ML18152A186

Forwards Exemption Requests to Provide Technical Basis for Continued Use of Thermo-Lag Radiant Energy Shields Relative to 10CFR50,App R,Section III.G.2.f Requirements.Exemption Justification Included

ML18152A186
Person / Time
Site:	Surry, North Anna
Issue date:	12/15/1995
From:	Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
95-007B, 95-7B, NUDOCS 9512190470
Download: ML18152A186 (25)

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VIRGINIA ELECTRIC A]S"D POWER COMPA:NY RICHMOND, VIRGINIA 23261 December 15, 1995 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Serial No.

NL&P/GDM Docket Nos.

95-0078 R1' 50-280 50-281 50-338 50-339 License Nos. DPR-32 DPR-37 NPF-4 NPF-7 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 NORTH ANNA POWER STATION UNITS 1 AND 2 EXEMPTION REQUEST TO 10 CFR 50 APPENDIX R THERMO-LAG RADIANT ENERGY SHIELD APPLICATIONS In our July 26, 1995 letter (Serial No. 95-007A), we stated that we would submit exemption requests to provide the technical basis for the continued use of Thermo-Lag radiant energy shields in containment relative to the requirements of 1 O CFR 50 Appendix R, Section 111.G.2.f. This basis has been developed and is included in Exemption Request No. 27 for Surry Power Station and Exemption Request No. 37 for North Anna Power Station which are provided in Attachments 1 and 2, respectively.

The justification for these exemptions pursuant to the requirements of 10 CFR 50.12 is provided in Attachment 3.

Pursuant to 10 CFR 50.12(a), you are requested to review and approve the attached exemption requests. Subsequent to your approval, Exemption Request No. 27 and Exemption Request No. 37 will be included in the next update of the Surry and North Anna Appendix R Reports, respectively.

If you have any questions or require additional information, please contact us.

Very truly yours,

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Senior Vice President - Nuclear

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9512190470 951215 -- *,- --~- \\

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Attachments cc:

U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, N. W.

Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station Mr. R. D. McWhorter NRC Senior Resident Inspector North Anna Power Station

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ATTACHMENT 1 EXEMPTION REQUEST FOR CONTAINMENT RADIANT ENERGY SHIELDS SURRY POWER STATION UNITS 1 & 2

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27. CONTAINMENT RADIANT ENERGY SHIELDS SURRY POWER STATION EXEMPTION REQUEST Per the provisions of 10 CFR 50.12, Virginia Electric and Power Company requests exemption from the specific requirement of 10 CFR 50 Appendix R, Section 111.G.2.f, requiring radiant energy shields to be noncombustible.

This exemption request applies to Surry Power Station Units 1 and 2.

Description of Exemption Thermo-Lag 330-1 fire barrier material was installed as radiant energy shields in Unit 1 and 2 containments. NRC Information Notice (IN) 95-32, "Thermo-Lag 330-1 Flame Spread Test Results," and IN 95-27, 'Thermo-Lag 330-1 Combustibility Evaluation Methodology Plant Screening Guide," concluded that the material cannot be considered as noncombustible. However, based on their current configuration, _the present radiant energy shields are expected to provide an equivalent level of protection as that required by 10 CFR 50 Appendix R, Section 111.G.2.f, and as that required for defense-in-depth.

Area Description Fire Areas 15 and 16 are the primary containments for Units 1 and 2, respectively.

Each primary containment is a multi-level structure with floor elevations of 47 ft.-4 in.,

18 ft.-6 in., (-)3 ft.-6 in., and (-)27 ft.-7 in. The outer shell of the containment is constructed of reinforced concrete with a fire rating in excess of three hours. The containment structure has a nominal inside diameter of 126 ft. and a nominal inside height of 185 ft. Containment is maintained at subatmospheric pressure, 8.9 - 11.8 psia, during reactor operation.

The containment ventilation system is a multidimensional system that employs three individual air recirculation flow paths to provide general area cooling and direct cooling to critical components. An iodine filtration system, used exclusively for containment ventilation, filters containment air 27-1

during power operations. The primary system components inside containment are located within concrete cubicles. The walkways and stairways in the containment are mostly steel grating. Equipment cubicles, spatial separation between equipment, and walkways eliminate the potential for congestion within containment.

Access into containment is through a personnel access air-lock on the 47 ft.-4 in. elevation and through an equipment hatch that opens into the yard area.

Electrical penetrations exist at two locations within containment. The primary electrical penetrations are located at approximately 15 ft.-0 in. elevation between columns 7 and 9 for Unit 1 and between columns 9 and 11 for Unit 2. These penetration areas go into their respective unit's cable vault/tunnel penetration areas. The second penetration area is into the fuel building above the 47 ft.-4 in. elevation between columns 5 and 6 for Unit 1, and between columns 12 and 13 for Unit 2.

Radiant energy shields in the form of either panels (flat sheets) or conduit wrap (conduit protective envelopes) have been provided to separate primary and alternate instrumentation or components which are less than 20 ft. apart (Station Appendix R Report, Chapter 2, Table 2-3). Exemption Request 17, "Separation of Instrumentation Inside Containment - Intervening Combustibles with Fire Stops," contains a number of figures that show the location and routing of the radiant energy shields. These shields are constructed of 1/2 in. thick Thermo-Lag 330-1 fire barrier material' in preformed conduit and panel shapes. The conduit wrap is provided until a distance of 20 ft. of horizontal separation is achieved, or until a rated fire barrier (such as a concrete cubicle wall) is encountered. The panels are used to form free standing shields or box enclosures to separate redundant components that are not separated by at least 20 ft.

The radiant energy shields (except for the one between the RHR motors) are generally in the annulus area where there is very little mechanical equipment and ample room is provided for personnel access.

Fire Protection System Description The containment has fire extinguishers located just outside containment at the personnel access hatch, and dry hose stations located within the containment annulus. If additional fire fighting equipment is needed, it is available at the point where the fire brigade will enter containment.

Fire fighting equipment located in 27-2

containment is manual, therefore, there are no deleterious effects from the inadvertent operation of fire suppression systems on unit shutdown capability.

Also, heat and smoke detectors are installed within containment. Specifically, smoke and heat detectors are installed in the containment electrical penetration area to the cable vault/tunnel, and smoke detectors are installed in the main recirculation air ducts. Heat detectors are also installed in the reactor coolant pump cubicles. These detectors annunciate in the continuously manned control room.

Safe Shutdown Eguipment The primary containments contain the instruments and cabling for the primary plant instrumentation required for safe shutdown. The ability of these systems to meet Appendix R separation requirements is discussed in Exemption Request 17. The Residual Heat Removal (AHR) System, which is required for cold shutdown, is also located in containment.

Fire Hazard Analysis The fire hazard analysis is divided into five sections. The first section discusses the combustibility of the radiant energy shield material. The next two sections describe Thermo-Lag fire endurance tests and provide a description of the combustibles and ignition sources in containment. The fourth and fifth sections discuss how the concept of defense-in-depth is preserved and why alternative approaches are not justified.

1. Combustibility Thermo-Lag 330-1 fire barrier material provides protection from a fire through a subliming process. The key components of Thermo-Lag 330-1 are: subliming powder, resin, and chopped fiber (partially composed of fiberglass). When a minimum heat flux of 750 BTUs per pound or greater is-directed towards the barrier, the subliming material boils off as the Thermo-Lag begins to change state. An endothermic process pyrolizes the resin (which holds the powder together) into a final state, known as the "char layer." The chopped fibers are an integral part of the char layer matrix.

27-3

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Testing performed to date by the NRC and UL documents that Thermo-Lag 330-1 material does exhibit some combustible behavior at temperatures in excess of 1000 °F or in the presence of large heat fluxes.

Thermo-Lag installations in the Surry containments are located such that there are negligible amounts of combustible material within 5 ft. of the radiant energy shields. Furthermore, since the containment is a multi-level structure, heat and hot gasses from a fire would be directed upward and away from the radiant energy shields. Therefore, the radiant energy shields are not expected to be exposed to high temperatures or large heat fluxes necessary to support combustion.

2. Fire Endurance Tests Section 111.G.2.f of Appendix R to 1 O CFR 50 requires cables, equipment, and associated non-safety circuits of redundant trains inside non-inerted containments to be separated by a noncombustible radiant energy shield.

Appendix R does not provide specific requirements for radiant energy shields.

Although not used in licensing Surry Power Station, the guidelines of Branch Technical Position (BTP)

APCSB 9.5-1, Section C.7.a.(1)b, indicate that radiant energy shields should have a 11fire barrier 11 fire resistance rating of 1 /2 hour. In Section 3. 7.1 of Generic Letter 86-10, the NRC has stated any material with a 1/2 hour fire rating should be capable of performing the function of a radiant energy shield. It should be noted, however, that fire barrier materials are typically tested to 1 and 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> ratings and not a 1/2 hour fire rating. This section goes on to state that non-fire-rated energy shields would also be

• acceptable if they have been demonstrated by a fire hazards analysis to provide protection against the anticipated hazard within the containment.

The NRG has noted that 11fire barriers 11 are rated for fire resistance by being exposed to the standard test fire defined by ASTM E-119, 11Standard for Fire Resistance of Building Materials.

11 BTP APCSB 9.5-1 and Appendix A to BTP APCSB 9.5-1 reference NFPA Standard 251, 11Standard Methods of Fire Tests of Building Construction and Materials, 11 which is identical to ASTM E-119, and define fire rating as:

11the endurance period of a fire barrier or structure; it defines the period of resistance to a standard fire exposure before the first critical point in behavior is observed.

11 27-4

l The NRC applies the ASTM E-119 or NFPA 251 acceptance criteria for non-bearing fire barriers to electrical raceway fire barriers (raceway protective envelopes). These criteria specify that the transmission of heat through the barrier 11shall not have been such as to raise the temperature on its unexposed surface more than 250 °F above its initial temperature.

11 It is generally recognized that the ambient air temperature is 75 °F at the beginning of a fire test. The resulting 325 °F cold side temperature criterion is used because the fire barrier function is to preserve the integrity of the cables and keep them free of fire damage. These test methods however do not portray the true function or use of a radiant energy shield. Since radiant energy is only one aspect of a full fire barrier test, it is expected that a test for a radiant energy shield would be less conservative than the E-119 fire test.

The subject radiant energy shields are constructed of 1/2 inch thick Thermo-Lag 330-1 material. The 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> fire endurance tests conducted by the NRC and the utility industry to determine the fire resistive properties of 1/2 inch Thermo-lag 330-1 material have shown the material will provide some varying duration of fire resistance, typically 20 minutes or more.

3. Combustible Loading and Ignition Sources The combustible loading analysis found in Chapter 8, Table 8-3, of the Appendix R Report provides a calculation of Equivalent Fire Severities (EFS) for the Fire *Area being analyzed. The EFS provides a method by which an area's combustible contents are related to the standard time-temperature curve. Fire Areas 15 (Unit 1 containment) and 16 (Unit 2 containment) have a high EFS. The fixed combustibles contributing to the combustible loading for containment are comprised of cable insulation (-80%) and lube oil (-:-20%). The contribution from Thermo-Lag is considered to be negligible since it is less than 1 %.

The radiant energy shields (except for the wall between the RHR pumps) are located in the annulus outside the concrete crane wall;- The only combustible of concern in this area is cable insulation. The original cable installed at Surry was purchased prior to issuance of IEEE 383, 11Standard for Type Test of Class IE for Electrical Cables.

11 The 5,000V and 600V power cables were required to pass a flame resistance test in accordance with IPCEA Standard S-19-81, Section 6.19.6. The 1,000V control cable and 600V instrument cable were required to pass a flame resistance test in 27-5

L accordance with ASTM D-2633.

In addition, control and instrument cables were required to pass a flame resistance test detailed in the purchase specifications.

Although the tests employed are not equivalent to IEEE 383, they do meet the intent of the standard in verifying the fire resistance and flame retardancy of the cable.

Specifications for cable installed at Surry since the approval of IEEE 383 has required the cable to meet the IEEE 383 standard. Cable insulation at Surry will not readily*

propagate flame due to its flame resistant nature. To further mitigate the potential of fire spread along the trays, vertical and horizontal fire stops (Marinite Board and silicone foam) have been installed where the cable trays constitute a potential intervening combustible threat between primary/alternate components and cables.

Metal cable tray top covers have been installed on the cable trays in the vicinity of the cable vault/tunnel penetration area in both Unit 1 and Unit 2 containments. In addition, a cable tray bottom cover has been installed in the lowest horizontal cable tray in this area. These cable tray covers provide protection to the trays from an exposure fire.

However, these tray covers are not required to provide adequate separation or mitigate intervening combustibles between primary and alternate trains of instrumentation, which is accomplished by fire stops.

The RHR pumps do not operate when the unit is at power, therefore, they are not considered an ignition source. Since there are n,o other ignition sources in the area of the RHR pumps, and cables in the RHR pump area are in conduit, the radiant energy shields between the pumps will have minimal fire exposure. The only pumps in containment that are operating while a unit is at power, and thus the only credible ignition source, are the reactor coolant pumps (RCP). Each of these pumps has an oil collection system and is separated from the balance of the containment by a concrete open-top cubicle. Therefore, the possibility of a pressurized oil fire affecting any cables or radiant energy shields outside the RCP cubicles is remote.

4. Defense-in-Depth The defense-in-depth approach for containment consists of design features, personnel, equipment, and procedures that provide an adequate balance in (a) preventing significant fires, (b) detecting and suppressing fires quickly, and (c) ensuring the capability to safely shutdown the plant.

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(a) The containment is a multi-level structure that uses concrete barriers to house primary components, provide separation, and eliminate congestion. Walkways are either steel grating or concrete and provide access to all areas of containment. Station operating procedures limit access to containment while the unit is operating, thereby limiting transient combustibles as well.

Transient combustibles during normal operation are essentially nonexistent. The lack of credible ignition sources within containment while the unit is operating makes it unlikely that a fire would occur in containment.

(b) Heat detectors are installed in the RCP cubicles, and heat and smoke detectors are installed in areas with significant concentrations of cables.

These detectors annunciate in the continuously manned control room and will ensure prompt response by operations and the fire brigade in the event of a fire. Fire extinguishers and hose stations are provided for the fire brigade to use within containment.

Fire fighting equipment located in containment is manual, therefore, there are no damaging effects from inadvertent operation on unit shutdown capability.

(c) Fire that is not quickly extinguished can only occur in the cable penetration area, where there are concentrations of cable, or in the RCP cubicles. The radiant energy shields are not located in the RCP cubicles, nor within the penetration area. To mitigate the potential for fire spreading within cable trays, vertical and horizontal fire stops have been installed. The radiant energy shields are used to separate primary and alternate instrumentation (i.e., RCS pressure, pressurizer level, and steam generator level). For each parameter there are at least three instrument circuits, usually routed in separate conduits. These passive measures ensure that a fire in containment that is not promptly extinguished will not prevent safe shutdown of the plant.

5. Alternative Approaches Alternatives to using the existing Thermo-Lag radiant-energy shields include replacing or overlaying Thermo-Lag with another fire resistant noncombustible material, use of fire rated cable, relocating cables and equipment to achieve 20 ft. separation, or installation of an automatic detection and suppression system. The level of protection provided by these modifications would not provide a significant increase over the current level of protection provided. Implementing any one of these alternatives would 27-7

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involve extensive cost and is expected to generate large quantities of radioactive waste and radiation exposure to personnel making the modifications.

Conclusions The current configuration of radiant energy shields in containment is expected to provide an equivalent level of protection as that required by 10 CFR 50 Appendix R, Section III.G.2(f) and requirements of defense-in-depth. The technical bases that justify this conclusion are summarized as follows:

1.

Based on containment design, separation between combustibles and radiant energy shields, and the conditions in which Thermo-Lag is used, if a fire were to start inside containment, radiant energy shields are not expected to be exposed to temperatures in excess of 1000 °F or to large heat fluxes.

Since the containment is a multi-level structure with open grating, heat and hot gasses from a fire would be directed upward and away from the radiant energy shields.

Fire that is not quickly extinguished can only occur in the cable penetration area, where there are concentrations of cable, or in the RCP cubicles. The radiant energy shields are not located in the RCP cubicles, nor within the penetration area.

2.

The guidance provided by Appendix R and GL 86-10 indicates a 1 /2 hour fire rated material or a non-fire-rated material justified by analysis is acceptable as radiant energy shields. Testing has shown panel and conduit shapes (conduit protective envelopes) of 1/2 inch Thermo-Lag 330-1 material when used as a fire barrier will provide some fire resistive rating, typically 20 minutes or more.

Since the testing for fire barrier configurations is considered to be more conservative than testing for radiant energy shield applications, we consider that the test results support the use of Thermo-Lag as a radiant energy shield.

3.

Cables in trays will not readily propagate flame due to their flame resistant nature. Vertical and horizontal fire stops have been installed to prevent cable trays from being intervening combustibles. Metal cable tray top covers are installed on all cable trays in the penetration area. The bottom of the lowest horizontal cable tray on elevation 15 ft.-0 in. in the penetration area has been 27-8

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equipped with a metal cable tray cover. Cable tray covers and fire stops are in excess of what is required by Appendix R, Section 111.G.2.f.

4.

The only ignition sources in containment while the unit is operating are the reactor coolant pumps. Each RCP has an oil collection system and is in a cubicle that will prevent exposure to the cable trays and penetration areas.

5.

Station operating procedures limit access to containment while the unit is operating, thereby limiting ignition sources and transient combustibles as well.

6.

Heat and smoke detectors, which annunciate in the control room, are installed in containment areas where there are concentrations of combustibles. This exceeds Appendix R requirements, since Section 111.G.2.d and f do not require any detection.

7.

The radiant energy shields are used to separate primary and alternate instrumentation (i.e., RCS pressure, pressurizer level, and steam generator level). For each parameter there are at least three instrument circuits, usually routed in separate conduits.

8.

No significant enhancements in fire safety would be achieved if modifications were performed.

The current level of protection and the ability to safely shutdown the units would not be significantly increased in proportion to the cost, radioactive waste, and personnel radiation exposure necessary to make the modifications.

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37.

CONTAINMENT RADIANT ENERGY SHIELDS NORTH ANNA POWER STATION EXEMPTION REQUEST Per the provisions of 10 CFR 50.12, Virginia Electric and Power Company requests exemption from the specific requirement of 1 O CFR 50 Appendix R, Section 111.G.2.f, requiring radiant energy shields to be noncombustible.

This exemption request applies to North Anna Power Station Units 1 and 2.

Description of Exemption Thermo-Lag 330-1 fire barrier material was installed as radiant energy shields in Unit 1 and 2 containments. NRG Information Notice (IN) 95-32, 'Thermo-Lag 330-1 Flame Spread Test Results," and IN 95-27, "Thermo-Lag 330-1 Combustibility Evaluation Methodology Plant Screening Guide, 11 concluded that the material cannot be considered as noncombustible. However, based on their current configuration, the present radiant energy shields are expected to provide an equivalent level of protection as that required by 1 O CFR 50 Appendix R, Section 111.G.2.f, and as that required for defense-in-depth.

Area Description Fire Areas 1-1 and 1-2 are the primary containments for Units 1 and 2, respectively.

Each primary containment is a multi-level structure with floor elevations of 216 ft.-11 in., 241 ft.-0 in., 262 ft.-1 O in., and 291 ft.-1 O in. The outer shell of the containment is constructed of reinforced concrete with a fire rating in excess of three hours. The containment structure has a nominal inside diameter of 126 ft. and a nominal inside height of 190 ft. Containment is maintained at subatmospheric pressure, 9.0 - 11.8 psia, during reactor operation.

The containment ventilation system is a multidimensional system that employs three individual air recirculation flow paths to provide general area cooling and direct cooling to critical components. An iodine filtration system, used exclusively for containment ventilation, can filter containment air 37-1

I L

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V during power operations. The primary system components inside containment are located within concrete cubicles. The walkways and stairways in the containment are mostly steel grating. Equipment cubicles, spatial separation between equipment, and walkways eliminate the potential for congestion within containment.

Access into containment is through a personnel access air-lock on the 291 ft.-10 in. elevation, and through an equipment hatch that opens into the yard area.

Electrical penetrations exist at two locations within containment. The primary electrical penetrations are located at approximately 259 ft. elevation between columns 7 and 9 for Unit 1 and between columns 9 and 11 for Unit 2. These penetration areas go into their respective unit's cab!e vault/tunnel (CV/T) penetration areas.

The second penetration area is into the fuel building located above the 291 ft. elevation between columns 5 and 6 for Unit 1, and between columns 12 and 13 for Unit 2.

Radiant energy shields in the form of either panels (flat sheets) or conduit wrap (conduit protective envelopes) have been provided to separate primary and alternate instrumentation or components which are less than 20 ft. apart (Station Appendix R Report, Chapter 2, Table 2-3). Exemption Request 27, 11Separation of Instrumentation Inside Containment - Intervening Combustibles with Fire Stops, 11 contains a number of figures that show the location and routing of the radiant energy shields. These shields are constructed of 1/2 in. thick Thermo-Lag 330-1 fire barrier material in preformed conduit and panel shapes. The conduit wrap is provided until a distance of 20 ft. of horizontal separation is achieved or until a rated fire barrier (such as a concrete cubicle wall) is encountered. The panels are used to form free standing shields or box enclosures to separate redundant components that are not separated by at least 20 ft.

The radiant energy shields (except for the one between the RHR motors) are generally in the annulus area where there is very little mechanical equipment and ample room is provided for personnel access.

Fire Protection System Description The containment has fire extinguishers located just outside the containment at the personnel access hatch, and dry hose stations located within the containment annulus. Adequate hose lengths are maintained outside containment to reach the areas inside containment. If additional fire fighting equipment is needed, it is available at the point where the fire brigade will enter containment. Fire fighting equipment 37-2

located in containment is manual, therefore, there are no deleterious effects from the inadvertent operation of fire suppression systems on shutdown capability.

Also, heat and smoke detectors are installed within containment. Specifically, smoke and heat detectors are installed at the containment electrical penetration area to the cable vault/tunnel, and smoke detectors are installed in the main recirculation air ducts. Heat detectors are also installed in the reactor coolant pump cubicles. These detectors annunciate in the continuously manned control room.

Safe Shutdown Eguipment The primary containments contain the instruments and cabling for the primary plant instrumentation required for safe shutdown. The ability of these systems to meet Appendix R separation requirements is discussed in Exemption Request 27. The Residual Heat Removal (RHR) System, which is required for cold shutdown, is also located within containment.

Fire Hazard Analysis The fire hazard analysis is divided into five sections. The first section discusses the combustibility of the radiant energy shield material. The next two sections describe Thermo-Lag fire endurance tests and provide a description of the combustibles and ignition sources in containment. The fourth and fifth sections discuss how the concept of defense-in-depth is preserved and why alternative approaches are not justified.

1. Combustibility Thermo-Lag 330-1 fire barrier material provides protection from a fire through a subliming process. The key components of Thermo-Lag 330-1 are: subliming powder, resin, and chopped fiber (partially composed of fiberglass). When the minimum heat flux of 750 BTUs per pound-or greater is directed towards the barrier, the subliming material boils off as the Thermo-Lag begins to change state. An endothermic process pyrolizes the resin (which holds the powder together) into a final state, known as the "char layer." The chopped fibers are an integral part of the char layer matrix.

37-3

,ii The testing performed to date by the NRG and UL documents that Thermo-Lag 330-1 material does exhibit some combustible behavior at temperatures in excess of 1000 °F or in the presence of large heat fluxes. Thermo-Lag installations in the North Anna containments are located such that there are negligible amounts of combustible material within 5 ft. of the radiant energy shields. Furthermore, since the containment is a multi-level structure, heat and hot gasses from a fire would be directed upward and away from the radiant energy shields. Therefore, the radiant energy shields are not expected to be exposed to the high temperatures or large heat fluxes necessary to support combustion.

2. Fire Endurance Tests Section 111.G.2.f of Appendix R to 1 O CFR 50 requires cables, equipment, and associated non-safety circuits of redundant trains inside non-inerted containments to be separated by a noncombustible radiant energy shield.

Appendix R does not provide specific requirements for radiant energy shields.

Although not used in licensing North Anna Power Station, the guidelines of Branch Technical Position (BTP) APCSB 9.5-1, Section C.7.a.(1)b, indicate that radiant energy shields should have a "fire barrier" fire resistance rating of 1/2 hour. In Section 3.7.1 of Generic Letter 86-10, the NRC has stated any material with a 1/2 hour fire rating should be capable of performing the function of a radiant energy shield. It should be noted, however, that fire barrier materials are typically tested to 1 and 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> ratings and not a 1/2 hour fire rating. This section goes on to state that non-fire-rated energy shields would also be acceptable if they have been demonstrated by a fire hazards analysis to provide protection against the anticipated hazard within the containment.

The NRC has noted that "fire barriers" are rated for fire resistance by being exposed to the standard test fire defined by ASTM E-119, 11Standard for Fire Resistance of Building Materials."

BTP APCSB 9.5-1 and Appendix A to BTP APCSB 9.5-1 reference NFPA Standard 251, "Standard Methods of Fire Tests of Building Construction and Materials, 11 which is identical to ASTM E-119, and define fire rating as: "the endurance period of a fire barrier or structure; it defines the period of resistance to a standard fire exposure before the first critical point in behavior is observed."

37-4

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The NRG applies the ASTM E-119 or NFPA 251 acceptance criteria for non-bearing fire barriers to electrical raceway fire barriers (raceway protective envelopes). These criteria specify that the transmission of heat through the barrier "shall not have been such as to raise the temperature on its unexposed surface more than 250 °F above its initial temperature." It is generally recognized that the ambient air temperature is 75 °F at the beginning of a fire test. The resulting 325 °F cold side temperature criterion is used because the fire barrier function is to preserve the integrity of the cables and keep them free of fire damage. These test methods however do not portray the true function or use of a radiant energy shield. Since radiant energy is only one aspect of a full fire barrier test, it is expected that a test for a radiant energy shield would be less conservative than the E-119 fire test.

The subject radiant energy shields are constructed of 1/2 inch thick Thermo-Lag 330-1 material. The 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> fire endurance tests conducted by the NRG and the utility industry to determine the fire resistive properties of 1/2 inch Thermo-lag 330-1 material have shown the material will provide some varying duration of fire resistance, typically 20 minutes or more.

3. Combustible Loading and Ignition Sources The combustible loading analysis found in Chapter 8, Table 8-3, of the Appendix R Report provides a calculation of Equivalent Fire Severities (EFS) for the Fire Area being analyzed. The EFS provides a method by which an area's combustible contents.

are related to the standard time-temperature curve.

Fire Areas 1-1 (Unit 1 containment) and 1-2 (Unit 2 containment) have a low EFS. The fixed combustibles contributing to the combustible loading for containment are comprised of cable insulation (-59%), lube oil (-34%), and charcoal (-7%).

The contribution from Thermo-Lag is considered to be negligible since it is less than 1 %.

The radiant energy shields (except for the wall between the RHR pumps) are located in the annulus outside the concrete crane wall. The only combustible of concern in this area is IEEE 383 rated cable insulation.

Cable insulation will not readily propagate flame due to its flame resistant nature. To further mitigate the potential of fire spread along the trays, vertical and horizontal fire stops (Marinite Board and silicone foam) have been installed where the cable trays constitute a potential intervening combustible threat between primary/alternate components and cables.

37-5

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l Metal cable tray top covers have been installed on the cable trays in the vicinity of the cable vault/tunnel penetration area in both Unit 1 and 2 containments. In addition, a cable tray bottom cover has been installed in the lowest horizontal cable tray in this area. These cable tray covers provide protection to the trays from an exposure fire.

However, these tray covers are not required to provide adequate separation or mitigate intervening combustibles between primary and alternate trains of instrumentation, which is accomplished by the fire stops.

The RHR pumps do not operate when the units are at power, therefore, they are not considered an ignition source. Since there are no other ignition sources in the area of the RHR pumps, and cables in the RHR pump area are in conduits, the radiant energy shields between the pumps will have minimal fire exposure. The only pumps in containment that are operating while a unit is at power, and thus the only credible ignition source, are the reactor coolant pumps (RCP). Each of these pumps has an oil collection system and is separated from the balance of the containment by a concrete open-top cubicle. Therefore, the possibility of a pressurized oil fire affecting any cables or radiant energy shields located outside the RCP cubicles is remote.

4. Defense-in-Depth The defense-in-depth approach for containment consists of design features, personnel, equipment, and procedures that provide an adequate balance in (a) preventing significant fires, (b) detecting and suppressing fires quickly, and (c) ensuring the capability to safely shutdown the plant.

(a) The containment is a multi-level structure that uses concrete barriers to house primary components, provide separation, and eliminate congestion. Walkways are either steel grating or concrete and provide access to all areas of containment. Station operating procedures limit access to containment while the unit is operating, thereby limiting transient combustibles as well.

Transient combustibles during normal operations are essentially nonexistent. The lack of credible ignition sources within containment while the unit is operating makes it unlikely that a fire would occur in containment.

(b) Heat detectors are installed in the RCP cubicles, and heat and smoke detectors are installed in areas with significant concentrations of cables.

These detectors 37-6

(<

)

annunciate to the continuously manned control room and will ensure prompt response by operations and the fire brigade in the event of a fire. Fire extinguishers and hose stations are provided for the fire brigade to use within containment.

Fire fighting equipment located in containment is manual, therefore, there are no damaging effects from inadvertent operation on shutdown capability.

(c) Fire that is not quickly extinguished can only occur in the cable penetration area, where there are concentrations of cable, or in the RCP cubicles. The radiant energy shields are not located within the RCP cubicles, nor within the penetration area. To mitigate the potential for fire spreading within cable trays, vertical and horizontal fire stops have been installed. The radiant energy shields are used to separate primary and alternate instrumentation (i.e., RCS pressure, pressurizer level, and steam generator level). For each parameter there are at least three instrument circuits, usually routed in separate conduits. These passive measures ensure that a fire in containment that is not promptly extinguished will not prevent safe shutdown of the plant.

5. Alternative Approaches Alternatives to using the existing Thermo-Lag radiant energy shields include replacing or overlaying Thermo-Lag with another fire resistant noncombustible material, use of fire rated cable, relocating cables and equipment to achieve 20 ft. separation, or installation of an automatic detection and suppression system. The level of protection provided by these modifications would not provide a significant increase over the current level of protection provided. Implementing any one of these alternatives would involve extensive cost and is expected to generate large quantities of radioactive waste and radiation exposure to personnel making the modifications.

Conclusions The current configuration of radiant energy shields in containment is expected to provide an equivalent level of protection as that required by 10 CFR 50 Appendix R, Section 111.G.2.f and requirements of defense-in-depth. The technical bases that justify this conclusion are summarized as follows:

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1.

Based on containment design, separation between combustibles and radiant energy shields, and the conditions in which Thermo-Lag is used, if a fire were to start inside containment, radiant energy shields are not expected to see temperatures in excess of 1000 °F or be exposed to large heat fluxes. Since the containment is a multi-level structure with open grating, heat and hot gasses from a fire would be directed upward and away from the radiant energy shields.

Fire that is not quickly extinguished can only occur in the cable penetration area, where there are concentrations of cable, or in the RCP cubicles. The radiant energy shields are not located within the RCP cubicles, nor within the penetration area.

2.

The guidance provided by Appendix Rand GL 86-10 indicates a 1/2 hour fire rated material or a non-fire-rated material justified by analysis is acceptable as radiant energy shields. Testing has shown panel and conduit shapes (conduit protective envelopes) of 1/2 inch Thermo-Lag 330-1 material when used as a fire barrier will provide some fire resistive rating, typically 20 minutes or more.

Since the testing for fire barrier configurations is considered to be more conservative than the testing for radiant energy shield applications, we consider that the test results support the use of Thermo-Lag as a radiant energy shield.

3.

Cables in trays are IEEE 383 rated. Vertical and horizontal fire stops have been installed to prevent cable trays from being intervening combustibles. Metal cable tray top covers are installed on all cable trays in the penetration area.

The bottom of the lowest horizontal cable tray on elevation 262 ft.-10 in. in the penetration area has been equipped with a metal cable tray cover. Cable tray covers and fire stops are in excess of what is required by Appendix R, Section 111.G.2.f.

4.

The only ignition sources in containment while the unit is operating are the reactor coolant pumps. Each RCP has an oil collection system and is in a cubicle that will prevent exposure to the cable -trays and penetration areas.

5.

Station operating procedures limit access to containment while the unit is operating, thereby limiting ignition sources and transient combustibles.

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6.

Heat and smoke detectors, which annunciate in the control room, are.installed in each containment area where there are concentrations of combustibles. This exceeds Appendix R requirements, since Section 111.G.2.d and f do not require any detection.

7.

The radiant energy shields are used to separate primary and alternate instrumentation (i.e., RCS pressure, pressurizer level, and steam generator level). For each parameter there are at least 3 instrument circuits, usually routed in separate conduits.

8.

No significant enhancements in fire safety would be achieved if modifications were performed. The current level of protection and the ability to safely shut down the units would not be significantly increased in proportion to the cost, radioactive waste, and personnel radiation exposure necessary to make the modifications.

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1 ATTACHMENT 3 EXEMPTION JUSTIFICATION CONTAINMENT RADIANT ENERGY SHIELDS SURRY AND NORTH ANNA POWER STATIONS UNITS 1 & 2

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EXEMPTION JUSTIFICATION 10 CFR 50.12 states that the Commission may grant exemption$ from the requirements of the regulations contained in 10 CFR 50 provided that: (1) the exemption is authorized by law, (2) the exemption will not present an undue risk to the health and safety of the public, (3) the exemption is consistent with the common defense and security, and (4) special circumstances as defined in 10 CFR 50.12(a)(2) are present.

1.

The Requested Exemption is Authorized by Law No law exists which would preclude the activities covered under this exemption request, thus the Commission is authorized to grant this exemption.

2.

The Requested Exemption Does Not Present an Undue Risk to the Public Health and Safety The existing radiant energy shield configurations in the Surry and North Anna Power Station containments will provide an equivalent level of protection as that required by 10 CFR 50 Appendix R, Section 111.G.2.f and the requirement for defense-in-depth. The plant specific temperature and heat flux conditions associated with postulated fires in containment are not expected to challenge the performance capability of the radiant energy shields. Furthermore, the plant specific cubicle and walkway designs in the containment allow for the upward dissipation of heat away from the shields.

Guidance in Appendix Rand Generic Letter 86-10 indicates that a 1/2 hour fire-rated material or a non-fire-rated material justified by analysis is acceptable as a radiant energy shield. Thermo-Lag testing has shown that panel and conduit shapes (conduit protective envelopes) of 1/2 inch Thermo-Lag 330-1 material when used as a fire barrier will provide a fire resistance rating of typically 20 minutes or more. Since testing for fire barriers is considered more conservative than testing for radiant energy shield applications, Thermo-Lag 330-1 is considered to meet the criteria for radiant energy shields.

Furthermore, vertical and horizontal fire stops have been installed in containment to prevent cable trays from being intervening combustibles. Metal cable tray covers have also been installed on cable trays in the containment electrical penetration area. Heat and smoke detectors, which annunciate in the control room, are installed in each containment area where a concentration of combustibles exists. The fire stops, cable tray covers, and heat and smoke detectors exceed the requirements of Appendix R, Section 111.G.2.f.

Ignition sources and transient combustibles are minimized in containment by station procedures that restrict containment entry while a unit is operating. The only in-containment ignition source is the oil from the RCPs which is controlled by an oil collection system and contained within the RCP cubicle.

These

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controls will prevent exposure of the cable trays and the penetration area to a fire concern in this area.

Based on the above. considerations, the requested exemption does not present an undue risk to the public health and safety.

3.

The Requested Exemption Will Not Endanger the Common Defense and Security

4.

The common defense and security are not an issue in this exemption request.

This request only addresses the use Thermo-Lag radiant energy shields in containment.

Special Circumstances are Present Which Necessitate the Request for an Exemption to the Regulations of 10 CFR 50 Appendix R, Section 111.G.2.f Per 1 O CFR 50.12(a)(2)(ii), the following special circumstance is present:

Application of the regulation in the particular circumstances is not necessary to achieve the underlying purpose of the rule. The intent of the rule is to prevent fire damage in the containment that could* impact safe shutdown of the plant. The proposed alternative continues to assure safe shutdown capability in the event of a fire in containment.

SAFETY IMPACT Virginia Electric and Power Company has reviewed this exemption and determined that the requested alternative for radiant energy shields in containment will not affect nuclear safety. Adequate assurance is provided by the existing radiant energy shield installations in the Surry and North Anna Power Stations' containments to prevent fire damage in the containments that could impact safe shutdown capability.

Thus operation of Surry and North Anna Power Stations in accordance with proposed alternative will not:

1.

Involve a significant increase in the probability or consequences of an accident previously evaluated. The radiant energy shields are presently installed to preclude fire damage to safe shutdown equipment in containment and are considered to meet the intent of the underlying requirement.

No physical modifications are being implemented by this exemption request. Therefore, this exemption would not increase the probability of an accident previously evaluated. Likewise, the consequences of an accident would not be increased since the radiant energy shields, in conjunction with design, procedural and personnel considerations, are capable of adequately protecting safe shutdown equipment.

2.

Create the possibility of a new or different type of accident from those previously evaluated.

The effect of the radiant energy shields in containment was previously evaluated when they were originally installed and determined to be

1.

acceptable. Maintaining the shields in containment would not create a new or different type of accident from those previously evaluated, since they still provide an adequate level of fire protection for safe shutdown equipment, and are not being modified in any way.

Although technically considered a combustible, the shield will not be subject to the temperatures or heat fluxes in containment applications necessary to exhibit combustible behavior.

Furthermore, the amount of material is insignificant in terms of existing combustible loadings in containment.

3.

Involve a significant reduction in a margin of safety.

Since no physical modifications are being implemented and the radiant energy shields in containment, in conjunction with design, procedural and personnel considerations, have been demonstrated to adequately protect safe shutdown equipment in the event of a fire, the margin of safety is not reduced.