ML14175A777
| ML14175A777 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 11/21/1983 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Carolina Power & Light Co |
| Shared Package | |
| ML14175A778 | List: |
| References | |
| NUDOCS 8312140199 | |
| Download: ML14175A777 (6) | |
Text
Enclosure 1 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of
)
CAROLINA POWER & LIGHT COMPANY
)
Docket No. 50-261 (H. B. Robinson Steam Electric
)
Plant Unit No. 2)
)
EXEMPTION I.
The Carolina Power and Light Company (the licensee) is the holder of Facility Operating License No. DPR-23 which authorizes operation of the H. B. Robinson Steam Electric Plant, Unit No. 2. This license provides, among other things, that it is subject to all rules, regulations, and Orders of the Commission now or hereafter in effect.
The facility is a pressurized water reactor at the licensee's site located in Darlington County, South Carolina.
II.
On November 19, 1980, the Commission published a revised Section 10CFR 50.48 and a new Appendix R to 10 CFR 50 regarding fire protection features of nuclear power plants (45 FR 76602). The revised Section 50.48 and Appendix R became effective on February 17, 1981.Section III. of Appendix R contains fifteen subsections, lettered A through 0, each of which specifies requirements for a particular aspect of the fire protection features at a nuclear power plant.
Two of these fifteen subsections, III.G and III.M, are the subject of these exemptions. Specifically, Subsection III.G.2 requires that one train of cables and equipment necessary to achieve and.maintain safe shutdown be maintained free of fire damage by one of the following means:
- a.
Separation of cables and equipment and associated non-safety circuits of redundant trains by a fire barrier having a 3-hour rating. Structural steel formi'ng a part of or supporting such. fire barriers shall be pro tected to provide fire resistance equivalent to that required of the barrier;
- b.
Separation of cables and equipment and associated non-safety circuits of redundant trains by a hofizontal distance of more than 20 feet with no intervening combustibles or fire hazards.
In addition, fire detectors and an automatic fire suppression system shall be installed in the fire area; or
- c.
Enclosure of cables and equipment and associated non-safety circuits of one redundant train in a fire barrier having a 1-hour rating. In addition, 3PDR ADoC O
PDR 1
F
fire detectors and an automatic fire suppression system shall be installed in the fire area.
Subsection III.M requires that penetration seal designs shall utilize only non combustible materials and shall be qualified by tests that are comparable to tests used to rate fire barriers.
III.
By letters dated January 9, 1981, March 1, 1982, and April 27, 1982, the licensee requested an exemption from the requirements of Subsection III.G.2, in four (4) fire areas; from Subsections III.M and 111.0.
By letter dated June 7, 1983, the licensee withdrew one fire area (Fire Zone 5) from the Subsection III.G.2 request.
The remaining items are as follows:
III.G -
RHR Pit (Fire zone 27)
III.G -
Service Water Pump Area III.G -
Component Cooling Pump Room (Fire Zone 5)
III.M -
Fire Barrier Cable Penetration Seal Qualification III.0 -
Oil Collection System The acceptability of the exemption request for three of these fire areas is addressed below. Two areas remain under review. More details are contained in the NRC staff's related.Safety Evaluation (SE) dated November __,
1983.
IV.
RHR Pit (Fire Zone 27)
Exemption Requested The licensee requested an exemption from III.G.2 of Appendix R to the extent that it requires 3-hour fire rated barriers be installed to separate redundant trains.
Fire Zone 27 is located west of the Auxiliary Building at elevation 203 feet.
The area is separated from other plant areas by concrete walls. Entrance into the area is through a hatch and down a 25-foot ladder. The ceiling height in the area is 27 feet 6 in. The fire protection in the area consists ofsmoke and heat detectors, standpipe hose stations and portable fire extinguishers.
Fire Zone 27 contains two residual heat removal (RHR) pumps and associated piping.
No equipment or circuit within this zone is required for hot shutdown, but one train of the RHR system is necessary to achieve and maintain cold shutdown.
Each RHR pump is mounted on a concrete pedestal approximately 4 ft. high with the top of the pump about 10 ft. above floor elevation. The redundant pumps are separated by a 22-ft-high concrete barrier which completely bisects the RHR pit into two individual pump bays.
Each pump bay has a sump approximately 3 ft. x 3 ft. x 6 in. deep with an installed sump pump. The sumps are adjacent to each other and separated by the same barrier which divides the zone. A hole approximately 4 in.
in diameter joins the sumps so each sump pump can serve as a backup to the other.
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The licensee indicates that a fire in the RHR pit would cause damage to both trains of the.RHR control and power cables; however, the licensee also indicates that the cables could be repaired within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, the time allowed by Sec tion III.G.1.
The combustible in Fire Zone 27 is lubricating oil contained in the RHR pumps.
Each pump contains 8 gallons of oil.
The oil comprises a fuel load of 6500 Btu/sq.
ft. which if totally consumed, would correspond to a fire severity of about 5 minutes on the ASTM E-119 standard time temperature curve.
The licensee justifies this exemption based on the following:
a)
Access to the area is limited.
b)
The in-situ combustible loading is light c)
Smoke and heat detection are provided.
d) A partial height (22 feet) concrete barrier separates the RHR pumps.
e)
An analytical model was employed to show that the magnitude of an exposure fire needed to ignite the in-situ lube oil is significantly higher than reasonably expected.
f)
Hot surfaces necessary to cause ignition of the lube oil do not exist in the area.
This area does not comply with Section III.G because the redundant RHR trains are not separated by 3-hour fire rated barriers, there is no automatic suppres-*
sion system, and there is no alternate cold shutdown capability independent of the area.
The NRC staff has evaluated this area with the following considerations. This area is normally locked and the pumps are not running. Even with the-pumps running, there are no hot surfaces in the area. The few cables for the pumps are in conduit. The only significant in-situ combustible in the fire area is the pump motor lubricating oil.
The probability of ignition of the oil is low because the lubricating oil has a high flashpoint (approximately 4500) and suf ficiently hot surfaces do not exist in this fire area to cause the ignition of the lube oil.
If a fire occurred in the RF4R pit, access into the pit for nomi nal fire fighting would be difficult due to the smoke and hot products of com bustion that would vent through the hatch entrance. We anticipate that manual fire fighting activities would be conducted from hatch entrance rather than from inside the RHR pit. This may result in water damage to both trains of RHR.
However, with proper fire fighting procedures along with the concrete wall sepa rating the pumps, such damage could easily be prevented. In addition, because the RHR pumps are only used during cold shutdown, there are emergency procedures which could be used to maintain safe conditions in the unlikely event of a fire and fire fighting activities that affect both pumps.
Because the area is normally locked, a partial height wall separates the RHR pump, the area contains few combustibles, and the pumps are only needed for cold shutdown, an automatic suppression is not necessary. The fire detectors should assure prompt detection of a fire should it occur. This arrangement would provide reasonable assurance that a fire would not damage both RHR pumps and the damage to cables would be limited so that it could be repaired within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
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Based on the above evaluation, the level of existing fire protection for this area does provide a level of fire protection equivalent to the technical require ments of Section III.G of Appendix R and, therefore, the licensee's exemption request is granted for this area.
Service Water Pump Area The licensee requests an exemption from Section III.G.2 of Appendix R to the extent that it requires 1-hour fire rated barriers or 20 feet of separation free of intervening combustibles to separate redundant divisions and an auto matic fire suppression system.
The service water pump area is located in the Intake Structure. This structure is formed by metal walls, concrete floor and an open roof. The area contains four service water pumps.
One pump is needed for safe shutdown. The pumps are aligned with 2 to 4 feet separation between pumps. The separation between A and D pumps is approximately 13 feet. Control and power cables to the pumps are routed in conduit through the concrete floor and terminate directly into the motor end of the pumps.
The in-situ combustible loading is 6 gallons of lubricating oil contained in each of the service water pumps.
The fire protection in the area consists of manual hose stations and portable fire extinguishers. The licensee justifies this alternative on the following:
a)
Manual fire fighting capability, b)
Television Camera Surveillance of the area in lieu of fire detection, and c)
An analytical model employed to show that the magnitude of an exposure fire needed to damage redundant components is significantly higher than reason ably expected.
The NRC staff's evaluation included the following considerations.
This area does not comply with Section III.G because it does not have an automa tic suppression system and twenty feet of separation free of intervening combus tibles. There is no alternate shutdown capability independent of this area and there is no automatic fire detection system. This area is under continuous television surveillance by security personnel.
The in-situ combustible load is light. The only cables in the room are two short sections per pump that rise from the floor near each pump and terminate at the pump. The lubricating oil is contained in the pump and there are no hot surfaces in the area.
The licensee has conducted,-an analysis to determine quantity of fuel, spilled on the floor of thY'area, that is needed to create a fire and corresponding heat flux of enough severity to cause cable damage. The analysis indicates that 17 gallons of acetone in an-_8-foot-diameter pool, is needed to effect damage.
Only administrative controls are available to prevent the accumulation of tran sient materials in individual plant areas. With the low combustible loading, and continuous surveillance in this area, there is reasonable assurance that a fire would be detected promptly and could be/extinguished manually.
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Based on our evaluation, the level of existing protection for this area does provide a level of,fire protection equivalent to the technical requirements of Section III.G of Appendix R and, therefore, the exemption for the Service Water Pump Area is granted.
F-ire Barrier Cable Penetration Seal Qualification The licensee requested an exemption for certain penetration seals from Section III.M.2 of Appendix R to 10 CFR 50 to the extent that the acceptance criteria for fire barrier cable penetration seal qualification requires that the temperature levels recorded on the unexposed side of the seal be analyzed to demonstrate that the maximum temperature be sufficiently below the cable insu lation ignition temperature. Subsequently, the licensee requested that the seals in question be accepted as two-hour rated seals in their installed locations.
On July 18, 1981, we met with the licensee to discuss the exemption request.
At the meeting, we agreed that the fire seal had sucessfully been qualified as having a 2-hour fire rating, and could be acceptable where justified that the fire barrier need only be rated at 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. We requested that the licensee identify the fire barriers that contain this seal and the fire loading on both sides of the seal.
By letter dated October 7, 1981, the licensee provided the requested information.
The NRC staff's evaluation included the following considerations. This alterna tive does not meet the requirements of Section III.M.2 of Appendix R, because 2-hour penetration seals are installed in 3-hour rated fire barriers.
The penetration seals meet Section III.M.2 acceptance criteria for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
The fire barriers in which the penetration seals are installed have been shown to separate fire areas which have a fuel load less than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
With the exception of the North Cable Vault, the in-situ fuel loading of the fire area is equivalent to a fire severity of approximately 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> or less.
Because the in-situ fuel loads have a fire severity considerably less than the fire resistive rating of the penetration shields, the probability of postulated fires propagating from one fire area to another through the 2-hour fire rated penetra tion seals is low.
The North Cable Vault has a fuel load equivalent to a fire severity of one hour and 59 minutes. However, this area is protected by (1) early warning fire detection, (2) automatic CO2 fire extinguishing system, and (3) manual fire fighting capability. The automatic fire suppression system and reasonable fire brigade response should be adequate to preclude failure of these seals during a fire.
Therefore, we agree with the licensee that the use of the 2-hour fire rated penetration seals in the fire barriers specified provides a level of protection equivalent to that required by Section III.M.2 of Appendix R.
Based on our evaluation, the 2-hour fire rated penetration seals in the fire barriers specified, provide a level of safety equivalent to the technical requirements of Section III.M of Appendix R and, therefore, the licensee's request for exemption from Subsection III.M for these areas is granted.
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V.
Accordingly, the Commission has determined that, pursuant to 10 CFR 50.12, an exemption is authorized by law and will not endanger life or property or common defense and security and is otherwise in the public interest and hereby grants the exemptions from the requirements of Appendix R to 10 CFR 50 to the extent discussed in Section IV above.
The NRC staff has determined that the granting of this Exemption will not re sult in any significant environmental impact and that pursuant to 10 CFR 51.5(d)
(4) an environmental impact statement or negative declaration and environmental impact appraisal neeed not be prepared in connection with this action.
FOR THE NUCLEAR REGULATORY COMMISSION Darrell G. Eisenhut, Director Division of Licensing Office of Nuclear Reactor Regulation Dated at Bethesda, Maryland this 21st day of November, 1983.
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