ML18114A301
| ML18114A301 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 01/03/1978 |
| From: | Robert E. Uhrig Florida Power & Light Co |
| To: | Desiree Davis Office of Nuclear Reactor Regulation |
| References | |
| Download: ML18114A301 (6) | |
Text
DISTEND BUT/ON AEZER ISSUANCE 0 ERATING LICENSE NRC FORM 196 IZ TSI UA NUCI EAA AEQULATOAYCOMMISSI OOCI!:ET NUMBEA3'35 NRC DISTRIBUTION PDA PART 50 DOCKET MATERIAL PII 8 NUM88R
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Mr. Don K, Davis FROM:
Florida Power
& Light Company Miami, Florida Robert Ei Uhrig OATS OP DOCUMENT 1/3/78 DATE RECEIVED 1/6/78 TTER Jg35AIQINAI CICOPY DESCRIPTION QNOTOAIZED
&UNCLASSIFIED PROP INPUT FORM ENCI OSUAE NUMBER OP COPIES RECEIVED Consists of info. concernigg Water Hammer in PWR Feedwa ter Sys tems ~ ~
St Lucie Unit No.
1 RJL 1/6/78 BRANCH CHIEF:
7 FOR ACTION/INFORMATION REG INTERNALOISTRI BUTION LPDR:
ZIC NS IC 5CRS 1
CYS SEVZ CATE EXTERNALOISTRIBUTION CONTROL NUMBER OOZOqSX
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qf Ii~i FLORIDAPOWER & LIGHTCOMPANY Office of Nuclear Reactor Regulation Attention:
Mr. Don K. Davis, Acting Chief Operating Reactors Branch I2 Division of Operating Reactors U.
S. Nuclear Regulatory Commission Washington, D.
C.
20555 Re:
St. Lucie Unit 1 Docket No. 50-335 Water Hammer in PWR Feedwater S stems January 3,
1978 L-78-5
~i'~+
Dear Mr. Davis:
By letter dated September 2, 1977, y'ou forwarded a request. for information concerning design and/or procedural modifications which might be necessary at St. Lucie Unit 1 to preclude water hammer in the steam generator feedwater system.
The intent of the staff's request was to gain assurance that feedwater hammer will not occur under normal and transient operating conditions.
As described
- below, FPL has already implemented feedwater system modifications at St. Lucie Unit 1 in accordance with vendor recommendations.
The design of the St. Lucie Unit 1 feedwater piping involves a very short horizontal run (essentially the feedwater nozzle and a 90'ownward turned elbow).
- Also, during 1976, a plant modification resulted in the removal of the bottom discharge standpipes and the installation of elbows on the top of the feedwater ring.
This modification helps prevent the draining of the feedwater ring during periods when the steam generator water level is below the feedwater ring and the feedwater flow has been reduced or interrupted.
Additionally,, the modifi-cation reduces the individual feedwater ring nozzle velocities to levels such that problems of vibration or erosion are minimized.
While the above do not prevent draining of the feedwater ring through the steam generator nozzle thermal sleeve (into the steam generator) if feedwater is completely stopped, this path is very small and several hours would be required to completely drain the fit>id.
(This has been verified in the testing described below.)
As auxiliary feedwater is normally established within minutes to maintain the steam generator level, it is extremely unlikely that the feedwater ring will be drained during any plant operating mode.
Furthermore, a feedwater hammer test was performed at St. Lucie Unit 1 as described in our letter of February 25, 1977 (L-77-59).
This test was observed by a member of the NRC licensing staff and a copy of the completed Pre-operational Test Procedure
- 0700080B, 78p060i6i PEOPLE... SERVING PEOPLE
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Mr. Dog K. Davis, ing Chief U. S. Nuclear Regulatory Commission Page Two Revision 2, was forwarded to your staff by our letter of March 2, 1977 (I-77-70).
The tests were completed satisfactorily, and there was no indication of a water hammer.
In addition, St. Lucie operating procedures (and installed equipment) for steam generator level below the feed ring restrict feed flow to levels which have been demonstrated not to cause feedwater hammer.
The operating experience since the modification of the feedwater
- ring, as well as follow-up testing, has demonstrated that feedwater hammer is not a problem at St. Lucie Unit l.
This is evident from the fact that no indications of feedwater hammer have been observed.
Therefore, we do not believe that, further modifications are required to assure that feedwater hammer will not occur.
One conclusion of the report (NUREG-0291, An Evaluation of PWR Steam Generator Water Hammer, Final Technical Report, June 1,
1976-December 31, 1976), which was commissioned by the USNRC and was prepared by CREARE, Inc., is that "the most immediate means available to reduce the frequency and severity of steam generator water hammer is for operating reactors to upgrade their systems within'the framework of the present PWR vendor recommendations."
As was described
- above, FPL's past action has been responsive to this conclusion.
Very truly yours, Robert E. Uhrig Vice President WAK:dt cc:
Mr. James P. O'Reilly, Region II Robert Iowenstein, Esquire
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