ML18227D478
| ML18227D478 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 07/11/1977 |
| From: | Robert E. Uhrig Florida Power & Light Co |
| To: | Lear G Office of Nuclear Reactor Regulation |
| References | |
| Download: ML18227D478 (7) | |
Text
NRC FoRM 195
, I2-25I.
UA. NUCLEAR REGULATORY MISSION OOC ET NUMBER NRC DISTRIBVTIONFoR PART 5D DOCKET MATERIAL PILE NUMSEA TO-Mr. George Lear FROM:
Florida Pwri & Light Company Miami, Fla Robert Ei Uhrig OATS OF OOCUMENT 7/11/77 OATS RECEIVEO 7/15/77 TTER RIG INAL OPY OESCRIPTION QNOTORIZEO
~NC LASS IFI E0 PAOP INPUT FOAM ENCLOSURE NUMBER OF COPIES AECEIVEO C.C DO NOT REMOVE'onsists of requested additional EGGS
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nformationi ~
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ACKNOWLEDGED (1-P)
(3-P )
PLANT NAME: Turkey Point Units 3 & 4 RJL 7/15/77 MANAGER!
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ASSXSL4VT:
FOR ACTION/INFORMATION ENVIRHNMENTAL ASSIGNED AD:
V~ MOORE LTR BRANCH CHIEF PROJECT MANAGER:
LICENSING ASSISTANT:
IMMAN INTERNAL0 IST B~ HARLESS RIBUTION PLANT SYSTEMS TEDESCO BENAROYA SITE SAFETY &
ENVIRON ANALYSIS DENTON & MULLER ENGINEERING IPPOLITO PERATING REACTORS RO TECH ERNST BALLARD GB 0
A I SITE ANALYSIS VOLLMER BUNCH J
COLLINS EXTERNALDISTRIBUTION CONTROL NUMBCR G IV J HAiiCHETT 1 6 CYS ACRS SENT CA GO NRC FORM 195 (2 75)
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P. 0, BOX 013100, MIAMI, FL 33101 FLORIDAPOWER 8l LIGHTCOMPANY L-77-217 July ll, 1977 IRegulatory Docket RIe Office of Nuclea Reactor Regul'ation Attention:
bh. George Lear, Chief Operating Reactors Branch 53 Division of Operating Reactors U.
S. Nuclear Regulatory Commission washington, D. C.
20555
Dear Mr. Lear:
Re:
Turkey Point Uni s 3 and 4
Docket Nos.
50-250 and 50-251 ECCS Information Re uest i,/~~
Cn On June 27,
- 1977, we received'a telecopied request from your staff for additional ECCS information.
The information you requesteci is attached.
Ver y yours, Robert E. Uhrig Vice President REU/~9 S/cpc Attachment cc:
Mr. Norman, C. Moseley, Region Il Robert Lowenstein, Esquire
~ I 771 <(0'7~q PEOPLE... SERVING PEOPI.E Id ELi~l >~i e BUILU FLORIDA
Pl
ATTACEBKilT Turkey Point Units 3 and 4
Docket Nos.
50-250 and 50-251 ECCS Information Re uest Question 1
Show that the critical break size (DECLG, CD = 0.4) remains unchanged in view of the fact that:
(a) plugging of steam generator tubes used in the analysis increased from 10% to 15%,
and (b) actual plugging 'of the steam generator tubes in Unit 4 is unsymmetrical and in one steam generator exceeds 15%.
Answer 1
Westinghouse has done sevexal LOCA analyses assuming plugged steam generator tubes.
In most cases, the analyses consist of doing the calculations for various levels of uniform steam generator tube plugging on the limiting break for a specific plant type.
Examination of key event occurrence times such as the end of bypass, end of blowdown and bottom of core recovery shows that, in general.,
they vary smoothly and predictably as the level of tube plugging. is changed.
An example of the well-behaved nature of the tube plugging LOCA anaLysis results is shown in HCAP-8696, "Pexturbation Technique For Calculating ECCS Cooling Performance",
Figure 2.
That Figuxe shows the increase in peak clad temperature as a function, of uniform steam generator tube plugging fox two loop, three loop, and four loop plants.
The worst bxcak size for these plants, which was used in this study, varied fxom the
- DECLG, CD = 0.4 to the
- DECLG, CD
= 1.0.
Since the sensitivity of PCT to steam generator tube plugging is between approximately 4.'F and 8.'F per percent plugging, it is reasonable to conclude that the DECLG break dis-charge coefficient does not significantly alter the effect of plugging tubes.
Furthex rationalization of that,. conclusion is that a significant part, of the tube plugging PCT penalty is due to the increased loop resistance to steam flow during the reflood phase of the accident is not choked, the break discharge coefficient
Page 2
ATTACHHENT Answer 1
. Continued assumed during blowdown does not effect steam flow during the reflood transient.
Therefore, the PCT. penalty attributed to the degradation of the core reflood rate should be the same for all large breaks.
In addition, a spectrum of three DECLG breaks has been analyzed for 0% and 5% uniform steam generator tube plugging levels for Turkey Point.
In both cases, the DECLG CD =
0 4 break (which is limiting) had a peak clad temperature more than 200'F higher than the peak clad temperature for the DECLG CD = 0.6 break, no shift in limiting break size was observed.
Question 2
Show that the unsymmetrical steam generator plugging in Unit 4, with plugged tubes in one steam generator exceeding 15%, would not have a significant nonconservative
'effect on peak clad temperature.
Answer 2
Studies have been performed to determine the effect of asymmetric tube plugging on peak clad temperature.
In order to bound the effects of asymmetric tube plugging, maximum asymmetry (i.e. all plugged tubes in 1) either the, broken loop or 2) the intact loops) was assumed.
The studies show that assuming all plugging in the broken loop results in a slightly lower peak clad temperature than symmetric plugging.
Assuming all plugging.in the intact loop results in a slightly higher peak clad temperature.
For the current Unit 4 plugging distribution (9.8%,
11.3$, 17.5~),
the worst case asymmetry in the intact loop is the average of the
.two.highest individual'team. generator plugging levels or 14.4%.
Since this is below 15% the peak clad temperature result would not exceed the peak clad temperature for the 15% symmetric plugging case.
Furthermore, if the plugging continues in Unit 4 up to a total plant level of 15% such that the intact loop plugging is maximized to 17.6%,
the effect on peak clad temperature is expected to be less than 5'F, and, therefore, insignificant.