ML20077M172
| ML20077M172 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 08/07/1991 |
| From: | Shelton D CENTERIOR ENERGY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 1966, GL-90-05, GL-90-5, TAC-80876, NUDOCS 9108130218 | |
| Download: ML20077M172 (3) | |
Text
-
q
. c..c.
d cannrsRMNr
. ENERGY Donald C. Shenon 3u0 Ma$ son Avenue Vce PresMent Nucler Toledo, OH 436520001 Davis Besse (419)249 2300 -
Docket Number 50-346 License Number NPF-3 Serial Number 1966 August 7,-1991 United States Nuclear Regulatory Commission
-Document Control Desk' Vashington, D. C.
20555 Subjects Request for Relief to Allow Temporary Non-Code Repr. irs of Service Water Piping in Accordance_vith Nuclear Regulatory Commission (NRC) Generic Letter (GL) 90-05
- Gen tlemen:
By-letter dated.aly 3, 1991 (Serial Number 1955),-Toledo Edison requested Nuclear Regulatory Commission (iJtC) approval of temporary-non-Code repairs for two through-vall leaks discovered on June 21, 1991 in service vater' system (SV) piping at the Davis-Besse Nuclear Power Station (DBNPS)
~
Unit 1.
The purpose of this letter is to clarify and expand information provided by Toledo Edison's July 3, 1991 letter as regnested by the NRC staff in a telephone ~ call on July 23, 1991.
The tyc leaks were discovered in moderate energy, American Society of Hechanical" Engineers ~(ASME)-Boiler and Pressure Vessel Code Section III, Class 3, SV piping.. One leak vas located in 4", Schedule 40 SV-piping in j
the: Decay Heat (DH) Cooler room. The other leak was discovered in 3",
l Schedule 40 SV piping in the Number 1 Emergency Core Cooling System (ECCS)
~
Pump room.
As stated in Toledo Edison's July 3, 1991 letter, bounding flav sizes of 15% of the pipe circumference vere evaluated for the combination of l
sustained (deadveight and pressure), thermal, and safe shutdown earthquake r1 stresses at the actual flav locations. The bounding flav sizes ("2a")
corresponding to 15% of the pipe circumference, are 2.12" for the 4" pipe and 1.65" for the 3" pipe. Toledo Edison's July 3, 1991 letter described the actual flav dimensions in comparison to the evaluated bounding flav sizes.
I 9109130218 910807 PDR ADOCK 05000346 P
PDR Operahng Companies j
leveland Electnc illummatmg
(
gu 0 0 8 3**""*"
y
k Docket Number'50-346
- 1,*** -
License Number NPF-3 Serial Number 1966 Fage 2 Consistent-vith the guidance provided by the NRC Safety Evaluation (Log Number 3303, dated August 20, 1990, TAC Number M77037) of Toledo Edison's previous request (Serial Number 1825 dated July 10,_1990) for approval of a non-Code repair under PRC Generic Letter (GL) 90-05 (Log Number 3258 dated June 15, 1990), the n,minal pipe thickness (tnom) is substitut-d for the Code minimum pipe thickness (tmin) in the "through-vall flav" appreach discussed in'GL 90-05.
For 3",
Schedule 40 pipe tnom is 0.216".
For 4",
Schedule 40 pipe tnom is 0.237".
Toledo Edison's letter da: a Jt'y 3, 1991 stated that Toledo Edison had.
evaluated the effects of 6 er. interactions (such as flooding, spraying vater on eqc' ors
- and it - si system flow) assuming the absence of the clamp and considering the flav location and area sump capacity, and found them to be negligible. The following expands the description of the factors considered by Toledo Edison in reaching this conclusion.
The components in the Decay Scat Cooler room and Numier 1 ECCS Pump room are spray protected and no adverse effects vill be created by water spray from the leaks in the service water piping. The leakage through the pipe flav vithout the pipe clamps installed does not spray on any electrical
-component. Therefore, the decay heat pump, high pressure injection pump, and the containment spray pump are not affected by the spray of the service water leaks.
In addition, the pipe clamps have a rubber liner to-seal the defect area and minimize any leakage.
The potential for flooding of the Decay Heat Cooler room and Number 1 ECCS Pump room as a result of the service water leaks has been rewieved.
Each room has two 75 gallon per minute (; o) capacity sump pumps. The sump pumps have level switches and assoca ted alarms, and are povered from an essential ous.
Should the pipe clamo come loose and the leak rate become sevare enough to potentially flood the room, the level alarms associated with the' sump pumps vill alert the control room.
At the current leak rates of approximately 4 gpm without the pipe clamps installed, flooding is not a problem.
Should the defects open to the maximum allovable size (i.e., 15% of the pipe circumference), the leak rates vill still be within the capacity of the sump pomps._ Veekly inspections of.the pipe clamps and assessment of leakage provide assurance that the pipe clamps are intact and flooding of the rooms is not occurring.
The ECCS room coolers in Number 1 ECCS Pump room are not affected by the leaks in the service water piping.
Airborne spray would be collected by l-the room coolers. The room coolers in this room are supplied with cooling L
vater under normal conditions by the unaffected Number 1 Service Vater loop.
The flow rates through the coolers are not af fected by the leaks in the Number 2 Service Vater loop.
The Numbers 1 and 2 ECCS Room Coolers are supplied from the Number 2 Service Vater loop.
Consequently, the flow rates.through these coolers could be affected by the pipe leaks.
- However, with the non-Code' repairs in place, flov through these ECCS room coolers are unaffected by the leak. At the current leak rate with the non-Code repairs removed, the maximum flow reduction through any one of these coolers is approximately 4 gpm and is acceptable considering the ambient and service water temperatures.
Veekly inspection of the non-Code repairs provides assurance that the Number 2 Service Water loop ECCS room coolers will not have reduced flow.
l
Docket Number 50-346 License Number NPF-3 Serial Number 1966
- Page 3 If you have any questions regarding the information provided by this
]
letter, please call Mr. R. V. Schrauder, Manager - Nuclear Licensing at (419) 249-2366.
Very truly yours, lf
'\\ i y. -.
PVS/ach Attachment cci P. M. Byron, NRC Region III, DB-1 Senior Resident Inspector A. B. Davis, Regional Administrator, NRC Region III J. B. Hopkins, NRC/NRR DB-1 Senior Prn,iect Manager Utility Radiological Safety Board
_ _ _ _. _ _ _ _ _ _. _ _. _ _ _. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _. __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _. _ _ _ _ _. _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _