B16607, Notifies NRC Staff of Condition in Outer Annulus Region of Unit 3 Containment,Deviating from Technical Position (BTP) Cmeb 9.5-1 Section C.5.b & C.7a

Notifies NRC Staff of Condition in Outer Annulus Region of Unit 3 Containment,Deviating from Technical Position (BTP) Cmeb 9.5-1 Section C.5.b & C.7a

ML20199D899
Person / Time
Site:	Millstone
Issue date:	11/13/1997
From:	Brothers M NORTHEAST NUCLEAR ENERGY CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RTR-NUREG-1031 B16607, NUDOCS 9711210049
Download: ML20199D899 (15)

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, Waterford, Ur W.E-0128 (N.0) 447 1791 Iat (860) 444 4277 W Nordet ti ilinet Symicia NOV l 31997 Docket No. 50 423 B16607 U. S. Nuclear Regulatory Commisrion Attention: Document Control Desk Washington, DC 20555 Millstone Nuclear Power Station Unit No. 3 Deviation from BTP CMEB 9.5-1 The purpose of this letter is to notify the NRC Staff of a condition in the outer annulus region of the Millstone Unit No. 3 containment which deviates from Branch Technical Position (BTP) CMEB 9.5-1 Section C.5.b and 0.7a. This condition has been evaluated in accordance with 10CFR50.59 and does not constitute an unreviewed safety question. In addition, Northeast Nuclear Energy Company (NNECO) is informing the NRC Staff that a change has been made to the shutdown methodology for certain fires postulated to occur inside containment for monitoring reactor coolant system (RCS) pressure.

In a letter dated December, 9,1985,' the U. S. Nuclear Regulatory Commission issued Supplement No. 4 to the Millstone Nuclear Power Station, Unit No. 3 Safety Evaluation Report (SER). Section 9.5.1 of this report (NUREG-1031 Supplement No. 4) documents the NRC Staff review and acceptance of the fire protection program at Millstone 3. Included in Section 9.5.1.4 is a discussion of " Fire Protection for Safe Shutdown Capability" which addresses, among other items, the safe shutdown pet.

capability for fires in containment. Section 9.5.1.4 includes an approved deviation from g Sections C,5.b and C.7.a of Branch Technical Position (BTP) CMEB 9.5-1 related to g-fire protection for safe shutdown capability in the containment electrical penetration g' area. Specifically, the electrical penetration area inside containment does not fully g, comply with section C.7a(1)(b) as redundant cables are not separated by the g, recommended horizontal distance of 20 feet, g.

As a result of recent design basis review for fire protection at Millstone 3, it was identified that some redundant cables and equipment in the outer annulus region, outside of the electrical penetration area, do not comply with Section C.S.b or C.7.a of BTP CMEB 9.5-1. This condition has existed since original plant construction.

Although there is an approved deviation f,or,the electrical penetration area, which is inh

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' B. J. Youngblood letter to J. F. Opeka, ' Issuance of Supplement No. 4 to \ \

NUREG 1031 - Millstone Nuclear Power Station. Unit No. 3," dated December 6,1985.

-9711210049 971113 I

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- U.S. Nuclear Regulatory Commission B16607/Page 2 the outer annulus area, the record doe' s not discuss these additional cases. The review also identified that a modification implemented in 1993 detrimentally affected the shutdown methodology for certain fires in containment for monitoring RCS pressure.

This condition was evaluated and it was determined that mod!'ications could be made to provide added assurance that Millstone 3 could achieve and maintain safe shutdown conditions in the event of a fire in the affected areas. These modifications were evaluated in accordance with 10CFR50.59 and do not constitute an unreviewed safety question. NNECO also evalusted the condition to the guidance provided in BTP CMEB 9.5-1 and determined that, although the change is safe. It devistes from that guidance.

This change affects the Millstone Nuclear Power Station, Unit No. 3 Safety Evcluation Report Section 9.5.1. The Millstone 3 BTP9.5-1 Compilance Report ir being updated to reflect those changes in accordance with procedural requirements.

Specific detail of this condition which deviates from BTP CMEB 9.5-1 is provided in Attachment 1.

Should you have any questions regarding this submittal, please contact Mr. David A.

Smith at (860) 437 5840.

Very truly yours.

NORTHEAST NUCLEAR ENERGY COMPANY Ab] h M. H. Brothers N \

Vice President - Millstone Unit No. 3 cc: H. J. Miller, Region i Administrator J. W. Andersen, NRC Project Manager, Millstone Unit No. 3 A. C. Cerne, Senior Resident inspector, Millstone Unit No. 3 W. D. Travers, Ph.D., Director, Special Projects Office

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- U.S. Nuclear Regulatory Commission B16607\ Attachment 1\Page 1 MILLSTONE UNIT NO. 3 CONTAINMENT-OUTER ANNULUS APEA Branch Technical Position BTP 9.5-1 position C.7.a(1)(b) states, inside noninerted containment one of the fire protect!on means stated in Position C.5.b.1 and C.S.b.2 or the following fire protection means should be provided:

separation of cables and e,quipment and associated nonsafety circuits of redundant trains by noncombustible radiant energy shield having a minimum fire rating of one-half hour. .

Position C.S.b.1 and C.S.b.2 are stated below.

Position C.S bl Fire protection features should be provided for structures, systems, and components important to safe shutdown. These features should be capable of limiting fire damage so that:

(a) One train of systems necessary to achieve and maintain hot shutdown conditions from either the control room or emergency control station (s)is free of fire damage; and (b) Systems necessary to achieve and maintain cold shutdown from either the control room or emergency control station (s) can be repaired within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

Position C.S.b 2 To moet the guidelines of Position C.S.b.1, one of the following means of ensuring that one of the redundant trains is free of fire damage should be provided:

(a) Separation of cables and equipment and at,sociated circuite of redundant trains by a fire barrier having a 3-hour rating. Structural steel forming a part of or supporting such fire barriers should bs protected to provide fire resistance equivalent to that required of the barrier; (b) Separation of cables and equipment and associated circuits of redundant trains by a horizontal distance of more than 20 feet with no

A '-4 4-A 4 > - -.- -a.. w-W--+= r- e 2-4.Ar 342 U.S. Nuclear Regulatory Commission B16607\ Attachment 1\Page 2 Intervening combustible or fire hazards. In addition, fire detectors and an automatic fire suppression system should be installed in the fire area; or (c) Enclosure of cable and equipment and associated circuits of one redundant train in a fire barrier having 1-hour rating. In addition, fire detectors and automatic fire suppression should be installed in the firo area.

Fire Protection Features and Previousiv Anoroved Confiouration The containment is a large fire resistant structure formed from concrete and steel. Combustibles are limited to lubricating oil, charcoal filter, and cabling.

During power operation, access to containment is limited. Fire Protection features for containment consist of the following:

o a wet piped sprinkler system installed in the electrical penetration area to protect redundant cabling that enter containment, o smoke detection to provide early warning of a fire condition, o heat detection at the lower elevation of containment and at the Reactor Coolant Pumps (RCPs),

o standpipe hose stations on all elevations, l

l o portable fire extinguishers at the containment entrance in the auxiliary building, o c seismically designed oil collection system for the RCPs.

Safe shutdown process monitonng instrumentation is routed below the 51' 4' l elevation in the containment outer annulus. The annulus is approximately 12 feet wide and extends through multiple elevations in wntainment. The -24'6",

3'8',24'6', and 51'4' elevations are separated primarily by steel grates, although some cont. rete platforms are used. Open stairs connect all elevations.

Automctic smoke Atectors have been provided in the annulus. The location of annulus smoke detectors was approved by NRC in Supplement 4 to NUREG-1031, dated December 1985.

In addition to the originally installed features, additional sprinklers have been instalKd in the electrical penetration area to extend the existing sprinkler coverage from the 37' elevation up to the 54' elevation. Tray covers and fire stops have also been insta!Ied in certain cable trays in the outer annulus to

U.S. Nuclear Regulatory Commission B16607\ Attachment 1\Page 3  ;

reduce the possibility of fire spread in certain cable trays and to exclude cables as intervening combustibles.

Combustible Materials The combustible material on the elevations of concern in the annulus consists prodominantly of exposed cable insulation in cable trcys. The cable trays contain.lEEE 383 qualified cables previded with circuit fault protection. As a ,

result, the cables in the trays am n)t an ignition hazard. The cables do, however, represent a potential intervening combustible material between redundant trains of process monitoring instrumentation in the containment outer annulus.

The cable trays are routed primarily in a horizontal configuration. A stack of cable trays, two and three trays deep, is routed just below the 24'6" elevation.

Another Stack of cable trays, between five and eight trays deep, is routed just below the 51'4" elevation. Additional cable trays are routed above the 51'4' elevation. The trays are typically open ladder bottom trays with sheet metal ,

covers provided on top of the trays.

Vertical trays / risers are typically not used in the annulus. Short runs of vertical trays are located between column lines 18-19 that extend from the trays above the 51'4' elevation to just below the 51'4' elevation. Vertical cable trays, protected by sprinklers, are also located at the electrical penetration area between column lines 1 and 3 at elevations 24'6" and 45'6". Other vertical cable runs in the outer annulus are routed primarily in conduit. Therefore, vertical fire ,

spread via exposed cable insulation between elevations containing required process monitoring instrumentation is not considered credible.

Horizontal fire spread via cable insulation in cable trays has been pos.lulated even though the type and arrangement of cables require a significant exposure fire to cause ignition and horizontal fire spread. The lack of transient combustible materiah, in containment during power operation, plus the RCP lube oil coliection systems inside primary containment, limits the potential for the required type of exposure fire that could cause ignition of, and horizontal fire spread in, exposed cebles in the cable trays. No other significont fire sources exist in the containment outer annulus.

The potential for fires in containment has been addressed in NRC SER Supplement 4, which states:

" redundant cables are located within 20 feet of one another in the electrical penetration area. To compensate for the limited spatial separation,

U.S. Nuclear Regulatory Commission B16607\Alischment MPage 4 the applicant has installed an automatic wet pipe sprinkler system that protects the cables where they are vulnerable to fire damage."

The SER goes further to identify that:

'If a fire were to occur in these locations in containment [...), the staff expects the existing fira detection system to actuate early, while the fire is in its formative stages and before significant flame propagation or temperature rise occurs. An alarm would be sent to the control room. The fire brigade would be dispatched and would ext,.,guish the fire using manual fire-fighting equipment. Until the brigade arrivod in containment or if rapid fire propagation occurred, the staff expects the automatic sprinkler system at the penetration area to actuate and control the fire and protect the shatdown-related cables.'

The conditions identified in NUREG-1031, Supplement 4 still exist in the electrical penetration area based on the existin0 and modified fire protection features. The following mitigating features are also applicable to the separation of the redundant instruments between column lines 1 and 3 in the electrical penetrations area and other arear between column lines 20 and 9, and provide additional justification for the acceptability of the configuration:

1. The installed detection system, which was accepted in NUREG-1031, Supplement 4, provides appropriate coverage. Potential fires that occur in, or present an exposure ha7ard to, the electrical penetration area or other portions of the outer annulus will be detected in the incipient stage.

Activation of the detection system will transmit an alarm to the continuously manned control room, which will also result in prompt dispatch of the fire brigade for manual suppression activities.

2. The absence of transient combustible materials during normal power operations, along with the use of IEEE-383 qualified cables with circuit fault protection, provide reasonable assurance that a cable-induced fire l would not occur ir, the electrical penetrations area. The fire would have to originate from a heat source in the annulus away from the penetrations area and spread along the horizontal cable trays to the penetrations area.

3. The only intervening combustibles between the redundant trains of l

process monitoring instrumentation in the electrical penetration area l between column lines 1 and 3 are cables in the vertical risers that are l

used to route cables to the containment penetrations. Sprinkler protection has been provided for the vertical risers in accordance with the approved deviation request.

U.S. Nuclear Regulatory Commission ,

B16607%ttachment 1\Page 5

4. Horizontal fire spread in the cable trays would be inhibited by both the fire retardant properties of IEEE-383 qualified cables and the use of sheet  :

metal covers on cable trays in containment. Vertical fire spread in the electrical penetration area to the vicinity of the redundant circuits would also be inhibited by the sprinkler protection provided for the vertical risors. Additional assurance is also provided in that the installed detection '

system would activate prior to the fire spreading in the manner required to damage redundant process monitoring capabilities, and that the fire brigade would respond to control and extinguish the fire. Therefore, fire damage to both trains of process monitoring capabilities in the electrical penetrations area is not considered credible.

The use of fire stops and cable tray covers (tops and bottoms) in selected

• trays in the outer annu!us will assure that, if a fire were to occur in the cable tray system, or if an exposure fire were to occur that exposes the cable tray system, the fire would not progress down the tray system and damage redundant components. Fire stops consist of a fire retardant material (fire foam) sandwiched between metal tray covers (top and bottom). Fires that progress down a tray would not pass these stops due to the fire resistant nature of tne Pro stops The installe'.lon of metal tray i

covers (tops and bottoms) over cables assures that an exposure fira will not ignite the cable inside. This is due to the limited amount of other combustibles inside containment, if a fire did ignite the cables inside the metal covers, the fire would not be able to exit the covered tray exposing the required circuits 'below" the caole trays that are on fire.

Process Monitorina System Separ.g.t[9D This scction id(ntifies the process monitoring instrumentation inside the containment outer annulus which does not, in all caseh, meet the separatiori requirements of 3TP9.51.

Neutron Monitorina Neutron monitoring can be accomplished by ensuring the availability of one out of two instruments given a fire in the containment outer annulus. The instruments are NME*DET1 or NME*DET2. Cabling for these two instruments are located on opposite sides of column line 2, between column lines 1 and 3, in the containment outer annulus.

The junction boxes and conduit runs for the two instruments are located partially within and partially above the suppression area i hlch was depicted in the original deviation request. The deviation request only addressed the lower l

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U.S. Nuclear Regulatory Commission B16607\ Attachment 1\Page 6 elevation of the penetrations area with respect to the ability of the wet pipe sprinkler system to prohibit redundant cables from being damaged by a fire, in order to provide an equivalent level of protection to that recommended by BTP CMEB 9.51, NNECO has extended the existing wet pipe sprinkler system coverage to the upper elevation of the electrical penetrations area above the junction boxes. Extension of the suppression system to above the 51'4" elevation, in conjunction with the configuration of neutron monitoring cable separation and the other fire protection features, provides protection equivalent to the approved deviation for the electrical penetrations area.

RCS Temperature Monitoring capability of RCS temperature can be accor plished by ensuring the availability of one out of three methods of instrumentation given a fire in the containment outer annu'us. The instrumentation methods are RCS hot leg temperature (Tw) and the orange and purple trains of core exit thermocouples (CET (O)), or (CET(P)). RCS cold leg temperature indication is available outside of containment and is not impacted by postulated containment fires. For purposes of assessing the availability of RCS temperature, containment outer annulus has been divided into " north" and " south" halves. The electrical penetration area between column lines 2 and 3 is on the " north" half of the outer annulus. The penetration area between column lines 1 and 2 is on tho " south" half of the outer annulus.

Ts and CET(P) cables are routed clockwise in the south half of the outer annulus in conduits at about the 16' and 38' elevations, respectively. Tu passes through the " south" side of the electrical penetration areu prior to exiting containment through the " north" side of the penetration area. CET(P) exits containment on the " south

• side of the penetration area. CET(0) cables are routed counterclockwise in conduit on the north half of the outer annulus, primarily at about the 24'6" elevation. (The conduit initially ,nters the annulus at about the 3'8" elevation prior to rising up to the 24'6' elevation.) CET(0) exits containment on the north side of the panetration area.

Redundant RCS temperature circuits on the same elevatian are separated by a minimum of 30 feet with two trays acting as intervening combustibles for half of the space between the instruments. To address tne combustibility of the cables, metal cable tray covers (tops and bottoms) are installed. These covers enclose the cable insulation, eliminating the possibility of fire propagation in this ar9a.

The area is void of other combustibles.

U.S. Nuclear Regulatory Commission B16607\AttJchment 1\Page 7 Pressurizer Level & Pressure Monitoring capability of pressurizer pressure (narrow range) and pressurizer level can be accomplished by ensuring the availability of either the Train "A" transmitters and cables (PT456 and LT460) or the Train *B' transmitters and cables (PT4558 and LT459C). Each pair of transmitters and associated cab!es are routed immediately adjacent to each other below the 24'6" elevation until reaching the electrical pv.strations area.

The redundant trains of pressurizer level and pressure are routed in opposite directions and terminate on opposite sides of the electrical penetrations area.

The redundani transmitters and cables are separated by approximately 30' in the containment outer annulus. The only intervening combustible materials are the cables in tM cable trays located above the transmitters. The cable runs for both sets of transmitters rise vertically in the annulus, intersecting the cable trays that contain the intervening combustibles.

There is a large horizontal separation of over 80' between the points where cables for the redundant instrumeM trains vertically intersect the cabl9 trays running horizontally above the transmitters. Automatic smoke detectors are located in the intervening space. There is also a ne:;!igible amount of intervening combustibles for at least 20' of the distance between where the instrument trains vertically intersect the cable trays.

l In order to ensure that a single fire does not adversely impact on both trains of pressurizer level and pressure, it is necessary to ensure that fire will not spread down the cable trays (over 80') to the point whure both trains could be damaged by a single fire. Fire stops are being installed in the ceble trays that run horizentally above the transmitters.

1 RCS Pressure Monitoring capability of RCS wide range pressure can be accomplished by ensuring the availability of one of three instrument loops given a fire in the l

containment outer annulus. The instrument loops are PT49, PT405B or PT50.

The transmitters for PT49 and PT405B are adjacent to each other, with the transmitter for PT50 about 25' away. All three transmitters are on the 3'8" elevation. Prior to 1993, compliance was based on the use of a sample line to install a presaure gauge outside the containment, which has been subsequently eliminated. For purposes of assessing the availsbility of RCS pressure indication, the containment outer annulus ;3 divided into " north" and " south' halves, respectively. The electrical penetration area between column lines 2

U.S. Nuclear Regulatory Commission B16607\ Attachment 1\Page 8 and 3 is on the " north" half of the outer annulus. The penetration area between column lines 1 and 2 is on the " south" half of the outer annulus.

PT49 and PT50 cables are routed clockwise on the south half of the outer annulus in conduits. PT49 is routed primarily on about the 16' elevation, while PT50 runs horizontally just above the 24'6" elevation before rising vertically and running at about the 38' elevation. PT49 passes through the south side of the penetrations area prior to exiting containment on the north side of the penetrations rea. PT50 exits containment on the south side of the penetrations area. PT405B is routed counterclockwise in conduit on the north half of the outer annulus below the 24'G" elevation. PT405B oxits containment on the north side of the penetrations area.

A fire on the " south" side of the electrical penetrations area will not damage the cable for PT4050, since PT4058 ! . not routed on or through the south side of the penetration area. A fire on the north side of the penetration area will not damage PT50, since PT50 !s not routed on or through the north side of the penetration area.

The transmitter for PT50 is separated from the other transmitters in the outer annulus by about 25', free of intervening combustibles. While the conduit for PT50 is routed in the immediate vicinity of the other two transmitters, the only intervening combustiblo materials are cables in trays located over 20' above the instruments and cables in trays located above the conduit run for PT49. To remove the intervening combustible from concern and to exclude the combustibles in the area of the instruments, metal cable tray covers (tops and bottoms) are installed. These covers enclose the cable insulation, eliminating the possibility of fire propagation in this area.

The conduit for PT405B is located about 15' above the transmitter for PT50 without intervening combustibles. From the transmitter, the PT50 conduit drops about 20' and the conduit for PT405B is routed in the opposite direction. While the conduit for PT50 is routed in the same direction as the conduit for PT49, it is located about 25' below PT49 for a distance of over 100'. There are no intervening combustibles in this horizontal and vertical separation between PT50 and PT49. PT50 rises vertically until it is about 25' above PT49 prior to continuing its run to the electrical penetrations area. While a fir's in this location could impact both PT50 and PT49, PT405B is routed in the cpposite direction over 100' away, and would not by affected by the same fire. Reasonable assurance is therefore provided that a single fire will not impact on all three transmitters given a fire in the outer annulus.

U.S. Nuclear Regulatory Commission B16607\ Attachment 1\Page g Steam Generator Level Monitoring capability of sham generator level can be accomplished by ensuring the availability of any two of four instrument loops given a fire in the containment outer annulus. The hstrument loops are LT501, LT502, LT503, LT504. The cables associated with these instrument loops are routed throughout the annulus, with the exception of routing between column lines 10 27d 12. .

LT504 and LT501 are ro!re . etween column lines 4 and 15. Therefore, a fire that is confined to the locaan between these two column lines will not impact LT502 or LT503.

LT501 and LT502 are rotted between column lines 15 to 20. Therefore, a fire that is confined to the location between these column linet, will not impact LT503 or LT504.

Cables for the four instruments, along with the Onsmitter for LT503, are located in the electrical penetration area between column lines 1 and 3. The penetrrbons area is provided with automatic sprinklers below ths 37'4' elevation. Modifications are underway that extend the sprinkler coverage vertically to above the 51'4" elevation. Extension of the suppression system to above the 51'4" elevation will bring the existing configuration of steam generator cable separation and the existing and proposed fire protection features, into compliance with the approved deviation request for the electrical penetrations area.

Conclygign NNECO has concluded that redundant process monitoring capabilities will not be damagw by a single fire and that reasonable assurance is provided that fire protection features in the containment outer annulus will limit the size and severity of postulated fires. The fire protection features (as modified) extend the cor ept of the previously appreved deviation to the balance of the containment outer annuluc. The bases for this conclusion are summarized as follows:

1. The installed detection system, which was accepted in SER Supplement 4, provides appropriate coverage.

2. The absence of transient combustible materials during normal pc,wer operations, along with the use of IEEE-383 qualified cables with circuit fault protection, provide assurance that a cable-induced fire would not occur in the containment outer annulus.

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B16607%ttachment 1\Page 10

' 3. Fires, should they occur in or present an exposure hazard to redundant trains of process monitoring instrumentation, will be detected in the incipient stage.

4. Activation of the detection system will transmit an alarm to the continuously manned control room which will also result in prompt dispatch of the fire brigade for manuac suppression activities.

S. The only in'.ervening combustibles between the redundant trains of process monitoring instrumente%n are cables in horizontal cable trays.

6. Fire stops and metal cable tray covers have been installed in specific locations to preclude fire spread and reduce the exposure cable fires have on redundant circuits.

7 Sprinkler protection has been provided for the vertical risers in the electrical penetrations, including the addition of sprinkler protection for the upper elevation of the electrical penetrations area.

8. The majority of the required circuits are either in metal conduits or metal junction boxes. Exposed portions of these cables are at the electrical oenetration area, which is protected by an automatic wet-piped sprinkler system.

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. Docket No. 50-423 B16607 Attachment 2 Millstone Nuclear Power Station, Unit No. 3 Commitments November 1997

U.S. Nuclear Regul tory Commission

. B16607%ttachment 2\Page 1

. Enclosure List of Regulatory Commitments The following table identifies t sose actions committed to by NNECO in this document.

Please notify the Manager - Regulatory Compliance, Millstone Nuclear Power Station Unit No. 3 of any question regarding this document or any associated regulatory commitments.

Commitment- Committed Date B16607-1 Modifications will be made to the fire Prior to Mode 4 protection features in the outer annulus to provide added assurance that Millstone 3 could achieve and maintain safe shutdown conditions in the event of a fire in the affected areas.

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