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MADISON AVENUE AT PUNCH BOWL ROAD
- MORRISTOWN, N.J. 07960
- 201539-6111 es.us u as oeneral Public Utilities Corporation
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January 15, 1974 flW[ pr p st9r %
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'J/W21 $76 F i-Mr. A. Giambusso g-g, L,i. [, "
S Deputy Director for Reactor Projects c;
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N Directorate of Licensing rc7TP,.,-['
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dnited States Atomic Energy Commission Washington, D. C. 20545
Dear Mr. Giambusso:
Subject:
Oyster Creek Station Docket No. 50-219
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Abnormal Occurrence Report No. 50-219/74/1 The purpose of this letter is to fomard to you the attached Abnormal Occurrence Report in compliance with paragraph 6.6.2.a of the Technical Spec-ifications. The attached report was prepared in accordance with the " Standard Format for Reporting Abnormal Occurrences" given in Appendix A of Regulatory Guide 1.16, Revision 1.
It is planned that all future Abnormal Occurrence Reports will be prepared and forwarded in this manner.
Enclosed are forty copies of this submittal.
Very truly yours, f y C Y.d /
i Donald A. Ross Manager, Nucler.r Generating Stations cs Enclosures 1
cc:
Mr. J. P. O'Reilly, Director 1
Directorate of Regulatory Operations, Region I i
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f OYSTER CREEK NUCLEAR GENERATING STATION FORKED RIVER, NEW JERSEY 08731 Abnormal Occurrence Report No. 50-219/74/1 Report Date:
January 14, 1974 Occurrence Date:
January 4,1974 Identification of Occurrence:
Violation of the Technical Specifications, paragraph 2.3.7, low pressure main steam line pressure switch (RE23C) was found to trip at a pressure less than 850 psig.
Additionally, in the. investigation and review of this event by the PORC, it was determined that an instrument sensing line head correction of 9 to 10 psig was not accounted for in the original switch trip set point of 850 psig, thus resulting in a condition whereby all the RE23 sensors have been set in violation of this specification since initial startup. This event is considered to i
be an abnormal occurrence as defined in the Technical Specifications, paragraph 1.15A and G.
Conditions Prior to Occurrence:
The plant was operating at steady state power.
The major plant parameters at the time of the event were as follows:
Power - Core, 1830 MWt Elec., 642 MWe (g) 6 Flow - Recirc., 60.2 x 10 #/hr.
- Feedt, 6.77 x 106 #/hr.
Stack Gas - 24,000 pCi/sec.
Description of Occurrence:
On Friday, January 4,1974, at 1105, while performing routine surveillance testing on the four main steam line low pressure switches, it was discovered that RE23C tripped at 841 psig. This was 9 psig below its set point of 850 psig.
As part of the review process for this occurrence, it was dis-covered that the 850 psig set pressure did not take into account the instru-ment sensing line head correction.
To account for this factor, the switch settings should have been as follows:
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Abnormal Occurrence Report No. 50-219/74/1 Page'2
'RE23A - 859 psig
.RE238 - 860 psig
.RE23C - 859 psig
.RE23D - 860 psig As found switch settings were:
3 RE23A.
850 psig i,
RE23B'- 851 psig RE23C -~841 psig
.RE23D -:851 psig c Apparent Cause of Occurrence:
' Design, procedure and unusual service condition are factors contributing
-to :the cause of this event.
Sensor. drift is a recognized problem and work is in progress to formulate a final solution.
An investigative program has been initiated by the
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manufacturer, but as yet, a formal report of the results has not been issued.
The failure to properly account for the. instrument sensing line head 3
pressure.has been attributed to an apparent improper application of the Technical Specification requirements.
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Analysis ~of Occurrence:
. As indicated in the bases of the Technical Specification, "The-low pressure isolation of the main steam lines at 850 psig was provided to give protection 4
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 for 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 pressures approximately.9-10 psi belcw the specified minimum value of 850 prig 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 pr er operation at' reactor pressures less than' 600 psig or for. power operation greater ~than '354 MWt with less than 10** recirculation flow.. Therefore, the consequences of a 9-10 psi Iower than normal reactor isolation and scram.
set point has 'no threatening effect what soever on the fuel cladding integrity.
The; effects 'oi' a too rapid cooldown 'due to the lower isolation set pressure
. are inconsequential sinceL there is only about' I'F ' difference between the
' saturation temperature for! 850'psig and 840 psig.
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Abnormal Occurrence. Report No. 50-219/74/1
- Page 3.
L The. adverse safety. effect' of RE23C actuating at 841 psig is in the -loss of system redundancy. : The. other three sensors, RE23A, B, and D,1would.have p
limited the; adverse consequences to those previously discussed.
,p Corrective Action:
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- The pressure switch RE23C,1upon discovery of the condition, was recalibrated
.and checked to actuate at 852 psig.
P The' following actions' are planned to' prevent repetition of this event:
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- 1. ' Evaluate " hydraulic noise" data collected and conduct further testing to determine whether, as an interim measure, the operating set point can be increased above the 850 psig.plus head correction
~ value, and still provide some reasonable operating margin to ovoid' spurious trips.
(Letter to Mr. A. Giambusso from Mr. D. A. Ross, dated December 24, 1973.)
It should be noted that the sensors have not been recalibrated to-take into consideration the head correction ~
I factor as of this time.
In making this decision, consideration was given to the test data already collected and the very minimal adverse safety significance of a.9-10 psiclower than required set pressure.
2.
To insure the avoidance of spurious trips, pursue an investigation into' the basis for the steam line low pressure setting of 850 psig and develop = a Technical Specification change to lower the ' set point if results of~ transient analyses indicate this possibility.
3.
Evaluate vendor recommendations as soon as they are available to possibly reduce or eliminate the sensor set point drift problem.
(Letter to Mr. A. Giambusso from Mr. D. A. Ross, dated December 24, L
1973.)
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- Failure Data:K
. 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
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m ADDENDUM TO ABNORMAL OCCURRENCE REPORT NO. 50-219/74/1 On Thursday, January 10, 1974, prior to recalibrating the low pressure cain steam line sensors to take the head correction factor into account, a j
surveillance check was again performed on these sensors.
In addition, set point repeatability of the' sensors was also checked by observing two con.secutive trip points on the test. The following results were obtained:
Final "As Left" Test #1 Test #2 Test #3 Set Point RE23A 832 840 860 860 RE23B 845 840 RE23C 855 875 875 860 860 RE23D 845 845
. Upon reviewing the re< ults of this surveillance check on Friday, January 11, 1974, it was decided to perform the check again for repeatability. The "as found" set points of this calibration check yielded the following results:
Before Calibration Test #1 Test #2 After Calibration RE23A 862 862 860 860 860 860 RE23B RE23C 860 860 860 RE23D 850 851 860 4
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