ML18227D808
| ML18227D808 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  (DPR-041) |
| Issue date: | 02/01/1978 |
| From: | Robert E. Uhrig Florida Power & Light Co |
| To: | Stello V Office of Nuclear Reactor Regulation |
| References | |
| L-78-40 | |
| Download: ML18227D808 (12) | |
Text
REGULATORY INFORMATION DISTRIBUTION SYSTEM <RIDS)
DISTRIBUTION FOR INCOMING MATERIAL 50-251 f
REC:
STELLQ V ORG:
UHRIG R E DQCDATE: 02/01/78 NRC FL PWR 5 LIGHT DATE RCVD: 02/07/78 DQCTYPE:
LETTER
,KJOTARIZED:
NQ COPIES RECEIVED
SUBJECT:
LTR 3 ENCL 3 ANALYSIS PROVlDING ADDITIONAL INFO.
CONCERNING PREVIOUSLY SUBMITTED REQUEST FQR AMEND.
TO OPERATING LICENSE WHICH WOULD REQUIRE THAT THE UNIT 4 STEAM GENERATORS BE lNSPECTED DURING THE NEXT REFUELING OUTAGE OR SOONER IF OPERATlNG EXPERIENCE SHOWED THAT A PLANT NAME: TURKEY POINT UNIT 4 REVIEWER INITIAL:
XRL DISTRIBUTOR INITIAL:
+++++++++++++++++ DISTRIBUTION OF THIS MATERIAL IS AS FOLLOWS GENERAL DISTRIBUTION FOR AFTER ISSUANCE OF OPERATING LICENSE.
<DISTRIBUTION CODF A001)
FOR ACTION:
INTERNAL:
BRANCHMHK R~~W/7 ENCL REG FILE44W/EN L HANAUER~4W/ENCL EISENHUT++W/ENCL BAER++W/ENCL GRIMES++W/ENCL J.
MCGQUGH++W/ENCL NRC PDR4+W/ENCL OELD++LTR ONLY CHECK++W/ENCL SHAQ++W/ENCL BUTLER44W/ENCL J.
COLLINS++W/ENCL EXTERNAL:
LPDR S MIAMIt FL++W/ENCL TIC+4W/ENCL NSIC++W/ENCL ACRS CAT 84~W/16 ENCL DISTRIBUTION:
LTR 40 ENCL 39 SIZE:
2P+4P THF END
'C o
~ '
~
P'ig)gg't3II/I II ~IMAI400, MIAMI. FL 33101
>yVlgir P /~13II3 FLORIDAPOWER & LIGHTCOMPANY February 1,
1978 L-78-40 Director of Nuclear Reactor Regulation Attention:
Mr. Victor Stello, Director Division of Operating Reactors U.
S. Nuclear Regulatory Commission Washington DC 20555
Dear Mr. Stello:
Re:
Turkey Point Unit, 4
Docket No. 50-251 Request for Amendment to Operating License DPR-41 Additional Xnformation PP On January 18,
- 1978, (L-78-23) we requested an amendment to our operating license which would require that, the Unit 4 steam generators be inspected during the next refueling outage or sooner if operating experience showed that an inspection was warranted.
Attached is an analysis providing additional information supporting this request.
As discussed with members of your staff, on November 24,
- 1977, Unit 3 was shut down to perform a steam generator inspection as required by the Unit's operating license, and to perform the annual refueling.
Unit 3 is still shut down with an estimated startup date of February 8,
- 1978, pending repairs to a main coolant pump seal.
St. Lucie Unit No.
1 has been experiencing spurious trips due to a malfunction in one of the Turbine Generator control circuits.
We are investigating the problem, but presently the unit's availability is less than optimal.
Xf Unit 4 is required to shut down before Unit 3 is returned to
- service, a loss of our St. Lucie unit could reduce our generating capability to less than desired in light of the cold weather and resultant high demand for electricity which we have been experiencing.
During month of January, peak demand exceeded last summer's peak.
Xt is therefore highly desireable to postpone shutting Turkey Point Unit 4 down until after Turkey Point Unit 3 is returned to service.
PEOPLE... SERVING PEOPLE
0
~ +.
Director of Nuclea actor Regulation Attention:
Mr. Victor Stello, Director Division of Operating Reactors Page 'wo If you should have any question in this matter, please feel free to contact me.
Very truly yours, Robert E. Uhrig Vice President REU/GDW/lsh CC:
Robert Lowenstein, Esq.
J.
P. O'Reilly
4 I
Turkey Point 4 was last inspected in May-June of 1977.
Based on that inspection, the appropriate tubes were preventively plugged to provide in excess of six months of additonal safe operation.
The plugging criteria and plugging pattern are based on conservative assumptions regarding the future growth of high plate strain and subsequent high tube strain.
Unit 4's operating experience and guaging inspection performed at other plants have confirmed 'the implemented plugging pattern to be overly conservative.
Analysis of thi.'s margin of conservatism has provided a basis for continued operation of Turkey Point Unit 4 for an additional three effective months with the present. plugging pattern.
Xn all previous evaluations of tube inspection results, the most severe rate of plate expansion (among the steam generators of a given plant) was used for all steam generators.
This is very conservative, and in the case of Turkey Point 4, severely penalized two of the three steam generators.
Figure 1 shows the flow slot closure history for all three steam generators.
The rate of closure used to develop the current stress pattern was
.12 in/mo based on the second tube support plate in steam generator B.
From this figure it can be seen that no plate in steam generators A and C
has a closure rate exceeding
.08 in/mo.
Based on this, and the direct relationship previously developed between growth of critical strain and closure rate, the plugging patterns used for steam generators A and C support safe operation for:
'.'12 (6)
=
9 months
.08 Since the return to power of Turkey Point 4 in August 1977, two other plants have ha'd a second round of inspections using the tube gauging approach to develop plugging patterns.
These re-.inspections have provided additional insight into the progression of tube restrictions and the development of plugging criteria and patterns.
Several observations can be made from these re-inspections to support an extension of the current operation period of Turkey Point 4.
a)
Upon re-inspection of the Surry 1 and Surry 2 sites, only a small number of tubes in the tube lane region developed severe restrictions (i.e., tubes'estricting
.540" probe) between inspections (less than twenty-five at Surry 2 and less than 5 at Surry 1).
b)
Of all the tubes at both 'Surry 1 and Surry 2 that restrict
.650" probes at both the previous and current outage, 70%
still passed the 0.610" probe and more than 94% passed the 0.540" probe at, the second outage.
c)
The re-inspection programs have indicated that the strain contour used to develop growth is a conservative representation of critical strain.
The critical strain is closer to 17% than the 14% previously used.
A re-evaluation of growth plots (Figuxe 2), considering the
) ~
l,
c)
(cont'd) progression of the 17% contour rather than the 14% contour, yields a reduction of the growth rates to.25 rows/month along the tube lane and
.5 rows/month at the outside columns.
Thus, for the Turkey Point 4 plugging pattern of 2 rows out along the tube lane and 4 rows out at the outside columns, this new rate allows for 8 months of operation, or an additional 2 months beyond the current operating period, for all three steam generators.
In addition to these observations, the results of the Turkey Point 3 inspection are of interest.
At Turkey;Point 3, there were a significant number of tubes (63) which restricted the 0.540" probe while only one tube leaked over nine months of operation.
It would not be expected that all of these become 0.540's overnight.
This is especially true since 31 of these tubes were in S/G B, which is approximately six months further along than A and C in terms of degradation, while A and C only ha've a combined total of 32 tubes that restricted the 0.540" probe.
- Thus, a statistical evaluation would find some tubes restricted by the 0.540" probe for in excess of six months and many for in excess of three months.
It is reasonable to expect 3 months of operation for a tube that has just restricted a 0.540" probe.
Since the implementation of the gauging program only 5 tubes have leaked near the tube lane at the Turkey Point and Surry sites.
This represents over 30 EFPH's of operation altogether.
Therefore, Florida Power 8 Light Company has concluded that good engineering judgement indicates that Turkey Point Unit 4 can be safely operated for an additional.
3 effective months'ith the current.-
plugging pattern.
First, the plugging pattern implemented at Turkey
'oint 4 is good for 9 months in two of the thr'ee steam generators based only on rates of flow slot closure and plate expansion.
- Second, the current plugging criteria have been shown to significantly limit the occurrences of 540" probe restrictions after six months'f operation.
Third, the strain growth "rates used to develop the six month operating period. were rather conservative:and could easily:.be"used to defend an 8 month operating period with the>same plugging.
Fourth, there is sufficient reason to believe that a great'majority
((95%) of all tubes that restrict the 0.540" probe remain in operation for more than 3
months before leaking.
Finally, thevery small incidence of leakage over the last nine months at all plants 'involved is testimony to the effectiveness of this approach.
1/3 rov/mo.
5.0 HONTIIS* BEYOND FULL CLOSURE 2,0 HONTIIS* PRIOR TO I:UI.L CLOSURE 12 HONTIIS* BEYOND FULL CLOSURE Note that only this one area of the plate (near the 3 and 9 o'lock wcdI,'c must bc examined sepa-rately with regard to growth of strain contours Xn all other regions, 1/3 rov/mo. is n con"er-vative grovtl> rate.
/
- Based on maximum expansion rate considered in analysis.
"Crovth" of lli7. 'Iloop Strain Contour Figure 2
3.0 TSP SYHBOL 1-0 2-0 6-0 SG SglGOL A - DOT B - BLACK C - X 2.5 SIGNIFICANT CRACKING IN TllIS PERIOD M
2.0 o
o o
1.5 o
fee 1.0
~SIGNIFICANT CRACKING IN TllIS PERIOD SOME CRACKING IN TllIS PERIOD.
.5 0
4 12 16 EFPW/AVT Figure '1 20 24 2/2/7 8 28
'32
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