ML20080G245

Forwards Steam Generator Mod ALARA Rept

ML20080G245
Person / Time
Site:	Mcguire
Issue date:	09/13/1983
From:	Tucker H DUKE POWER CO.
To:	Adensam E, Harold Denton Office of Nuclear Reactor Regulation
References
NUDOCS 8309200173
Download: ML20080G245 (4)

Text

Duxe POWER GOMPANY P.O. Box 33180 CHAMLOTTE. N.C. 28242 HAL H. rUCKER Teternons vrom ramssonov (704) 373-4531 September 13, 1983

=*"-a" Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Attention:

Ms. E. G. Adensam, Chief Licensing Branch No. 4 Re: McGuire Nuclear Station, Unit 2 Docket No. 50-370 Steam Generator Modification ALARA Report

Dear Mr. Denton:

My letter of June 15, 1983 transmitted the subject report for Unit 1.

Attached is a supplemental report which provides the infonaation on Unit 2.

Please advise if there are questions concerning this report.

Very truly yours, b

fh Hal B. Tucker GAC/php Attachment ec:

Mr. W. T. Orders NRC Resident Inspector McCuire Nuclear Station Mr. James P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30303 8309200173 830913 lA PDR ADOCK 05000370 P

PM

McGuire Nuclear Station - Unit 2 Steam Generator Modification ALARA Report McGuire Unit 2 shut down on June 17.-1983 after 4.86 effective full power 1 days to perform the necessary modifications to the preheater section of the steam generator. By comparison, Unit 1 had operated 191 effective full power days at the time of shutdown for the modifications.

Due to the limited operating time on the unit, Health Physics surveys indicated

-90 percent of the Reactor Building as having a general area dose rate'of less than 5 mR/hr.,'and Reactor Coolant System contact dose rates were less than 25 mR/hr.

In addition, smear survey results for Unit 2 showed no detectable levels of contamination, allowing the modification to proceed without protective clothing-dress requirements. The negligible dose rates on contact with the SG shell also allowed the job to be. accomplished without shielding.

Unit 2, being a mirror image of the Unit 1 containment, required the same inter-ferences to be removed to access the feedwater nozzle area and the same temporary work platforms to be built to stage the. equipment necessary to support the modifi-

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l cation..A separate RWP was written for-dose accountability for the staging and interference removal and replacement.

.A total of 1.085 person-Rem was accumulated on these activities.

Lessons learned during the Unit 1 modification and' subsequent modifications at other utilities required several changes to be incorporated in the procedures 4

and-col determine component fitups prior to final welds.. Extremely low radiation levels of 70 mR/hr. on contact with the tubes through the feedwater nozzle allowed experienced Westinghouse personnel to' install the protective shroud.. catch basin and bolts.

(Higher than estimated radiation levels of 3.2 R/hr. prevented the use of these personnel on Unit 1.)

This contributed to the lower than estimated exposure for the modification.-

The exposure accumulated.on Unit 2 is shown on Table 1.

The exposure was con-siderably lower than the estimate due to:

fl) Lower dose rates than projected on steam generator tube bundles and tube sheets; 2). Experience of the modification crews; and

-3)

Efficiency of the modification crews since they were not encumbered with protective clothing.

Table 2 shows the doses, estimated and' actual, for the eddy current testing per-formed following the modification work. Two factors contributed to the lower than r

estimated doses. These were:

i-f

'l)

Lower dose rates on the primary side of the tube sheets than estimated; and

2) Excellent performance of the hardware which resulted in less time than estimated to accomplish testing.

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c TABLE 1 Dose for Modification Work TASK ESTIMATE ACTUAL Steam Generator 2A 1.780 0.730 person-Rem Steam Generator 2B 1.470 0.775 person-Rem Steam Generator 2C 1.470 0.550 person-Rem Steam Generator 2D 1.470 0.760 person-Rom Area Staging and Interference Removal 1.030 1.085 person-Rem TOTAL 7.220 3.900 person-Rem The estimate for Steam Generator 2A was higher due to its being the first to be modified.

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TABLE 2 Dose for Eddy Current Testing TASK ESTIMATE ACTUAL Steam Generator 2A 0.590 0.225 person-Rem Steam Generator 2B 0.590 0.395 person-Rem Steam Generator 2C 0.590 0.210 person-Rem Steam Generator 2D 0.590 0.125 person-Rem Work Platform Staging 0.100 0.075 person-Rem TOTAL 2.460 1.030 person-Rem

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