ML20076N132

Affidavit of L Ward in Support of Applicant Response to Board 910122 Memorandum & Order

ML20076N132
Person / Time
Site:	Vogtle
Issue date:	03/07/1991
From:	Ward L GEORGIA POWER CO., SOUTHERN CO.
To:
Shared Package
ML20076N108	List: ML20076N106 ML20076N112 ML20076N123 ML20076N132 ML20076N146 ML20076N150
References
90-617-03-OLA, 90-617-3-OLA, OLA, NUDOCS 9103280116
Download: ML20076N132 (6)

Text

_ _ _ _ _ _ _ _ _ _

l

\ .

UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION ATOMIC SAFETY AND LICENSING BOARD In-The Matter of I 8

Georgia Power Company, I it Rl. t (Vogtle Electrio DOCKET NO. 50-424-OLA Generating Plant, t 50-425-OLA Units 1 and 2) 1 ASLB1 F 3. 90-617-03-OLA AFFIDAVIT OF LEWIS WARD IN SUPPORT OF APPLICANTS' RESPONSE TO THE BOARD'8 MEMORANDUM AND ORDER OF JANUARY 22, 1991 I, Lewis Ward, having first been duly sworn, hereby depose and state as follows:

2. I am employed by Southern Nuclear Operating Company as Manager, Nuclear Maintenance and Support - Vogtle. My office is located in Birmingham, Alabama,

2. I previously provided an Affidavit listed as Exhibit 8 to "Georg i. Power Company's Supplemental Statement Concerning atters Raised By The Board During The Pre-Hearing Conference" which was filed with the Nuclear Regulatory Commission Atomic Safety and Licensing Board on or about November 14, 1990.- This affidavit is submitted in connection with Georgia Power's Response To The Board's Memorandum And Order Of., January 22, 1991.

910~.1280116 910320 PDR ADOCK 05000424 0 PDR

l I

3. This Board, in its January 22, 1991 Memorandum and ordor, posed the following questions under question number 4:

How is the calibration of the Calgon (sic) sensors locked into place *t Why does the calibration drift?

4. In order to understand the answer to the above questions, it is helpful to understand the operation of the Calcon Temperature Sensor Mcdel A3500-W3 which is used to sense the jacket water temperature. Attachment A to this Affidavit depicts one of these sensors, with the metal "thermowell" around the sensor disk probe removed. As shown on Attachment A, a calibration ring surrounds the poppet disk. The poppet disk has a radial pin which fits into a vertical slot-in the calibration disk, which allows the poppet disk to move freely in the vertical direction (thus trip or reset) but not to rotate unless the calibration disk also rotates. The pop!'t disk is finely threaded onto a dick shaft. Rotating the alibration ring clockwise or counter clockwise also turns the poppet disk on the non-rotating disk shaft. Turning the calibration ring, then, varies slightly L

! the-length-af the disk shaft from the bottom of the poppet disk to the tip of the shaft (below the sensor _ disks in the L diagram).'

l I

,

• The same rotation varies the distance from the bottom of-the poppet disk to the base gasket at the poppet.

2

Calibration of the' sensor involves the setting of the disk shaft langth-relative to the chosen setpoint so that, once-the setpoint is reached, the " poppet" is pushed by the poppet disk downward and vents the air, which is under pressure, out the vent port. This venting is the actuation of the protective trip (e.g. two venting HJWT sensors during surveillance testing would trip the diesel generator).

The portion of the sensor below the " base" in the diagram is, as installed in the diesel-generator, located in a metal "thermowell". The well surrounds the spacer tube and sensor disks, which can be view =d as the " probe" of the sensor.

5. Again, in order to calibrate the Calcon temperature sensor, thn caldbration ring in the sensor is rotated. The calibration ring is " locked" into place by an o-ring loca'ted between the calibration disk and the body of the sensor.

This o-ring provides an airtight joint to prevent air leakage around the outside of the calibration ring and,.due to its tight fit, previents the calibration ring from unintentionally rotating.

6. Variation between the calibrated setpoint of a Calcon sensor and an activation value as detected by an installed senser could result from a number of factors.. Historically, air' leakage und internal contamination of new and installed sensors were determined to result in variation of 30*F or 3

l

more. See, specifically, Attachment B to Exhibit 8 of the Applicants' Supplemental Statement of November 14, 1990, page II-3 and II-4 of Wyle Laboratories Test Report No. 17133-1.

Variation of lesser amounts might have resulted from calibration methodology, including temperature stabilization prior to calibration, contamination on the sensor disks (in the form of slight calcium coating if the sensor is immersed directly into aqueous calibracion bath), minor variation associated with calibration equipment (sensor vis-a-vis water bath thermocouple), water bath heat-up rate, and looseness of set-screws of the thermowel) which surrounds the probe. Id.,

pages I-4 and I-5 of Test Report No. 17133-1. These sources of variation associated with calibration methodology have been addressed adequately in revised procedures and instrumentation training so as to minimize the possibility of significant calibration errors. Attachment C to Exhibit 8 of the Applicants' Supplemental Statement, VEGP Procedure 22981-C. Additionally, the actuation setpoint of an installed sensor can change over time (this is commonly referred to as setpoirt " drift"). Any factor that affects the point at which the poppet valve vents the air changes the setpoint (e.g., contamination on sensor disks, relaxation of sensor tension spring or the poppet spring, foreign material, air leaks and looseness of the spacer tube). These changes, 4

although small, are the reason that the sensors are periodically removed to check their calibration,-thereby providing adequate assurance of the appropriate setpoint actuation.

7. The facts contained in this Affidavit are true and correct and based upon my personal knowledge.

Lewis Ward Sworn to and subscribed before me this j day of /7/o_d , 1991.

M etW NotardPublic MY COMMISSION EXPlR(S JANUARY 12,1993 wpdocs\gpe\ ward.aff 5

l l

l

~ '

~e CALC 0b TEMP $RATUR$:SENS05 MODEL A3500-W3 TOP PLATE I

TOP PLATE GASKET I

m O >

0-RING

• CALIBRATION RING DISK SHAFT - e POPPET DISK r POPPET AIR INLET - r POPPET SPRING BASE GASKET g' SPRING RETAINER VENT PORT /  !

(ROTATED)  :

SENSOR TENSION SPRING BASE -

SPACER TUBE I

i g SENSOR DISKS e

mv cnux 1,