2CAN109703, Requests Exemption from Requirements of Section III.G.2 of 10CFR50,App R,For Lack of Automatic Suppression Sys & Lack of Automatic Detection Sys for Area Below Elevation of Unit 2 Intake Structure
| ML20217H576 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 10/08/1997 |
| From: | Mims D ENTERGY OPERATIONS, INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 2CAN109703, NUDOCS 9710160150 | |
| Download: ML20217H576 (10) | |
Text
- - -
"O f7 j
Ent:rgy Oper: tion 2,Inc.
J
(@
1448 SR 333 Rutver AR 72801 Td 501825000 October 8,1997 2CAN109703 U. S. Nuclear Regulatory Commission Document Control Desk A
Mail Station OPl.17 Washington, DC 20555
Subject:
Arkansas Nuclear One - Unit 2 Docket No. 50-368 License No. NPF-6 10CFR50 Appendix R Exemption Request from Section III.G.2 for the Intake Structure Gentlemen:
Entergy Operations requests an exemption from the requirements of Section III.G.2 of 10CFR50 Appendix R for lack of an automatic suppression system and lack of an automatic detection system for the area below the 354' elevation of the Arkansas Nuclear One, Unit-2 (ANO-2) intake structure. The attached information provides the justification for this request.
Should you have any questions, please contact me.
Very truly yours, khC 7)W Dwight C. Mims Of y# j r
Director, Nuclear Safety
~
/
DCM/nbm Attachment 9710160150 P" *"
0060 llllli IlOllllllll!!!Ill,!Ollilillll
' U. S. NRC October 8,1997 2CAN109703 Page 3
'cc:
Mr. Ellis W. Merschoff Regional Administrator U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 NRC Senior Resident inspector Arkansas Nuclear One P.O. Box 310 London, AR 72847 Mr. George Kalman NRR Project Manager Region 1//ANO-1 & 2 U. S. Nuclear Regulatory Commission NRR Mail Stop 13-H-3 One White Flint North 11555 Rockville Pike Rockville, MD 20852 I
Attachment to
-2CAN109703 -
Page1of5
- ANO 2 Intake S;ructure Appendia R Esemption Introduction On July 1,1982, the results of the required 10CFR50 Appendix R compliance review were submitted to the NRC (OCAN078202). The compliance review divided the ANO-2 intake structure invs three levels: 1) below elevation 354', 2) elevation 354' (ground level), and 3) elevation 366'. Although no rated fire barriers separated these levels, each level was analyzed separately. Redundant safe shutdown equipment on all levels of the intake structure is limited to equipment associated with the service water (SW) system.
Physical Characteristics The ANO-2 intake structure is approximately 32 feet by 26 feet on three levels. There are no rated fire barriers between the three levels. Below elevation 354' are the intake bays which contain SW piping and conduits. The bays are approximately 7 feet by 32 feet and are separated from one another by two foot thick non-rated concrete walls. The bays are separated from ground level by an 18 inch thick, non-rated concrete slab on metal decking. The floor of the bays is typically covered with water approximately 16 feet deep.
The ceiling height is approximately 14 feet above normal pool level and approximately 30 feet above the bottom of the bay. ' Of the three bays, only the bay for the red train SW pump (2P4A) contains redundant cables. Access to each bay is obtained by removing a metal hatch cover / metal grating on elevation 354'. Each bay is administratively controlled as a "confmed space" thus limiting access by personnel during routine operations and i
precluding the accumulation of combustibles, Water to the bay is normally provided 1
i through a sluice gate for the bays where the circulating pumps take suction.
Background
On March 22,1983 (0CNA038328), an exemption to 10CFR50 Appendix R, Section llI.G.2 for lack of an automatic fire suppression system was granted for the area below elevation 354' based on the low probability of an exposure fire and the availability of alternate fire protection features (i.e., portable fire extinguishers, manual hose reels,
- automatic detection, and 20 feet separation between redundant cables).
When the exemption request was submitted, the intent was to reroute redundant cables in this portion of the intake structure in order to provide separation of the redundant circuitry by more than 20 feet. However, due to the physical characteristics of the intake structure and its associated duct banks, the desired separation was unachievable.
In lieu of providing 20 feet separraion, a 1-hour rated fire wrap around the redundant conduits was installed per modification package DCP 83-2178. Due to the high humidity environment below elevation 354' (i.e., the SW bays), a moisture barrier for the 1-hour fire wrap was provided. The moisture barrier consisted of a galvanized sheet metal box which completely encompassed the conduits requiring fire wrap in the SW bays (see attached photo).
l Attachment to 2CAN109703 Page 2 of 5
' Subsequent to the installation of the 1-hour fire wrap, the power cabling to the swing SW pump (2P4B) was modified by routing two separate power cables (one red and one green) from the safety-related switchgear rooms to a common transfer switch located in the j
i intake structure (elevation 366'). During the development of the modification package which installed the new cabling (DCP 83-2006), failure to comply with *be basis of the original exemption request (i.e., provide 20 feet separation for conduits below elevation i
~
354') was noted. Rather than submit a clarification to the exemption, a 3-hour fire wrap on redundant conduits was ins:alled in order to provide full compliance with 10CFR$0 Appendix R Section Ill.G.2.a. This was documented in the supplemental information for 4
the Appendix R reanalysis dated August 30,1985 (0CAN088508).
During the implementation of DCP 83-2006, the correct conduit (EA1007) requiring protection, failed to be identified. It appears that the fire wrap designers were unaware of the moisture barrier and the fact that the SW pump power cables were routed in conduits encapsulated by the box - Consequently the 3-hour fire wrap was installed on the wrong conduit (B8019).
This condition was documented in CR 2-94-0023 and in NRC inspection report 50-368/94-06. (Note: A portion of the Thermolag in the "C" SW bay has been removed.)
l Since the existing physical conditions and fire protection features are different from_those 4
previously approved on March 22,1983 (0CNA038328), Entergy Operations seeks to obtain an exemption from the requirements of 10CFR$0 Appendix R,Section III.G.2 for lack of an automatic suppression system and lack of an automatic detection system for the area below elevation 354' in the ANO-2 intake structure.
s CombustibleI adias d
{
The insitu combustible loading below elevation 354' is minimal and consists of Thermolag installed on two conduits _ and approximately 90 feet (30 feet per bay) of two inch diameter L
polyvinyl chloride (PVC) piping associated with the chemical addition system. The insitu loading report (89-R-0003-01) computed the value of the insitu combustibles as 3,469,060 c
BTUs. This combustible loading will support a fire severity equivalent to a standard fire deation of approximately 3.5 minutes. This value reflects the loading of the Thermolag i
and PVC piping contained in all three bays. Although the walls that separate the bays are
.not fire rated, they act to effectively shield the loading in each individual bay from the 3
j effects of the loading in the other bays. Furthermore, during normal operations, a portion of the PVC piping is submerged beneath water and therefore, is not'a contributor to the combustible loading.
i 2
- Attachment to 2CAN109703 Page 3 cf 5
'There are no cable trays in the SW bays; therefore, there are no exposed cables and no combustible loading due to cable insulation. The accumulation of transients is precluded by the fact that the floor of this area is normally beneath water level. The exception would be when the bay is drained to allow infrequent maintenance activities.
Current administrative controls require a continuous fire watch to be posted whenever combustible materials are allowed la the SW bays.
Existian Protection Features Conduit EA1007 (see attached drawings) contains the power to 2P4A. This conduit is enclosed by the moisture barrier and is protected by 1-hour HEMYC fire wrap. Conduit EA2036 (formerly numbered as EA5004) contains the green trsin power cables to 2P48, the swing SW pump. This conduit is also enclosed by the moisture barrier and protected by 1-hour HEMYC fire wrsp. Both of these conduits enter the 2P4A SW bay from an exterior duct bank and immediately turn and vertically run along side the intake wall.
{
Conduit EA2007 enters the 2P4A SW bay approximately six feet (horizontally) from i
EA1007 and contains the power cable for 2P4C, the green train SW pump. The red train f
power cables to 2P4B (swing pump) do not enter the intake stmeture below elevation 354'.
)
l The upper two levels (elevations 354' and 366') of the intake structure have flame l
detectors and/or ionization smoke detectors and a preaction suppression system. Portable fire extinguishers and a hose reel station (located in the adjacent ANO-1 intake structure) are available for manual fire suppression.
In the upper levels, the cabling in the conduits for the SW pumps are located in raceways and are either: 1) protected by 1-hour barriers, 2) separated by greater than 20 feet, 3) embedded in the floor slabs, or 4) the subject of an existing approved exemption to the separation requirements of 10CFR50 Appendix R, Section III.G.
Safe Shutdown Analysis Service water is required to be available to supply cooling for various safe shutdown components including the diesel generators and the_ shutdown cooling heat exchangers.
Additionally, SW can be aligned to the emergency feedwater system in the event that the desired condensate sources are depleted. The SW system consists of three pumps which can be aligned to two flow paths. The swing pump,2P4B, can be aligned to either flow path. Only one flow path needs to be established to provide safe shutdown capability.
l The time critical function would be to supply cooling for the diesel generators.
I Calculations have determined that the diesel generators (and therefore the SW system l
components) are not required to be operated during the first 30 minutes of the postulated
_ fire event.
' l Attachment to 2CAN109703 Page 4 cf 5 q
'Pumo Alinnments I
L2P4A and 2P4B (green train alignment) in service: EA1007 and EA2036 are enclosed by the_ moisture barrier and protected by the 1-hour fire wrap systems. 2P4B can also be realigned to the red train via conduit EA1008 which does not enter the bay Currently, the i
safe shutdown capability assessment (Calculation 85-E-0087-01) allows operator actions to manually align the SW system. Manual actions were justified after the analysis determined that the charging pumps and diesel generators were not required during the first 30 minutes of the event.
2P4A and 2P4C in service: EA1007 (2P4A) is enclosed by the moisture barrier and protected by the 1-hour fire wrap. EA2007 (2P4C) is approximately six feet away and is currently covered by "3-hour" preshaped Thermolag sections. No credit is taken for the l
Theimolag to meet the requirements of Appendix R.
2P4B (red train alignment) and 2P4C in service: The red train cable to the swing pump does not enter the area below elevation 354',' Instead it is routed through an embedded conduit (EA1008) and thus is not subject to damage by a fire in this portion of the intake structure. This is the only pump alignment where the bay containing the redundant cables would be allowed to be drained and therefore, be subject to the accumulation of transient combustibles. Although current administrative procedures require a fire watch to be posted, the fire watch would not be needed because no redundant SW pump circuits are in the SW bays during this pump alignment.
Other Safe Shutdown components Power and control cables for the sluice gates are routed in conduits EB1008, ECll40, EB2008, and EC2132 which are located in the SW bays. Sluice gate valves 2CV1470-1, 2CV1472-5, and 2CV1474-2 are normally open which correspond to the safe shutdown -
position. The redundant control cables are separated horizontally by approximately eight feet. As stated previously, the time critical function of the SW system is to provide cooling to the diesel generators. If a fire were to somehow cause the sluice gates to spuriously close, adequate time (i.e., 30 minutes) is available to perform manual realignment of any affected component._ Consequently, no additional fire protection measures are warranted to address the redundant circuitry associated with the sluice gates.
Conclusion The intake structure SW bays contain a minimal amount of combustible material and no credible ignition sources. Consequently, the likelihood of an exposure fire occurring in the SW bays is extremely remote. Additionally, the elevations above the SW bays contain flame detectors and/or ionization detectors that will provide early indication of a fire in the intake structure.
Attochment to 2CAN109703 Page 5 of 5
,In the unlikely event of a fire occurring in the SW bays, two of the four conduits that supply power to the SW purnps are protected by a fue protection material that will prevent damage to more than one train. While one of the remaining conduits is enclosed with Thermolag, no credit is taken for the fire resistive properties of the installed configuration. The fourth conduit is embedded in concrete and therefore, not subject to l
damage f om a fire in the SW bays.
All other cables associated with safe shutdown components (i.e., the sluice gates) are not l
required. Manual actions em be taken to mitigate the effects of any postulated cable i
damage.
Considering these factors, Entergy Operations believes that an automatic suppression system and automatic detection system installed within the SW tays will not provide significant enhancements to the existing fire protection features. The present protection is adequate to assure that at least one safe shutdown path la preserved.
i
>[~[@
"4 st $
k.
7.
zw
~
~.
/
.,(. 3 p,-
e Thennolag N,1, $ 1 7
- /,J 1L
.. g..
a 1-t
. t..
1 1.,. e
? ~,,
k e
'l'
, g,g, ;,'
w, j\\ *w1 l
,,.. w ;. g..,ji a.
k:).h_y..'. hf "A" Service Water Bay A galvanized sheet metal bor serves as a moisture barrier.
Conduits EA1007 and EA2036 are covered with one hour fire barrier material. Both are enclosed by the sheet metal box. Thermolag applied to the incorrect conduit is visible on the far side of the box.
i
-l 1
.l Arrangement of Service Water Pump Power Cables in the intake Structure 2P4C 2P4B 2P4A i
1 Hr. Wrap 1 Hr. Wrap 2A5j T
2B43 4-1 Hr. Wrap i
i N
I i Elev. 354' 1 Hr. Wmp 1 Hr. Wmp M36 +
EA1007 ->
EA2007
- - B8019 Thermolag Thermolag Em W (partially removed)
EA1008 I
From 2B4 2A4 (outside intake structure) 2A3 Green Train Figure 1 Red Train Power Power
l CONDUlT LAYOUT INTAKE STRUCTURE - BELOW ELEVATION 354' EL. 354'-8" is g
o L
EL. 350* 6" t
EL. 348'-5" THERMOLA0 REMOVED ON THIS PORTION OF CONDUli
(*C" SW CAYl d (C) 10)
(A)
EL. 322'-8" 2*-t' 7*-R" 2*-q 7*.2*
2*. q' 7 * - 2" 2*.q ELEVATION VIEW LOOKING NORTHWEST EA1008 EL. 354'-8" ii L.8 T
T T
4 T
1 ll ll ll EC2132 EB2008 i s i s i ll ll ll 0o oo ll ll ll ll ll ll
!l ll ll EA2007 ECil40 88019 EA1007 EB1008 EA2036 6'- 4 "
SECTION A-A LOOKING NORTHEAST