ML19257A670

Responds to IE Bulletin 79-21, Temp Effects on Level Measurements. Steam Generator & Pressurizer Level Measuring Sys Is of Delta Pressure,Open Column,Uninsulated Ref Leg Type

ML19257A670
Person / Time
Site:	Arkansas Nuclear
Issue date:	09/24/1979
From:	Trimble D ARKANSAS POWER & LIGHT CO.
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
IEB-79-21, NUDOCS 8001070154
Download: ML19257A670 (9)

Text

.

[ //C

/

ARKANSAS POWER & LIGHT COMPANY POST OFFICE BOX 551 LITTLE ROCK ARKANSAS 72203 (501) 371-4000 Septenber 24, 1979 1-099-17 2-099-17 Mr. K. V. Seyfrit, Director Office of Inspection & Enforcement Region IV U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011

Subject:

Arkansas Nuclear One - Units 1 and 2 Docket Nos. 50-313 and 50-368 License Nos. DPR-51 and NPF-6 Response to IE Bulletin No. 79-21 (Files: 1510.1, 2-1510.1)

Gen tl emen:

The following is provided in response to IE Bulletin 73-ci for Arkansas Nuclear One Units 1 and 2.

Iten 1 Review the liquid level measuring systens within containment to deter-mine if the signals are used to initiate safety actions or are used to provide post-accident monitoring information. Provide a description of systens that are so enployed; a description of the type of reference leg shall be included, i.e., open column or sealed reference leg.

Response AN0-1 The liquid level measuring systems for the steam generators, pressurizer and Reactor Building sump have been examined. The steam generator and pressurizer level measuring systens are of the delta pressure, open column, uninsulated reference leg type. The level measuring systen for the Reactor Building Sump is a float type.

None of these systens initiates a safety action. The steam generator water level is monitored to provide an indication and a control of the steam generator water inventory below 15% power. The pressurizer water level is monitored to provide an indication of reactor coolant inventory and to control makeup. The float type Reactor Building sump level indi-cating systen is not affected by ambient tenperatures and therefore will not be discussed further.

1692 242 e

8001070 MEVOEA MICCLE SCUTH UTiUTIES SYSTEM

1-099-17 2-099-17 Mr. K. V. Seyfrit Septenber 24, 1979 Response ANO-2 The liquid level measuring systems for the steam generators, pressurizer and Containment Building sump have been examined. The steam generator and pressurizer level measuring systens are of the delta pressure, open column, uninsulated reference leg type. The level measuring systen for the Containment Building sump is a float type.

The steam generator level measuring systen provides a reactor trip signal on low level and is used to monitor and control steam generator water inventory. The pressurizer level measuring systen does not ini-tiate a safety action but is monitored to provide an indication of reactor coolant inventory and to control make up. The float type Con-tainment Building sump level indicating systen is not affected by ambient tenperatures and therefore will not be discussed further.

Iten 2 On those systens described in Iten 1 above, evaluate the effect of post-accident ambient tenperatures on the indicated water level to detennine any change in indicated level relative to actual water level .

This evaluation must include other sources of error including the effects of varying fluid pressure and flashing of reference leg to steam on the water level measurements. The results of this evaluation should be presented in a tabular fonn similar to Tables 1 and 2 of Enclosure 1.

Response ANO-1 The effect of reference leg tenperature on the level measurenent systens identified in Item 1 above is listed in Tables 1-AN0-1 and 2-AN0-1 (a ttach ed) . The effects of varying fluid pressure and flashing of the reference leg to steam have been considered.

Respons e ANO-2 The effect of reference leg tenperature on the level measurenent systens identified in Item 1 above is listed in Tables 1-ANO-2, 2-AN0-2 and 3-AN0-2 (attached) . The effects of varying fluid pressure and flashing of the reference leg to steam have been considered. The effects of flashing in the reference leg were negligible and therefore were not included in the Tables.

Iten 3 Review all safety and control setpoints derived fran level signals to verify that the setpoints will initiate the action required by the plant safety analyses throughout the range of ambient tenperatures encountered by the instrumentation, including accident tenperatures. Provide a listing of these setpoints.

1692 243

1-099-17 2-099-17 Mr. K. V. Seyfrit Septenber 24, 1979 Response AN0-1 No reactor protection system actions are initiated by these instruments therefore no safety systen setpoints are affected.

Response ANO-2 Reactor protection systen actions are initiated by the steam generator level measurement system. This systen initiates a reactor trip at 46.5%

indicated level . Ambient tenperature effects on the reference leg were previously considered in development of setpoints. This is discussed in Section 2.3.2.5 of CEN - 98(A)-P submitted to Mr. J. Stolz by our letter of February 28, 1979. Therefore no action is required for the low steam generator level setpoint.

The pressurizer level measurenent systen does not initiate a safety action therefore no action is required for this systen.

Iten 4 Review and revise, as necessary, energency procedures to include spe-cific information obtained from the review and evaluation of Itens 1, 2 and 3 to ensure that the operators are instructed on the potential for and magnitude of erroneous level signals. All tables, curves, or cor-rection factors that would be applied to post-accident monitors should be readily available to the operator. If revisicns to procedures are required, provide a canpletion date for the revisions and a completion date for operator training on the revisions.

Response ANO-1 Correction factors are appropriate fran Tables 1-ANO-1 and 2-AN0-1 will be made readily available to the operators for post accident monitoring.

Instruction will be provided as to its use. This will be canpleted by Novenber 15, 1979.

Response AN0-2 Correction factors as appropriate fran Tables 1-AN0-2 and 2-ANO-2 will be made readily available to the operators for post accident monitoring.

Instruction will be provided as to its use. This will be canpleted by Novenber 15, 1979.

Very truly yours, b6 1692 244 David C. Trimble Manager, Licensing

1-099-17 2-099-17 Mr. K. V. Seyfrit September 24, 1979 DCT/JTE/vb cc: Mr. Norman C. Moseley, Director Division of Reactor Operations Inspection Nuclear Regulatory Canmission 4350 East West Highway Bethesda, Maryland 20555 Mr. W. D. Johnson U. S. Nuclear Regulatory Canmission P. 0. Box 2090 Russellville, Arkansas 72801 1692 245

TABLE 1-ANO-1 Correction to indicated water level for post-accident temperature effects of the steam generator operate level, steam generator full range level, and pressurizer level .

Correction to Reference leg tenperature indicated level (%)

( F) of full span 100 + 2.0 150 + 3.0 200 + 5.0 250 + 7. 0 300 + 9.0 350 + 12.0 400 + 15.0 Note: The increase in reference leg tenperature causes the measured level to indicate higher than actual level.

1692 246

TABLE 2-AN0-1 Correction to indicated water level for post-accident tenperature effects on the steam generator start-up level .

Correction to Refers indicated 1(vel (%)

.e leg)tenperature (F _

of full span 100 + 2.0 150 + 3.0 200 + 5.0 250 + 8. 5 300 + 12.0 350 + 16.5 400 + 21.0 Note: The increase in reference leg tenperature causes the measured level to indicate higher than actual level.

1692 247

TABLE 1-ANO-2 Correction to steam generator water level due to Reference Leg Heatup effects.

Reference Lea Tenperature, *F Correction to S/G Level (% of Scan) 120 + 0%

200 + 4%

250 + 7%

300* + 10%

350 + 14%

400 + 18%

450 + 23%

Level Calibration Pressure 900 PSIA Reference Leg Calibration Temperature 120 F Reference Leg Tenperature assumed equal to Containment tenperature (before reference trip) 1692 248

TABLE 2-AN0-2 Corrections to allowable indicated steam generator water level for Reference Leg Heatup and varying fluid pressure effects to assure that true level is between the level taps.

Correction to Correction to Reference Leg Minimum Allowed Maximua Allowed Tenpera ture Indicated Level Indicated Level F  % of Span  % of Soan 120 + 1 -4 200 + 5 -4 250 + 8 -4 300* + 11 -4 350 + 15 -4 400 + 19 -4 450* + 24 -4 Basis:

Level Calibration - 900 psia Reference Leg Calibration Tenperature - 120 F Applicable Pressure Range - 2500 psia to 50 psia.

Flashing in the Reference Leg is not assumed.

1692 249

TABLE 3 - ANO-2 Corrections to allowable indicated pressurizer water level for Reference Leg Heatup and varying fluid pressure effects to assure that true level is between the level taps.

Correction To Correction To Reference Leg Minimum Allowed Maximum Allowed Tenperature Indicated Level Indicated Level

• F  % of Soan  % of Span 120* + 4 -7 200 + 9 -7 250* + 13 -7 300 + 18 -7 350* + 23 -7 400 + 29 -7 450* + 36 -7 Basis:

Level Calibration Pressure - 2250 psia Reference Leg Calibration Tenperature - 120 F Applicable Pressure Range <2500 psia Flashing in Reference Leg is not assumed 1692 250