ML20248D160

Forwards RAI Re GL-96-06, Assurance of Equipment Operability & Containment Integrity During Design Basis Accident Conditions, Dtd 960930.Info to Be Submitted within 45 Days from Date of Receipt of Ltr

ML20248D160
Person / Time
Site:	Peach Bottom
Issue date:	05/28/1998
From:	Thadani M NRC (Affiliation Not Assigned)
To:	Geoffrey Edwards PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
References
GL-96-06, GL-96-6, TAC-M96848, TAC-M96849, NUDOCS 9806020329
Download: ML20248D160 (5)

Text

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8 May 28, 1998 Mr. Garrett D. Edwards Director- Licensing, MC 62A-1 PECO Energy Company Nuclear Group Headquarters Correspondence Control Desk P.O. Box No. 195 Wayne, PA 19085-0195

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION (RAl) FOR PEACH BOTTOM ATOMIC POWER STATION, UNITS 2 AND 3, GENERIC LETTER (GL) 96-06 (TAC NOS. M96848 AND M96849)

Dear Mr. Edwards:

GL 96-06, " Assurance of Equipment Operability and Containment integrity Duiing Design Basis Accident Conditions," dated September 30,1996, included a request for licensees to evaluate potential waterhammer and two-phase flow conditions in cooling water systems that serve containment air coolers. By letters dated January 28 and February 10,1997, PECO Energy Company (the licensee) provided its assessment of water hammer and two-phase flow conditions for cooling water systems that serve containment air coolers at Peach Bottom Atomic Power Station (PBAPS), Units 2 and 3.

The Commission's technical staff, in reviewing the licensee's responses, has concluded that additional information as outlined in the enclosure is required to facilitate closure of the issues .

raised in GL 96 06.

We request that the licensee provide its response to the enclosed RAI within 45 days from the date of the receipt of this letter to support a timely completion of the staffs actions on the issues raised by GL 96-06.

Sincerely,

/S/

Mohan C. Thadani, Senior Project Manager i Project Directorate 1-2  !

Division of Reactor Projects -1/11 Office of Nuclear Reactor Regulation Docket Nos. 50-277 l and 50-278 I

Enclosure:

As stated , g

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} ,y 1 UNITED STATE 8 s* 1' NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 3000641001 May 28,1998 Mr. Garrett D. Edwards Director- Lloonsing, MC 62A-1 PECO Energy Company Nuclear Group Headquarters Correspondence Control Desk P.O. Box No.195 Wayne, PA 19085 0195

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION (RAl) FOR PEACH BOTTOM ATOMIC POWER STATION, UNITS 2 AND 3, GENERIC LETTER (GL) 96-06 (TAC NOS. M96848 AND M96849)

Dear Mr. Edwards:

GL 96-06, " Assurance of Equipment Operability and Containment Integrity During Design Basis Accident Conditions," dated September 30,1996, included a request for licensees to evaluate potential waterhammer and two-phase flow conditions in cooling water systems that serve containment air coolers. By letters dated January 28 and February 10,1997, PECO Energy Company (the licensee) provided its assessment of water hammer and two-phase flow conditions for cooling water systems that serve containment air coolers at Peach Bottom Atomic Power Station (PBAPS), Units 2 and 3.

The Commission's technical staff, in reviewing the licensee's responses, has concluded that additional information as outlined in the enclosure is required to facilitate closure of the issues raised in GL 96-06.

We request that the licensee provide its response to the enclosed RAI within 45 days from the date of the receipt of this letter to support a timely completion of the staff's actions on the issues raised by GL 96-06.

Sincerely, ha ro nager Project Directorate 1-2 Division of Reactor Projects - t/il Office of Nuclear Reactor Regulation

! Docket Nos. 50-277 and 50-278

Enclosure:

As stated cc w/ encl: See next page i

. I

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? i i  !

Mr. Garrett D. Edwards Peach Bottom Atomic Power Station,  !

PECO Energy Company Units 2 ard 3 oc:

J. W. Durham, Sr., Esquire Chief-Division of Nuclear Safety

, Sr. V.P. & General Counsel PA Dept. of PECO Energy Company Environmental Resources 2301 Market Street,626-1 P.O. Box 6469 Philadelphia, PA 19101 Harrisburg, PA 17105 846g PECO Energy Company ATTN: Mr. T. N. Mitchell, Vice President Board of Supervisors i I

Peach Bottom Atomic Power Station Peach Bottom Township 1848 Lay Road R.D.#1 )

Delta, PA 17314 Delta, PA 17314  ;

PECO Energy Company Public Service Commission of Maryland ATTN: Regulatory Engineer, A4-5S Engineering Division Peach Bottom Atomic Power Station Chief Engineer 1848 Lay Road 6 St. Paul Centre Delta, PA 17314 Baltimore, MD 21202-6806 {

Resident inspector Mr. Richard McLean j U.S. Nuclear Regulatory Commission Power Plant and Environmental l Peach Bottom Atomic Power Station Review Division  !

P.O. Box 399 Department of Natural Resources Delta, PA 17314 B-3, Tawes State Office Building Annapolis, MD 21401 i Regional Administrator, Region i U.S. Nuclear Regulatory Commission Dr. Judith Johnsrud 475 Allendale Road National Energy Committee -

King of Prussia, PA 19406 Sierra Club 433 Orlando Avenue Mr. Roland Fletcher State College, PA 16803 Department of Environment i 201 West Preston Street Manager-Financial Control & Co-Owner i Baltimore, MD 21201 Affairs  !

Public Service Electric and Gas A. F. Kirtiy, lll Company Extemal Operations - Nuclear P.O. Box 236  !

Hancocks Bridge, NJ 08038-0236 Delmarva Power & Light Company P.O. Box 231 Wilmington, DE 19899 Manager-Peach Bottom Licensing PECO Energy Company PECO Energy Company Nuclear Group Headquarters j Plant Manager Conospondence Control Desk l Peach Bottom Atomic Power Station P.O. Box No.19:i 1848 Lay Road Wayne, PA 19087-0195 Delta, PA 17314 i

?

i REQUEST FOR ADDITIONAL INFORMATION FOR RESOLUTION OF GL 96-06 ISSUES AT PEACH BOTTOM 2 & 3 (TAC NOS M96848 AND M96849)

Generic Letter (GL) 96-06, " Assurance of Equipment Operability and Containment integrity During Design-Basis Accident Conditions," dated September 30,1996, included a request for licensees to evaluate cooling water systems that serve containment air coolers to assure that I they are not vulnerable to waterhammer and two phase flow conditions. PECO Energy Company (the licensee) provided its assessment of the waterhammer and two-phase flow issues for Peach Bottom 2 & 3 in letters dated January 28, and February 10,1997. The licensee indicated that ,

cooling water to the containment air coolers is provided by the non-safety related Drywell Chilled )

Water-System (DCWS), a closed-loop system, or (during a loss of power), by the reactor building closed-cooling-water (RBCCW) system. The licensee determined thet the elevated head tank in the RBCCW system and pressure in the DCWS expansion tank would prevent the formation of steam bubbles such that waterhammer is not a possibility. Also, since the containment air coolers do not perform a safety-related heat removal function, the licensee concluded that two-phase flow was not a concem. In order to assess the licensee's resolution of these issues, the following additional information is requested:

1. Discuss specific system parameter requirements that must be maintained to assure that waterhammer will not occur (e.g., RBCCW head tank and DCWS expansion tank level, temperature, pressure), and state the minimum margin to boiling that exists, including ,

consideration of measurement and analytical uncertainties. Describe and justify reliance of any non-safety-related instrumentation and controls for assuring that waterhammer will not occur, and explain why it would not be appropriate to establish Technical Specification requirements for maintaining these parameters.

2. The GL' 96-06 response indicated that for small break LOCAs, operators will re-establish drywell cooling using existing emergency procedures before containment temperatures reach a point where steam generation could occur. Describe in detail the actions required by EOPs for this situation, operator response and the timing involved, and the minimum margin to boiling that will exist, including consideration of inherent uncertainties.

3. In order to more fully address the two phase flow concem, provide the following information:

a. Provide a detailed description of the " worst case" scenario for two-phase flow, l taking into consideration the complete range of event possibilities, system l configurations, and parameters. For example, temperatures, pressures, flow l rates, load combinations, and pctential component failures should be considered.

l Additional examples include:

. the consequences of steam formation, transport, and accumulation;

. cavitation, resonance, and fatigue effects; and 1

. erosion considerations.

Enclosure

6

{

2-Licensees may find NUREG/CR-6031, " Cavitation Guide for Control Valves,"

helpfulin addressing some aspects of the two-phase flow analyses. (Note: it is important for licensees to realize that in addition to heat transfer considerations,

' two-phase flow also involves structural and system integrity concems that must be addressed).

I

b. Identify any computer codes that were used in the two-phase flow analysis and describe the methods used to benchmark the codes for the specific loading conditions involved (see Standard Review Plan Section 3.g.1).

c. Describe and justify all assumptions and input parameters (including those used in any computer codes), and explain why the values selected give conservative results. Also, provide justification for omitting any effects that may be relevant to the analysis (e.g., flow-induced vibration, erosion).

l d. Determine the uncertainty in the two-phase flow analysis, explain hcw the uncertainty was determined, and how it was accounted for in the analysis to assure conservative results.

e. Confirm that the two-phase flow loading conditions do not exceed any design specifications or recommended service conditions for the piping system and components, including those stated by equipment vendors; and confirm that the system will continue to perform its design-basis functior.s as assumed in the safety analysis report for the facility, and that the containment isolation valves will remain operable.

4. Confirm that the waterhammer and two-phase flow analyses included a complete failure modes and effects analysis (FMEA) for all components (including electrical and pneumatic failures) that could impact performance of the cooling water system and confirm that the FMEA is documented and available for review, or explain why a complete and fully documented FMEA was not performed.

5. Explain and justify all uses of "engineeririg judgement."

6. Provide a simplified diagram of the affected systems, showing major components, active components, relative elevations, lengths of piping runs, and the location of any offices and flow restrictions.

7. Describe in detail any modifications that have been made (or will be made) to system design or operating requirements to resolve the waterhammer and two-phase flow issues.

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