 15,1997 j j i J Attachment 1-j Page 6 of 13 I significant quantities of combustible or flammable materials into an FCA. AP 0042 provides guidance on how to evaluate the significance of transient combustible and 4 ' flammable materials in an FCA, including an evaluation of the potential risk to plant

equipment and personnel safety.

~ In ' addition to the administrative controls applied to FCAs, introduction of transient l

combustible materials are further limited by radiological controls applied to the entire l

Reactor Building. Therefore, if a fire involving transient combustibles materials were to  :

i occur, it would involve a very limited quantity of combustible materials.  !

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3.3.4 Fire Havards Analvsis and Adeauncv of Existina and Planned Fire Protection Features s

I The following is a detailed discussion on the adequacy of fire protection features in the ,

Reactor Building fire zones for which compliance is based on Appendix R Secten Ill.G.3

.i criteria. The existing and planned fire protection features are evaluated against the i fixed and transient combustible materials that could present an exposure fire hazard to I safe shutdown capability in the zone.

. Fire Zone RB-1 and Fire Zone RB-2 The safe shutdown strategy given a fire in Fire Zones RB-1 or RB-2 relies on safe 9

shutdown capabilities that are located outside the affected fire zone. Postulated fires in either Fire Zone RB-1 or Fire Zone RB-2 would have to spread outside the fire zone in -

[ which the fire occurs in order to adversely impact safe shutdown. Based on the i information provided below, fire spread outside either fire zone is not a credible event.

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L Fire Zone RB1 and Fire Zone RB2: ComerRooms and HPCIRoom The southwest comer room,232ft elevation, has a combustible loading of under 2

l 10,000 Btu /ft . Each elevation of the remaining corner rooms and the HPCI room has a 2

l combustible loading of under 20,000 Btu /ft . The combustible materials corsist primarily cf cable insulation in trays, oil inside pumps, and transient combustible materials. With i' the exception of the 213ft elevation of the southeast corner room, smoke detection is  !

provided at ceiling level in each room.

i L The combustible loading in each room is low and postulated fires would tend to spread towards the ceiling prior to spreading out into the torus room. It is reasonable to expect that postulated fires in a corner room or in the HPCI room would be detected and the fire brigade would respond prior to the fire spreading out of the room into the torus room.

Should products of combustion from a corner room fire spread into the torus room, the c torus room detection systems would actuate prior to ignition of combustible materials in the torus room.

i e As previously described, redundant safe shutdown capabilities are located outside each l corner room and outside the HPCI room. Additionally, alternative shutdown capabilities

for each room are located outside the room's fire zone. Reasonable assurance is

'provided that postulated fires in a comer room or in the HPCI room would not spread

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'# . United States Nuclear Regulatory Commission January 15,1997  ;

Attachment 1 Page 7 of 13 i l

l outside of the room, and potentially damage redundant high pressure safe shutdown capability prior to actuation of the detection system and prompt fire brigade response.

In the unlikely event that fire does spread out of the room of origin, attemative shutdown  !

capability is available outside of the fire zone should the spread of fire result in damage to redundant high pressure safe shutdown capability.

Fire Zone RB1 and Fire Zone RB2: Torus Room The primary combustible materials in the torus rooms consist of exposed cable insulation in horizontal cable trays located near the ceiling or below the Torus Catwalk.

. Any exposed cable in the CFZs are coated with a fire retardant material. The cable trays run around the outside perimeter walls of the torus and the combustible materials are essentially evenly distributed throughout the locations. The north (Fire Zone RB-1) and south (Fire Zone RB-2) sides of the torus room have average combustible loadings of under 8,000 Btu /ft2 . The potential use and buildup of transient combustible materials are limited since the zones are identified as FCAs and are radiologically controlled locations.

l A postulated fire involving cable insulatien would develop slowly during the initial stages of the fire. A floor-based transient combustible material fire would be expected to develop more rapidly, generate more heat during the initial stages of the fire, and tend to be shorter in duration due to the limited quantities, and lack of continuity, of such materials typically present in the torus. The detection systems in Fire Zones RB-1 and RB-2 are installed to detect both types of pcstulated fires as described below. l Automatic smoke and heat detection systems are provided at ceiling level in the forus rooms of Fire Zones RB-1 and RB-2. lonization smoke detectors are provided at ceiling level near the perimeter walls of the torus area above the vicinity where cable trays are routed to detect both floor based fires and cable tray fires. Heat detectors are provided closer in from the perimeter walls of the torus area above the torus itself to detect heat rising up around the back of the torus prior to impacting on the cable trays, lonization detectors are also located at cei!ing level in the HPCI room to meet the requirements of a general area detection system.

I Postulated fires occurring in either floor-based transient combustible materials or in the exposed cable trays located below the torus catwalk or near the ceiling would be promptly detected by the smoke and heat detectors in the incipient stages of the fire.

Detection of postulated fires in the incipient stages would result in an alarm in the Control Room. The fire brigade would respond rapidly to the scene for manual fire fighting activities. The fire brigade would have direct access to 213ft elevation via multiple stairways from the 252ft elevation to either tne north or south side of the torus.

The fire brigade could initiate manual suppression activities from the 213ft elevation to fight floor-based transient combustible material fires and overhead cable tray fires. The fire brigade also has direct access to the Torus Catwalk from two locations on the 252ft elevation for fighting fires that occur in the cable trays iocated below the catwalk or near the ceiling above the catwalk.

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• VERMONI YANKEE NUCLEAR POWER CORPORATION United States Nuclear Regulatory Commission l

' January 15,1997_ l Attachment 1 i Page 8 of 13 1 l

. l Reasonable assurance is provided that postulated fires in either the north or south side i of the torus room in Fire Zone RB-1 or Fire Zone RB-2 will not adversely impact l redundant or alternative safe shutdown capability. This conclusion is based on the combination of (a) low combustible loading, (b) smoke and heat detection at ceiling level ,

that will result in prompt detection of postulated fires, (c) the rapid fire brigade response for manual fire fighting, (d) the portable extinguishers and hose stations that are available for use in the torus room, (e) the unobstructed access to combustible materials for manual fire fighting activities from the floor level and from the Torus Catwalk, (f) the lack of continuity of combustible materials that could result in fire spread to upper elevations in the Reactor Building and (g) comprehensive administrative controls. i Therefore, the lack of a fixed suppression system in the torus rooms of Fire Zone RB-1 and RB-2 does not adversely impact safe shutdown capability.

Fire Zone RB-3 1 1

Division SI safe shutdown cables (RHR, CS) and 2 of 4 SRVs are routed along the west wall of the northwest corner to Fire Zone RB-4. Division Sll cables (RHR, CS) and 2 of 4 SRVs are routed along the east side of the suppression area prior to turning east and traveling through the balance of Fire Zone RB-3. Altemative safe shutdown capabilities are separated by a minimum of 18ft, or are protected by a 1-hour rated fire barrier, in the northwest corner, in accordance with the exemption requests approved by NRC by letter dated 12/1/86. Cables required for operation of HPCI and RCIC are routed in the northwest corner and in the main open area of Fire Zone RB-3 to the east of the northwest comer, necessitating the use of depressurization and low pressure injection altemative shutdown compliance strategies in the zone.

in order for there to be an adverse impact on safe shutdown capability, fire would have to damage both divisions of safe shutdown capability. One scenario requires a fire in the northwest corner to result in damage to both divisions of safe shutdown capability in

, the northwest comer. A second scenario requires a fire that occurs east of the northwest comer to spread into the northwest corner and damage bo'h divisions of safe  !

shutdown capability. Based on the information provided below, damage to both divisions of safe shutdown capability as a result of a fire in Fire Zone RB-3 is not a credible event.

There are negligible quantities of fixed combustible materials at floor level in Fire Zone RB-3, Combustible materials in Fire Zone RB-3 consists primarily of cable insulation in cable trays located near the ceiling. Smaller quantities of other combustible materials (e.g., rubber, plastic, and Thermo-Lag over the TIP room that has been abandoned-in-place) are also located in Fire Zone RB-3. Cable insulation makes up about 90% of the exposed fixed ano transient combustible materialloading in the zone. The average 2

combustible loading on the elevation is under 30,000 Btu /ft . The potential use and buildup of transient combustible materials are limited since the zone .s identified as an FCA and is a radiologically controlled location.

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Smoke detectors are provided in the northwest comer for early detection of postulated i floor-based or cable tray fires that could impact on either the redundant high pressure,  ;

or the altemative depressurization and low pressure injection, safe shutdown capabilities  :

' in this location. Smoke detectors are also located at ceiling level on the east side of Fire I - Zone RB-3 in the vicinity of the CFZ and the drywell ante room. Smoke detectors are  ;

not provided in Fire Zone RB-3 at ceiling level above the TIP room, inside the TIP room, .!

E inside the elevator machinery room, inside the north personnel airlock, at ceiling level in i the open area east of the elevator shaft or in the stair enclosure which leads to the open i i stairway in the northeast comer. VY plans to install additional ceiling 'evel smoke l detectors above the TIP room and in the open area of Fire Zone RB-3 east of the l J northwest comer to the vicinity of the open stair to the northeast comer rooms. The (

3 planned smoke detectors will be located to meet the spacing and location criteria of the ]

edition of NFPA 72 in effect at the time of the design.

Postulated fires occurring in either floor-based transient combustible materials or in the j exposed cable trhys located near the ceiling would be promptly detected by the existing ,

and planned smoke detectors in the incipient stages of the fire. Detection of postulated l

! fires in the incipient stages would result in an alarm in the Control Room. The fire j l brigade would respond rapidly to the scene for manual fire fighting activities. The fire i

brigade would have direct access to Fire Zone RB-3 from either the airlock entrance

! through the north wall of the zone or from the airlock entrance into Fire Zone RB-4. i

} The ceiling area of Fire Zone RB-3 is relatively uncongested for manual fire fighting i activities. The ceiling is about 25ft above the floor, and there are no obstructions that i would prevent application of a hose stream to postulated fires in combus'ible materials located near the ceiling. Cable trays above the ceiling of the TIP Room aad the Ante l

J Room can be accessed for manual fire fighting by permanent plant ladders installed F along the walls of both rooms. The two groups of stacked cable trays in the northwest I comer can also be accessed for manual fire fighting from either the ceiling of the TIP  :

room, or through the use of portable la9ders available in the northeast comer of Fire l l Zone RB-3. The fire brigade is cognizant of the precautions in application of hose {

streams in the vicinity of important equipment and energized electrical equipment to t I

ensure that water spray is not inadvertently applied to equipment not involved in the fire.

' The northwest comer of Fire Zone RB-3, which contains the highest concentration of cable trays near ceiling level, is provided with smoke detection systems at ceiling level and automatic suppression at ceiling level and below the cable trays. The cable trays in the northwest comer consist of two separate groups of stacked trays, with one group along the west side and one group along the east side. A majority of the trays are solid bottom with sheet metal covers. The remaining trays are open ladder type with sheet metal covers. The metal covers "are utilized on cable trays to prevent fire from migrating from tray to tray in a vertical bank" (Vermont Yankee UFSAR, page 8.4-8).

Only conduits are routed between the two groups of cable trays in the northwest corner where they are separated by less than 20ft. The raceways (trays and conduits) in the l

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United States Nuclear Regulatory Commission January 15,1997

Attachment 1 g Page 10 of 13 e

northwest comer containing redundant or attemative safe shutdown capability are

separated by a minimum of 18ft with no intervening combustibles or are provided with a 1-hour rated fire barrier in accordance with the Ill.G.2 compliance strategy approved by NRC in the 12/1/86 SER.

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(There are two cable trays in the northwest comer that branch off of the stack of trays l 4

c routed along the west wall near the wall of the northwest corner. The two trays run in a l

east < rly direction over the TIP room near the north wall of the steam tunnel. The trays j are not located within the 18ft separation distance between redundant and/or attemative  !

safe shutdown capability in the northwest comer. The trays are coated with a flame retardant material for a distance of 20ft from where they branch off of the cable tray l stack to over the roof of the TIP room. Coating of the cables in the trays was not +

required to comply with the Ill.G.2 exemption request or resultant NRC SER. The cable i coating was added as defense-in-depth to support the revisions to the safe shutdown

! compliance strategies in the northwest comer.)  ;

e The existing fire hazards are not severe enough to challenge either the redundant or  !

attemative safe shutdown capabilities given a fire in the northwest comer. In the ,

unlikely event that a severe fire does occur in the northwest comer, the suppression system provided at ceiling level and/or below the cable trays would actuate, depending  !

! on the location of the fire. The suppression system in the northwest corner would act to I control and/or extinguish postulated fires prior to arrival of the fire brigade, regardless of  ;

the tray type (open ladder or solid bottom, covered or uncoverod). The following  :

1 analyses addresses postulated fire scenarios occurring at floor level, and fires that occur  ;

in open ladder and solid bottom cable trays with and without tray covers. ,

The suppression system coverage provided below and/or above the cable trays would j

- actuate given a floor-based transient combustible material fire. The suppression system l

- would be effective in limiting the size and duration of a fire occurring at floor level and i prevent damage to redundant high pressure and attemative depressurization and low l pressure injection safe shutdown capabilities.

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.l A postulated fire involving cable insulation in the cable trays would develop slowly during f the initial stages of the fire. The sheet metal covers on the solid bottom or open ladder l trays would inhibit the growth of any postulated fire in the cable trays. In such a  !

scenario, the smoke generated from the fire would activate the detection system t resulting in prompt fire brigade response prior to the fire challenging cables in the stack  !

of trays on the opposite side of the suppression area. l The suppression system located at ceiling level would actuate given a fire in either  !

group of cable trays that produces enough heat to impact redundant / alternative  !

- shutdown chble trays on the opposite side of the suppression area. (The presence of tray covers would increase the amount of time required to generate sufficient heat to

challenge cables on the opposite side of the suppression area.) Once actuated, the  ;

I~ suppression system would control any postulated fire in the fray stack in which the fire f i

i i

f

-i

l il , .,f VERMONT YANKEt NUCLEAR POWER CORPORATION United States Nuclear Regulatory Commission - .;

January 15,1997 ,

Attachment 1 Page 11 of 13 l

originates. The presence of sheet metal covers would prevent water from being applied directly into the trays from the sprinkler heads located at the ceiling. The trays in the  ;

'l

middle of each stack may be further shielded from direct water application by the upper trays in the stack. _ However, water from the sprinkler head (s) would spray in the i minimum 18ft separation distance between the groups of cable trays, and would also  !

- run down the outside of the cable tray stack in which the fire originates. i Actuation of the sprinkler system would prevent direct fire spread outside of the tray -

stack in which the fire occurs. The sprinkler system would cool any smoke or hot gases  ;

produced by the fire, and also minimize convective and radiative heat transfer across -  !

f the 18ft separation area to redundant and attemative shutdown cables in the stack of j trays on the opposite side of the suppression area. As such, the ceiling level  ;

. suppression system would control the spread of fire occurring in cable trays where direct

water application might not occur. The effects of such a fire would be confined to the

} stack of cable trays in which the fire occurs until arrival of the fire brigade for manual fire l fighting activities. l

! i Reasonable assurance is provided that postulated fires in Fire Zone RB-3 will not  !

adversely impact redundant or altemative safe shutdown capability. This conclusion is  ;

i based on a combination of (a) low combustible loading, (b) existing and planned smoke i detection at ceiling level in the zone that will result in prompt detection of postulated fires, (c) the rapid fire brigade response for manual fire fighting, (d) the portable extinguishers and hose stations that are available for use in the fire zone, (e) the  !

unobstructed access to combustible materials for manual fire fighting activities, (f) the  !

18ft of separation between redundant and/or altemative divisions that are not protected  :

with 1-hour fire barriers, (g) the multi-level suppression system provided in the northwest j i comer of the fire zone, (h) the ability of the suppression system to confine postulated cable tray fires to a single stack of cable trays and (i) comprehensive administrative i controls. Therefore, the !ack of a fixed suppression system in Fire Zone RB-3 does not  ;

i adversely impact safe shutdown capability, j 4  !

Fire Zone RB-4 \

, A fire in Fire Zone RB-4 could impact Division SI safe shutdown capabilities in the zone.

. RHR, CS, and 2 of 4 SRV cables are located in the zone. (HPCI and RCIC steam supply isolation and injection valves in the steam tunnel, and cables for the valves that ,

l are routed in the main open area of Fire Zone RB-4, necessitate the use of depressurization and low pressure injection compliance strategy in the zone.)  !

i l In order for there to be an adverse impact on safe shutdown capability, a fire in Fire Zone RB-4 would have to spread outside the zone to Fire Zone RB-3. Based on the i information provided below, damage to both divisions of safe shutdown capability as a l result of a fire in Fire Zone RB-4 is not a credible event.

E There are negligible quantities of fixed combustible materials at floor levelin Fire Zone RB-4. Combustible materials in Fire Zone RB-4 consists primarily of exposed cable j t

er -w, , - - . --.m ,,*m, .m,- .-,-v v , - - , , , , . -i- , - - , - -- , - , , - , ,

- - . - - -- , - - . . _ - _ . _ . . - ~ . . - - . . . .-__ - . . _ . . . .

. ' VERMONT YANXEE NUCLEAR POWER CORPORATION

~

United States Nuclear Regulatory Commission i ~ January 15,1997 ,

, Attachment 1 -

Page 12 of 13 }

i

' insulation in cable trays located near the ceiling. Smaller. quantities of other combustible materials (e.g., rubber and plastic) are also located in Fire Zone RB-4. Cable insulation i makes up'about 90% of the exposed fixed and transient combustible materialloading in 2

< the zone. The average combustible loading on the elevation is under 30,000 Btu /ft ,

The potential use or buildup of transient combustible materials are limited since the zone is identified as an FCA and is a radiologically controlled location. A postulated fire  !

l Involving cable insulation would develop slowly during the initial stages of the fire. A i postulated fire in floor-based transient combustible materials would develop more i rapidly, generate more heat during the initial stages of the fire, and tend to be shorter in duration due to the limited quantities, and lack of continuity, of such materials in the

- zone. l

(

2 Smoke detectors are provided adjacent to, and inside of, the CFZ separating Fire Zones  !

• RB i and RB-3 on the east side of Fire Zone RB-4. The smoke detectors are provided l

to detect floor-based or cable tray fires near the CFZ, and to detect fires spreading up to

} Fire Zone RB-4 through the open stair from the southeast comer room, before the fire

spreads out of Fire Zone RB-4 to Fire Zone RB-3. The main open area of Fire Zone

< RB-4 west of the CFZ, the west personnel airlock, the ante room that abuts the CFZ, the

steam tunnel, and the railroad airlock are not provided with automatic detection or [

r suppression capability. VY plans to install additional ceiling level smoke detection in the

open area of Fire Zone RB-4, the ante room, the steam *unnel and the railroad airlock to meet the spacing and location criteria of the edition of NFPA 72 in effect at the time of .

the design.

J

. Poctulated fires occurring in either floor-based transient combustible materials or in the l exposed cable trays located near the ceiling would be promptly detected by the existing l and planned smoke detectors in the incipient stages of the fire. Detection of postulated

! fires in the incipient stages would result in an alarm in the Control Room. The fire i brigade would respond rapidly to the scene for manual fire fighting activities. The fire j brigade would have direct access to Fire Zone RB-4 from either the personnel airlock entrance through the west wal! of the zone or from the personnel airlock entrance into i Fire Zone RB-3.

i

' The combustible loading in Fire Zone RB-4 consists primarily of exposed cable insulation in overhead cable trays. The combustible loading is essentially evenly distributed throughout the fire zone without concentrations of combustible materials in any particular location. The ceiling area of Fire Zone RB-4 is rr'atively uncongested.

- The ceiling is about 25ft above the floor, and there are no obstructions that would prevent application of a hose stream to postulated fires in combustible materials located

- near the ceiling. Cable trays above the ceiling of the Ante Room can be accessed for i manual fire fighting by permanent ladders installed along the wall of the room. The fire brigade is cognizant of the precautions in application of hose streams in the vicinity of important equipment and energized electrical equipment to ensure that water spray is not inadvertently applied to equipment not involved in the fire.

J i __u___.________ _ _ _ _ _ .________.__..-.: . ., . . _ __ J,. . , , .

• VERMONT YANKEE NoctEAR POWER CORPORATION United States Nucieer Regulatory Commission l

{

' January 15,1997 Attachment i 1 Page 13 of 13 4

2 j Reasonable assurance is provided that postulated fires in Fire Zone RB-4 will not .

adversely impact redundant or attemative safe shutdown capability, This conclusion is j l

i~ based on the combination of (a) low combustible loading, (b) the existing and planned smoke detection at ceiling levelin the. main open area of the rest of the fire zone that will ,

result in prompt detection of postulated fires, (c) the rapid fire brigade response for i manual fire fighting, (d) the portable extinguishers and hose stations that are available

! for use in the fire zone, (e) the unobstructed access to combustible materials for manual  !

i fire fighting activities, (f) the location of redundant and altemative safe shutdown  !

{ capabilities outside of the fire zone and (g) comprehensive administrative controls. .

Therefore, the lack of a fixed suppression system in Fire Zone RB-4 does not adversely i i

?. Impact safe shutdown capability.

L 3.3.5 Summarv of Fire Proie.hi Fantures and Fire Havards:

The existing and planud fire protection features (detection, suppression, hose stations l

, . and portable extinguishers) provided in Fire Zones RB-1 through RB-4 provide adequate .

protection for one train of systems required for fire safe shutdown based on the in-situ j and transient combustible fire hazards in the zones.

The primary combustible material in all four zones consists of exposed cable insulation in overhead cable trays which would be expected to propagate slowly once ignited by an

i. exposure fire. The locations containing the majority of combustible materials that could present a hazard to systems relied on for fire safe shutdown are provided with automatic detection systems at ceiling level. Actuation of the detection systems would result in l prompt fire brigade response to initiate manual suppression activities. Hose stations and portable extinguishers are available for fire briga# use in the zones. Automatic preaction sprinklers are also provided in the northwest corner of RB-3, both at ceiling level and below obstructions, so that postulated fires would not spread and impact more

than one train of systems relied on for fire safe shutdown. Lastly, comprehensive administrative procedures control activities that could compromise Vermont Yankee's fire protection capability.

l 4

- 3.3.6

Conclusion:

Based on the information detailed above, Vermont Yankee believes that existing and 7

planned fire protection features provide the capabilities necessary to limit the probability of a fire growth and damage thereby minimizing reliance on alternative shutdown capability. Vermont Yankee therefore believes that the underlying intent of 10CFR50,

i. Appendix R, section Ill.G.31s achieved without the installation of detection and fixed l suppression system throughout the rooms and zones under consideration.

L l

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