ML18059A540
| ML18059A540 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 11/24/1993 |
| From: | Roberts W, Slade G CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| LER-93-008, LER-93-8, NUDOCS 9312070323 | |
| Download: ML18059A540 (13) | |
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GB Slade General Manager Palisades Nuclear Plant: 27780 Slue Star Memorial Highway, Covert. Ml 49043 November 24, 1993 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT - LICENSEE EVENT REPORT 93-008-01, INOPERABLE SAFEGUARDS ROOM COOLERS RESULTING FROM IMPROPER THERMAL OVERLOAD PROTECTION DESIGN - SUPPLEMENTAL REPORT Licensee Event Report (LER) 93-008-01, Supplement 1 is attached. This event was originally reported to the NRC in accordance with 10 CFR 50.73(a)(2)(ii).
No further updates to this LER are expected.
Gerald B Slade General Manager CC Administrator, Region Ill, USNRC NRC Resident Inspector - Palisades Attachment 9312070323 931124 PDR ADOCK 05000255 S PDR A CMS NE'RGY COMPANY
NRC Fa<m 388 U.S. NUCLEAR REGULATORY COMMISSION 19-831 APPROVED OMB NO. 3160-0104 EXPIRES: B/31/86 LICENSEE EVENT REPORT (LERI FACILITY NAME 111 DOCKET NUMBER 121 PAGE 131 Palisades Plant I I I I I I I o 5 o o o 2 5 5 1 I OF 1 Io TITLE 141 INOPERABLE SAFEGUARDS ROOM COOLERS RESULTING FROM IMPROPER THERMAL OVERLOAD PRO'T'Fr.'T' *nN nFc; Tr.N EVENT DATE 161 LER NUMBER 1111 REPORT DATE 181 OTHER FACILITIES INVOLVED 181 SEQUENTIAL REVISION FACILITY NAMES MONTH DAY YEAR YEAR I. NUMBER NUMBER MONTH DAY YEAR N/A 0161010101 I
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-- 60. 7 31ol1211viiillAI 60.7 31oll211viiil!BI 60.731*11211*1 beilow end in Text, NRC Form 388AI LICENSEE CONTACT FOR THIS LER 1121 NAME TELEPHONE NUMBER William L. Roberts, Staff Licensing Engineer sARIEA1cl°~ I 1 I s I 4 I -I aI s I , I 3 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT 1131 MANUFAC* REPORTABLE MANUFAC- REPORTABLE CAUSE SYSTEM COMPONENT TUR ER TO NPRDS CAUSE SYSTEM COMPONENT TUR ER TO NPRDS I I I I I I I ****.**..* >' I I I I I I I
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I I I I I I I .*. *.*. . I I I I I I I SUPPLEMENTAL REPORT EXPECTED 1141 MONTH DAY YEAR h-i EXPEC°TED SUBMISSION I YES Vf YH* * ,,,,.,... EXPECTED SUBMISSION DATE! NO DATE 1161 I I I ABSTRACT UJmit"' 1400-*** i.e., ._;,,,.r.1y fiftHn aing*-* typewritten lineal 1181 On August 24, 1993, at approiimately 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br />, with the plant in cold shutdown following refueling,.a technical specifications surveillance test was being performed on the engineered safeguards room cooling and ventilation system. During performance of the test, the V-270 safeguards room cooling fan motor failed to start. Investigation found that the contactor for the fan motor had tripped on thermal overload. Further investigation revealed that a recent reduction in the thermal overload protection may not have allowed continuous operation of all the engineered safeguards room cooling fans, causing both trains of *engineered safety features to be considered inoperable.
The cause of this event is attributable to inadequate design control and post maintenance testing.
Corrective actions include the following: reanalyzing, revising, and testing the fan motor thermal overload settings to provide operability margin; reviewing all thermal overload setting changes made in 1993 to .ensure that appropriate post maintenance testing was performed; forming a multi-disciplinary *group to review the event and evaluate corrective actions; and stopping further protection device setting changes until the multi-disciplinary group reviews are complete.
NRC Form 38' U.S. NUCLEAR REGULATORY COMMISSION 19-831 APPROVED OMB NO. 3150-0104 EXPIRES: 8/31186 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FA' DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER PALISADES PLANT 0500025593 0 8 Q 1 Q 2 OF 1 Q EVENT DESCRIPTION On August 24, 1993, at approximately 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br />, with the plant in cold shutdown following refueling, the operations staff was in the process of performing the technical specification surveillance procedure Q0-30, "Engineered Safeguards Room Cooling and Ventilation System." During performance of the test, the engineered safeguards room cooler fan V-27D [BP;MO] failed to start. Investigation found that the contactor for the fan motor had tripped on thermal overload.
Earlier, on August 19, 1993, engineered safeguards room cooler fan V-27C had failed to start during a similar test. At that time the operators found the thermal overloads for the motor contactor had tripped, they reset the overload heater, and started the fan.
The fan ran only a few minutes then tripped again on thermal overload. At this point, V-27C was declared inoperable and a corrective action document initiated. Initial investigation of this event centered on locating the cause for the tripping of the thermal overload heater associated with the V-27C fan. At that time the evaluation for the potential of a common mode failure of all the engineered safeguards room cooler fans had not yet been completed.
Later, on August 24, 1993 when it was realized that the V-27D fan failed in a similar manner, the common mode failure was apparent and all four of the engineered safeguards room cooling fans were declared inoperable. The existing plant conditions did not require these fans to be operable.
Two engineered safeguards room cooler fans (V-27C and V-27D) failed to operate due to tripped thermal overloads and all four engineered safeguards room cooler fans had the same thermal overload settings. Therefore, it was conservatively determined that the four engineered safeguards room cooler fans (V-27A, 8, C, and D) may not have continuously operated if required. Conservatively all four engineered safeguards room cooler fans and their two associated coolers (VHX-27A and B) were declared inoperable.
With inoperable room coolers, equipment in the safeguards rooms is also considered inoperable.
When the common mode nature of this event was .realized, one of the immediate actions taken was to measure the running load amperage (RLA) for all four engineered safeguard fan motors. The data taken on August 23, 1993, showed variations in RLA between 22.4 and 24.2 amps. Based on these values, the overload heaters were re-specified by System Protection Engineering from the installed Cutler-Hammer Hl043(C) having a trip range(!) of 24.0 to 21.6 amps to an Hl044(C) having a trip range(!) of 27.3 to 24.6 amps (Figure 1). The Hl044(C) overload heaters were then installed in each fan motor's control circuitry. The fans were run on August 25, 1993 to verify their operability.
(l}"Trip range" represents a range of possible trip points acknowledging the accuracy of the heater. The range is defined by the expected trip point, and e.
NRC Fc><m 388A U.S. NUCLEAR REGULATORY COMMISSION 19*831 APPROVED OMB NO. 3160-0104 EXPIRES: 8/31196 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION
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FACILITY NAME 11) DOCKET NUMBER 12) LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER PALISADES PLANT q o 1s* _ oI i qJ OF Upon further engineering review, calculations were completed on October 25, 1993, which showed that the thermal overload heaters should be further upgraded. The calculations showed that the thermal overload sizing should be raised and the use of an Hl046{A) heater featuring a trip range of 33.0 to 29.7 amps was then specified (Figure 1). This specification considered potential degraded grid voltage conditions, overload heater setting tolerances, a.reconfirmed shaft horsepower requirement for the fan and a new measurement of RLA taken in October 1991 ranging from 25.7 to 19.3 amps. The change assured that margin exists between the lowest possible overload trip setting for an Hl046(A) overload heater of 29.7 amps and the highest possible motor RLA of 28.9 amps.
On October 25, 1993, the Hl046(A) heaters were then installed in each motor's control circuitry using a plant modification program process. Follow-up testing for the fans verified their operability on October 27, 1993.
This event is reportable in accordance with 10 CFR 50.73{a)(2)(ii) as an un-analyzed condition that significantly compromised plant safety.
CAUSE OF THE EVENT The engineered safeguards room cooling fan motor contactors tripped on thermal overload because of insufficient margin between the overload trip point and the actual running current. Personnel specifying the thermal overload settings did not consider that the actual running current was very close to the motors' rated full load amperage.
The cause of this event was failure to verify by field measurement the actual running load amperes (RLA) carried by the engineered safeguards motors, and thereby confirming a design assumption which was used as input to the setting specification. Motors driving fans are typically sized for load to draw approximately 80% of nameplate full load amperes (FLA). Our electrical protective device setting methodology assumes that actual RLA is 80% FLA. The methodology does not call for field verification of small horsepower motor RLA as part of the setting specification design.
NRC Fann 388A U.S. NUCLEAR REGULATORY COMMISSION 19*831 APl'ROVEO OMB NO. 3160-0104 EXPIRES: 8/31186 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION
.. t-::-:=~"."'.":"'.~--------.------------,-------------.--------1 FACILITY NAME 111 DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER PALISADES PLANT 010 18 01 1 Ol 4 OF 1 I 0 ANALYSIS OF THE EVENT General Description of Equipment Engineered safeguards room fans V-27A and B and their associated cooler provide post accident cooling for the right channel east safeguards room equipment and V-27C and D and their associated cooler provide cooling for the left channel west safeguards room equipment. Each of the two engineered safeguards rooms has one cooler with two fans, with only one of the fans and the cooler required to perform the design basis function.
V27 A and C are powered from left channel motor control center number one. V27 B and D are powered from right channel motor control center number two.
One channel of safeguards equipment is located within each engineered safeguards room; a high pressure safety injection pump, a low pressure safety injection pump, containment spray pump(s), and associated electrical, instrument and control components. Since the thermal overload setting for each of the four engineered safeguards room cooler fan motor's was set at or near the motors running load amperes (RLA), it was concluded that the fans operability was not assured and that the safety related equipment in both rooms may not have been cooled by operating cooler fans after the onset of a design basis accident.
Plant Technical Specifications require that both channels of engineered safeguards equipment be operable when the reactor is critical.
History of Engineered Safeguards Room Cooler Fan Motors Overload Heater Setting In 1984 the engineered safeguards room cooling fan motors were replaced as part of an environmental qualification upgrade. The engineering specification for the motor heater size did not include a thermal overload setting reduction to acknowledge the T-frame design. Consequently, prior to May 2, 1993, the engineered safeguards room cooler fan motors were protected by Cutler-Hammer thermal overload heaters Hl044(D) featuring a trip range of 28.0 to 25.2 amps (Figure 1).
In 1986 an internal effort was initiated to establish the bases for the plant protective device settings. In 1991 that effort identified that setting criteria established in 1970-1971 for thermal overloads for T-frame motors had not been used since the late 1970's. That criteria called for: 1) a reduced setting of the thermal overload for T-frame motors which use the Cutler-Hammer No. 789 overload relay, 2) another setting I*
reduction for motors with a service factor of 1.0.
In January 1992 the thermal overload setting criteria for the reduced settings on "T-frame" motors was re-instituted. Since then, 12 thermal overload settings have been recalculated using the criteria, four of which were for the engineered safeguards room cooling fans. The remaining eight motors were non-safety related and our reviews found them to be acceptable as is.
- NRC F0<m 388A U.S. NUCLEAR REGULATORY COMMISSION 19-831 APPROVED OMB NO. 3160-0104 EXPIRES: 8/31186 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME l1J DOCKET NUMBER 12) LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER PALISADES PLANT 0500025593 0 Q 8 - Q 1 Q 5 OF 1 Q Specifically the following steps were given in the redefined January 1992 relay setting criteria to determine the heater sizing for the overload relays.
- 1. Using the motor full load ampere (FLA) rating and the NEMA motor starter size, an overload heater size and position was selected from Cutler-Hammer publication 12484: Since the V-27 motors have a FLA of 24.5 and the NEMA size 2 motor starter, the selected overload heater was size Hl045(C).
- 2. Since the motors service factor was 1.0, the overload heater selected in 1 above was reduced one size to Hl044(C).
- 3. Since the motors were of T-frame construction and use the No. 789 overload relay, the overload heater size was reduced one more size to Hl043(C) featuring a trip range of 24.0 to 21.6 amps.
On May 2, 1993, while the plant was down for a short outage, Hl043(C) heaters as specified by the above criteria, were installed in all four engineered safeguards room cooling fans and tested satisfactorily.
While the above criteria protected against motor failure, it did not consider all operating conditions and thus lead to insufficient margin between running current and thermal overload current.
The methodology also did not call for field verification of small horsepower motor RLA as part of the setting specification design. Based on this assumption, our System Protection Engineering group typically sets overload protection at approximately 115% to 125% FLA (for service factor = 1.0 to 1.15 motors) to provide a compromise between close motor protection and reliable motor operation. To eliminate the potential for undesired motor trips, this setting typically provides margin to account for degraded voltage conditions and overload heater setting tolerances. As evidenced by the margins observed between degraded voltage RLA and lowest possible overload heater trip setting during our review of other safety related motors, the assumption and practice employed by our System Protection Engineering group was therefore generally justified.
The engineered safeguards fan motors represent the only known configuration where the setting assumption, described above, fails. The nameplate rates the motors at 20 HP and 24.5 FLA. At these ratings, overload heater Hl045(C) would have been specified with a trip range of 30.75 (=125% FLA) to 27.7 amps. In response to recently discovered heater manufacturer's recommendations for the 1.0 motor service factor and the motor T-frame design, system protection engineering lowered the motor protection by two settings to a Hl043(C) heater with a trip range of 24.0 to 21.6 amps. The Systems Protection Engineering group was satisfied with this setting under the belief that operating margin still existed since the assumed RLA was 80% FLA or 19.6 amps. System Protection Engineering's confidence in the adequacy of these settings was also supported by the motor thermal damage curve which showed non-continuous overload capability greater than
- e ot taken field measurements to validate the RLA desi n
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- NRC F0<m 388A U.S. NUCLEAR REGULATORY COMMISSION j
18*831 APPROVED OMB NO. 3160-0104 EXPIRES: 8/31 /86 LICENSEE EVENT REPORT ILER) TEXT CONTINUATION FACILITY NAME 111 DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER PALISADES PLANT o I5 Io IoIo I2 I5 I5 e 13 - o 10 1s Q 16 OF assumption, the System Protection Engineering group did not realize that actual RLA varies between 25.7 amps (105% FLA) and 19.3 amps. As a result, thermal overload trips of the engineered safeguards motors occurred.
As indicated by the RLA slightly above FLA, the motors in this case were matched to the load, from a nameplat~ perspective. In reality, the motors are more rugged than is implied by the nameplate. To environmentally qualify the motors used in our engineered safeguards cooling application, the vendor installed a stronger insulation system (Class H instead of the typical Class B). This motor has since been shown by the designer to be capable of carrying a 10% overload continuously for 40 years. The thermal damage curves provided by the manufacturer did not represent this additional motor capacity. A recent analysis shows the maximum fan shaft horsepower carried by the motor to be 21.8 BHP which is less than the 22 HP continuous rating recently established by the motor designer. At 21.8 BHP, the motor will draw 26.7 amps at 100% voltage and 29.7 amps at 90% voltage. In the end, engineering specified and installed an Hl046(A) heater with a trip range of 33.0 to 29.7 amps.
An independent analysis of the fan shaft horsepower load was commissioned to determine if the motors were overloaded. The analysis concluded that under normal conditions maximum shaft load is 21.8 BHP, the shaft load under accident conditions would be slightly less. The motor designer provided an analysis confirming that although the motor nameplate indicated 20 HP, the motor has a stronger insulation system due to their environmental qualification. The motor designer concluded that the motor is capable of providing a 22 HP continuous output over a 40 year period.
Operability Determination Recognizing the need to perform, as close as possible, an as found test of the right channel east safeguards room cooling fan motors, the V-27 A and B fans were test run on September 22, 1993 with the heater overload setting that existed prior to August 19, 1993. V-27A ran for 2-2 1/2 hours. V-27B ran for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, when it was manually stopped, indicating that it could have run continuously. However this test did not use the original installed thermal overload heaters and as such is not an absolute proof test. By existing analysis only one fan is required for a cooler to perform its design function of providing cooling for an engineered safeguards room.
Initially we believed that we had incorrect thermal overload settings that were in place from May 2, 1993 until replacement in August 1993. The equipment would have only required to be operable while the reactor was critical which would have been from May 16 through June 5, 1993. Analyses to evaluate the potential effect on the safeguards equipment assuming the safeguards room cooling fans failed to function during a postulated accident condition due to actuation of a Hl043(C) heater is discussed in the safety significance section below.
- NRC Form 3SSA l&-831 U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3160.()104 EXPIRES: 8/31 /85 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION
- FACILITY NAME Ill DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER PALISADES PLANT o I s I o I o I o I 2 1*s I s s I3 - o 10 1s 011 017 OF 11 0 Later, additional reviews put into question the operability of the safeguards room cooling fan motors beginning when the environmentally qualified fan motors were installed in 1984. Prior to May 2, 1993, thermal overload heater H1044(D} was used.
The operability of the room cooling fans from June 1984 till May 1993 is addressed as follows:
The calculations performed in October 1993 determined that the maximum fan horsepower requirement could cause the motor to draw as much as 26.7 amps at 100% voltage. If the voltage degraded to a point just before the 2400 V under voltage relays tripped, the running current of the fan motors could be as high as 28.9 amps. At 26.7 amps the thermal overload heater H1044(D} could actuate if the actual trip point was 5% below the expected trip point of 28 amps (Figure 1}. Therefore at 28.9 amps the heater would actuate.
The maximum fan horsepower occurs if both fans in a room are running simultaneously; and service water temperature to the room coolers is at 32°F.
This assumes that the maximum density air is moved by the fans. The fans are thermostatically controlled with the second fan starting only if the first fan does not cool the room.
The only time both fans are postulated to *be running in a po~t accident condition is when both safeguards buses are energized which is also when significant heat addition to the room slightly decreases the air density and lowers the fan horsepower. If the Service Water temperature is about 55°F or higher, the current to the motors would be less than the minimum point that the H1044(D} thermal overload heater could actuate. As the service water temperature decreases from about 55°F down to 32°F, the motor RLA gradually increases into the possible trip range of the overload heater. As such, if the Service Water temperature is 32°F, the heater would actuate if the actual trip point is 5% lower than the expected trip point.
Data taken between 1981 and 1992 indicate that the 345 KV system which feeds the transformers was at 100% voltage or higher for greater than 99.8% of the time.
Also, since 1988 the power to the class IE distribution system has been fed through an automatic tap changing transformer, ensuring that the voltage is always at 100%.
Based on the conditions needed to cause a thermal overload heater to actuate, and in consideration of the above stated voltage control results, it is highly likely that the fans would have functioned as needed to cool the Engineered Safeguards Rooms following a Design Basis Accident. However, using the maximum 10% tolerance in the heater set point, the maximum fan horsepower, and the maximum degraded voltage, it cannot be shown that the engineered safeguards room cooler fans would have been operable 100% of the time.
- I NRC Form 31111A U.S. NUCLEAR REGULATORY COMMISSION (8*831 APPROVED OMB NO. 3160-0104 EXPIRES: 8/31186 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION
- FACILITY NAME 11 J DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAL I I REVISION YEAA NUMBER NUMBER PALISADES PLANT 0 I 5 I 0. I 0 I 0 I 2 I 5 I 5 I9 I3 I - I 0 I 0 I 8 I - I 0 I 1 I 0 18 OF 11 0 Cl>
Safety Significance Analysis of the effect of the loss of the engineered safeguards room cooling fans indicate that the temperatures in the west and east safeguards rooms would continue to rise during the post accident condition following the onset of recirculation of the containment sump. The west engineered safeguards room contains the shutdown cooling heat exchanger and has the larger heat load. It takes several days for the environmental qualification temperature of the most vulnerable equipment to be affected.
The time to failure of equipment with the loss of safeguards room cooling fans would be dependent on the containment sump temperature, the room heat loss, and the heat added from the equipment operating in the rooms and the result of heat degradation on the equipment. Another factor is whether one or both trains of safeguards equipment is operable.
The preliminary analysis indicates that if only the east or west safeguards room equipment were in operation it would take several days to reach the limiting environmental qualification (EQ) temperature for the most vulnerable equipment, i.e.,
the high pressure safety injection and the containment spray pumps motors. The limiting EQ temperature does not signify component failure but only the lack of qualification testing above that temperature.
Indication of failure of a fan motor overload heater is available in both the control room and the cable spreading room. Control room indication of the motors running is via lights on the control panel. These are readily visible, however, there are no steps in the emergency operating procedures to periodically verify the motors are running. A procedure step exists to manually start the fan motors at the onset of containment sump recirculation but no follow-up prompts exist.
Action can be taken to restore the fans to operation should the overload heater be the cause of failure. Locally, the overload heaters can be reset at the breakers. If they were to intermittently or continuously trip, the heaters could be bypassed by holding in the reset button or by jumpering them electrically out of service. The motor breakers are located in the cable spreading room which is accessible following a design basis accident.
CORRECTIVE ACTION The following corrective actions have been completed:
A. The thermal overload settings for all four of the engineered safeguards room cooling fans were reanalyzed, revised, and tested.
- NRC Form 31111A 19-831 U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3160-0104 EXPIRES: 8/31186 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME 111 DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant 0500025593 0 0 8 - 0 1 0 9 OF 1 0 B. The eight other thermal overload setting changes made using the re-implemented "T-Frame" criteria ("T-frame" motors with a service factor of 1.0 using a Cutler-Hammer No. 789 relay) were reviewed. The review found that the measured equipment running current was sufficiently below the overload setting.
C. Additional thermal overload setting changes and breaker changes made during 1993 (approximately 40), other than the twelve "T-Frame" motors mentioned in corrective actions A and B above, were reviewed to ensure appropriate post maintenance testing was performed.
D. A review of all 480V safety related motors at Palisades where thermal overload heaters are applied was completed including a measurement of RLA.
Adequate operability margins were verified for each motor by comparing the RLA at reduced voltage to the ]owest possible heater trip setting. Safety related motor operated valves were not reviewed as part of this effort since the thermal overloads for these motors are wired to annunciate only; not to trip the motors.
E. To provide confidence in our setting specification methodology, a circuit protective device setting specification was requested from an independent design engineering organization for the engineered safeguards room fan motors, and for five other power circuit protection schemes installed in the plant. This independent specification for the engineered safeguards room fan motors confirmed the preference for Hl046(A) heaters. The independent specifications for the other protection schemes identified no other inadequate settings or inappropriate setting methodology.
F. Further protection device setting changes will not be made until the multi-disciplinary group reviews described below are complete and effective design control measures are implemented.
The following corrective actions are planned:
A. A multi-discipline group was formed to review this event and others involving electrical design or modification. The review evaluated additional corrective actions to be implemented. The review has been completed with the following results.
The multi-disciplinary group identified plant activities that could result in the implementation of design changes without proper design change controls. In particular, the review of maintenance, and system engineering activities found that activities had been implemented through the work order process which may be design changes. Operability determinations were perfor~ed if safety related equi~ment was affected. However, these
- NRC Form 3HA U.S. NUCLEAR REGULATORY COMMISSION 19-831 APPROVED OMB NO. 3160-0104
. I EXPIRES: 8/31186 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER PALISADES PLANT olslololol2lsls sl3 01 01 8 - 0 11 llO OF ~ 0 possible design changes occurred in less than 1% of approximately 1350 work orders reviewed. Planning for longer term actions in the area of design control compliance are ongoing.
B. Setting sheet implementation from a design control perspective was reviewed to determ1ne necessary changes. This action was completed with the following summary results.
All setting sheet changes after November 2, 1993 will be completed using the specification change procedures of the plant modification and design control process. Also effective after November 2, 1993, specification changes affecting safety related equipment or having the potential for impact on plant availability, will be submitted to a multi-disciplinary design review effort as is typically conducted for facility changes. The multi-disciplinary design review requires a dedicated design review team meeting.
The purpose of the meeting is to assure a collective understanding of design purpose, proposed configuration, and physical and functional design requirements to be verified and assures that proper verification test methods are specified for determining operability.
C. Review protective device setting methodology to determine if any other weaknesses exist and determine necessary changes. The effort will include the review of our system protection setting methodology by an experienced engineering consultant. In addition, an engineering design guidance document will be developed for specifying circuit protective device settings. The guidance document will require the incorporation of the following into the setting specification: device tolerances, degraded voltage conditions, the availability of information to the operator on protective device trip status, and field measurement of running amps.
D. Determine appropriate post maintenance testing for implementation of setting sheet changes.
E. Analyses to evaluate the potential effect on the safeguards equipment assuming the safeguards room cooling fans failed to function during a postulated accident will be completed.
ADDITIONAL INFORMATION None
FIGURE I 1C 28.0 27.3 Hl044D Hl044C 25.2 25.7 24.6
- ~:JC
] MAY 1993 21.6 MEASURED ESR COOLER MOTOR AMPERE RANGE FAN--~
19.3 ESR COOLER FAN MOTORS V27A-D ROOT CAUSE OF INADVERTANT TRIPPING 10.0
FIGURE 2 40.0 ESR COOLER FAN MOTORS V27A-D THERMAL OVERLOAD HEATER SELECTION WITH -10% TOLERANCE AND DEGRADED VOLTAGE 33.0 l046A FINAL SELECTION 30.75 29.7 l045C 24.S AMPS, 20 BHP, lOOt V
- 43C MAY 1993 121. 6