ML20205F207
| ML20205F207 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 10/24/1988 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| IEB-88-008, IEB-88-8, NUDOCS 8810280011 | |
| Download: ML20205F207 (4) | |
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t' TENNECOEE VALLEY AUTHORITY CH ATTANOOo A. TENNESSEE 374ol
$N 157B Lookout Place 00T 241988 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.
20555 Centlement In the Matter of
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Docket No.
50-259 Tennessee Valley Authority
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50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN) - RESPONSE TO IE BULLETIN 88-08, SUPPLEMENTS 1 AND 2 - THERMAL STRESSES IN PIPING CONNECTED TO REACTOR COOLANT SYSTEMS This letter provides TVA's response to the subject IE Bulletin including Supplements 1 and 2 for BFN. This bulletin requested licensees tot (1) review their teactor coolant system (RCS) to identify any unisolable piping which could be subjected to temperature distributions which would result in unacceptable thermal stresses, and (2) take action, where such piping to identified, to ensure that the piping will not be subjected to unacceptable thermal stresses.
All injection interfaces with the reactor coolant pressure boundary have been reviewed. The details of this review are presented in enclosure 1.
As discussed in this enclosure, the potential for the conditions described in the subject bulletin could exist only during high pressure coolant injection (HPCI) and reactor core isolation cooling (RCIC) systems surveillant:e testing. Such infrequent ope:ation, combined with the existing system flow paths which have been designed to minimize thermal stresses, is not suffic'.ent to induce thermal cycling stress fatigue in the reactor feedwater piping.
Therefore, there are no unisolable sections of piping connected to the RCS which can be subjected to stresses from temperature stratification or temperature oscillations which could induce unacceptable cycling stress fatigue.
8810280011 89102 86 PDR ADOCK 05CcceS9
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g An Equal Opportunity Employer
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v U.S. Nuclear Regulatory Comission Qg g g Please refer any questions regarding this submittal to Patrick P. Carter, L
Manager, BFN Site Licensing (205) 729-3570.
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Very truly yours, f
TENNESSEE VALLEY AUTHORITY
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. ger Nuclear Lice ing and Regulatory Affairs Subscribed and sworn ore me is.f4'/May of 1988.
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/AAdi h Notary Public My Comission Expires 7
f Enclosures cc (Enclosures):
Ms. S. C. Black, Assistant Director for Projects IVA Projects Division U.S. Nuclear Regulatory Comission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. F. R. McCoy, Assistant Director for Inspection Programs TVA Projects Division U.S. Nuclear Regulatory Comission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Browns Ferry Resfdent Inspector Browns Ferry Nuclear Plant Route 12. Box 637 Athens, Alabama 35611
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ENCLOSURE 1 REVIEW OF PIPING CONNECTED TO THE REACTOR COOLANT SYSTEM WHICH COULD RESULT IN UNACCEPTABLE THERMAL STRESSES The reactor coolant pressure boundary is defined by 10CFR50.2 as all those pressure containing components, such as pressure vessels, piping, pumps, and valves, which are:
(1) Part of the reactor coolant system, or (2) Connected to the reactor coolant system, up to and including any and all of the following:
(1)
The outermost containment isolation valve in system piping which penetrates primary reactor containment, (ii)
The second of two valves normally closed during normal teactor operation in system piping which does not penetrate primary reactor containment, (iii)
The reactor coolant system safety and relief valves.
For nuclear power reactors of the direct cycle boiling water type, the reactor coolant system extends to and includes the outernest containment isolation valve in the main steam and feedwater piping.
All applicable injection interfaces with the reactor coolant pressure boundary have been reviewed.
The results of this review are rumnarized below for each type of injection interface:
Reactor Feedwater Interfaces The high pressure coolant injection (HPCI) and reactor core isolation cooling (RCIC) systems connections with the reactor feedwater piping downstream of the outer containment isolation valves were reviewed. The HPCI and RCIC injection points are into separate feedwater lines.
Both inject through thermal sleeves designed to protect the piping f rom excessive thermal stresses.
Under normal plant operating conditions, flow paths are isolated from the HPCI and RCIC feedwater injection points by normally closed motor operated isolation valves and the HPCI/RCIC systems pressures are below the reactor feedwater system pressure. HPCI and RCIC systems flow rates at normal reactor vessel operating pressure are verified every three months as required by Technical Specification Surveillance Requirements 4.5.E and 4.5.F.
Therefore, thermal stratification or oscillation induced by leakage past the isolation valves could only exist during extremely short periods of surveillance testing.
The injection thernal sleeves minimize the potential for thermal piping stresses at the injection points. Such infrequent operation is not sufficient to induce thermal cycling stress fatigue in the reactor feedwater piping.
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4 The control rod drive (CRD) and reactor water clean up (RWCU) systems flov
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returns indirectly to' the feedwater piping through the HPCI and/or RCIC
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thermal sleeves. These flow paths have been routed through the thermal t
sleeves to minimize the potential for thermal cycling stress fatigue in the t
reactor feedwater piping. The CRD system is isolated from the feedwater piping by a normally closed motor operated valve under normal plant operating conditions, and the RWCU system is normally aligned to the feedwater system.
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Peactor Recirculation Interfaces L
i The residual heat removal (RHR) system injects into the reactor recirculation piping during low pressure coolant injection (LPCI) and shutdown cooling l
modes. Under normal plant operating conditions, flow paths are isolated from the reactor recirculation piping by normally closed motor operated isolation valves and the RHR/LPCI systems pressures are below the reactor recirculation system pressure. There is not a potential for cooler RHR/LPCI a
system water to leak into the reactor recirculation piping and induce thermal 1
cycling stress fatigue.
l RHR Head Spray Interface i
This interface has been removed from unit 2 and is being removed f rom units 1
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4 and 3 during the extended outages for these units. There will not be a potential for cooler RHR system water to leak into the reactor vessel.
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l Core Spray Interfaces i
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I The core spray system injects directly into the reactor vessel during certain f
1 emergency conditions. Under normal plant operating conditions, the core spray i
lines are isolated from the reactor vessel by a normally closed motor operated i
isolation valve and the core spray system pressure is well below the reactor vessel pressure. There is not a potential for cooler core spray system water to leak into the reactor vessel and induce thermal cyctfug stress fatigue.
Standby Liquid Control System Interface
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The standby liquid control system (SLCS) has the ability to inject cold water into the RCS at normal operating pressure. Explosive squib valves are utilized to isolate the SLCS from the RCS. Squib valves are designed to be I
sero leakage valves. Therefore, the potential for the leakage of cold water
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into the RCS and inducing thermal cycling stress fatigue is considered highly
- unlikely, i
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I 1
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