ML18106A435

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LER 98-006-00:on 980227,incorrect Scaling of First Stage Turbine Impulse Pressure Transmitters Noted.Cause Indeterminate.Implemented Procedure Changes & re-scaled Affected Turbine Impulse Pressure transmitters.W/980330 Ltr
ML18106A435
Person / Time
Site: Salem PSEG icon.png
Issue date: 03/30/1998
From: Bakken A, Bernard Thomas
Public Service Enterprise Group
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-98-006-01, LER-98-6-1, LR-N980156, NUDOCS 9804080060
Download: ML18106A435 (8)
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Text

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e OPS~G Public Servi_ce Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038-0236 Nuclear Business Unit MAR 3 o 1998 LR-N980156 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 LER 311/98-006-00 SALEM GENERATING STATION - UNIT 2 FACILITY OPERATING LICENSE NO. DPR-75 DOCKET NO. 50-311 Gentlemen:

This Licensee Event Report entitled "Incorrect Scaling of the First Stage Turbine Impulse Pressure Transmitters" is being submitted pursuant to the requirements of the Code of Federal Regulations 10CFR50.73(a)(2)(i)(B).

Sincerely, A. C. Bakken Ill General Manager -

Salem Operations Attachment BJT c Distribution LER File 3.7

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9804080060 980330 PDR ADOCK 05000311 S PDR The power is in your hands.

95-2168 REV. 6194

NRC FORM 366 U.S. NUCL: REGULATORY COMMISSION APP ED BY OMB NO. 3150-0104 (4-95) EXPIRES 04/30/98 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLECTION REQUEST: 50.0 HRS. REPORTED LESSONS LEARNliD ARE INCORPORATED INTO THE LICENSING PROCESS AND FED

  • LICENSEE EVENT REPORT CLER) BACK TO INDUSTRY. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH IT-6 F33), U.S. NUCLEAR REGULATORY COMMISSION. WASHINGTON. DC (See reverse for required number of 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150*

0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON. DC digits/characters for each block) 20503.

FACILITY NAME 111 DOCKET NUMBER (2) PAGE (31 SALEM GENERATING STATION UNIT 2 05000311 1 OF?

TITLE 141 Incorrect Scaling of the First Stage Turbine Impulse Pressure Transmitters EVENT DATE 15) LER NUMBER 16) REPORT DATE 17) OTHER FACILITIES INVOLVED 18)

MONTH DAY YEAR YEAR I SEQUENTIAL NUMBER IREVISION NUMBER MONTH DAY YEAR FACILITY NAME SALEM UNIT 1 DOCKET NUMBER 05000272 02 27 98 98 -- 006 -- 00 03 30 98 FACILITY NAME DOCKET NUMBER OPERATING 5 .THIS REPORT JS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: !Check one or morel 111)

MODE 191 20.2201(b) 20.22031all2)(v) x 50. 731all2llil 50. 731all2)(viii)

POWER 000 20.22031a)(1) 20.22031all311il 50. 731a)(2){ii) 50. 731a112llxl LEVEL (10) 20.2203la)(2)(i) 20.2203(a)(3){ii) 50. 73(all2lliiil 73.71 20.2203(a)l2lliil 20.22031all41 50. 731a)(2)1iv) OTHER 20.22031a)(2)(iii) 50.361c)(1 l 50. 731all211vl Specify in Abstract below or in NRC Form 366A 20.22031a)(2)(iv) 50.361c)(2) 50. 731a)(2)1vii)

LICENSEE CONTACT FOR THIS LER 1121 NAME TELEPHONE NUMBER (Include Area Coda)

Brian J. Thomas, Licensing Engineer 609-339-2022 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT 113)

CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE CAUSE SYSTEM COMPONENT* MANUFACTURER REPORTABLE TO NPRDS -, TO NPRDS x 'YES

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SUPPLEMENTAL REPORT EXPECTED (141 (If yes, complete EXPECTED SUBMISSION DATE).

I 'NO EXPECTED SUBMISSION DATE (15)

MONTH 05 DAY 29 YEAR 98 ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) 116)

On February 27, 1998, Engineering personnel determined that a scaling error of the first stage pressure transmitter existed when Salem Unit 2 operated from August 1997 to February 1998. The P-13 permissive (1 of 2 Turbine impulse chamber pressure channels;;::: a pressure equivalent to 11 %

of rated thermal power) is an "or input along with permissive P-10 (2 of 4 Power Range Neutron Channels ;;::: 11 % of rated thermal power) for the P-7 permissive as defined in Technical Specification (TS) Table 3.3-1. Therefore only one of either of the P-13 or P-10 permissives is necessary to actuate the P-7 permissive. The P10 permissive was not affected by the scaling problem and therefore would have actuated the P-7 permissive at the proper value. However with the first stage pressure transmitters scaled at a higher pressure for 100% thermal power, the P-13 permissive setpoint was actually higher than the value required by TS Table 3.3-1 (above 11 % thermal power).

The cause of occurrence is still under investigation and the results of this investigation will be reported in a supplement to this LER. Procedure changes have been implemented and the affected turbine impulse pressure transmitters have been re-scaled. Additional corrective actions will be identified, as appropriate, upon completion of the investigation.

This event is being reported in accordance with 10 CFR 50. 73(a)(2)(i)(B), any condition _prohibited by the plant's Technical Specifications.

NRC FORM 366 14-951

  • NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

SALEM GENERATING STATION UNIT 2 05000311 YEAR I SEQUENTIAL NUMBER I REVISION NUMBER 2 OF 7 98 - 006 - 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

PLANT AND SYSTEM IDENTIFICATION Westinghouse - Pressurized Water Reactor Reactor Control and Protection (RCP) {JC/-}*

  • Energy Industry Identification System (EllS) codes and component function identifier codes appear as {SS/CCC}.

CONDITIONS PRIOR TO OCCURRENCE At the time of discovery, Salem Unit 2 was in Mode 5 and Salem Unit 1 was in Mode 4.

DESCRIPTION OF OCCURRENCE On February 27, 1998, Engineering personnel determined that a scaling error of the first stage pressure transmitter existed when Salem Unit 2 operated from August 1997 to. February 1998. The first stage pressure transmitters, 2PT505 and 2PT506, were incorrectly scaled for the turbine pressure expected at 100% power. During the period of operation of Unit 2 above, the first stage turbine pressure was identified as reading approximately 555 psia with the Unit at 100% thermal power. 2PT505 and 2PT506 were calibrated in accordance with setpoint calculation SC-MS-002-01, Revision 1, dated May 29, 1997. In accordance with SC-MS-002-01, Revision 1, pressure transmitters 2PT505 and 2PT506 were scaled with a span of 0 to 690 psia corresponding to Oto 120% power. The equivalent pressure at 100% thermal power based on this scaling is 575 psia.

Therefore the first stage pressure transmitters were indicating a lower first stage turbine pressure when Unit 2 was at 100% thermal power.

The basis of the 690 psia is derived from the original thermal performance (heat balance) data developed by Westinghouse for the Unit 2 Turbine-Generator and documented in Public Service Blue Print (PSBP) 131382 dated February 15, 1972. During the Salem Unit 2 outage prior to September of 1997, the Unit 2 low pressure turbine blades were replaced. As a result of the new low turbine pressure blades, Westinghouse provided new thermal performance (heat balance) data. The new thermal performance data for the new low pressure turbine blades lowered the first stage turbine pressure corresponding to 100% thermal power as compared to the 1972 value.

NRC FORM 366A (4-95)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT {LER)

TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

SALEM GENERATING STATION UNIT 2 05000311 98 - 006 - 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

DESCRIPTION OF OCCURRENCE (cont'd)

The first stage turbine pressure transmitters provide inputs to the Reactor Protection and Control system. The first stage turbine pressure transmitters provide input for the following safety and non-safety related functions:

Safety Related

  • The high steam line flow variable setpoint is adjusted based on the first stage turbine pressure. High steam line flow coincident with either low Tavg or low steam line pressure generates a Safety Injection (SI) signal and a Main Steam Isolation (MSI) signal.
  • The P-13 permissive (1 of 2 Turbine impulse chamber pressure channels ~ a pressure equivalent to 11% of rated thermal power) is an "or" input along with permissive P-10 (2 of 4 Power Range Neutron Channels~ 11 % of rated thermal power) for the P-7 permissive as defined in Technical Specification (TS) Table 3.3-1. Therefore only one of either of the P-13 or P-10 permissives is necessary to actuate the P-7 permissive. The P-7 permissive prevents or defeats the automatic block of the reactor trip on low flow in more than one primary coolant loop, reactor coolant pump undervoltage and under-frequency, pressurizer low pressure, pressurizer high level, and the opening of more than one reactor coolant pump breaker.
  • Permissive P-2 inhibits the automatic rod withdrawal on low turbine impulse pressure below a setpoint equivalent to 15% of full power.

Non-Safety Related

  • The AMSAC circuitry is armed at a first stage turbine impulse pressure equivalent to 40%

reactor power.

  • AT-ref (reactor coolant temperature reference value) signal based on first stage impulse pressure provides an interlock for the condenser steam dumps.
  • The Advanced Digital Feedwater Control System (ADFCS) uses the first stage turbine.

impulse pressure for Steam Generator Water Level Control, programmed Steam Generator water level (from 33% to 44% level with a corresponding turbine load of Oto 20%), and to generate a main turbine runback due to a Steam Generator Feedwater pump trip when turbine load is above 70%.

  • The rod control system receives a T-ref signal based on first stage turbine pressure for comparison with Nuclear Instrumentation System (NIS) power level to determine direction and speed of control rod motion.
  • First stage turbine impulse pressure also provides a T-ref input to the Main Control Room indicator for reactor coolant temperature.

NRC FORM 366A (4-95)

-J NRC FORM 366A u.s~ NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

SALEM GENERATING STATION UNIT 2 05000311 YEAR I SEQUENTIAL NUMBER I REVISION NUMBER 4 OF 7 r

98 - 006 - 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

DESCRIPTION OF OCCURRENCE (cont'd)

With the actual first stage turbine impulse pressure corresponding to 100% Reactor Power being at a lower value than the pressure transmitters were scaled, for a given pressure of turbine load the actual reactor thermal power level would be at a higher value (i.e., 10% turbine load based on impulse pressure would be greater than 10% reactor thermal power).

Technical Specification (TS) Table 3.3-1 requires a P-7 setpoint of "... 1 of 2 Turbine Impulse chamber pressure channels.~ 11 % of RATED THERMAL POWER". With the first stage pressure transmitters scaled at a higher pressure for 100% thermal power, the P-7 (P-13 turbine load input) permissive setpoint was actually higher than the value required by TS Table 3.3-1 (above 11 % thermal power).

Since the actual turbine impulse pressure for the P-7 permissive correlated to a Rated Thermal Power above 11 %, the setpoint for the P-13 permissive input to the P-7 permissive was non-

  • conservative. There was no impact to the P-10 permissive input for the P-7 permissive. Therefore.

for the period of September 1997 to. February 1998, Salem Unit 2 operated with a non-conservative TS setpoint. The sensor calibration procedures for the Unit 2 first stage turbine impulse pressure channels I (2PT505) and II (2PT506) were revised on February 28, 1998. The first stage turbine pressure channels 2PT505 and 2PT505 were calibrated using the revised procedures prior to Unit 2 entering Mode 2. This event is reportable in accordance with 10CFR50.73(a)(2)(i)(B)., any condition prohibited by the plant's Technical Specifications.

Also during the review of the scaling of the first stage pressure transmitters, a region of non-linearity of twbine load (first stage pressure) with respect to reactor thermal power was identified. This area of non-:-linearity existed at the lower end _of the first stage turbine impulse transmitters. The non-linearity of the turbine pressure with respect to the reactor thermal power also caused the setpoint for the P-7 (P-13 input for turbine pressure) permissive to be set at a non-conservative value for Salem Units 1 and 2. In the past, the P-7 permissive was set at a value of 10% turbine load based on the turbine impulse pressure, however based on the review of the non-linearity of the transmitter a 1.6%

offset for Unit 1 and 1.9 % offset for Unit 2 existed. Therefore the actual Rated Thermal Power level for the P-7 permissive for the turbine impulse transmitters would correspond to 11.6% for Unit 1 and 11.9% for Unit 2. These setpoints did not comply with the requirements of TS Table 3.3-1.

The channel calibration procedures for the Unit 2 first stage turbine impulse pressure channels I and II were revised on March 3, 1998. These procedures were revised to reflect the re-scaling of the Unit 2 first stage pressure transmitters and to ensure the proper setting of permissive P-13. However during a review of the corrective actions associated with this LER, no work order was identified as having performed the re-calibration of the P-13 permissive prior to Unit 2 entering Mode 2. Upon NRC FORM 366A (4-95)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILllY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

SALEM GENERATING STATION UNIT 2 05000311 YEAR I SE,fillJ~J~AL I~~~~ 5 OF 7 98 - 006 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

DESCRIPTION OF OCCURRENCE (cont'd) discovery that the revised channel calibration had not been performed, on March 26, the Unit 2 bistables associated with permissive P-13 were placed in the tripped condition. Placing the P-13 bistables in the tripped condition ensures that all the reactor trips associated with permissive P-7 are enabled at all reactor power levels. Subsequently, the P-13 permissive was re-calibrated using the revised channel calibration procedure.

CAUSE OF OCCURRENCE The cause of occurrence is still under investigation and the results of this investigation will be reported in a supplement to this LER. Preliminary results of the investigation have identified that the revised Westinghouse thermal performance data for the low pressure rotor replacement was not evaluated for impact to the first stage turbine pressure transmitters. The reason for this occurrence is still under investigation. Also investigation for the failure to re-calibrate the Unit 2 P-13 permissive prior to restart of Unit 2 is continuing.

PRIOR SIMILAR OCCURRENCES A review of LERs for prior similar occurrences will be performed upon completion of_the cause of occurrence.

SAFETY CONSEQUENCES AND IMPLICATIONS As discussed previously, the first stage turbine impulse pressure transmitters provide inputs to both safety related and non-safety related reactor protection and control systems.

  • The impact of the improper scaling for the safety related functions associated with the first stage turbine pressure transmitters is as follows:
  • High Steam Flow Reference Setpoint:

With the actual first stage turbine pressure lower than the scaling for 2PT505 and 2PT506, the setpoint for the high steam flow trip was conservative. The steam flow trip setpoint would be at a lower value for the actual reactor power level and therefore would be conservative.

NRC FORM 366A (4-95)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

' FACILITY NAME(1)

TEXT CONTINUATION DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

SALEM GENERATING STATION UNIT 2 05000311 YEAR I SEQUENTIAL NUMBER I REVISION NUMBER 6 OF. 7 98 - 006 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

SAFETY CONSEQUENCES AND IMPLICATIONS (cont'd)

  • P-7 Permissive The P-7 permissive is an "or" combination of the P-13 (turbine impulse pressure) and P-10 (NIS power) inputs. Although the P-13 portion of the P-7 permissive was set in the non-conservative direction, the P-10 permissive, 2 of 4 Power Range Neutron Channels ;::: 11 % of Rated Thermal Power, would ensure that the P-7 permissive operated at the proper value.
  • P-2 Permissive The P-2 Permissive inhibits the automatic withdrawal of control rods below a turbine impulse pressure setpoint equivalent to 15% rated thermal power. The actual value that the P-2 permissive was set at was approximately 18.5% rated thermal power. Therefore, automatic control rod withdrawal was blocked up to 18.5% rated thermal power which is conservative for this function.

Blocking the automatic withdrawal of the control rods at low power levels requires the control room operators to perform control rod movement and oversee any changes of reactivity at low power levels.

Based on the above, although the first stage turbine pressure transmitters were scaled incorrectly, the reactor protection system would have operated when required to protect the health and safety of the public.

Although the first stage turbine pressure transmitters provide input to the Rod Control System, Steam Generator Level control, ADFCS, steam dump controls, and the T-ref recorder in the control room, these non-safety related control systems do not affect the ability of the reactor protection system to generate a reactor trip or initiate the required Engineered Safety Feature (ESF) equipment.

In accordance with the Salem UFSAR and the NRC safety evaluation report for AMSAC, the AMSAC system is armed at a value of 40% rated thermal power. The AMSAC interlock (C~20) for arming the system is set at 40% turbine impulse power. Setting the C-20 interlock at 40% turbine impulse power does not ensure that the AMSAC system is armed prior to 40% rated thermal power. However, in accordance with WCAP-11293-A the AMSAC system is designed to prevent overpressurization of the reactor coolant system. The Westinghouse analysis demonstrates that the AMSAC system is not required to actuate below 70% rated thermal power in order to limit the peak pressure in the reactor coolant system. Since AMSAC would continue to be armed before 70% rated thermal power, there is no safety consequences associated with the incorrect scaling of the first stage turbine pressure transmitters.

NRC FORM 366A (4*95)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACIUrY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

SALEM GENERATING STATION UNIT 2 05000311 YEAR I SEQUENTIAL NUMBER I REVISION NUMBER 7 OF 7 98 - 006 - 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

CORRECTIVE ACTIONS

1. Setpoint calculation SC-MS002-01, 'Turbine Impulse Pressure Scaling/Uncertainty Calculation" was revised on February 28, 1998. This calculation revised the scaling of the first stage turbine pressure transmitters for Salem Unit 2 to equate a turbine pressure of 555.69 psia for 100%

reactor power.

2. Setpoint calculation SC-MS002-01 was revised on March 9, 1998, to ensure that Permissive P-13 is set at a value not to exceed 11 % Reactor Thermal Power.
3. The associated instrument calibration database information was revised on February 28, 1998, to reflect the re-scaling of the Unit 2 first stage turbine pressure trans~itters.
4. The sensor calibration procedures for the Unit 2 first stage turbine impulse pressure channels I (2PT505) and II (2PT506) were revised on February 28, 1998. The first stage turbine pressure channels 2PT505 and 2PT506 were calibrated using the revised procedures prior to Unit 2 entering Mode 2.
5. The channel calibration procedures for the Unit 2 first stage turbine impulse pressure channels I and II were revised on March 3, 1998. These procedures were revised to reflect the re-scaling of the Unit 2 first stage pressure transmitters and to ensure the proper setting of permissive P-13.

The re-calibration of the P-13 permissive was completed on March 26, 1998.

6.
  • The channel calibration procedures for the Unit 1 first stage pressure transmitter channels 1PT505 and 1PT506 will be revised prior to Unit 1 entry into Mode 2 to reflect the proper setting of permissive P-13. Calibration of these channels will be performed prior to Unit 1 entering Mode 2 using the revised procedures.
7. Procedure SC.IC-PT.SSP-0014(Q), "AMSAC Functional Test," was revised to reflect the re-scaling of the Unit 2 first stage turbine impulse pressure transmitters. This procedure adjusted the setpoint of the C-20 interlock for the arming of the AMSAC system. The revised AMSAC functional procedure was performed prior to Salem Unit 2 entering Mode 1. The revised AMSAC procedure was completed on Unit 1 on March 19, 1998.
8. The cause of the occurrence of the events identified in this LER are still under investigation. This LER will be supplemented by May 29, 1998, to reflect the completion of the investigation.

NRC FORM 366A (4*95)

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