ML20040C959
| ML20040C959 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 01/21/1982 |
| From: | Lentine F COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0452, RTR-NUREG-452 NUDOCS 8201290410 | |
| Download: ML20040C959 (3) | |
Text
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[D Commonwealth ECson
,) One First National Plaza. Chictgo, tlhnois 7
kC ] Address Reply to: Post Office Box 767 Q, Chicago, lilinois 60690 Janua ry 21,'1982 o
Q
' Mr. Harold _ R. Denton, Director g
Of fice of. Nuclear Reactor-Regulation RECEIVED U.S.. Nuclear ~ Regulatory Commission 2
' Washington, DC 20555 9;
JAN 2 81982>. d2
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Subject:
Zion Station Unit 1 Proposed Change to Facility
/s /
ime s
s Operating License No. OPR-39 c
9 NRC Docket No. 50-295 Reference (a):
February 6, 1978, letter from A. Schwencer to R. L. Bolger.
Dear-Mr. Denton:
Commonwealth Edison hereby requests a temporary change to
' Facility' Operating License No. DPR-39.
A change is lequested to Technical Specification 3.3.3.E to amend the limit for steam generator tube leakage by the addition of the following note:
"For the period of January 21, 1982, through March 4,
- 1982, the 18 steam generator tube leakage may be allowed to exceed 500 gpd.
The lgpm limit on the total tube leakage from all steam generators shall remain in effect,"
~
This change is.necessary to preven't an unscheduled shutdown for 18 steam generator tube repairs prior to the Unit 1 refueling-outage scheduled for March 4, 1982.
The first indications of possible tube leakage in the 18 steam generator were observed-in May and. June o f 1981.
These indications apparently disappeared for the
~
period July through August and then reappeared in September.
Since that time, the measured leakage rate has displayed a slow, steady increase.
At the present rate of increase, the leakage rate is projected to exceed ~500 gpd prior to the scheduled refueling date of March 4, 1982.
This amendment is requested on an emergency basis because-j.
of the ' possibility that the 18 steam generator tube leakage may exceed the 500 gpd limit as early as January 21,~1982.
of The limits on steam generator tube leakage were developed for the Wertinghouse Standard Technical Specifications (NUREG 0452)
L, and-incorporated into Zion's Technical Specifications in Amendment W/c/W8 Nos'. 34 and 31 to Facility Operating Licenses DPR-39 and DPR-48, respectively.
As described in the NRC's SER for those amendments,fipocoo 2
the purpose of establishing.a -specific leakage limit for steam generator-tubes is to assure that an acceptable level of tube inte-grity will-be maintained during all normal and accident conditions.
As ~ described 'in Zion's Technical Specification bases,- the limit of 1 gpm on the total tube leakage from all steam generators ensures that 8201290410 820121 PDR ADOCK 05000295 P
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- 11. R. Denton January 21, 1982 the offsite dose will be limited to a small fraction of 10CFR100 limits in the-event of either a steam generator tube rupture or a steam line_ break.
The lgpm limit is consistent with the assumptions-
-used in the analyses o f those accidents.
The basis for the limit of 500 gpd on the tube leakage from any one steam generator is as follows.
Based on test results, it has.been determined that a steam generator tube having a through-wall crack of up to 0.5 inches in length will not rupture under any normal or accident condition.
(The most severe' accident condition from the standpoint of steam generator tube integrity is a steam line break, which subjects the tubes to a very high differential pressure.)
A crack of 0.5 inches in length has been demonstrated by test to result in a t ;be leakage rate of 0.4 gpm under normal operating conoitions.
Therefore, the Technical Specification limit of 500 gpd (0.35 gpm) from any one steam generator ensures that, even if all the leakage were due to a single crack in.a single tube, tube integrity would be maintained under all normal and accident conditions.
The justification for the temporary suspension of the 500 gpd limit for the IB steam generator is as follows.
First, although it cannot be directly confirmed from the leakage rate measurements, it is believed that the measured leakage from 18 steam generator is due to more than one leaking tube.
This is based, in part, on the results of.the inspection of that steam generator that was conducted during the last refueling outage in January and February, 1981.
At that time, 20 tubes were plugged, based on the results of eddy current examination.
If the present leakage is due to more than one leaking tube, then the size of and single crack is less than 0.5 inches; and therefore, there are ao concerns regarding continued tube integrity under all normal and accident conditions.
Second, even if it is assumed that all the leakage is from a single crack in a single tube, the increase in the probability of occurrence of a steam generator tube rupture due to continued operation with such a crack present is small in comparison to the i
overall probability of occurrence normally associated with steam generator tube rupture accidents.
Specifically, using the probabilities of occurrence for steam line break and steam generator tube rupture determined in the Zion Probabilistic Safety Study, and assuming that the occurrence of a steam line break on -the 1B steam generator would result in the rupture o f the leaking tube, it has i
been determined that the overall probability of occurrence of a steam generator tube rupture would be increased by less than one i
percent.
In addition, it should be noted that the results of the Zion Probabilistic Safety Study indicate that steam generator tube rupture events do not contribute significantly.to the total risk associated with unit operation.
l-i
y
,. i' -
H. R. Denton Janua ry 21, 1982 i
It should be emphasized that during the period of the tem-parary exemption' requested, the Igpm limit on the total tube leakage from all steam generators will remain in effect.
Westinghouse has confirmed that tube integrity will be maintained under normal operating conditions if the leakage rate is limited to that amount.
As described in Zion's Technical Specification bases, adherence to the lgpm limit will ensure that the offsite dose resulting from FSAR design-basis accidents will be below 10 CFR 100 limits.
- Also, Technical Specification limits on the release of radioactive ef fluents during normal operation will continue to be met.
The proposed Technical Specification change has been reviewed by Commonwealth Edison On-Site and Off-Site Review with the conclusion that there are no unrevieweo safety questions.
Pursuant to 10 CFR 170, Commonwealth Edison has determined that the proposed amendment is a single Class III amendment.
As such, Commonwealth Edison has enclosed a fee remittance in the amount of $4,000 for this proposed amendment.
Please address any questions concerning this matter to this o f fice.
Three (3) signed originals and thirty-nine (39) copies of.
this transmittal are provided for your use.
Very truly yours, M
F.
G. Lentine Nuclear Licensing Administrator 1m Attachment SUBSCRIBED and SWORN to before me--this f/gfday o
of h as 1982
\\ Notary Publi'c 3277N i