ML20213A428
| ML20213A428 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 01/22/1987 |
| From: | Heider L YANKEE ATOMIC ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20213A430 | List: |
| References | |
| RTR-NUREG-0844, RTR-NUREG-844 FYR-87-09, FYR-87-9, NUDOCS 8702030273 | |
| Download: ML20213A428 (9) | |
Text
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Telephone (617) 872-8100 TWX 710380-7619 YANKEE ATOMIC ELECTRIC COMPANY
/ *~ [Y 2.C2.1 Y.
1671 Worcester Road, Framingham, Massachusetts 01701
.Ym ust January 22, 1987 FYR 87-09 United States Nuclear Regulatory Commission Document Control Douk Washington, DC 20555 Referencost (a) License No. DPR-3 (Docket No. 50-29)
(b) USNRC Conoric Letter 85-02, dated Apell 17, 1985 (c) USNRC NUREG-0844, Apell 1985 (d) YAEC Lotter to USNRC, dated August 12, 1985 (c) USNRC NUREG-0492, Rovlsion 4 November 1981
Subject:
Technical Specification Governing Steam Conorator Tube Integrity Testing Daar Slet Pursuant to Section 50.59 of the Commission's Rulco and Regulations, the Yankoo Atomic Electric Company (YAEC) hereby requesto the authorization to make the following changot P_r_oposed Chango Reference la made to the Technical Specifications of Llconso No. DPR-3 of the Yankoo Nuclear Power Station. We propose to modify the Technical Specifications governing the integelty tooling of steam generator tubco.
Those modifications wills a.
Provido flexibility in the samplo alzing specifications, b.
Provido floxibility in the sample selection critoria to accurately reflect actual plant-opecific tooting experience, c.
Provido appropriato cold los toot critoria, and d.
Correct a number of administrative flaws within thoso Technical Specifications.
The upacifle changes are described in Attachmont A.
Roanon and Baals for Chango As doacribed in Attachment A.
l4#I33 QdY oI 0702030273 070122 g(6.OD DR ADOCK 0300 9
Unitcd St0t:3 Nucic r R:gulttery Commicalen Jcnu:ry 22, 1987 l
Attention: Document Control Desk Page 2 FYR 87-09 Safoty Consideration This change has been ovaluated and determined not to involvo a significant hazards consideration. The amendment has been proposed to improve the Steam Conerator Tube Inspection Program and to provido flexibility without compromising the intent of the program. The changen are supported by staff publication (NUREG-0844) and 26 years of operating history. Overall, these changes enhance the current Technical Specifications and do not decrease the program offectiveness.
The results achloved will provide a better assurance in determining the extent of the tubo defect potential by encouraging a larger sample size and a more extensive lnspection of the tubo length.
The current Standard Technical Specifications for steam generator tube integrity tooting are based on Regulatory Guido 1.83 and have stood unchanged for over a decado. Meanwhlic, the testing technology has advanced and the body of toot results has grown to the point where the generic specifications no longer reflect the optimum program for YAEC. Thoroforo, this change is requested in order to enhance the current Standard Technical SpecLfications with the introduction of cold los testing critoria and with provisions for flexibility in sample alzing and selection critoria which will allow plant-specific operating experienco to dictate the optimum test program.
Yankoo's experience with the testing of steam generator tubos spans the development of, and predates, oddy current technology. The statistics of that experience total 4% plugged tubos in 26 years.
They also indicato a relatively uniform degradation resulting from a single failure mechanism (pin hole from the OD) which producou a leak well before break.
Yankee oporated for 15 yearn before oddy current technology became offective and for more than 20 years before comprohansivo cold log testing was introduced. History would indicate that tooting frequency is not a safety issuo.
NUREG-0844 concurs with this concluolon.
Test results at Yankeo do not support the popular promise of preferential degradation in the hot leg of steam generator tubing. Overall, the test results are approximately evenly divided betwoon hot and cold les defecto.
There is, thoroforo, no basin for specifying proforential inspections of the hot los sido of all steam generators. A best effort test program initiated from either the cold log or hot los side would be equally valid and would moot or exceed the intent of the current speelfications. Given performance historios and the proposed flexibility in samplo and entry point selection, YAEC would optimizo a test program for each individual steam generator.
A potential for delays in testing certain currently speciflod surface arcan within tho tube array to acknowledged and justiflod with reference to historical performance, reprouentative campling, and improved tanting critoria defined in terms of a best offort inspection program. The not offect will be a gain in testing offectivonoso. Those areas of potential concern are small in comparison to the total tubo surface area which actually in tested.
In fact, the total area which may be doforced is smaller than that allowed to be missed entirely under current Technical Specifications. Thorofore, the tubo surface area subject to tooting under the now critoria will norve an a
United Stct:0 Nuciscr R:gulctory Commiccicn Jcnu:ry 22, 1987 Attenticn: Document C:ntrol D:sk Pcg3 3 representative sample as well as, or better than, is currently specified. As such, this proposed change would not:
a.
Involve a significant increase in the probability or consequences of an accident previously evaluated. Steam generator tube integrity testing is specifically designed to reduce the probability or consequences of accidents. Since those changes are designed to enhance the testing program, the effects of the testing program on the probability or consequences of an accident will be improved or remain the same, b.
Create the possibility of a new or different kind of accident from any previously analyzed. The acttvition described in those Technical Specifications are surveillances conducted in refueling mode. Therefore, these changes would not directly create the possibility of a new or different kind of accident from any previously analyzed. Further, thoro is no provision in these proposed changes that would allow any now or dif ferent configuration or condition of the plant.
c.
Involve a significant reduction in a margin of safety. Those changes would tend to increase the margin of safety by virtue of the increased effectiveness of the steam generator tube integrity testing program.
Based on the consideration contained herein, it is concluded that thore is reasonable assurance that oporation of the Yanken plant, consistent with the proposed Technical Specifications, will not endanger the health and safety of the public. This proposed change has been reviewed by tro Nuclear Safety Audit and Review Committoo.
Fen An application foo of $150.00 is enclosed in accordance with 10CFR170.21.
Scheduto of Chango These changes to the Yankoo Technical Specifications will be implemented upon Commission approval. A timely review and approval of this submittal would be appreciated.
Unitcd Stct0c Nucl00r R:gulctcry Ccmmiccicn Jcnunry 22, 1987 Attention:
Document Control Desk Page 4 FYR 87-09 We trust that you will find this submittal satisfactory; however, should you desire additional information, please contact us.
Very truly yours.
YANKEE ATOMIC ELECTRIC COMPANY
. H. Heider Vice President / Manager of Operations LHH/dhm Attachments COMMONWEALTil 0F MASSACHUSETTS)
)ss MIDDLESEX COUNTY
)
Then personally appeared before me, L. H. Helder, who, being duly sworn, did state that he is Vice President and Manager of Operations of Yankee Atomic Electric Company, that he is duly authorized to execute and file the foregoing document in the name and on the behalf of Yankoo Atomic Electric Company and that the statements therein are true to the best of his knowledge and belief.
W Robert H. Croce Notary Public My Commission Expires August 29, 1991 i
i
l j
ATTACHMENT A l
i 1.
DESCRIPTION OF CHANGE:
In the ACTION statement of LCO 3.4.10, change l
the word "about" to "above",
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{
REASON FOR CHANGE: This will correct a typographical error which was j
introduced with a previous amendment.
l 1
I BASIS FOR CHANGE:
The word "above" reflects the Westinghouse Standard l
Technical Specifications, reference (e).
i 2.
DESCRIPTION OF CHANGE:
Insert the following Surveillance Requirement:
l 4.4.10.0 Each steam generator shall be demonstrated OPERABLE by performance of the following augmented inservice j
inspection program and the requirements of j
Specification 4.0.5.
V REASON FOR CHANGE:
Steam generator inspections are a supplement to l
Inservice Inspections and this change defines their relationship.
i l
BASIS FOR CHANGE: The wording reflects the Westinghouse Standard Technical Specifications, reference (e).
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j 3.
DESCRIPTION OF CHANGE:
Eliminate the existing asterisk and related l
footnote from Surveillances 4.4.10.1 e.nd 4.4.10.3.
l
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REASON FOR CHANGE: This footnote was inserted into the Technical J
Specifications by Amendment 68 to provide a one-time extension to the surveillance periods in 1980-1981.
The events described in Amendment 68 have passed and the footnote no longer has any meaning, i
f BASIS FOR CHANGE: This footnote is not required for any purpose nor does it appear in Westinghouse Standard Technical Specifications, j
reference (e).
I I
4.
DESCRIPTION OF CHANGE:
In Surveillance 4.4.10.2.b.1, change the words l
"( 20%)" to "(greater than 20*.')."
I REASON FOR CHANGE: This will correct a typographical omission which
]
occurred with a previous amendment.
BASIS FOR CHANGE: The words reflect those of Westinghouse Standard Technical Specifications, reference (e).
t I
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Attachment A Page 2 5.
DESCRIPTION OF CHANGE: Add the following additional Sample Selection and Inspection criteria to Surveillance 4.4.10.2:
d.
Samples sets for each steam generator may be combined, provided that:
1.
The size of the combined sample set meets or exceeds the sum of the C-2 minimum tube requirement of Table 4.4-5.
2.
The response to the test results is prescribed according to the Action Required by the higher of the combined Sample Inspection criteria.
3.
The partial tube inspection described in Surveillance 4.4.10.2.c is not used if the combined sample includes the 1st Sample Inspection.
REASON FOR CHANGE:
The current Standard Technical Specifications, including reference (e), are structured and effective for the statistical treatment of sample sizes assuming a program of minimum compliance.
They provide for minimum sample sizes and Action Requirements which generate additional, larger sample criteria upon the discovery of defects.
However, they do not effectively address a program oriented toward maximum benefit (i.e., the maximum sample sizes).
Specifically, when used to assess the results of a large sample of tubes, the existing specifications require some further judgement to generate an appropriate Action Requirement.
1 The reason for this change, therefore, is to introduce the statistical flexibility to allow for the large sample sizes normally in use at Yankee. This is accomplished by specifically defining rules under which the sample size criteria may be combined and the Action Requirements of Table 4.4-5 appropriate to the combined sample.
Meanwhile, it is important to preserve the ability to use statistics to characterize the condition of a steam generator with a minimum sample size because there may be times when, for reasons of practicality or ALARA or both, a small sample will be all that is available. This proposed change, therefore, defines rules to govern large sample sizes without disturbing the existing and standard rules.
BASIS FOR CHANGE:
Because the existing criteria have required judgement in selecting appropriate Action Requirements, Yankee has carefully consulted with both the Region 1 Office of Inspection and Enforcement and with the Office of Nuclear Reactor Regulation during recent refueling outages.
Both agencies have urged Yankee to formalize the decision process via this proposed change.
Current technology makes it possible, with little additional exposure, to acquire large samples for which statistical uncertainties all but vanish.
Therefore, this change is more conservative than the existing Standard Technical Specifications since it will encourage the use of t
larger samples.
i b
Attachment A Page 3 These changes provide criteria for expanding the existing Standard Technical Specifications such that larger samples are encouraged and that the appropriate Action Requirements are clearly understood.
6.
DESCRIPTION OF CHANGE:
In Surveillance 4.4.10.3.a, change the word i' degraded" to " degradation".
REASON FOR CHANGE: This will correct a typographical error which was introduced with a previous amendment.
BASIS FOR CHANGE: The word " degradation" reflects the Westinghouse Standard Technical Specification, reference (e).
7.
DESCRIPTION OF CHANGE:
In Surveillance definition 4.4.10.4.a.8, delete the words "(hot leg side)".
REASON FOR CHANGE: These words constitute an invariable specification requiring that steam generators always be tested from the same side (point of entry). There are two reasons for removing the specification of the point of entry:
a.
The first reason for this change is to bring the test criteria up to date in terms of reflecting actual operating experience and thus enhancing test effectiveness.
The basis for the current specification of the hot leg as the only valid point of entry is an assumption that defects occur preferentially in the hot leg of steam generator tubes.
Plant specific test results have demonstrated this to be inaccurate and may even be detracting from the program effectiveness at Yankee. Of the 4% tubes plugged over the past 26 years, the Yankee steam generator tube defects have been approximately evenly divided between the hot and cold legs. There is, therefore, no reason to specify that steam generators should invariably be tested from only one side.
To date this has not become a critical issue for the industry because the eddy current technology has advanced to the point where valid test results can be obtained from either side of the steam generator.
Simply by driving the probe over the "U" bend to the other side the whole length of the tube can usually be inspected.
However, while technically valid, there are practicalities such as the inability to test both sides of tight radius bend tubes which make the arbitrary specification of hot leg entry a potential detraction from an effective program. This proposal would remove the hot leg specification and align the entry point selection with existing tube sample selection criteria.
Specifically, the technical specifications already require that tube sample selection be based on "those areas where experience has indicated potential problems" (e).
Removing the hot leg specification still leaves the requirement to utilize plant specific operating experience.
Attachment A Page 4 b.
The second reason for this change is to clear a potential licensing constraint. One steam generator surveillance inspection, due in 1987, may not be capable of completion under current entry point specification.
During the past 26 years of operation, Yankee has observed a slow buildup of a layer of magnetite (popularly known as a " crud layer") on the inside surface of the steam generator tubes.
Chemical and physical analysis indicates nothing unusual about the material itself. The thickness of the layer is related to the high heat transfer areas, but is not uniform. During the past several inspection programs (refueling cycles), some deposits have grown to a sufficient magnitude to interfere both mechanically with the probe body and electronically with the eddy current signal.
While most affected areas are randomly dispersed small patches causing no real concern, one affected area precludes inspection from the hot leg side of one of four steam generators. Available alternate eddy current probes have been tried and the industry experience has been scanned for similar problems and/or solutions. No commercially available and acceptable solutions have been found.
Meanshile, Yankee has engaged Oak Ridge National Laboratory (ORNL) contractually to develop a new probe design specifically to address this difficulty.
Early indications from this R&D effort are promising, but there are no guarantees that the engineered solution will resolve the problem in 1987 when the inspection is normally due. Consequently, this change will serve a dual function by allowing for a valid test of this particular steam generator in its scheduled test year. An inspection of this steam generator from the cold leg side, using the criteria described in part 8 below, will actually produce a set of test results that is equal to or more conservative than is currently specified.
BASIS FOR CHANGE: Actual test results at Yankee indicate no basis for consistently selecting the hot leg side as entry point for all steam generators. They do indicate that each test should reflect actual operating experience for each steam generator. The existing criteria applicable in Surveillance 4.4.10.2.b.2 and in the notation to Table 4.4-4 already specify that sample selection criteria include operating experience.
Removing the specification of the hot leg as the only allowable point of entry extends these criteria to include entry point selection.
Establishing a licensed alternative will not result in the termination of efforts to develop an engineered solution to the magnetite problem.
Yankee has, in our own interest, always conducted steam generator testing far beyond the licensed requirements and intends to continue doing so. The purpose of this proposed change is to gain the flexibility needed to ensure a sound engineered solution.
Attachment A Page 5 The alternative provided represents both an improved testing program and the avoidance of a conflict between the license and good engineering judgement.
The removal of these words from the Technical Specification does not eliminate the designation of an entry point, rather it changes that designation from the outdated and, in hindsight, arbitrary designation to one that is based on the same performance criteria currently used for sample selection.
8.
DESCRIPTION OF CHANGE:
In Surveillance definition 4.4.10.4.a.8, change the words " completely around the U-bend to the top support of the cold leg" to " include the full length of the t2be".
REASON FOR CHANGE: This change is to reflect the common practice at Yankee, which is to inspect as much of each tube as is practical.
BASIS FOR CHANGE: The new wording is more conservative than the existing wording in that it requires the testing of more of the tubing surface than is currently specified.