ML20107B061

Proposed Tech Specs,Reducing Total Number of Tubes Which May Be Excluded in Each Steam Generator & Incorporating Criteria Intended to Increase Assurance That Significantly Degraded Tubes Will Not Be Excluded

ML20107B061
Person / Time
Site:	Millstone
Issue date:	02/08/1985
From:	NORTHEAST NUCLEAR ENERGY CO.
To:
Shared Package
ML20107B040	List: ML20107B039 ML20107B061
References
TAC-52339, NUDOCS 8502200218
Download: ML20107B061 (7)

Text

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l Docket No. 50-336 l Attachment 1 l Millstone Nuclear Power Station, Unit No. 2 Proposed Rewording of Technical Specification Change Request February,1985 8502200218 850208 PDR ADOCK 05000336 P PDR

TABLE 4.4-5 25 MINIMUM NtlMRER OF STEAP GENERATORS TO BE INSPECTED DURING INSERVICE INSPECTION C3

• t Preservice Inspection Yes H

na No. of Steam Geaerators per Unit Two 4

First Inservice Inspection One j Second & Subsequent Inservice Insperttons One l

i

,, Table Notation:

s i [ 1. The inservice inspection may be Ifmited to one steem generator on a rotating sc..edule n

encompassing 3 N 1 of the tubes (where N is the number of steam generators in the plant) if the results of the first or previous inspections indicate that all steam generators are performing in a like nenner. Note that under some circumstances, the operating con-

' ditions in one or more steam generators may be found to be more severe than those in other steam generators. Under such circumstances the sample sequence shall be modified to inspect the most severe conditions.

i 4

1 9

9 e

g i

,_ v

~r

• ~~

TAntf' 4.4 G

g. .

vs

.e STE AM GFNrnATOft TtiftE INSPECTION e 151 SAMi l.t INSrtCTION 7 Hip SAMet.r INSPECilCN 311D SAMPt.E INSI'[CTION c .- -

i ~. Sample S.te Result Actino ni.p iecit fleu.it r Action ieveuircel fletutt Action Hertuired

-e -

to A minimism of C.I None N/A N/A' N/A N/A S lobes pee ._

5. G.

C .2 peratr defeettve C-f . None N/A N/A

,, '[" , sepalr defeetIve C-I None C-2 b and insp g,y ,,,,,, j,,,g ,,, g ,, ,

in,this 3.C.

in this S.C. Peeloem action for R C-3 C-3 result of first

• • umple f Perloem action for g C-3 C-3 result of first sampfe N/A N/A C-3 Inspect all ^ H O "'r' tubes in 'his 5. C.. 5. G s are None N/A N/A repair defective tees C-I and nspect 25 tubes in each other 5.G.. Sneae S. G.s p,,go,m action foe N/A N/A See No'e 1. C-2 leul no C-7 result of seconel r lilitional 3,mpt, -

Prompt notifi a! Ion S G. are to NnC pesens.snt C-3 In specification A,t.g,tional Inspect all G 9.t .  ;. G. is C-3 tubes in each 5.G .

. and repast defective -

subes'. Pronvipt N/A notification to NRC N/A pursuant to  !

5pecification 6.9.1.

5ee Note 1.

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N wl ,e N le clie numlie, of steam generatoes le the unit. end n is the numfiec of steam generefors lospected

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• 3 ;, 5 .i...i..I n inipeciion i

• Repair of defective tubes shall be lir-l'ed to plur,ging with the exception of those tuhest which may be sleeved. Tubes with Jc: etive sleeves shall be plugged

Table 4.4-6 Table Notation l'. Tubes required to be inspected pursuant to Action C-3 which are blocked by the remote inspection equipment may be excluded from the inspection pattern performed pursuant to Action C-3 provided that no tube within 5 lines or 3 rows is degraded. No more than ten tubes in the steam generator shall f all into this category.

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- MILLSTONE - UNIT 2 3/4 4-7e

Docket No. 50-336 Attachment 2 Millstone Nuclear Power Station, Unit No. 2 AdditionalInformation Steam Generator Tube Inspection Requirements l February,1985

Steam Generator Tube Inspection Requirements Additional Information Personnel Radiation Exposure Northeast Nuclear Energy Company recognizes that tubes blocked to the automatic test equipment can typically be inspected manually. Equipment was developed to automatically and remotely perform the inspections of steam generator tubes to avoid the personnel radiation exposure involved with the inspections. The radiation levels present in the steam generators at Millstone

- Unit No. 2 typically result in an exposure of 0.3 - 0.5 person-rem for each steam generator tube end (i.e. 0.6 to 1.0 person-rem per tube) which is manually Inspected. Exclusion of only ten tubes from manual inspection can therefore save as many as 10 person-rem. The requirements of 10CFR20.1 specify that every reasonable effort must be expended to maintain personal radiation exposures "as low as reasonably achievable". NNECO considers it reasonable to save exposuret - this magnitude from inspection of tubes for which a high level of confidence exists regarding their integrity.

Criteria to Assure Low Likelihood of Defect The only tubes to be excluded from inspection shall be those tubes that are

-located more than five (5) lines and eight (8) rows from any degraded tube. This criterien assures that as many as 92 tubes free of flaws will surround a tube proposed to be deleted from the inspection pattern. Experience at Millstone Unit No. 2 has demonstrated that steam generator tube defects tend to be localized and readily grouped into patterns. As such, the criterion outlined

above provides an appropriate basis on which to draw conclusions regarding the integrity of an uninspected steam generator tube.

' Practices to Assure Excluded Tubes are Later Inspected Steam generator tubes which are scheduled for inspection but are deleted from the inspection pattern are listed. The record of these tubes is then introduced _ ,

into the plant inspection and work control system. This system has been utilfred E

in the past to ensure a followup inspection of steam - generator tubes.

Specifically, during the Cycle 5 refueling outage, steam generator tube degradation was identified which required a 100% inspection in accordance with Category C-3 of Technical Specification 4.4.5.1.2.c. During the inspection, 54 i- tubes in an area of the tube bundle scheduled for inspection were inaccessible to the automatic testing equipment without extensive modifications to the equipment would - have necessitated - additional personnel radiation exposure.ll) Itwhich was mutually agreed'to by our staffs that NNECO would inspect 22 of.these tubes during the next outage.(2) These tubes were entered into the p plant inspection. and work control system which - ensured that appropriate personr.el responsible for inspection ' remained cognizant of the need to inspect these specific tubes during the subsequent outage.

- (1) W. G. Counsil letter to R. A. Clark, dated February 12,1982.

-(2)- E. L. Connor letter to W. G. Counsil, dated March 5,1982.

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Practices to Facilitate Tube Identification Steam generator tube inspections are planned in advance in accordance with the

. requirements of the Technical Specifications. The specific tubes to be inspected are chosen from areas of the tube bundle where defects have historically been identified and include the tubes which had reportable wall penetration and were not plugged. This is required by Technical Specification 4.4.5.1.2.b.

As part of-the inspection process, a full size, numbered template is fabricated.

The . template is installed on the tube sheet face prior to beg.naing the inspection. The template defines the tubes to be inspected. It is secured in place with plugs which are installed into certain steam generator tubes. Proper positioning of the template is verified by identification of specific ' landmarks' on

. the.tubesheet.

The examiner or equipment technician who positions the inspection probe carrier views the position on closed circuit television. The line and row numbers on the template identify the tube end being entered. This individual initials the data sheet indicating that the location of the tube inspection has been verified.

Each location of a defect is independently verified by a second examination of

' the suspect tube. This verification establishes that the flaw " signature" seen on the original examination is, in fact, present at the line/ row originally identified.

Discrepancies, if any, are resolved by identifying the extent of the inspection which is suspect and reexamining all tubes suspected of improper identification.

Future advances in automated tooling hold the promise of eliminating the need for the tubesheet - templates. Micro-processor controlled positioners should result in reduced personnel radiation exposure and increased assurance of accurate inspection location.

QA Requirements Applicable to Inspection Work

All inspection work is performed in accordance with station procedures for Quality Assarance (QA) work and is subject to audit, surveillance and monitoring by QA permnel.-

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