ML20214W547

Application for Amend to License DPR-54,revising Tech Spec 4.17 Re Use of Sleeving to Mitigate once-through Steam Generator Tube Leaks.Supporting Documentation Encl.Fee Paid

ML20214W547
Person / Time
Site:	Rancho Seco
Issue date:	09/24/1986
From:	Julie Ward SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Miraglia F Office of Nuclear Reactor Regulation
Shared Package
ML20214W550	List: ML20214W547 ML20214W616 ML20214W655
References
A00L-860924, AL-860924, JEW-86-249, NUDOCS 8610030130
Download: ML20214W547 (8)

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$SMUD SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 S Street. P.O. Box 15830, Sacramento CA 95852-1830 (916) 452-3211 AN ELECTRIC SYSTEM SERVING THE HEART OF CALIFORNIA JEW 86-249 September 24,1986 DIRECTOR OF NUCLEAR REACTOR REGULATION ATTENTION FRANK J MIRAGLIA DIRECTOR PWR-B DIVISION U S NUCLEAR REGULATORY COMMISSION WASHINGTON DC 20555 DOCKET N0. 50-312 LICENSE NO. DPR-54 PROPOSED AMENDMENT NO. 134 In accordance with 10 CFR 50.90, the Sacramento Municipal Utility District proposes to amend its Operating License DPR-54 for Rancho seco Nuclear Generating Station Unit No. 1.

Proposed Amendment No. 134 revises various parts of Specification 4.17 (Steam Generators) to add sleeving as a method of mitigating 0TSG tube leaks.

Basically, the wording " plug defective tubes" is changed throughout Specification 4.17 and its bases to " plug or repair defective tubes." In addition, Specification 4.17.2.b.1 revises the first sample inspection to exclude tubes with previous detectable wall penetrations if they have been plugged or sleeve repaired in the affected area.

These changes are proposed to permit the use of steam generator tube sleeving as an alternate to tube plugging. The process, developed and qualified by Babcock & Wilcox, can be performed remotely, thus minimizing exposure to maintenance personnel. Additionally, steam generation through sleeve repaired tubes continue with only a slight thermodynamic reduction whereas in plugged tubes, steam generation is completely terminated.

In the future, should the District choose to repair the OTSG tubes in a manner different from that presented in this proposed amendment, the alternate method, including a different sleeving method, will not proceed without prior NRC approval of the method.

The proposed changes are discussed in detail in Attachments I, II and III, which are the Safety Analysis, "No Significant Hazards" Evaluation, and Description of Proposed Changes, respectively.

Pursuant to 10 CFR 50.91(b)(1), the Radiological Health Branch of the California State Department of Health Services has been informed of this proposed amendment by mailed copy of this submittal.

Enclosed is a check in the amount of $150.00 as required by 10 CFR 170.21,

" Schedule of Fees."

861003o130 DR 860w4 60 ADOCK 05000312 t

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l' Should you require any further information with respect to this Proposed Amendment, please contact Mr. Ron W. Colombo at Rancho Seco Nuclear Gen-eratin Station Unit . 1.

-. E. WARD DEPUTY GENERAL MANAGER, NUCLEAR Attachments cc: RegionV(2)

INP0 MIPC (2)

Subscribed and sworn to before me this 7 4+h day of_ h 1986

!an Q Notary Public r-~ g v

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ATTACHMENT I SAFETY ANALYSIS Proposed Amendment No. 134 revises various parts of Specification 4.17 (Steam Generators) to add tube sleeving as a method of mitigating OTSG tube leaks.

The method, developed by Babcock & Wilcox, is presented in detail in a proprietary B&W report, BAW-1823P, Once-Through Steam Generator Mechanical Sleeve Qualification, which is being mailed under separate cover to Mr.

Sidney Miner, NRC Project Manager. A non-proprietary version, BAW-1823, t is enclosed with this proposed amendment.

The report addresses pertinent aspects of the sleeving process which affect nuclear safety; such as strength and leakage of the mechanical sleeves, corrosion resistance, effect on plant performance, vibration, method of installation, examination for defects ar.d verifications of p~oper installation, radiological exposure and analysis for transient and accident conditions.

The report concludes that the mechanical tube sleeves are qualified for use in degraded 0TSG tubes and are strong enough and sufficiently leak-free to be used as a permanent remedy to keep degraded tubes in service. It also recommends that up to 10,000 of these mechanical sleeves (5,000 per steam generator) can be installed to correct or prevent tube degradation.

A comparison of the report BAW-1823P with the System Design evaluation for the steam generators in Section 4.3.4 of the USAR indicates the design basis for the sleeves is enveloped by the USAR. The report includes an evaluation of the reduction in flow and superheat that would be expected for the worst case in each 0TSG and concludes that the effect on plant operations is considered minimal. The B&W report provides sufficient details to conclude that the sleeve repair of up to 10,000 0TSG tubes does not alter the design basis and therefore does not involve an Unreviewed Safety Question.

Prior to beginning work, all personnel involved in steam generator tube sleeving operations will have received GET plant-specific training on site in radiological protection, and special training in a full-scale mockup of the upper head of the steam generator. This on site training will incorporate all applicable provisions of Reg. Guides 8.13, 8.19 and 8.27.

Actual dose rates observed at Ranchn Seco in February and March, 1986, were compared to those assumed in BAW-1823P. It was found that the actual rates are generally lower than those assumed in the B&W report by factors of 2 to

6. The observed dose rates at Rancho Seco are as follows:

Location Dose Rate 1" from tubesheet 5 R/h 18" from tubesheet 3 R/hr centerline of manway 0.8 R/hr 3 ft. outside manway 200 mr/hr low background area 40 mr/hr cutside staging area 10 mr/hr

Applying the above dose rates to elapsed time measured by B&W in their proving run results in the estimated exposures shown on the attachment to this safety analysis. The " Conservative" column shown includes allowances for expected contingencies in the sleeving operation.

Note that setup and removal of the remote manipulator would add an additional estimated 1.0 manrem to the total exposure for sleeving in each 0TSG. An allowance of about 30 percent should also be included for various support activities such as health physics, QC, tool engineers, video engineers and profilometry.

Arkansas Power & Light Company (AP&L) sleeved 5 defective ( > 40% through wall degradation) and 5 good steam generator tubes at their AN0 1 unit as a demonstration case for B&W's tube sleeving program. The NRC approved AN0's Technical Specification amendment which allowed the sleeving of the 10 steam generator tubes. The 10 sleeved tubes at ANO have performed in an operating reactor for one full cycle without any signs of problems.

On the basis of the above analysis and on review of the above referenced B&W proprietary report on qualification of the proposed tube sleeving method, the District has concluded that tube sleeving as an alternate to plugging of defective tubing in the OTSGs would not affect the safety of the plant or the health and safety of the public.

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o - 1 A'17ACHMENT ,

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r No Contingency Conservative Rancho Seco Elapsed Estimated Elapsed Estimated Time, Dose, Time, Dose, Activity Area Dose Rem /hr Hr. Manrem Hr. Manrem (Batch of 20 Sleeves

.80 .008 .006 .013 .010 Flare tubes .058 .500 .100

.20 .292

.04 450 .018 .500 .020

.750 .082 1.013 .130

.80 .186 .149- .250 *200 Insert Sleeves .833 .167

.20 .734 .147

.04 2.850 .144 3.000 .120 3.770 .410 4.083 .487

.80 .017 .014 .025 .020 Upper Roll .250 .050

.20 .194 .039 ,

.04 1.222 .049 1.500 .060 1.433 .102 1.775 .130

.80 .025 .020 .033 .026 Lower Roll 1.250 .250

.20 1.092 .218

.04 5.783 .231 7.000 .280 6.900 - .469 8.283 .556

.80 .017 .014 .025 .020 EC Examination .333 .067

.20 .233 .047 (sleeve baseline) .022 1.000 .040

.04 .550

.800 .083 1.358 .127,

.01 24.000 .480 36.000 .720 Containment Support (2 Men)

Total 20 sleeves 1.626 2.150 f

per sleeve avg. 0.081 .108 4

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ATACl#ENT II "N0 SIGNIFICANT HAZARDS" EVALUATION Proposed Amendment No. 134 revises various parts of Specification 4.17 (Steam Generators) to add internal sleeving as a method of mitigating future tube leaks in the once-through steam generators (OTSGs) at Rancho Seco. The method has been developed and qualified by Babcock & Wilcox (B&W) through extensive analyses, laboratory tests and in a prototype test at an operational nuclear power operating facility (M.01).

Sleeving has-been shown to be a safe and effective method of repair for defec-tive steam generator tubes. Several thousand tubes have been successfully sleeved in steam generators throughout the world. A B&W report, BAW-1823, Revision 1, "Once-Through Steam Generator Mechancial Sleeve Qualification",

provides a description of the analysis and testing performed to demonstrate the acceptability of the mechanical sleeve design. A copy of this report is enclosed with this proposed amendment. Mechanical strength, vibration, leak resistance, corrosion resistance, installation process control, inservice inspection techniques, and plant performances are described and shown to meet all expected NRC acceptance criteria.

The District has reviewed the proposed method of sleeving defective OTSG tubing and concluded that the use of this alternate to tube plugging would not:

1. involve a significant increase in the probability or consequences of an accident previous evaluated.

The USAR conservatively evaluated a double-ended rupture of a steam generator tube. A severed tube with a mechanical sleeve installed in it has been shown by tests to have mechanical strength at least

as great as that of a new tube. Thus, a sleeved tube is no more likely to rupture than any other tube in the generator.

A sleeved tube is functionally equivalent to an unsleeved tube except for less effective heat transfer due to the air gap and slight pressure drop due to the primary flow constriction. Analysis has shown that if 5000 sleeves were installed in each generator the steam scperheat temp-erature would be reduced by 7.7 F at full power and primary flow would be reduced by less than-1%. These differences have been compared to the existing plant safety analysis calculations and it was found that up to 5000 tubes per steam generator may be sleeved without invalidating the existing analysis basis of the units.

2. create the possibility of a new or different kind of accident from any accident previously evaluated.

3 The only equipment affected by sleeving is the steam generator. The most severe malfunction of a steam generator is a tube rupture, and the consequences of a ruptured sleeve are no worse than the consequences of a ruptured tube. Sleeving does not increase the probability of steam generator failure because the sleeved tube has been shown to be mech-anically stronger than an unsleeved tube. Thus a steam generator ,

with sleeved tubes would perform in the same manner as one without sleeved tubes, and there is no risk of a new or different accident.

ATTAC K NT II "N0 SIGNIFICANT HAZARDS" EVALUATION con't...

3. involve a significant. margin of safety.

The integrity of steam generator tubes is enhanced by the installa-tion of sleeves due to the increased vibration stability margin and the ability to bridge over imperfections and degradations. Thus the margin of safety is not reduced.

On the basis of the above, the District concludes that the proposed use of internal sleeving for mitigating future OTSG tube leaks does not constitute a significant hazard, and in no way endangers the health and safety of the public.

ATTAC MENT III DESCRIPTION OF PROPOSED CHANGES

1. Specification 4.17.2b.1., page 4-52: Added: "or sleeve repaired" after the word " plugged."

2. Specification 4.17.4a.3., page 4-54: Added: "in the pressure coundary" after the word " tube."

3. Specification 4.17.4a.4., page 4-54: Deleted: "a tube containing" after the word "means" in the first sentence, and replaced the second sentence in its entirety with the sentence: "A tube or sleeve contain-ing a defect in its pressure boundary is defective, and shall be either plugged or repaired by sleeving."

4. Specification 4.17.5a., page 4-54: Changed " tubes plugged" to " tubes plugged or repaired."

5. Specification 4.17.7b., page 4-55: Changed "will be plugged" to "will be plugged or repaired."

6. Specification 4.17 Bases, page 4-55a: Changed " Plugging will be re-quired" in the third sentence of the top paragraph to " Repair or plug-ging will be required."

7. Specification 4.17 Bases, page 4-55a: Inserted the following as the second paragraph:

" Degraded steam generator tubes can be repaired by the installation of sleeves which span the area of degradation and serve as a replace-ment pressure boundary for the degraded portion of the tube, thus per-mitting the tube to remain in service."

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