ML091170535

Response to Request for Correction to NUREG-0847, Supplement 18, Related to Carbon Dioxide Fire Suppression System

ML091170535
Person / Time
Site:	Watts Bar
Issue date:	07/15/2009
From:	John Lamb Watts Bar Special Projects Branch
To:	Swafford P Tennessee Valley Authority
Lamb J, 415-1727
References
NUREG-0847 S18, TAC ME0876
Download: ML091170535 (8)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 July 15, 2009 Mr. Preston D. Swafford Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 3R Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 SUB..IECT: WATTS BAR NUCLEAR PLANT, UNIT 1 - REQUEST FOR ADDITIONAL INFORMATION REGARDING REQUEST FOR CORRECTION TO NUREG-0847, SUPPLEMENT 18, RELATED TO CARBON DIOXIDE FIRE SUPPRESSION SYSTEM (TAC NO. ME0876)

Dear Mr. Swafford:

By letter dated March 13, 2009 (Agencywide Document and Management Systems Accession No. ML090750783), Tennessee Valley Authority (TVA) requested a correction to NUREG-0847, Supplement 18, "Safety Evaluation Report related to the operation of Watts Bar Nuclear Plant, Units 1 and 2, Docket Nos. 50-390 and 50-391" (ML070530364). The requested correction to NUREG-0847, Supplement 18, was related to the carbon dioxide (C0 2) fire suppression system in the auxiliary instrument rooms.

On page 80 of NUREG-0847, Supplement 18, it states, "the system must maintain at least 50-percent concentration for 15 minutes ..." which is different from the information in the TVA letter dated May 26, 1995 (ML073230886). The TVA letter stated that, "The soak time will be to maintain CO 2 concentration greater than 45% for at least 15 minutes."

In order to evaluate the ability of the C02 fire suppression system as-installed for the Watts Bar Nuclear Plant, Unit 1 Auxiliary Instrument Room to provide an equivalent level of 'fire protection to that required by General Design Criteria 3 of Appendix A to Title 10 of the Code of Federal Regulations (10 CFR), Part 50 and Appendix R to 10 CFR Part 50, the U.S. Nuclear Regulatory Commission staff requires additional information.

The specific questions are detailed in the enclosed request for additional information (RAI).

Based on discussions with Mr. Michael Brandon of your staff on July 14, 2009, we understand that you plan to respond to the enclosed RAI within 30 days of the date of this letter.

P.Swafford -2 If you have any questions regarding this issue, please feel free to contact me at (301) 415-3100.

Docket No. 50-390

Enclosure:

As stated cc: Distribution via Listserv

REQUEST FOR ADDITIONAL INFORMATION REGARDING REQUEST FOR CORRECTION TO I\JUREG-0847, SUPPLEMENT 18, RELATED TO CARBON DIOXIDE FIRE SUPPRESSION SYSTEM (TAC NO. ME0876)

WATTS BAR NUCLEAR PLANT, UNIT 1 TENNESSEE VALLEY AUTHORITY DOCKET NO. 50-390 By letter dated March 13, 2009 (Agencywide Document and Management Systems Accession No. IVlL090750783), Tennessee Valley Authority (TVA) requested a correction to NUREG-0847, Supplement 18, "Safety Evaluation Report related to the operation of Watts Bar Nuclear Plant, Units 1 and 2, Docket Nos. 50-390 and 50-391" (ML070530364). The requested correction to NUREG-0847, Supplement 18 (supplemental safety evaluation report (SSER)), was related to the carbon dioxide (C0 2 ) fire suppression system in the auxiliary instrument rooms for Watts Bar Nuclear Plant (WBN), Unit 1.

In order to evaluate the ability of the C02 fire suppression system as-installed for the WBN, Unit 1 Auxiliary Instrument Room to provide an equivalent level of fire protection to that required by General Design Criteria (GDC) 3 of Appendix A to Title 10 of the Code of Federal Regulations (10 CFR), Part 50 and Appendix R to 10 CFR Part 50, the U.S. Nuclear Regulatory Commission (NRC) staff requires additional information, as discussed below.

1. TVA letter, dated March 24, 2009 (ML090840302), Enclosure 1, page E1-1, states that, "Contrary to the above, since receipt of the operating license on February 7, 1996, until the present, the CO2 system for the auxiliary instrumentation room was not designed in accordance with the 1973 Edition of the NFPA [National Fire Protection Association] 12 and SSER No. 18, in that, the CO2 system was unable to deliver and maintain a minimum gas concentration of 50 percent in the upper portion of the room for 15 minutes. .. "

The NFPA 12 Standard on "Carbon Dioxide Extinguishment Systems," 1973 Edition, the Code of Record (COR) for WBN Unit 1 installation, Section 2421 specifies 50 percent design concentration for deep seated fire. Section 2232 states, "For deep seated fires, the required extinguishing concentration shall be maintained for a sufficient period of time to allow the smoldering to be extinguished and material to cool to a point at which re-ignition will not occur when the inert atmosphere is dissipated. .. "

Provide a basis for why you believe it is adequate for the total flooding automatic C02 fire suppression system installed in the Auxiliary Instrument Room to achieve a concentration of only 45 percent (rather than at least 50 percent) for 15 minutes in the upper portion.

Enclosure

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2. TVA letter, dated March 24, 2009, Enclosure 1, page E1-1, states that, "This section of Appendix R requires a fixed fire suppression system for the auxiliary instrumentation room area since it contains safe shutdown equipment and alternative safe shutdown was selected for this area. .. "

TVA evaluation in a letter, dated March 24, 2009, did not discuss effects of fire damage on equipment required for safe-shutdown. Discuss the effects that fire damage would have on the equipment that is associated with cables likely to sustain damage, and provide a basis for adequacy of damage (Le., provide a basis for determining that, in spite of damage, adequate safe-shutdown will be maintained).

3. TVA letter, dated March 24, 2009, Enclosure 1, page E1-2, states that, "TVA will revise the system design description for the CO2 system supplying the auxiliary instrument rooms (Units 1 and 2) to include a minimum soak time. The soak time will be to maintain CO2 concentration greater than 45% for at least 15 minutes. The revision will be completed by June 30, 1995.... "

If the above commitment was incorporated in the WBN Unit 1 Fire Protection Report (FPR), the NRC staff requests that the TVA to provide copy of revised FPR pages with docketed date and revision number.

4. TVA letter, dated March 24, 2009, Enclosure 1, page E1-2, states that, "The fact remains, however, that WBN's CO2 gas suppression system was designed for and can achieve a 50% concentration after discharge in accordance with NFPA 12, 1973 Edition. It will also, as committed, maintain a concentration greater than 45% for at least 15 minutes. .. "

Have any CO2 system or other plant modifications, subsequent to the original discharge tests of the CO2 fire suppression system, been made in the Auxiliary Instrument Room that could potentially affect C02 concentrations, such as C02 piping changes or timer adjustments or new room dampers or penetrations that might leak? If such modifications have been made, what subsequent testing or evaluation was performed to ensure that proper concentrations were maintained for the required soak time? If concentration decreased due to leakage, where does the C02 gas migrate and describe your evaluation on the effects to plant operation and operator actions.

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5. TVA letter, dated March 24, 2009, Enclosure 2, page E2-1, states that, "The primary function of the automatic CO2 fire suppression systems is to extinguish a fire or control and minimize the effects of a fire until the fire brigade can respond and extinguish it. .. "

Manual fire-fighting of large amounts of burning cables is a considerable challenge even to the most well-trained and equipped fire brigade. Further, many rooms of this nature have cable trays located high above the floor which may be inaccessible to the fire brigade personnel. Describe how the facility fire brigade personnel have been instructed about the potential for deep-seated 'fire hazards associated with cable re-ignition. Further, discuss the methods to manually extinguish or control and minimize the effects of a deep-seated fire located high above the floor in inaccessible locations (if WBN Unit1 Auxiliary Instrument Room has any inaccessible locations).

6. TVA letter, dated March 24, 2009, Enclosure 2, page E2-1, states that, "Full discharge tests for representative rooms in conjunction with door fan pressurization tests have been conducted to validate CO2 concentration and soak times. The duration of the discharge is determined by the area requirements and is controlled by the discharge timer. .. "

Provide the most recent full discharge test results of the CO2 fire suppression system installed in the Auxiliary Instrument Room, including the following:

• Concentration levels

• Soak time

• Number, location, and height of sensors in room.

Also, provide copies of the original discharge test results for review.

7. TVA letter, dated March 24, 2009, Enclosure 2, page E2-3, states that, "TVA calculation WBN-IPE-004, "Zone of Influence" determined that the only ignition source is two air handling units in the Corridor on Elevation 708.0. .. "

"TVA calculation EPM-DOM-012990, "Combustible Loading Data (CLD)" establishes the Fire Severity Index for. .. "

"TVA calculation WBN-IPE-004, "Zone of Influence," determine that the only ignition source. ..

"Based upon this evaluation, all these areas were screened out from the detail review, and were screened out due to a lack of significant fire ignition source and/or the presence of automatic detection and suppression ability. .. "

-4 Confirm that there are no ignition sources other than two air handling units in this fire area.

Provide a summary and the results of the "Zone of Influence" calculations.

8. TVA letter, dated March 24,2009, Enclosure 2, page E2-3, states that, "TVA detection and suppression systems would detect and suppress any fire with the potential of severity needed to include a deep seated fire. .. "

TVA evaluation did not specify cable construction information (Le., insulation and jacket material, such as cross-linked polyethylene (XLPE)/polyvinyl chloride (PVC) for all cables installed in cable trays and conduits or exposed (such as air drops). Identify the types of cable insulation and jacket materials within the Auxiliary Instrument Room.

9. TVA letter, dated March 24,2009, Enclosure 2, page E2-3, states that, "The defense in depth fire protection at Watts Bar ensures that the fire protection provided for the Unit 1 Auxiliary Instrument Room is in compliance with the applicable sections of NFPA 12- 1973 and therefore meet the regulatory requirements found in Branch Technical Position (BTP) 9-5.1, Appendix A, paragraph F.6 and 10 CFR 50, Appendix R, paragraph II/.G.3. .. "

The NRC staff requests that the TVA provide a description of the defense-in-depth features in the Unit 1 Auxiliary Instrument Room.

10. TVA letter, dated March 24, 2009, Enclosure 2, page E2-4, states that, "The automatic CO2 suppression system provided for the Unit 1 Auxiliary Instrument Room is adequately designed for a deep seated fire. The detection system and suppression system would detect and suppress any fire with the potential of the severity needed to induce a deep seated fire. .. "

Provide a description of the detection system currently installed in the Auxiliary Instrument Room. Discuss how the CO2 fire suppression system actuation occurs in the Auxiliary Instrument Room.

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11. Part X - NFPA Code Evaluation of the Fire Protection Report, Revision 29 (ML052780278), September 30, 2005, provides point-by-point comparison of the conformance with NFPA codes. Page X-19 cross-references the applicable section of NFPA 12,1973 Edition and provides additional information for compliance with code.

NFPA 12-1973 "Carbon Dioxide Systems" TVA System 39 Compliance Summary Matrix Code Section Summary Topic/Remarks 2421 Comply Flooding factor for specific hazards (50% for deep seated fire locations such as board rooms, instrument rooms, etc.)

However, TVA letters, dated March 13, and 24, 2009, are not consistent with the above code compliance evaluation documented in Unit 1 WBN FPR. Discuss and provide a basis for this discrepancy.

P.Swafford -2 If you have any questions regarding this issue, please feel free to contact me at (301) 4133100.

Sincerely, IRAI John G. Lamb, Senior Project Manager Watts Bar Special Projects Branch Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-390

Enclosure:

As stated DISTRIBUTION:

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