ML19262A190

Abnormal Occurrence 50-289/75-03:on 750123,during Routine Insp of Hydraulic Shock Suppressors,One Snubber Found Inoperative Due to Loss of Fluid.Caused by Loose Reservoir End Caps & Possible Leakage at Cylinder End Caps

ML19262A190
Person / Time
Site:	Three Mile Island
Issue date:	02/02/1975
From:	Arnold R METROPOLITAN EDISON CO.
To:
References
NUDOCS 7910260519
Download: ML19262A190 (4)

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Dear Sir:

Operating License DPR-50 Docket #50-289 In accordance with Technical Specifications for the Three Mile Island Nuclear Station Unit 1, we are reporting tha. following abnormal occurrence:

(1) Report Number: A0-50-289/ 75-03 (2a) Report Date: F.B 2 1575 (2b) Occurrence Date: January 23, 1975 (3) Facility: Three Mile Island Nuclear Generating Station Unit 1 (4) Identification of Occurrence:

Title:

Loss of Fluid from Hydraulic Shock Suppressor Type: An abnormal occurrence as defined by the Technical Specifications, paragraph 1.8d, in that the loss of fluid from a hydraulic shock suppressor threatened to cause an Engineered Safeguards feature or system to be incap-ble of performing its intended function.

(5) Conditions Prior to Occurrence:

The reactor was at hot standby with major plant parameters as follows:

Power: Co re : 1%

Elec: 0 !f4 (Gross)

RC Flow: 140 x 106 lb/hr ,-

RC Pressure: 2155 psig h2 1308

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RC Temp.: 536 F PRZR Level: 200 in.

PRZR Temp. : 650 F (6) Description of Occurrence:

During a routine inspection of all hydraulic shock suppressors (snubbers) inside the Reactor Building's secondary shicid, one snubber (MUE-43, located on the C high pressure injection line) was found to be inoperative due to a loss of fluid. The snubber was replaced with an identical unit that had been rebuilt with ethylene-propylene seals and the new tait was filled with fluid.

The inspection of snubbers ins /de the Reactor Building secondary shield was completed and no other inoparable snubbers were f o und .

(7) Designation of Apparent Cause of Occurrence:

Subseque- inspection of the defective unit revealed that the reservoir end caps were loo se . There was some evidence, although inconclusive, of leakage at the cylinder end caps. No indication of seal deterior-ation was obse rved. The cause of the occurrence , there f ore , was mate rial .

(8) Analysis of Occurrence:

The worst possible consequence of the loss of fluid f rom MUE-43 would take place during a seismic event. Excessive vibration could cause the overstress and possible f racture of the C high pressure injection line; however, since the high pressure injection lines are very conservatively designed, such a f racture is considered unlikely under any circumstances.

If such a break did occur, a check valve at the point where this line connects to the Reactor Coolant piping loop B cold leg downstream of the C Reactor Coolant Pump would prevent loss of the primary coolant. During an emergency safeguards actuation, the control room operator would notice a high flow rate in the C high pressure injection line and a rising level in the Reactor Building Sump. He would then isolate the C high pressure injection line. In any case, . a make-up pumps would supply an adequate flow to the other three high pressure injection lines to fulfill their design function.

(9) Corrective Ac*icn:

Immediate corrective action was taken as described above to replace the defective snubber.

Long-term preventative action continues with the snubber inspection and seal replacement program as described in the letter f rom R. C. Arnold to A. Giambusso dated February 14 , 1974.

The Plant Operations Review Committee and the Station Superintendent have reviewed and approved the corrective actions .

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(10) Failure Data Previous Failures:

See Abnormal Occurrence Reports A0 50-289/74-14, 74-20, 74-23, 74-25, and 74-30.

Equipment Identification :

Snubber Assembly Brand - Grinnel Cylinder Type - Lynair Bore - 2.5 in.

Stroke - 5 in.

Sincerely, f .~ l i \\-

N(j;j',d4

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R. C. Arnold Vice President RCA/RSB/tas cc: Directorate of Regulatory Operations, Region 1 Nuclear Regulatory Commission 631 Park Avenue King of Prussia, Pennsylvania 19406 File: 20.1.1 7.7.3.5.1 2