ML20204E553

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Forwards Rev 1 to Executive Summary Static-O-Ring Differential Pressure Switch Investigation, Per 860718 Request
ML20204E553
Person / Time
Site: LaSalle Constellation icon.png
Issue date: 07/24/1986
From: Turbak M
COMMONWEALTH EDISON CO.
To: Harold Denton
Office of Nuclear Reactor Regulation
References
1896K(2), NUDOCS 8608010129
Download: ML20204E553 (10)
v • d • e


Text

T % .-

. /m .. N Commonwealth Edison Y

{s i )'~'

One Fest National Address Plaza.

Reply to: Post Chicago, Offic) Box 767 Illinois

\/ Chicago, Illinois 60690 0767 July 24, 1986 1

Mr. Harold R. Denton U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, DC. 20555 -

Subject:

LaSalle County Station Unit 2 Additional Information Regarding Differential Pressure Switches NRC Docket No. 50-374

Dear Mr. Denton:

At a meeting with your staff on July 18, 1986, Commonwealth Edison was asked to supply information concerning the SOR differen-tial pressure switches installed in LaSalle County Station Unit 2, and to describe the actions which have been taken to ensure these switches operate reliably and operate within technical specification limits. The enclosed information should satisfy the staff request.

Please direct any additional questions regarding this issue to this office.

Very truly yours,

h. s. < _

M. S. Turbak Operating Plant Licensing Director

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{

cc: R. Bernero T, Bournia Resident Inspector-LaSalle 1896K(2)

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8608010129 860724 PDR ADOCK 05000374 I P PDR

Revision 1 7/25/86 EXECUTIVE

SUMMARY

STATIC-O-RING DIFFERENTIAL PRESSURE SWITCH INVESTIGATION PURPOSE: The purpose of this summary is to provide information concerning the SOR differential pressure switches installed in LaSalle County Station Unit 2, and to describe the actions which have been taken to ensure these switches operate reliably and operate within technical specification limits.

BACKGROUND SOR series 102 and 103 differential pressure switches were installed in LaSalle County Station Unit 2 during the 2nd quarter of 1985 as part of environmental qualification modifications. A total of 59 switches are installed in Unit 2. These switches are used to actuate various safety system functions including the reactor protection system, emergency core cooling system and primary containment isolati.on system. The attached Table 1 lists the system application and function for each SOR switch.

On June 1, 1986, LaSalle 2 experienced a feedwater transient that resulted in low water level in the reactor vessel. One of four low level trip channels actuated, resulting in a half scram. The operator recovered level and power operation was continued.

However, subsequent reviews raised concerns that the level apparently had gone below the scram setpoint and the reactor scram system did not actuate. This event is described in more detail in reference 1.

After recalibrating the reactor protection system low level (Level

3) switches, switch performance was tested by lowering water level in the reactor (level drop test) and reading levels indicated on level transmitters when each of the four Level 3 switches tripped.

At 950 pSIG reactor pressure, the switches tripped at levels between 3.9 inches and 10.8 inches. At 0 pSIG reactor pressure, the switches tripped at levels between 10.7 inches and 13.5 inches. These measurements are relative to instrument zero which is 161.5 inches e5ove the top of active fuel. The Technical Specifications established the allowable trip point for Level 3 at 11 inches above instrument zero.

Testing of other SOR Model 102 and 103 differential pressure switches used to actuate emergency core cooling system, primary containment isolation system and other engineered safety feature systems revealed that these switches displayed the same type of behavior as the switches used for reactor protection system Level 3.

Document 40501

Revision 1 T/25/86 SPECIAL TESTS AND SEPOINT REVISIONS The initial investigation to determine the source of the variability in SOR differential pressure switches setpoint concluded that additional special testing was required to quantify the setpcint variability. These setpoint characterization tests measured the shift in setpoint due to the differences in static pressure between calibration and operation, the effects of cycling the switch during calibration, and the random repeatability of the switch setpoint. These tests were performed on a special test rig which allowed simultaneous testing at operating static pressure and the specified differential pressure setpoint. This testing program was described in detail in Reference 2. ,

l For setpoint shift with static pressure and setpoint repeatability the results of these setpoint characterization tests are shown in Table 2. The effects of cycling were confirmed and will result in revised calibration l procedures. In Table 2, the results reported for the change in setpoint due to static pressure are for switches held at operating pressure for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. ,

Information justifying the validity of 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> test results was submitted to l the NRC by reference 3 and 4. Further validation was provided by matching the l1 '

level drop test results and 2h hour Static pressure shift test results for the Level 3 switches (see Table 3).

On the basis of the setpoint characterization tests described in the preceding paragraphs, setpoints of the LaSalle County Station Unit 2 SOR l1 differential pressure switches will be revised to provide additional margin for static pressure shift and repeatability. The revised setpoints and margins are listed in attached Table 4. These revisions will increase the margin between the existing Technical Specification allowable limit and the calibration setpoint; therefore Technical Specification changes are not necessary at this time.

CONCLUSIONS The setpoint variability of the SOR differential pressure switches installed in LaSalle County Station Unit 2 has been characterized -and will be incorporated into new setpoints. In addition to the margin and basis l1 for switch actuation included in the revised setpoints listed in attached Table 4, corrective actions listed in attached Table 5 will be completed.

These actions ensure the SOR differential pressure switches will perform within Technical Specification limits with high reliability.

REFERENCES Reference 1 - Letter to J.G. Keppler from C. Reed, dated July 1, 1986.

Reference 2 - Letter to H.R. Denton from M.S. Turbak, dated July 18, 1986.

Reference 3 - Letter to H.R. Denton from M.S. Turbak, dated July 21, 1986.

Reference h - Letter to H.R. Denton from M.S. Turbak, dated July 23, 1986. l1 Document 40501

Revision 1 TABLE 1 7/25/86 LASALLE COUNTY STATION UNIT 2 LIST OF INSTALLED SOR DP SWITCHES l1 Tag Number Service Range Setpoint Model Number B21-N024A,B,C,D Rx. Level 3 7"-100" W.C. 63.78" W.C. 103-8212 B21-N031A,B,C,D Rx. Level 2 20-200" W.C. 143.3" W.C. 103-B203 B21-NO37AB,BB Rx. Level 2 20-200" W.C. 145.5" W.C. 103-B203 CB,DB Rx. Level 2 20-200" W.C. 145.5" W.C. 103-B203 B21-N037AA,BA Rx. Level 1 40-300" W.C. 200" W.C. 103-BB205 CA,DA Rx. Level 1 40-300" W.C. 200" W.C. 103-BB205 E22-N006 HPCS Min. Flow 5-35" W.C. 18.1" U.C. 103-BB202 E21-N004 LPCS Min. Flow 5-35" W.C. 11.01" W.C. 103-8202 E12-N010AA RHR LPCI "A" Flow 5-35" W.C. 6.2" W.C. 103-B202 AB Alarm 5-35" W.C. 13.3" W.C. 103-B202 BA RHR LPCI "B" Flow 5-35" W.C. 6.2" W.C. 103-B202 BB Alarm 5-35" W.C. 13.3" W.C. 103-B202 CA RHR LPCI C" Flow 5-35" W.C. 6.2" W.C. 103-B202 CB Alarm 5-35" W.C. 13.3" W.C. 103-B202 B21-N038A,B Rx. Level 3 7-100" W.C. 63.14" W.C. 103-B212 B21-N026AB,BB Rx. Level 2 20-200 W.C. 143.3" W.C. 103-BB203 CB,DB Rx. Level 2 20-200 W.C. 143.3" W.C. 103-BB203 E31-N008A,B,C,D Main Steam Line Break 100-500 psid 111 psid 102-B305 E31-N009A,B,C,D Main Steam Line Break 100-500 psid 111 psid 102-B305 E31-N010A,B,C,D Main Steam Line Break 100-500 psid 111 psid 102-B305 E31-N011A,B,C,D Main Steam Line Break 100-500 psid 111 psid 102-B305 E31-N012AA,BA RHR Shutdown Cooling 20-200" W.C. 170" W.C. 103-B203 E31-N012AB,BB RHR Shutdown Cooling 20-200" W.C. 170" W.C. 103-B203 E31-N007AA,AB RCIC Steam Hi Flow 20-200" W.C. 117" W.C. 103-B203 E31-N007BA,BB RCIC Steam Hi Flow 20-200" W.C. 87" W.C. 103-8203 E31-N013AA,BA RCIC Steam Hi Flow 20-200" W.C. 170" W.C. 103-B203 E31-N013AB,BB RCIC Steam Hi Flow 20-200" W.C. 170" W.C. 103-B203 B21-N101B Rx. Level 8 7-100" W.C. 33.27" W.C. 103-8212 II-2 l ~ DOCUMENT ID 39921/00031

Revision 1 -

7/25/86 SOR DIFFERENTIAL PRESSURE SWITCil INVESTIGATION

  • TABI.E

SUMMARY

OF SETPOINT CilARACTERIZATION TESTS RESULTS l l 24 HOUR STATIC l l SWITCif APPI.TCATION l SAMPLE SIZE l PRESSURE SHIFT l REPEATABILITY l I l l l l l l 1 1

-REACTOR VESSEL LEVEL 3 10014 2.2 - 6.1 INCHES W.C. l Less Than 21b l 1 (6 switches) l l l

-REACTOR VESSEL LEVEL 2 l l . l l l l 2.5 - 6.9 INCHES W.C.

p (441L7 switches) l l Less Than 21b l l

l1

-REACTOR VESSEL LEVEL 1 l l i I l l

-REACTOR VESSEL LEVEL 8 l 100% l 3.4 INCliES W.C. l Less Than 21L l l_ (1 switch) l l l

-RilR/RCIC STEAMLINE BREAK l l l l l l l l

-RIIR SliUTDOWN COOLING LINE l 81b l 6 INCllES W.C. (Conservative) l Less Than 214 l l k (1 switch) l l l

-RCIC STEAM LINE BREAK l l l l l l l l

! I I I

-RilR LPCI-A,B,C MIN. FLOW l .l l l l l l l

-LPCS MIN. FLOW l > 25% l 1.5 INCllES W.C. l Less Than 2% l l (2 switches) l l l

-lIPCS MIN. FLOW l l l l

-MAIN STEAM I.INE HI FLOW 1001L l 2 - 11 PSID 1.45 - 9.34 PSID(2) l1 l (16 switches)l l l NOTES: (1) SWITCHES EXCEEDING 3.0 INCHES W.C. WERE REPLACED WITH SWITCHES 3.0 INCHES W.C. OR LESS. l1 (2) BASED ON DATA FROM 11 0F 16 SWITCHES. l1 Dociunent 40431

Revision 1

- T/25/86 SOR DIFFERENTIAL PRESSURE SWITCH .i4VESTIGATION TABLE - 3 COMPARISON OF LEVEL DROP TEST DATA WITH SETPOINT CHARACTERIZATION TEST PROGRAM DATA FOR REACTOR WATER LEVEL 3 SWITCHES

(" W.C. AT SWITCH)

SWITCH NUMBER 2B21-N024A 2B21-N024B 2B21-N024C 2B21-N024D LEVEL DROP 66.1 69.7 67.6 65.3 TEST 1 (1000 PSIG)

TEST PROGRAM 66.0 69.2 68.3 65.6 STATIC SHIFT (TIME T = 24 HOURS)

DESIRED TRIP POINT WAS 63.1" W.C.

l l -

l l

DOCUMENT 40431 i

Revision 1 I.ASALLE COUNTY STATION UNIT 2 SOR DIFFERENTIAL PRESSURE SWITCif INVESTIGATION ,

TABLE 4 SETPOINT CHARACTERIZATION TESTING CONCLUSIONS

_SWITCll APPI.ICATION l MARGIN FROM LCO l l l l (4)I EXISTING TECH I l EXISTING I NEW

} STATIC SHIFT l REPEATABILTTY l SPEC. DRIFT l TOTAL l L.C.O. I SETPOINT I I I I I I

-REACTOR VESSEL LEVEL 3 l 4.2" RWL I 2.6" RWL i 1.5" RWL I 8.4" RWL l lI.0"RWL l19.4" RWL I I I I I I

-REACTOR VESSEL LEVEL 2 l 11.2" RWL I 5.0" RWL I 7.0" RWL I 23.2" RWL l-57.0" RWL l -33.8" RWL I I I I I I

-REACTOR VESSEL LEVEL 1 l 11.2" RWL I 7.3" RWL I 7.0" RWL I 25.5" RWL l-136.0" RWLl-110.5" RWL I I I I I I

-REACTOR VESSEL LEVEL 8 I 5.0" RWL l 2.6" RWL I 0.5" RWL I 8.1" RWL l 56.0" RWL l 48.0" RWL I I I I I I

-RHR/RCIC STEAMLINE BREAK l 8.0" W.C. l 3.6" W.C. l 5.0" W.C. I 16.6" W.c. I 128" W.C. l111.4" W.c.

I I I I I I

-RilR S:lUTDOWN COOLING LINE l 8.0" W.C. l 3.6" W.C. I 6.0" W.C. l 17.6" W.C. l 186" w.c. 1168.4" W.c.

I I I I I I

-RCIC STEAM LINE BREAK I 7.2% RATED FLOW l 3.0% RATED FLOW l 5.0% RATED FLOW l 15.2% RATED 1295% RATED I 280% RATED l l l l FLOW l FLOW I FLOW l i I I i 1

-RHR LPCI-A,B C MIN. FLOW l 237 GPM i 73 GPM l 450 GPM i 1427 GPM i 550 GPM i 1977 GPM i i l i l l

-LPCS MIN. FLOW l 233 GPM l 71 GPM l 110 GPM l 1079 GPM i 640 GPM i 1719 GPM I I I I l I

-HPCS MIN. FLOW l 151 GPM l 50 GPM i 100 GPM i 640 GPM (3) i 900 GPM l 1540 GPM I I I , I I I

-MAIN STEAM LINE HI FLOW l (5) l (5) I 5.0 PSID l (5) I 116 PSID l (5) l I I I I I NOTES: INCLUDES ADDITIONAL MARGIN OF 1) 666 GPM FOR LPCI 2) 664 GPM FOR LPCS AND 3) 339 GPM FOR HPCS

4) For applications other than main steam line high flow repeatability for each switch tested was less than 2%

of range; therefore 2% was used for repeatability. For mainsteam line high flow switches, repeatability of the most variable switch in service was used. Repeatability was calculated for each switch to bound 95% of the data with a 95% confidence level.

5) Setpoint development pending completion of testing and replacement of switches with static shift or repeatatility above limits.

Incuent 40431

Rerisien 2

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SCR S'a*ITCM INVESTIGATICN TABLE CORRECTIVE AC'"ICNS

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2. Flcw Testing to Verify ECCS Ccmpleted Minl=um Flcw switch setpcints
3. Reactor water level drcp tests to verify During startup Level 3 switch setpcints. Tests will be fol'.cWing curren r e . ."^- r..ed a t a:. ---. -.d - -o e ..s c e, a := _G , :. v- =. .c u- . _ c L.. ea .-. e .a a--r e--e - -

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4. C =plete calibration pr:cadure revisiens. 06
a. New setpcints including: static pressure shift, repeatability margin and drift margin.
b. New calibration methods including: The "As-Found" 4

set;cint will be the first actuaticn and during calibraticn the switch will be cycled fres ,

the appropriate 0*s or 100*5 cf differential pressure span to ne set;cint.

c. "As-Feund" setpcint acceptanca
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Revision 2 7/25/So

,4 . Complete calibration procedure revisions (continued)

(c) "As-Found" setpoint acceptance limits (continued)

(2) Rejection Limit (d) + (2% of Adjustable Range + Tech. Spec.

Margin for drift)

(b) For mainsteam line high flow this limit is (Repeatability + Tech. Spec. drift) for the i

most variable switch in service.

Repeatability was calculated for each switch to 95% of the data with a 95%

confidence level.

(c) If this limit is exceeded the switch will be rejected.

5. Complete recalibration of switches with revised Prior to startup setpoints and revised procedures. from current outage. 1
6. Implement Increased Surveillance After Startup from current outage.
a. Categories
1. Level 3 switches (6 switches) - The Level 3 switches will be calibrated 2 weeks after startup, 4 weeks after startup, 2 months after startup and 4 months after startup. After the 4th month, the Level 3 switches will remain on a quarterly frequency. Note that this schedule assumes no problems occur with the limits as described above.
2. Main Steam Line Break Switches (16 switches) - At least 4 of the Main Steam Line (MSL) switches will be calibrated 4 weeks after startup. Of the remaining 12 switches at least 4 of the MSL switches will be calibrated 8 weeks after startup. Of the remaining 8 switches, at least 4 of the MSL switches will be calibrated 12 weeks after startup. The maximum interval for each individual switch will be limited to a quarterly frequency.
3. Remaining switches (37 switches) - A sample (grouped by model nunters) representative of the remaining switches (approximately 1/3) will be calibrated 4 weeks after startup. Of the 2 remaining switches, approximately 1/3 will be calibrated 2 months after startup. The remaining switches will be calibrated 3 months after startup. The maximum interval for each individual switch will be limited to a quarterly frequency. The representative samples will be chosen, where possible, to include a sampling of various switch model numbers.
7. Complete evaluation of alternative level sensing Instruments to replace SCR l-1-87
a. Review Requirements
b. Review vendor environmental qualification data.
c. Review vendor performance test data.
d. Reccmmend Technically acceptable alternatives.
e. Complete preliminary conceptual design and obtain reviews and approval. General description of key features effecting design installation, operation and maintenance and project plan.
f. Initiate detailed conceptual design.

Document 40501 _ __ _ . . _ _ _

~ . . .-

Revision 1 7/25/86

.. "*8. Establish eccapttnca limits for n:w SOR Completed l1 switches. The Purchase Order with SOR will be revised to require tests similar to i setpoint characterization tests including a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> test and to require switches

? perform within the static shift and repeatability limits.

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i l Document 40501

. _ - . . . . . . . _ _ __.. . . - _ . - - . _ _ . _ . _ _ _ _ , _ _ . _ _ . , . _ . . _ , . . _ . . .__.___ _ _ . __ _ _ ,_ _

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