ML20086L149

Ao:On 731112,setpoint Shift Found on Reactor Pressure Switches PS-2-3-49A & PS-2-3-50A & Reactor Vessel Level Switch LITS-2-3-73A.Caused by Setpoint Drift.Switches Recalibr & Tested for Repeatability

ML20086L149
Person / Time
Site:	Peach Bottom
Issue date:	11/23/1973
From:	Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8402070417
Download: ML20086L149 (3)

Text

O n U

V PHII.ADELPHIA ELECTRIC COMPANY .

2301 MARKET STREET PHILADELPHI A. PA.19101 (21518414ooo 1

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November 23, 1973 C .A N

O: R[Q.Ib' I e /[] r7 Mr. A. Giambusso g. NOV$g7

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g Deputy Director of Reactor Projects et

' United States Atomic Energy Commission p y dy (( [ Jr Ag g' Directorate of Licensing 1 4 r.

Washington, D. C. 20545 f, fG

Reference:

Peach Bottom Atomic Power Station - Unit 2 Facility Operating License DPR-44 Docket No. 50-277

Subject:

Abnormal Occurrence During the week of November 12, 1973, the performance of routine surveillance tests disclosed three instrument deficiencies. Two pressure switches monitoring primary system pressure were found to be out of calibration. Also, a reactor vessel level switch was found to be out of calibration. These deficiencies were reported to Mr. Walter Martin, A.E.C. Region 1, Regulatory Operations Office on November 17, 1973 In accordance with Section 6 7 2.A of the Technical Specification Appendix A of DPR-44 for Unit 2 Peach Bottom Atomic Power Station, these setpoint shif ts are being reported to the Directorate of Licensing as Abnormal Occurrences.

t Reactor Pressure Switches PS-2-3 49A and PS-2-3-50A A calibration procedure performed on pressure switch PS-2-3-49A disclosed that the set point of the device had shifted beyond the limits given in the Technical Specification. Technical Specification Table 3 2.8 requires that this device produce a trip at greater than or equal to 900 psig. The switch was found to trip at 853 psig. Pressure switch PS-2-3-50A, which was immediately tested af ter the f ailure of PS-2-3-49A, was found to have experienced a setpoint shif t also. This switch is also required to trip at greater than or equal to 900 psig.

Its setpoint was found to be 879 psig. -

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o -,- O Investigation and Corrective Action Both pressure switch PS-2-3-49A and PS-2-3-50A were immediately recalibrated to trip at 926 and 925 psig respectively. Also, both de-vices were tested for repeatability of setpoint with sat'isf actory results.

A thorough inspection of both switch mechanisms revealed no mechanical malfunctions. Additionally, pressure switches PS-2-3-490 and PS-2-3-50B were tested. These devices also displayed a' shif t in setpoint, but were both within the Technical Specification limits. P3-2-3-498 was found to trip at 904 psig and PS-2-3-50B tripped at 908 psig. These devices i were recalibrated to trip at 923 psig and 924 psig respectively. Due to the setpoint drif t of all four devices a calibration check will again be performed in approximately two weeks. At that time a further eval-uation will be conducted based on the new calibration data.

Safety Implications Pressure switches PS-2-3-49A and PS-2-3-50A comprise one-half of a one-out-of-two-twice logic in the Low Pressure Coolant Injection System (LPCI). The correct two pressure signal trips provide a per-missive to the LPCI break detection logic circuits. Failure of both of these devices would not render the logic system inoperable. LPCI break detection and loop selection would have been initiated by the other two switches in the logic, PS-2-3-498 and PS-2-3-508. As pre-viously stated, both of the latter were found to trip within the acceptable limit. The setpoint shif t of these two switches, therefore, have no safety implications. The reactor has been in a cold shutdown condition since November 6,1973 Reactor Vessel Level Switch LITS-2-3-73A A calibration procedure performed on level switch LITS-2-3-73A disclosed that the setpoint of the device had shif ted beyond the limits given in the Technical Specification. Technical Specification Table 3 2.B requires that this device produce a trip at greater than or equal to 312 inches above vessel zero. The switch was found to; trip at 308.4 inches above vessel zero. '

Investigation and Corrective Action Level switch LITS-2-3-73A was tested immediately for repeat-ability of setpoint and found to be satisf actory. The device was then recalibrated to trip at 334 5 inches above vessel zero. A review of previous calibration data indicated that the device had drifted in setpoint by approximately 12 inches over the past three months. An inspection of the switch mechanism revealed no mechanical difficulities.

The setpoint change is attributed to switch drift.

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Safety Implications Level Switch LITS-2-3-73A is in the permissive circuit for the 3

Containment Spray mode of the Residual Heat Removal System (RHR). This device prevents the manual initiation of containment spray during an 1

accident condition if reactor level is above 2/3 core height. This '

setpoint failure would have allowed manual initiation of containment spray 3 6 inches belew 2/3 core height. However, the level permissive signal may be manually overridden by the use of a keylocked switch.

This small change in setpoint has no safety implications.

Very truly yours,

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M. J. Cooney ,!', -

Assi t Gen'l Superintendent Generation Division MJC:kam cc: Mr. J. P. O'Reilly Director, Region i United States Atomic Energy Conunission 631 Park Avenue King of Prussia, Pa. 19406 S

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