ML19098B428

Response to Letter of 4/21/1977, in Reference to IE Inspection Reports 50-280/77-4 & 50-281/77-4, Advising No Proprietary Information Is Contained in Reports

ML19098B428
Person / Time
Site:	Surry
Issue date:	05/16/1977
From:	Stallings C Virginia Electric & Power Co (VEPCO)
To:	Moseley N NRC/RGN-II
References
IR 1977004, Serial No. 171/042177
Download: ML19098B428 (4)

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RESPONSE TO THE NON-COMPLIANCE ITEM REPORTED IN IE INSPECTION REPORT NO. 50-280/77-4 AND 50-281/77-4 NRG Comment Contrary to Technical Specification 4.4.B.a and the provisions of Section 6 of ANS 7.60 (April 29, 1970), sensor output of thermometric devices used to obtain temperature and humidity data during the Unit 2 containment integrated leak rate test on April 24-27, 1976, were not com-pared over the expected operating range with a reference the1mometer of established calibration traceable to standards with a known valid relation-ship to the National Bureau of Standards or other recognized standard.

Response

The above infraction is correct as stated. It is recognized that all instr~mentation is required to be calibrated to standards traceable to the National Bureau of Standards prior to use, even though the maximum deviation from that instrument is included in the error analysis.

Specifically, pursuant to section 2.-201 of the }..TRC' s "Rules of Practice",

Part 2, Title 10, Cod_e of Federal Regulations, the following information is submitted:

1. Corrective steps taken and the results achieved, specifically in NRG Request (Item 2)

Any calibration performed subsequent to the Type A test which reconfirmed that the results of the test stated in your report SR-S2-76-01 remain valid.

Response

a) . In December 1976, a test was performed to confirm the accuracy of the installed containment air temperature RTD's. This involved a comparison of the RTD's computer output with the reading of a portable temperature detector adjacent* to the installed RTD. Two of .the installed RTD's were tested in this manner, and agreement was within the 1/2 degree accuracy of the instrument.

A computer sensor calibration was performed prior to the unit containment integrated leak rate test to verify in-strument repeatability. In addition, all RTD's responded in unison to the air temperature changes which occurred during the test period.

Based on their performance during the leak rate test, the computer repeatability check and the RTD accuracy test of December 1976, it' is concluded that the accuracies of the contai_nrnent air temperature RTD' s were within the

• d *for thei'r use 1.'n the containment air accuracy require

• --* e mass calculations as shown in the error analysis.

• b) In January 1977, a test was performed to verify the accuracy of the installed dew cells which were used in the contain-ment air mass calculations. This test involved comparison of the dew cell output with results obtained from a hand held psychrometer adjacent to the dew cells. Results in-dicated that the installed dew cells were in .error in ex-cess of the manufacturers specifications. In all cases, the reading obtained from the installed dew cells was lower than the actual value.

Computer sensor calibration checks of the dew cell. signals indicated acceptable repeatability for all dew cells. The dew cells responded in unison- to the humidity changes which occurred during the test period. These results indicate that during the containment integrated leak rate test, the installed dew cells were operational, with acceptable re-peatability, but were low in their indications.

The dewpoint temperature is used to determine a vapor pressure correction to the overall containment pressure.

A small variation of dew point temperature was experienced during this test; therefore, the repeatability of the dew cells is of greater significance than the instruments over-all accuracy in these calculations.

The error in dew cell indication did produce a small error in leakage rate calculations due to the non-linear relation-ship between vapor pressure and dew point temperature. A study was performed to determine the maximum effect which this error could have produced in overall test results.

All calculations for both the reference and absolute method were performed with corrections for the worst *case dew cell error. These calculations indicate that assuming the worst observed dew cell error; only a small conservative error.

in the overall leak rate calculation results. Based on these results, it is.concluded that any error due to dew cell inaccuracies was in the conservative direction, and of such.

magnitude that there was no significant effect on overall results.

'NRG Request (Item 3)

Those actions taken which assure that flow measurement devices, used to obtain Type C local leak rate, have been calibrated in accordance with the current approved quality assurance program re-quirements, and this calibration confirmed the Type C data of your report SR-S2-76-0l.

Response, Nine rotameters were used for air flow rate measurements with the three, which were traceable to the NBS and certified to~ 1%,

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• used wherever ,.possible. :The remainder were tested using the non-traceable instruments, which are certified to+/-5% by the manufacturer.

In order to verify the accuracy of-these instruments, each of the non-traceable instruments was cross-calibrated with a traceable instrument. *The* average error of the non-traceable instruments was found to **be *considerably better than the 5% stated by the man-ufacturer.

Therefore, the Type C error of 5%, assumed for the calculations in report SR-S2-76-0l, was conservative.

Additional rotameters, traceabie to the NBS, have been received.

These instruments should eliminate the need for use of non-traceable rotameters in Type C testing. All instruments used for Type C test-ing, including pressure gages and rotameters will be calibrated within 90 *days prior to their use. Calibration will be done by the man-ufacturer, or by our calibration staff via cross-calibration with an instrument of known accuracy.

2. Corrective steps which will be.taken to avoid further non-compliance, specifically in response to:

NRC Request (Item 1)

Those actions which assure that temperature and humidity mea-

. surement instrument calibrations are on a calibration schedule con-sistent with your current quality assurance program requirements.

Response

The RTD's, due to their design and principle of operation, have been and continue to be accurate and reliable. Therefore, a calibra-tion within 90 days prior to the contairnnent integrated leak test is proper and will verify the acceptability of the temperature data for use in the containment air mass calculations.

The calibration of the dew cells will-also occur within 90 days prior to the contairnnent integrated leak test.

3. The date when full compliance will be achieved:

.As the calibrations and subsequent error analysis cf both the Type A and Type G tests have been completed' satisfactorily .and the temper-ature and humidity measurement instruments are on a schedule con-sistent with our quality assurance program requirements, full com-pliance has been achieved.