ML20153D651
| ML20153D651 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 02/18/1986 |
| From: | Leblond P COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 1298K, NUDOCS 8602240207 | |
| Download: ML20153D651 (34) | |
Text
-
[h gommonwealth Edison (O
j'One First Natiorni Pitzt, Chic 1go. librioia 7 Address Reply to. Post Office Box 767 N
j/ Chicago, Illinois 60690 February 18, 1986 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Constission Washington, DC 20555 o
Subject:
Zion Nuclear Power Station Units 1 and 2 Fire Protection NRC Docket Nos. 50-295 and 50-304
Reference:
January 7, 1986 letter from J. A. Norris to D. L. Farrar.
Dear Mr. Denton:
The referenced letter requested that Commonwealth Edison Company provide additional information in support of the NRC's review of exemption requests for Zion Station. The requested information is contained in tha attachment to this letter.
Ten (10) copies of this letter and its attachment are provided for your review. If any questions arise concerning this matter, please direct them to this office.
Sincerely, 4
P. C. LeBlond i
Nuclear Licensing Administrator 1m Attachment ec: Resident Inspector - Zion J. A. Norris - NRR g
$80**N
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F 1298K t
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i QUESTION 280.1.
Provide drawings and detailed descriptions to clearly illustrate j
the arrangement of all ceiling and duct-mounted detectors for.the Main Control Room (Fire Zone 2.0-0, page 7-8), and the Auxiliary Electric Equipment Rooms (Fire Zones 5,6-1 and 5.6-2, page 7-14).
The.information should, as a
- minimum, include the location of detectors relative to ceiling-heights, HVAC registers, exposed ceiling beams and other ceiling projections, and-fixed l
combustibles.
Verify if these detectors are selected ~and installed in accordance with NFPA-72E.
t I
RESPONSE
The Main Control Room, Fire Zone 2.0-0, is located on the 642-ft elevation of the Auxiliary Building.
Figures 1 and 2 l
depict the layout of this zone on a plan and elevation basis.
It I
l has mean dimensions of approximately 106.5 ft by 47.5 ft for a l
floor area of approximately 5060 ft2 The clear floor to ceiling l
height is approximately 23 ft.
An aluminum egg crate ceiling, located approximately 11 ft above the floor, is provided over the i
main open floor area of the Main Control Room.
Cable trays, HVAC l
ducts, roof beams and
- girders, lights, 'and smoke detectors are all located above the egg crate ceiling.-
As can be seen on Figure 1, there are five main roof girders i
i i
running in an east-west orientation.
Three of the girders are 45 in. in depth, with two girders 57 in. in depth.
Five roof beams run perpendicular to the girders in a north-south orientation.
Of the five beams, four project 4-6 in, below the ceiling while one projects 9 in, below the ceiling.
e
(
Page 1 L
7.,
.y j'
'e.
a v
' code edition appearing >in:the 1978 : edition offthe' National Fire.
Codes which corresponds with.the March 1978 SER; reference for E
' adding detectors in the. Main Control:iRoom),
the five girders result-in six separate bays for purposes. of-uetector coverage. ;
f.
'Four'of the ceiling beams-are less -than~8 in. in depth, which-is.
the breakoff point for smooth ceiling' construction..The'fifth; beam, which is 9 in.
in'~ depth,-requires reduced' spacing of~ spot type smoke detectors perpendicular to it.
j-Figure 2 is an elevation view of the Main Control-Room.-
As can be seen from this figure, detectors along column lines;20 and'
(
j.
19 are located at the bottom of the girders.
The remaining l i.
I detectors are located at the ceiling- (or, as in the case of one' detector in the northeast corner of ~ the zone, located on the
- i bottom of a beam less than-8 in.
in depth)..
Figure 2 also l
[
indicates the relative locations of cable trays and supply and exhaust air ductwork.
Although not indicated in Figures 1 or 2,-
two smoke detectors are provided-in the one exhaust-duct.in the zone, with one located near each unit's -control boards. ' An F
additional two detectors are also provided.in the ductwork:at.the i
[
HVAC_ fans (located in a separate fire area)'for purposes of fan shutdown.
l' t
The existing spacing.and location of detectors in~the Main Control Room has been evaluated as~part of a review'of compliance 1
{
~ vith the criteria of NFPA 72E-1974.
.This evaluation indicates v
s Page 2-F
.I 1
g
the need-to relocate and/or add new detectors in order to conform with the criteria of NFPA-72E-1974.-
Figure 1 indicates where detectors should either be relocated or added in order to conform with code-criteria.
(Detectors that could be relocated are those attached to the bottom of the girders along column lines 20 and 19.
The decision on whether or not. these' detectors will be relocated, as opposed to-solely installing additional detectors, is dependent upon the ease of relocating versus adding detectors.)
These modifications will be completed by the end of 1986.
In the Auxiliary Electric-Equipment Rooms (AEER),
the locations of detectors were identified in the 1977 Fire Hazards.
Analysis for Zion Station and the resultant March 1978 SER.
Detector coverage was deemed to be acceptable in these locations per Sections 5.4 ar.d 8.0 of the SER.
Results of the code conformance review of detector locations against the criteria of
~
NFPA 72E-1974 indicates that the AEERs are in compliance with the spacing and location criteria of the code.
QUESTION 280.2 The statement is made on pages 7-13 and 7-71-that structural steel supporting exterior boundaries are not ' protected by
" fire-rated materials" because there are no adjacent safe shutdown components or exterior fire hazards.
Verify that failure of exposed structural
- steel, due to an interior fire, will not affect any other required boundaries or safe shutdown equipment.
Page 3
o
RESPONSE
o Unprotected structural steel supporting. exterior boundaries-are referenced in five (5) separate locations of Section 7.
Two-are in Section 7.2,-
on pages 7-7 and 7-11, which is the Main Control Room. fixed suppression exemption request.
Both references-identify unprotected-structural steel supporting the roof of the Main Control Room.
A third location is on page 7-13 in Section 7.3, which is the fixed suppression exemption request for both Auxiliary Electric Equipment. Rooms (AEERs).
This reference identifies unprotected structural steel-supporting the roof.
It should be pointed out, though,'that this reference is t
]
apparently in error.
All exposed structural
- steel in the AEERs j
is protected.
The final two references are on pages 7-70 and 7-71 in Section 7.8, which is the exemption request addressing exposed structural steel.
This exemption request identifies exposed structural steel supporting the following exterior barriers:
o Main Control Room (Fire Zone 2.0-0).- beams supporting the roof; o
Unit 1 Diesel Generator Switchgear Rooms (Fire Areas 5.1-1, 5.2-1 and 5.3-1)
.one flange of one embedded column in the west wall of two of the areas, and one flange of two embedded columns in Fire Area 5.2-1; o
Unit 2 Diesel Generator Switchgear Rooms (Fire Areas 5.1-2, 5.2-2 and 5.3-2)
'one' flange of one embedded column in the west wall of two of.the areas, and one flange of two embedded columns in Fire Area 5.2-2; 1
Page 4
r-o Unit 1 4160V. Nonessential Switchgear Room (Fire. Area 5.4-1) - one flange.of two embedded columns in the west
~
wall and beams supporting the roof; o
Unit 2 4160V. ' Nonessential Switchgear Room (Fire' Area 5.4-2) - one flange of two embedded columns'in the west wall and beams supporting the roof; o
The-Unit 1
and Unit 2
Auxiliary Electric Equipment Rooms (Fire Areas 5.6-1 and 5.6-2) - beams supporting.
the roof.
(Note:
This is apparently in error as all exposed structural steel in these two areas is protected); and o
The Auxiliary / Fuel Building Fire Area beams supporting the roof of the 642 ft elevation; one flange of-each column in-the north and. south walls of this elevation; and one flange of one-column-in the south wall of Fire Zone 14.4A-0 on the 617 ft elevation.
Although not specifically identified, exposed structural steel also supports the exterior boundaries of the following two areas:
o Unit 1 Rod Control Drive MG Set Room (Fire Area 5.5-1)-
- beams supporting the roof; o
Unit 2 Rod Control Drive MG Set Room (Fire Area 5.5-2)
- beams supporting the roof; These areas are located between the 4160V Nonessential Switchgear Room and AEER of each unit.
The roof steel of Fire Areas 5.5-1 and 5.5-2 passes over the wall to support the roof of the adj~acent 4160V Switchgear Room.
The roof steel also. butts up against the wall of the adjacent AEER and, due to differences in ceiling heights, does not pass over or carry through the wall-for structural support of the AEER.
Page 5 a
Impact of Combustible Loadings on Catastrophic Steel' Failure-The highest combustible-loadings adjacent to the previously identified barriers are 29 minutes in the Main Control Room (Fire Zone 2.0-0) and 28-minutes on the 642 ft elevation of the Auxiliary Building (Fire Zone 11.7-0).
The loadings'in the Unit I and Unit 2 Diesel Generator Switchgear Rooms vary from 16-21 minutes, while those in the remaining identified plant locations are all under 10 minutes.
The impact of the 29 minute fire severity associated with the combustible loading in the Main Control Room is mitigated by virtue of the area being continuously manned by trained operators.
Reasonable assurance is provided that postulated fires would be detected and extinguished promptly.
The' impact of
^
l a
the combustible loading on the 642 ft elevation of the Auxiliary.
Building is mitigated by virtue of the majority of the i
combustible loading (21 of the 28 minute fire severity is associated with charcoal) being protected by deluge water spray systems.
The Diesel Generator Switchgear
- Rooms, with fire severities between 16 and 21
- minutes, are all provided with automatic detection systems.
These systems provide reasonable assurance of prompt fire brigade response to postulated fires in these areas.
The-purpose of the previous discussion is not to state that the exposed structural steel could not potentially be damaged by I
Page 6
postulated' fires in the identified areas.
The purpose-is to -
clarify the following assumption-which-provided the bases.for the structural steel analysis and proposed modifications identified in the July 1984 Appendix R submittal:
Catastrophic failure of-exposed ~ structural steel-is not postulated.
While the combustible loadings.
in the identified-fire ' areas could raise the L
0 temperature of the steel above 1000 F,'the. main impact would be for deformation of the steel.
Steel deformation could result-in avenues for fire-spread through t,he barrier which it supports;-
- however, the barrier would remain essentially intact and would not collapse.
Based on this assumption, deformation of exposed' structural steel supporting exterior boundaries that (1) does not pass over a boundary fire barrier to support a barrier in an adjacent' fire area or, (2) is not structurally connected-to-or tied into a barrier of an adjacent fire area, will not result in fire spread to adjacent fire areas.
Fire spread will be solely to the-exterior.
Structural steel supporting the exterior boundaries of the following fire areas fall into this category:
s o
Main Control Room (Fire Zone 2.0-0) - beams supporting the roof; and o
The Auxiliary / Fuel Building Fire Area beams supporting the roof of the 642 ft elevation; one flange
~
of each column in the north and south wallsaof this elevation; and one flange of one column'in Fire Zone 14.4A-O on the 617 ft elevation.
1 i
Page 7
=
As such, deformation of the structural steel in the exterior boundaries of the two identified fire areas will not result in fire spread to adjacent fire areas and will not impact on redundant safe shutdown capability.
Exposed Structural Steel Supporting the Roof The steel supporting the roof of each units Nonessential Switchgear Room passes over/through the vall separating it from the adjacent Rod Control Drive MG Set Room.
The roof steel in each Rod Control Drive MG Set Room butts up against, but is not structurally tied into, the adjacent Auxiliary Electric Equipment Roem.
Fire
- could, therefore, spread between the adjacent Nonessential Switchgear Room and Rod Control Drive MG Set Room of each unit given a fire in either area.
Since neither area is required for safe shutdown purposes, fire spread between the two areas of each unit will not impact on redundant safe shutdown capability.
Fire will not spread to the adjacent AEER given a fire in either area as exposed structural steel does not pass through and is not structurally tied into the barrier separating the areas.
Exposed Flanges of Embedded Columns There are three Diesel Generator Switchgear Rooms per unit located on the 617 ft elevation., One embedded column in the west wall of two of the areas in each unit (Fire Areas 5.1-1 and 5.3-1 in Unit 1 and Fire Areas 5.1-2 and 5.3-2 in Unit 2) has a flange Page 8
m j
exposed to'the fire area.
These' columns. travel up to the roof of 642 ft' elevation and are'not exposed ~onJthe 642 ft elevation.
As such, deformation of the steel in 'the two areas of each~ unit on the 617 ft elevation will result in' fire: spread solely to the exterior and not to the level above..
The remaining area in each unit.on.the 617 ft elevation,.
Fire Area 5.2-1 for Unit 1 and: Fire Area-5.2-2 in Unit 2, have two embedded columns in the west wall.
Each column has one flange exposed to the fire area that travels up to the roof'of the 642 ft elevation.
On the 642 ft elevation,-the_two columns are embedded in the west wall of Fire. Areal 5.4-1 in Unit 1 and-5.4-2 in Unit 2.
The two embedded columns in each area have one flange exposed to the fire area.
Therefore, the potential exists for fire to spread to/from the Diesel Generator Evitchgear Room' of each unit to/from the Nonessential Switchgear Room above via steel deformation.
Fire spread to the Nonessential Switchgear Rooms of either unit (5.4-1 or 5.4-2) will not impact on redundant safe shutdown capability as they are not' required for safe shutdown purposes.
Should fire spread to the Diesel Generator Switchgear Room of either unit (5.2-1 or 5.2-2),
redundant safe shutdown capability is available in adjacent fire areas.
QUESTION 280.3 Provide additional information to substantiate that installation of a fixed suppression system in the Auxiliary Electric Equipment' Page 9
s Rooms (page 7-17, 'Section. 7.3.5) has a potentially detrimental impact on safety due to freezing of instrumentation and relays should an inadvertant operation of the suppression system occurs.
RESPONSE
The AEERs are located on the ~642-ft elevation of the Auxiliary Building.
Equipment within each area that is required for safe shutdown purposes has only been designed and specified 0
0 l
for temperature ranges of 75 F
+10 F, for an effective range of 0
0 65 F to 85 F.
Outside of these ranges,.the validity of signals received by the equipment cannot-be assured.
l At the time of inadvertent CO2 or Halon System actuation, the potential exists to lower the temperature in the area to less 0
than 65 F.
This is regardless of the location of discharge nozzles or which suppressant is used.
The instrumentation and i
relays will not freeze at this temperature.
- However, 0
temperatures lower than 65 F are beyond the lower range of operating temperatures specified for the equipment in these areas.
The potential for invalid signals and
- hence, jeopardization of safe shutdown capability, overrides the beneficial impact of installing an automatic gaseous suppression system in the AEERs.
~ Supplemental Information Appendix R
Section III.G.3 addresses conditions whereby alternative shutdown capability shall be provided in the area, Page 10
room, or zone under consideration.
Section III.G.3(b) indicates that fire detection and a fixed fire suppression system shall be installed in the area,
- room, or zone under consideration. _The AEERs are the
- areas, rooms, or zones under consideration; therefore, a fixed suppression exemption request was submitted for review.
The exemption request was submitted even though a potential basis for Appendix R nonapplicability exists.
Sections 2.3.5.9 and 2.3.5.12 of the 1977 Fire Protection Report for Zion Station (submitted in response to the criteria of Appendix A to BTP APCSB 9.5-1) described in detail the location of passive and active fire protection for these two areas, along with the existing safe shutdown capabilities.
Figure 2.3-2, Sheets 1
and 3 of 4, graphically depicted the two areas and the existing fire protection capabilities.
The March 1978 SER on Zion Station was based on the information contained in this report.
Section 5.4 of the SER specifically addressed the fire protection and safe shutdown capabilities for the AEERs.
Section 5.4.6 addressed modifications to the fire protection features of these areas (fire doors, fire dampers, coating structural steel, and providing ladders for firefighting in adjacent areas).
These modifications were completed.
With respect to safe shutdown capability, Section 5.4.6 required the performance of a
separation analysis, with alternate shutdown capability to be Page 11
i..
~.
1--
-I provided if required.
Based,on the modifications' identified in'
~ t Section 5.4'.6, the fire, protec#clon i features in the AEERs.vas found to be acceptable.
s-i
' QUESTION 280.4 Provide additional-information with regard to routing-of safe..
shutdown cables in the Fuel-Building fire area (page 7-25,l Section'7.4.4).
The' information should include, as a minimum separation between redundant circuits-and identification of' intervening combustibles.
Also include fire loading in the areas of routing.
RESPONSE
[
The Fuel Builkling is part of a
larger fire area that also includes the Auxiliary Building.
The Fyel Building is located west of column line R ith the-Auxiliary @ui ding to the east.
Safe shutdown equipment and/or cables are rpt located in or s
routed through the Fuel Building portion of' the fire l area; al'1 1
equipment and cables,for safe shutdown purposes are-in the Auxiliary Building portion of the area.
Figures 7.4-1 through 7.4-6 in the Appendix.R submittal graphically depict theLlogatihn, e
and
- touting of safe shutdown equipment and cables M the.
s s
AufliaryBuildingportionof the fire area. - Please note that t
the solid horizontal line appearing near the ' top of each page rgughly corcesponds with
, column line *R.
These figures, when utilized in conjunction with the text portion of S'ction 7.4, e
provide detailed information on the routing of safe nihutdown cables, including separation distances, locations of interyening i
(
Page 12.
9-
4 combustibles, and the fire loadings in the vicinity of the safe shutdown cables.
QUESTION 280.5 Provide additional information to substantiate that redundant centrifugal charging pump and RHR pump cubicles meet the criteria of Appendix R,Section III.G.2(a).
The statement made on pages 7-27 and 7-34 indicates that unrated access doors, with sheet metal. transoms, are provided for these cubicles.
RESPONSE
The RHR pumps are located on the 542 ft elevation'of-the Auxiliary Building.
They are enclosed by reinforced concrete barriers.
A three hour rated wall with a three hour fire damper in the HVAC duct separates redundant RHR pumps within each unit.
i As
- such, the barrier separating redundant pumps meets the criteria of Section III.G.2(a) of Appendix R.
The remainder of the_ barriers, including unrated access doors and undampered HVAC.
ducts, were identified in the 1977' FHA for Zion Station and accep'ted in the March 1978 SER for the plant.
See Section 8.0 of the SER for further information.
An exemption is neither requested nor required for the unrated access doors and e
undampered HVAC ducts in those portions of the barriers previously accepted under the Appendix A process.
See pages 7-26 through 7-27 for additional discussion.
The CVCS centrifugal charging pump cubicles are located on the 579 ft elevation of the Auxiliary Building and are enclosed by reinforced concrete barriers.
A three hour rated wall with-a Page 13
v d
three hour fire damper in the HVAC duct separates redundant centrifugal pumps within each unit.
As
- such, the barrier separating redundant pumps meets the criteria of Section III.G.2(a) of Appendix R.
The remainder of the barriers, including unrated access doors and undampered HVAC ducts, were identified in the 1977 FHA for Zion Station and accepted in the March 1978 SER for the plant.
See Section 8.0 of the SER for further information.
An exemption is neither requested nor 1
required.for the unrated access doors and undampered HVAC ducts in those portions of the barriers previously accepted under the Appendix A process.
See pages 7-35 through 7-38 for additional discussion.
QUESTION 280.6 Verify that intervening combustibles on the 560 ft elevation (page 7-31) in the vicinity of the.CCW pumps consist only of two groups of four cable trays and that each tray has a solid bottom and is provided with a tray cover.
RESPONSE
The type, quantity and location of intervening combustibles-in the vicinity of the CCW pumps were field verified by Franklin Institute, Rolf Jensen, CECO, and EPM personnelLon December 11, 1985.
Each of the identified trays (two groups of four)~is provided with a solid bottom.
Page 7-31 cf the exemption request identified that each tray would be " appropriately fire stopped (i.e., provided-with tray covers)."
Due-to'the potential for Page.14
).
tray covers to be removed, each tray was fire-stopped.
Two 2-ft sections of materials which were previously approved for penetration seals as identified in' the March 1978 SER for Zion Station were used for the fire-stopping materials.
The sections in each tray are located approximately 10 ft apart so as to ensure.that' cable tray fires, or fires occurring below the cable trays, will not impact on at least'two of the five CCW pump power feeds.
A minimum of two pump power feeds are required to safely shut down both units simultaneously.
The locations of the firestops were identified and verified by Franklin Institute, Rolf Jensen, CECO and EPM personnel during the December 11, 1985 site walkdown.
QUESTION 280.7 Confirm that all five CCW pumps located in close proximity on elevation 560 ft (Page 7-31) are not subject to damage from fire suppression activities or from the. rupture or inadvertent operation of the installed CO2 local fire suppression system.
RESPONSE
The CCW pumps are located on the 560 ft elevation of the Auxiliary Building in Fire Zone 11.2-0.
Two of the five pumps are required to safely shut down both units simultaneously.
The pumps are side by side on the east wall of Fire Zone 11.2-0, with-a centerline-to-centerline separation distance of 14 ft 1 in.
The two most remote pumps have a
centerline-to-centerline separation distance of 56 ft 4 in.
Page-15
'I
y, Fire Brigade Activities The fire fighting agents that could be appliedJto the CCW pumps are water from the nearby manual hose stations and CO2 either from portable extinguishers or from the automatic-CO2 system protecting each pump.
A fire involving a CCW pump would either be the result of transient combustibles or, most likely, an electrical fire involving the motor.
The fire brigade has been properly trained on hose and extinguisher handling techniques.
Because the pumps are 14 ft 1 in on centers, the l.
fire brigade has adequatt room to direct a narrow " power cone"
?
spray pattern to effectively control a
fire in one motor.
]
Therefore, water or CO2 applied by the' fire brigade to one CCW:
pump will not damage adjacent pumps.
i Standpipe Rupture The potential for flooding conditions was reviewed on the 1
560 ft elevation of the Auxiliary Building due to the presence of three vertical standpipe runs and the horizontal ring header for the standpipes on this elevation.
As each-standpipe is located in the vicinity of an open stair which does not have a raised lip around its perimeter, water can freely flow -down to the 542 ft elevation. The high and low points of the ring header are 575 ft-5'in. and 567 ft 5-1/2 in.,
respectively.
The horizontal ring 1
header runs east-west to the south of - CCW: pump OE and then runs north-south behind, or to the east of, all~five CCW pumps.' The Page 16 4
+
y v--
L~
ring header is, therefore, located approximately 10 ft to the east of all five pumps.
Pipe rupture of the standpipe system is only being postulated for fire-induced failure of the systems.
Pipe rupture of the standpipe system would have to be of the catastrophic variety to impact on safe shutdown equipment.
A catastrophic failure of suppression piping would result in large diameter openings relative to the diameter of the piping itself.
Water exiting from these openings would have a relatively short in-air travel distance.
Due to the expected spray pattern resulting from a
catastrophic failure of the standpipe
- piping, water is not expected to impinge on more than two pumps prior to spreading out evenly along the surface of this elevation.
As with failure of the vertical standpipes, water can flow freely down the open stairs.
In
- addition, the CCW pumps are located on bases a minimum of three inches high, precluding flooding conditions from negatively impacting on redundant CCW pu.T.ps simultaneously.
CO2 Suppression System Operation A local application CO2 system is provided ev(r all five-pumps.
Two headers are
- provided, with pumps OA and OB to the north protected by one
- header, and the middle pump, pump OC, protected by both.
The CO2 P ping for ea:h pump is similar in i
Page 17
that CO2 nozzles apply liquid CO2 - directly around the motor land l-pump.
Liquid CO, having a temperature rating of.approximately -
2 0
110 F, may cause thermal shock ~ to the motors and' prevent them from properly operating.
9 Due to the arrangement' of heat detectors with respect ta) the selector valve on the CO2 piping, a f;re in the vicinity of-pump OC could have resulted in CO2 discharge over all~five pumps
+
simultaneously.
This represented an unacceptable' suppression-effect due to the potential for thermal-shock-to electrical components of the pump motor.
To preclude the possibility of a fire in the vicinity of CCW pump OC resulting in simultaneous.
i discharge of CO2 over all five pumps, the heat detector over pump OC associated with the CO2 header protecting pumps OA, OB.and OC vas removed form the system.
While pump OC is still protected by' both CO2 headers, removing the identified heat detector'provided-reasonable assurance that a fir,e in the vicinity of pump OC will only result in CO2 discharge from the-header protecting pumps OC,
{
This is consistent with existing power. cable separation, as the power feeds for. pumps OA andLOB run to the north half of the Auxiliary
- Building, while those for pumps OC, OD-and OE run to the south half of the' building.
QUESTION 280.8 Verify that the licensee proposes no automatic-suppression.
(partial or full area) -in Fire Zone 11.3-0 (Figure No. 7.4-3) containing redundant Unit. 1 centrifugal chargingL pump power feeds,: motor-driven AFW pump ~ power feeds and the turbine-driven Page-18 r
f e
,n m
,.m e-'
>+v..
a e
,-+w.
n
,-m-ne r-p,
-me
AFW pump.
This information will be used to evaluate the licensee's request for exemption from the requirements that full area detection and automatic suppression systems be installed and from the required 20-ft separation between redundant circuits for the Auxiliary Building Fire Area.
RESPONSE
Charging Pump Power Feeds Outside of the charging pump
- cubicles, the minimum cable separation and protection exists for the Unit 1 charging pump power feeds.
On the 579 ft elevation, a one-hour-rated wrap is provided for the power feed for charging pump 1A.
(On the Unit 2 side, the power feeds for pumps 2A and 2B are well in excess of 20 ft apart free of intervening combustibles.. The power feed for pump 2A is routed out'the rear of the charging pump cubicle and into a totally enclosed horizontal pipe chase.
The chase is a high radiation area with locked access.
The power feed for pump 2B is not routed in this location.)
AFW Pumps and Associated Power Feeds The AFW pumps arc located on the 579 ft elevation.
Heat detectors are provided directly over the pumps for actuation of the local application CO2 system protecting the pumps of each unit, and smoke detectors are located at ceiling level in the vicinity of the pumps.
The turbine and motor-driven pumps of each unit are protected by separate headers of the CO2 system, for a total of two headers per unit.
The AFW pumps consist of two motor-driven and one turbine pump per unit.
The power feed Page 19
for the motor-driven pump furthest from'the turbine-driven ~ pump of each unit has been provided with a one-hour-rated _ fire wrap on this elevation.
Since the turbine-driven pump does not have a power
- feed, it will not be affected by a
fire -on other elevations, and the separation of motor-driven pump power feeds I
on other elevations is not an issue of concern.
As such, the power feeds that are protected with one-hour-rated material need only be protected on this elevation.
Intervening combustibles located in cable trays passing between pumps A and C of each unit will be appropriately fire stopped.
l The Unit 1 turbine driven pump is approximately 23 ft from the' furthest motor-driven pump (which has the one hour protected power feed).
The Unit 2 turbine-driven pump is approximately 16 ft from the furthest motor-driven pump (which has the protected power feed).
Due to a separation distance of only.16 ft between redundant AFW pumps for Unit 2,
the exemption request includes the criteria for 20 ft of horizontal separation distance.
(As previously noted, automatic detection and automatic suppression are provided over all pumps, but not throughout this area.
In addition, intervening combustibles will be appropriately fire stopped.)
Mitigating factors that substantiate the 16 vs. 20 ft of separation distance include a part-height,_part-width concrer.e barrier between the turbine and motor-driven pumps of each unit and steel plate enclosures around the motors of the motor-driven Page 20
pumps.
The concrete barrier and steel plate enclosure prevent direct line of site contact between the turbine and motor-driven pumps of each unit.
As such, a single fire should not impact on redundant AFW pumps of either unit.
See Pages 7-38 through 7-41 of the exemption request for additional discussion.
QUESTION 280.9 Estimate the time in which the hot gas layer from an affected Main Control Board will reach the unaffected Main Control Board.
This questions is associated with the scenario of-smoke spread described on Page 7-54, Section 7.5, between the affected an unaffected Main Control Boards in the Control Room.
RESPONSE
A fire in one unit of the Main Control Room would begin to affect the other unit only after the hot gas layer had banked down to the level of the contacts for the control board switches.
The switches are located on the outside face of the control boards between 3-5 ft off the floor of the Main Control Room, with the contacts located inside the control boards.
In
- addition, the contacts are either totally enclosed or are protected by rubber covers.
The floor area of the Control Room is approximately 5060 ft2 with a ceiling height of approximately 23 ft.
Figures 1 and 2~ depict the layout of this zone on a plan and elevation basis.
Combustible Materials The combustibles in the two unit Control Room consist of:
9700 lb of cable insulation in trays; 9900 lb of cable insulation in cabinets; and, 1500 lb of fiberglass insulation on HVAC ducts.
Page 21
Located above each units control boards are three stacks of four trays each.
The lowest tray in each stack is located about 14 ft. above the floor with the highest tray about 17 ft above the floor.
These stacks are approximately 50 ft long running east-west over the boards of each unit.
The stacks of trays do not run north-south between units.
Each tray is less than 30%
filled by volume.
The caoles are loosely packed into the trays, with the solid tray bottoms visible in most trays.
The worst case scenario for speed of smoke spread between units would be for fire to occur within the cable trays as opposed to within the enclosed control boards.
Fire within the control boards would be slower to develop due to the constriction of the boards themselves and due to the function of the HVAC system, which exhausts air through.the bottom of the control boards.
Therefore, fire occuring within the control boards of one unit would tend to be confined to the control boards.and not spread to the opposite unit.
HVAC System i
The Main Control Room HVAC systen supplies air into the room through registers located immediately above an aluminum egg-crate ceiling.
Air is directed downward, resulting in the plenum above the egg-crate ceiling remaining essentially stagnant.
Smoke or hot gases due to a cable tray fire in the Main Cohtrol Room rises Page 22
directly into this upper plenum region due to the location of I
cable trays.
The HVAC system does not actively transport gases i
from the plenum region elsewhere until the gases bank down to.the
-level of the registers.
Even with the assistance of the supply air registers, smoke propagation downwards will essentially j
i remain a function of the size of the cable tray fire.
This is because the downward push from the registers. is not readily evident, even when standing directly underneath one.
Air is exhausted through filtered vents near the base of the control boards.
During a
Control Room cable tray fire, the boards would be continually purged with clean cool air until the time when the hot gas layer had banked down to approximately two feet above the floor.
The region immediately above the floor and the interiors of the control boards would be the last places that clean cool air would exist before smoke and hot gases were exhausted from the zone.
The effect of continual HVAC system' operation during a Control-Room fire, therefore, is that a
fire in one unit would begin to affect the other unit only after the het gas layer hsd-banked down to the level of the control board vents,less than two feet above the floor.
Therefore, a hot gas volutae of 5060 ft2 x 21 ft = 106260 ft3 i
is required for the smoke to spread down to-the level of the
~
control board. exhaust vents.
l 1
Paga 23 V
g
4 Estimate of Smoke-Propagation The cables in the Main' Control Room have been qualified'by flame tests at least as severe as those listed in IEEE-383. EPRI has determined a
surface-controlled burning rate of 0.1 lb/ min /ft2 for IEEE-383 qualified cables in trays [Ref. 1].
If a very severe fire is postulated for the Control Room that. involves the continuous burning of 100 ft2 of cable tray area until all cable insulation is consumed, the mass burning rate would be:
100 ft2 x 0.1 lb. min /ft2 = 10 lb/ min.
(Please note that the assumption of 100 ft2 og cable tray continuously burning, thereby defining the steady state fire, would require one of the following:
o Burning along one surface of over 16 ft of all.four-18 in, wide trays in one stack simultaneously; o
Burning along one surface of over 8
ft:of all four 18 i
in, wide trays in two side by side stacks simultaneously; or o
Burning along one surface of approximately 5.1/2'ft of all four 18 in, wide trays. in all three side by side stacks simultaneously.
The conservative aspects of this assumption are. evident.'from a comparison with surface flame spread rates of 6-10 ft per hour in horizontal cable trays observed in the Browns Ferry fire).
The air to fuel mass ratio for the combustion process is conservatively assumed to be the stoichiometric ratio ~for the j
combustion of pure polyethylene, which is' approximately.
j Page 24 i
4 I
c,-
15 lb air /lb fuel (Ref. 2).
An estimate for the generation rate of hot gases is therefore:
10 lb/ min-x 15 lb air /1 lb fuel = 150 lb/ min.
The volume of smoke produced by the generation of 150 lb/ min of hot combustion gases can be estimated by conservatively estimating the air temperature of the smoke.
In this manner,'the density of the smoke can be-assumed to be the density of the air.
During FMEC/EPRI [Ref. 1] large scale tests on hypalon cable, the temperature measured by thermocouples 6' 5" above the top tray of a 12 tray array (2 stacks of 6
as opposed to Zion Stations 3 0
stacks of 4) was 840 F.
With a
top tray elevation 'of approximately 6 ft below the ceiling, the temperature of the air at ceiling level can also be assumed to be approximately 840 F.
0 Postulating this to be a
uniform smoke temperature (which would be conservative-also, as the further away_from.the burning tray stacks, the lower the smoke temperature) and treating it as air at the same temperature results in a
smoke density of approximately 0.0315 lb/ft3 (Ref. 3].
This results'in a hot gasE layer growth rate of 150 lb/ min 3
0.0315 lb/ft" = 4762 ft / min An estimate of the time for the layer to reach the exnaust-air filters to the main-control boards (filling a volume of-10G260 ft3), given no fire brigade or operator response, can be estimated as:
l l
Page 25
106260Rft.3 4
4762 ft*/ min = 22.3 min.
The development of a- ' fire involving. 100'ft2.of cable. tray 4
area would take a considerable amount of time, and'the ability to detect and suppress such a fire in the Control Room in less than-20 minutes is very credible.
References:
I
[1]
" Categorization of Cable Flammability Intermediate Scale Fire Tests of Cable Tray Installations,"
EPRI, NP-1881, 1982.
4.
[2]
" Fire Hazards of Materials,"
Section 4,
Fire Protection Handbook, 15th Edition, NFPA,'1981, pp. 4-122, 5-93.
[3]
W.M.
Rohsenow and H.Y.
- Choi, Heat, Mass, -and Momentum-Transfer, Prentice-Hall, Inc.,
Englewood Cliffs, NJ, 1961,
- p. L22.
QUESTION 280.10 Section 7.8 (page 7-69) describes the basis for exemption from the requirements that exposed structural steel ~ forming.part of a fire area boundary be protected. commensurate.with.that i
required of the barrier.
To facilitate the staff's review, 1
provide the following:
(a) Provide the burn rates at which the calculated fuel load I
(minutes) in Table 7.8-1 was determined.
Confirm that these. rates are valid for the combustibles within each-Zone.
l (b) Evaluate the effects of localized heating due to direct exposure to fire plumes from local combustible packages.
1 (c) Confirm that the time-temperature profile of ASTM E-119 4
is conservative-relative to.the heat release rate,of the installed combustibles and to a ventilation controlled-1 fire.
Page 26'
RESPONSE
The basis for the effective fire-rating analysis of. exposed structural steel at Zion Station was the evaluation technique described in Chapter 9 -
" Confinement of Fire,in Buildings", in Section 5 "Firesafety in Building Design and Construction", of the Fire Protection Handbook (lSth
- Edition, NFPA, 1981).. The concept of a fire-rating for a
barrier is based on the barrier performance in a
furnace test that follows the ASTM E-119 standard (also NFPA 251),
in which the furnace atmosphere must closely follow the time-temperature curve specified in the standard.
The intent of this testing standard is to provide a bounding exposure for comparing the relative abilities of different materials to resist the spread of fires.
In this context, a computational method was devised to simulate an ASTM E-119 furnace test to effectively rate the fire resistance of the exposed structural steel.
The fuel burn rates or heat release rates of combustibles requested in 280.10(a) and 280.10(c) would be useful -for a barrier exposure analysis if a
design basis fire were to be employed to represent the limiting fire severity.
This approach would include the burning characteristics of combustibles, room configurations, ventilation conditions, -and the hydrothermal behavior of fires and fire plumes.
Instead.of-using this less Page 27
v conservative or best estimate fire modeling approach,- the limiting fire severity was determined for each fire area containing exposed structural steel as. part of a
boundary barrier.
The fire load-fire severity relationship presented in the 15th edition of the NFPA Handbook (p. 5-90) was utilized in this analysis.
The heats of combustion for all combustibles located within the area were used together with the associated combustible mass inventory, to compute a maximum energy release l
potential for the fire area.
This energy content was then divided by the floor area of the fire area to derive a normalized heat potential, which can be directly related to a standard barrier exposure duration using Table S-9B in the handbook.
An l
equivalence of 80,000 Btu /ft2 fire load with one hour of ASTM E-119 furnace test exposure is evident up to fire severities of three hours.
i No derating of fire loads due to enclosure of combustibles l
in steel cabinets or fluid containers, allowed-as indicated on pg.
5-91 of the
- handbook, was used in the analysis.
A significant reduction in fire severity could have been accomplished through derating, since much of the fire load.was' cable insulation within cabinets and combustible liquids that were completely contained.
In
- addition, the. standard time-temperature curve was developed for fire loads' in l
compartments with ceiling heights similar to residential, office Page 28
and. light commercial rooms..
The ceiling ' heights in the fire areas with the exposed structural steel range between 23 and 70 ft., which implies a significant conservatism in the use of_the ASTM E-119 equivalence.
With the exception of the -Diesel Fuel Oil Storage Tank Room (Fire Area 10.3-1), all of the area fire loads associated with 2
exposed structural steel are below 50,000 Btu /ft (38 min. equi-valent exposure), which is considered a
low or' slight fire load' per pg. 5-92 of the handbook.
With fire loads of this size, the expected fire severity or the time-temperature relationship for barrier exposure during a fire is suggested by curve A in Fig.
5-9E on pg.
5-93 of the handbook.
The standard ASTM E-119 time-temperature relationship used in the structural steel exposure analyses (curve E of Fig. 5-9E) is far more severe for the first 90 minutes of the fire.
The possible effect of limited ventilation of an area that reduced the burning rate from a fuel surface controlled rate to a
ventilation controlled rate, would only be to impede the development of the fire and further reduce the temperatures to which the barriers would be exposed.
In summary, the use of total combustible loading within a fire area to derive a duration of exposure to the ASTM E-119 standard temperature
- relation, without any derating to account for enclosed combustibles, high ceilings or ventilation conditions, results in conservative representations of. barrier exposure Page 29
severity.
In short, developing an equivalent fire rating for the structural steel is more conservative than modeling a credible design basis fire and the steel response.
The direct exposure of structural steel to flames or a plume arising from-burning material adjacent to the member, referenced in 280.10(b), may result in highly localized temperatures that exceed those reached in the first few minutes of'an' ASTM E-119 furnace test.
After only ten minutes, -however, the furnace temperatures are of the order of typical flame temperatures.
Though the structural steel analyses performed for Zion Station did not treat localized design basis fires specifically, the assumption that the entire length of all exposed members within a i
fire area were simultaneously exposed Eto the equivalent E-119 test duration was deemed to be a
greater threat to barrier integrity.
QUESTION 280.11 The description of the Auxiliary. Building' fire area in Section 7.4-1 (pages 7-20 through 7-46) identifies several nonrated fire barrier components in the area boundary wall.
Provide the technical baris for acceptability of each nonrated component as-well as identify what is deficient about such a component that prevents it from being a three-hour-rated barrier.
TEGPONSE 1.
Page 7-21. The two unrated doors identified on this page that are controlled by Health Physics go to the exterior.
Page 30
Access is not provided via these doors to' adjacent. interior fire areas.
An exemption is neither requested nor required for these door openings.
2.
Page 7-21.
The other two unrated doors identified on this page have been replaced by rated fire doors.
Factory Mutual Research Corporation has evaluated the frames of these door assemblies and has found them as being acceptable for fire rated door assemblies. An exemption is neither requested nor required for these door openings.
3.
Page 7-22.
The Primary Containment. airlocks are typical-entrance points into containment for all plants. These airlocks provide adequate protection based on an identified fire loading of approximately 23400' Btu /ft2 in the main open floor area adjacent to these openings.
In addition, fire ratings are generally not available for airlock door access openings.
4.
Page 7-22.-
The unrated doors to the Fuel Building 4
identified on this page are not located in a fire area boundary wall.
An exemption is neither requested nor required for these door openings.
5.
Page 7-23.
The unrated doors to the Fuel Building identified on this page are not located in a fire area boundary wall.
An exemption is neither requested nor required-for these door openings.
6.
Pages 7-26 and'7-35.
See the response to Question 280.2 for the discussion of-the unrated
-doors ~ to the RHR and centrifugal charging pump cubicles.
Page 31
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