ML19343C225

AO 50-219/74/35:on 740705,main Steam Line Low Pressure Switches RE23B,C & D Tripped at Pressure Less than Min Required Value of 860 Psig.Caused by Switch Repeatability. GE Requested to Investigate Feasibility of Tech Specs Mod

ML19343C225
Person / Time
Site:	Oyster Creek
Issue date:	07/15/1974
From:	JERSEY CENTRAL POWER & LIGHT CO.
To:
References
AO-50-219-74-35, NUDOCS 8103040504
Download: ML19343C225 (4)

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Jersey Central Power & Light Companyf %d MADISON AVENUE AT PUNCH BOWL ROAD

• MORRISTOWN.N.J.07960

• 201-539-6111

- . . anne n r s General g, Public Utilities Corporation

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OYSTER CREEK NUCLEAR GENERATING STATION FORKED RIVER, NEW JERSEY 08731 Abnormal Occurrence Report No. 50-219/74/35 Nr JM'o "

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July 5, 1974 Identification of Occurrence Violation of the Technical Specifications, paragraph 2.3.7, main steam line low pressure switches RE23B, C, and D were found to trip at pressures less than the minimum required value of 860 psig. This event is considered to be an abnormal occurrence as defined in the Technical Specifications, paragraph 1.15A.

Conditions Prior to Occurrence The plant was in a routine startup.

The major plant parameters at the time of the event were:

Power: Reactor, 1200 FMt Electric, 399 FMe Flow: Recirculation, 8.6 x 104 gpm Feedwater, 4.5 x 10 6 lb/hr Reactor Pressure: 1020 psig Description of Occurrence On Friday, July 5, 1974, at 1540, while performing a routine surveillance test on the four main steam line low pressure switches, it was discovered that switches RE23B, C, and D tripped at 845, 857, and 854 psig, respectively. These

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2 Abnormal Occurrence No. 50-219/74/35 Page 2 values are below the minimum required trip point of 860 psig which is derived by adding to the Technical Specification limit of 850 psig a 10 psig head correction factor.

Th "as found" and "as left" switch settings were:

"As Found" Settings "As Left" Settings RE23A 864 psig 864 psig RE23B 845 psig 862 psig RE23C 857 psig 863 psig RE23D 854 psig 862 psig Apparent Cause of Occurrence Design is considered to be a major factor contributing to this event. Switch repeatability is a recognized problem and work is in progress to formulate a final solution.

Analysis of Occurrence As indicated in the bases of the Technical Specifications, "The low pressure isolation of the Main Steam Lines at 850 psig was provided to give protection against fast reactor depressurization and the resultant rapid cooldown of the vessel. Advantage was taken of the scram feature which occurs when the Main Steam Isolation Valves are closed to provide the reactor shutdown so that high power operation at low reactor pressure does not occur, thus providing protection for the fuel cladding integrity safety limit."

The adverse consequences of reactor isolation occurring at reactor pressure approximately 15 psig below the specified minimum value of 860 psig is limited to those effects attendant to a greater than normal reactor cooldown rate. The fuel cladding integrity safety limit only comes into effect for power operation at recctor pressures less than 600 psig or for power operation greater than 354 FMt with less than 10's recirculation flow. Therefore, the consequences of a 15 psig lower than normal reactor isolation and scram setpoint has no threatening effect whatsoever on the fuel cladding integrity.

The effects of a too rapid cooldown due to the lower isolation pressure are incensequential since there is less than 2*F difference between the saturation temperature for 850 psig and 835 psig.

Corrective Action The corrective actions being taken at this time are:

1. Formal correspondence was initiated with General Electric Company on March 26, 1974 following numerous attempts at informal resolution of this problem. Since then, additional follow up conversation and correspond-ence, as recent as June 4, 1974, has ensued. General Electric has been

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Abnormal Occurrence No. 50-219/74/35 Page 3 requested to investigate the feasibility of a change to the Technical Specifications which would allow for tolerances or deviations on all instrumentation connected with safety systems and proteccive functions.

If this approach cannot be technically justified, General Electric has been requested to develop a basis for a Technical Specification change to reduce the main steam low pressure setpoint considerably lower than the present 850 psig but with an acceptable margin to the 600 psig fuel cladding integrity limit for power operation. The above actions, if taken, will resolve the problem of the main steam line low pressure deviations.

Unfortunately, the approach and response by General Electric has not been entirely satisfactory and has caused delay in our resolution of the matter.

2. He Ashcroft switch that was reported in Abnormal Occurrence Nos. 50-219/74/10, 50-219/74/12, and 50-219/74/22 to have been undergoing tests, has been found to give excellent repeatability under contr611ed conditions. However, under conditions similar to that presently found during the surveillance of the Barksdale switches, the repeatability of the Ashcroft switches vary within their design limitations (+ 1% of full scale). hhereas they may be somewhat superior to the Barksdale switches, they still are unsatisfactory for the Technical Specification limiting safety system settings.

Testing is continuing. Consequently, the above stated results are still considered to be preliminary in nature.

3. He General Office Review Board has been involved in every instance of instrument setpoint repeatability and has assigned to the General Public Utilities Service Corporation's Electrics 1 Engineering Department the task of problem investigation. He item has been pursued in various Genera?

Office Review Board meetings when appropriate abnormal occurrences have been discussed, and the General Office Review Board, as well as the Plant Operations Review Co=mittee, is committed to following the problem to a final solution. To date, a total of thirteen abnormal occurrences have 3

been identified this year to be the result of instru=entation repeatability I problems. Most, if not all of the setpoint inaccuracies, however, fall within the manufacturer stated tolerances for the instrument involved. This implies that repeatability as such is not in question. Consequently, the preferred action identified in "1" above would appear, at this time, to be l

the only reasonable solution for this condition. Six of the thirteen reports have been generated as a result of " repeatability" of the cain steam l

line low pressure switches. In this case, the alternate action in "1" above will be pursued in the event that the preferred action is not feasible.

l Additionally, the General Public Utilities Service Corporation's Electrical l

Engineering Department has identified other means of monitoring this i parameter and has made recommendations to correct the problem, all of which l involve redesign of the monitoring network from either a techanical and/or electrical standpoint. The Jersey Central Power 6 Light Cocpany Generation Engineering Department is currently investigating with General Electric Co=pany the feasibility of several of these alternate plans recoc= ended by both General Public Ut'lities Service Corporation and the plant staff.

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I Abnormal Occurrence No. 50-219/74/35 Page 4 Manufacturer data pertinent to these switches are. as follows:

Meletron Corporation (subsidiary of Barksdale)

Los Angeles, California Pressure Actuated Switch Model 372 Catalog #372-6SS49A-293 Range 20-1400 psig Proof psi 1750 G Previous abnormal occurrence reports involving these switches are:

1. Letter to Mr. A. Giambusso from Mr. D. A. Ross, dated December 24, 1973.

2. Abnormal Occurrence Report No. 50-219/74/1

3. Abnormal Occurrence Report No. 50-219/74/9

4. Abnormal Occurrence Report No. 50-219/74/10

5. Abnormal Occurrence Report No. 50-219/74/12

6. Abnormal Occurrence Report No. 50-219/74/22 b

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