ML18059B184

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LER 94-008-01:on 940329,30 & 0409,discovered That Some Class 1E Circuits Not Isolated or Separated from non-Class 1E Circuits Due to Lack of Engineering Design Guides.Subj Deviations Corrected W/Exception of CETs.W/940829 Ltr
ML18059B184
Person / Time
Site: Palisades Entergy icon.png
Issue date: 08/29/1994
From: Gire P, Rogers D
CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-94-008, LER-94-8, NUDOCS 9409130421
Download: ML18059B184 (9)
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Text

David W. Rogers c Plant Safety and Licensing Director l'OWERINli 11/llCHlliAN"S l'ROliRESS Palisades Nuclear Plant: 27780 Blue Star Memorial Highway, Covert, Mi 49043 August 29, 1994 Nuclear Regulatory Commission Document ~ontrol Desk Washington, D. C. 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT-LICENSEE EVENT REPORT 94-00S-~OI - LACK OF SEPARATION OR ISOLATION BETWEEN IE AND NON-IE CIRCUITS - SUPPLEMENTAL REPORT Licensee Event Report (LER) 94~008~0I is attached. ~This supplement addresses four discrepancies_ first reported April 28, I994 ana eight *others found--*as a result of ongoing investigations. These discrepancies are reportable in accorijance with IOCFR50.73(~)(2)(ii)(B) as conditioris outside the design basi~

of the plant.

  • David W. Rogers Plant Safety and Licensing Director CC Administrator, Region III, USNRC NRC Resident Inspectbr ~ P~lisades Attachment Jr: ... (,,,*.* (). .

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A CM5 ENE'RGY COMPANY

NRC Form 366 .

19*83)

  • -LICENSEE EVENT REPORT (LERI

.e* U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB N0."3160*

0104.

  • EXPIRES: 8/31/B6 FACILITY NAME 111 DOCKET.NUMBER 121 PAGE 131 Palisades Plant o 5 o o o 2 s 5 OF Q 8 T1TLE14_1 LACK OF SEPARATION OR ISOLATION BETWEEN.1E AND NON-1E CIRCUITS -

SUPPLEMENTAL REPORT EVENT DATE (61 REPORT DATE 161 OTHER FACILITIES INVOLVED (Bl REVISION FACILITY NAMES MONTH DAY YEAR YEAR NUMBER MONTH DAY YEAR N/A o 5 o o o*

0 3 2 9 9 4 9 4 0 0 8 0 1 082994 N/A 0 6 0 0 0 THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §:(Check one or more oUhe followingl 1111 OPERATING N 1--..-2-o.-40_2_1b1----------.......--.----------------.......--.-----------------..--......-1-3.-11~1b-1------------1 MOOE 191

. 20.4061*111 Iii) 73.71 lei 20.4061*111 !Iii) OTHER !Specify in Abstract 20.406!0111 lliii) below ft:t in.Text, 20.4061*111 llivl . NRC Form 366AJ 20.4061*111J(v) 60.731*11211iii) 50.731*ll211xr

. LICENSEE CONTACT FOR THIS LER 1121 NAME

  • TELEPHONE NUMBER

'** AREA CODE Paul J. Gire, Staff Licensing Engineer 6 7 6 4 8 9 MANUFAC* REPORTABLE MANUFAC* REPORTABLE CAUSE SYSTEM COMPONENT TUR ER TO NPROS CAUSE SYSTEM COMPONENT TUR ER TO NPRDS SUPPL EM ENT Al REPORT EXPECTED 114 l *

  • MONTH DAY YEAR EXPECTED SUBMISSIO N

YES Uf yes, complete EXPECTED SUBMISSION DA TE'i NO DATE 116)

ABSTRACT (Umit to 1400 $paces, i.e., approximeto/y fifteen llingltt-space rype.;,ritten lines) (16)

Between March 29, and May 3, 1994, with the plant in cold shutdown, twelve discrepancies were identified where Class 1 E and non-Class 1E equipment was not isolated or separated as .

required by the Palisades FSAR and IEEE 279 - 1971. These discrepancies are reportable as required by 10CFR~O. 73 (a)(2)(ii)(B) as conditions which were outside the plant's design basis.

      • * -~:,Causes tor ~he devi.ations from sep_aration or is~lation ~riteria include inadeguate design ;reviews:;:

and design 1nstallat1on controls utilized at the time of either plant construction or subsequent

  • modifications in the 1980's that added cabling or additional control circuits to the plant.

, ....,....Eleven of the twelve discrepancies have been corrected. The twelfth will remain in pl~ce: under~~

. -* an NRC approved deviation until the 1995 refueling outage. Longer term corrective actions

-j--

include full utilization of the recently enhanced moaification review process, providing training to design reviewers regarding specific separa~ion or isolation modification _guidelines previously developed, and developing accurate schematics for affected systems. This report addresses all of the plant's discoveries made as a result of a review of isolation and separation issues.

  • NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION 19-831 APPROVED OMB NO. 3150-0104 EXPIRES: 8/31/85 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME Ill DOCKET.NUMBER 121 LEA NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant 0 5 0 0 0 2 5 5 9 4 - 0 .o 8 - 0 0 2 OF 0 8 Event Descriotion:

On March 29 and 30, and April 9, 1994, with the plant in cold shutdown, it was discovered that some Class 1E (safety-related) circuits were not isolated or separated from non-Class 1E circuits. Requirements for electrical independence arid isolation are defined in the Palisades FSAR, Chapters 7 and 8, which commit to IEEE 279-1971. These require that non-Class 1E circuits be isolated from Class 1E circuits so that a fault in a non-Class 1E circuit would not affect the Class 1E circuit.

  • Four discrepancies were identified involving isolation or separation of circuits for the Reactor Protection System (RPS), Engineered Safety Feature.s (ESF), and on the Subcooled Margin Monitor (SMM). Subsequently, it was discovered*that additional Class 1E (safety-related) circuits were not isolated from non:--Class 1E circuits. The plant was in cold shutdown at the time of discovery of all.the deficiencies. The following discrepancies were
  • noted:

Low Temperature Overoressure Protection: The first discovery on March 29, -1994, .. involved a .

lack of isolation between Class 1E Primary Coolant System (PCS) temrerature transmitters that provide inputs to the Reactor Protection System (RPS) via the Therma Margin Monitor (TMM)

  • and the Class .1 E Low Temperature Overpressure Protection (LTOP) system. These circuits were not isolated from non-Class 1E PCS temperature indicators used for plant control. The .

LTOP is considered to have been outside the requir~d isolation design basis since its installation I in 1989. . * * . . * **

  • Thermal Margin Monitor: Also on March 29, it was found that four channel circuit independence was not provided between the-safety related "upper" and "lower" nuclear power range signals-nor between the safety related TMM circuits. Redundant channels in both the nuclear power ran~e indication system and the TMM systems are routed through the same raceway. In addition, each of these systems is connected to both the non-Class 1E Critical Function Monitorin9 System (CFMS) and plant data logger without adequate circuit Class 1E to non-Class 1E iso.lat1on. *An analysis of the effects of both discoveries lead to *the conclusion

. that the TMM had been outside the plant's separation and.isolation design basis since the TMM was installed in 1988.. . * * . * . .

Inverter Power Cables: As a result of ongoing drawing reviews and physical walkdowns of systems, another discrepancy was identified on March 30, 1994. The power cables from inverters to RPS and ESF instrument loops were not se.Parated in accordance with Palisades design basis cable separation criteria. Cables for "right channel inverters Y20 and Y40 were routed together in the same cable tray, as were cables for "left" channel inverters Y10'and ** **

Y30. This condition had existed since original plant construction. .

Subcooled Margin Monitors: On April 9, in the course of further examinations prompted by the previous discoveries, plant personnel identified that power feeds to the Class 1E Subcooled Margin Monitors (SMMs) were not isolated from power feeds to non-Class 1E devices. The SMMs had been installed in 1980 to meet requirements of NUREG 0737 Item 11.F.2. One requirement was that primary and backup display channels should be electrically independent,*

~~~E~ied from Class 1 E sources, and physically separated from other devices per Reg Guide

NRC Form 388A 19*831

  • .*"* U.S. NUCLEAR REGULATORY COMMISSION
  • APPROVED OMS NO. 3160*

0104 EXPIRES:. 8/31 /86 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME l 11 DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant 0500025594-008 -o 0 3 OF 0 8 Reactor Protection System: On April 17, 1994, it was found that there was no isolation between Reactor Protection System (RPS) "B" channel and a 120-volt standard power outlet installed in the same cabinet. Both are supplied by the same breaker. The RPS channel is Class 1E while the outlet, which may be used for any purpose, is not restricted to class 1E loads.

This condition had existed since original plant construction.

Auxiliary Feedwater: Class 1E Auxiliary Feedwater (AFW) -flow control and indication circuits and non-Class 1E Main .Feedwater (MFW) recirculation control circuits were found*on April 17, 1994, unisolated. Circuits were protected by the same fuses. This condition resulted from modifications in 1982 and 1.984. * * , * . .~ . *

  • Condensate Storage Tank Level: One of the two Class 1E Condensate Storage Tank (CST) level indication circuits was found April 19, 1994, to be protected by the same fuse as the non-Class 1E diesel fuel oil tank level circuit and the non-Class 1E engineered safeguards room cooler temperature instrument circuit. This condition appears to have resulted from a modification

. made in 1981 or was left in place from original plant construction.

  • connection from a breaker used for the Reactor Protection System (RPS) temperature protection and Thermal- Margin Monitor (TMM), both Class 1 E, was also used for the non-Class 1E audible count rate drawer. This discrepancy was identified on April 20, 1994. This condition appears to have resulted from modifications made jn 1980 or 1988, or:.~ was left in place from original plant construction. * * * * .* * . . .
  • Inverter output: On April 22, 1994, it was* found that Class 1E breakers are used as isolation devices between Cle1ss 1E and non-Class 1E circuits on all four of the plant's safety related

.. inverters. The impact of a short circuit on any one of the non-Class 1E circuits isolated by

. these breakers could reduce output voltage on all four inverters below the manufacturer's * *

  • design amount. This could result in an extended trip time of the breaker, allowing a reduced voltaae to feed the Class lE loads until the breakers tripped. This condition resufted from a combination of original plant construction and modifications made in 1984. **

Core Exit Thermocouoles: On April 27, 1994, it was found that there was no isolation device separating the 16 Class 1E qualified Core Exit Thermocouples (CETs) to the hon-Class* 1E

~>rimary data logger computer. The plant had initially committed to removing the 16 qualified CETs from the primary data logger. A request for a deviation from that previous commitment was made to the Commission on May 20, 1994, and was subsequently approved by the'NRC * **.**'*

on June 1, 1994. The CETs were connected to the Primary Data Logg~r as part of a modification in 1988. *

-..* M r in M ni or I ola ors: On April 28, 1994, the plant identified that Primary *

..

  • oolant ystem Instrumentation Class 1E isolators were not fully qualified in accordance with Reg. Guide 1.97 and Re9. Guide 1. 75 because they were-not tested to demonstrate acceptable isolation from output to input. The instrumentation affected included hot and cold leg
  • temperature indicator channels, four channels of the Thermal Margin Monitors (TMM), two
  • channels of the Low Temperature Overpressure Protection system (LTOP), two SMMs and two recorders. This condition appears to have *resulted from modifications made in 1980 and 1988.

NRC Form 388A

. *-19-831

  • U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3160*

0104 EXPIRES: B/31 /86 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME 111 DOCKET NUMBER 121

  • LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant 0 I5 I0 I0 I0 I2 I5 I5 9 14 - 0* 01 I8 - 0 I1 0 I4 OF 0 I8 Main Steam Isolation Valves: On May 3, 1994, ongoing reviews identified that the Class 1E main steam isolation valve solenoids were not electricalfy isolated from non-Class 1E equipment.

Non-Class 1E equipment powered from the same fuse as Class 1E equipment included main feedwater block solenoid valves, atmospheric steam dump solenoid valves, turbine bypass solenoid valves and a non-safety related solenoid valve associated with the auxiliary feedwater pump steam supply. This condition had existed since original plant construction.

  • For each isolation or separation deficiency identified above, operability determinations were made and the appropriate equipment was declared inoperable. Those cases which required resolution
  • prior to startup from the maintenance outage were identified and corrected. Because each I condition iden~ified to date showed ~.he plant outside its design basis, they are reportable in accordance with 10CFR50.73(a)(2)(11)(8). * * . .

Cause Of The Event:

For al! of the .discrepancies ad~res.sed in this reP.~rt an inad.equate or jncomplete revie.w of*. *

. electrical. design allowed the c1rcu1ts to be mod1f1ed or left in place without adequate 1solat1on or separation. A contributor to the problem was a lack of engineering design guides identifying standards; methods, and examples that are needed to achieve isolation or separation. A second contributor was a lack of composite schematic diagrams for use by engineering.

Analvsis of the Event* and Safety Significance Low Temperature Overoressure Protection: This discrepancy involved a lack of electrical isolation between Class 1 E and non-Class 1E temperature monitoring circuits. In two cases, a single .fuse was utilized to power non-Class 1E temperature monitoring instrumentation as well as Class 1E temperature monitoring loops' which provide input to the Reactor Protection System (RPS) and low temperature overpressure protection (LTOP). The fuse also provided power to the Thermal Margin Monitor (TMM) which provides input signals to the RPS for variable low pressure and high power trips .. A fault in the non-Class 1E temperature monitoring instrumentation could have caused the fuses to blow, resulting in a loss of Class 1E functions. This fault would have been immediately apparent to the operators as a loss o~ power to the TMM would result in generation

  • Faults resulting in blowing fuses Would also affect the LTOP_ system. Loss of the temperature input would cause the LTOP to alarm, however, the low temperature input to the system .would .*

als.o result in generation of a signal to open the primary coolant system (PCS) power opera~ed relief valves (PORV). An alarm would be generated to alert the operator to the PORV opening.

During power operations, opening of a PORV would not be of any consequence as the PORV block valves are normally closed. Opening of a PORV during reduced temperature operations would result in a pressure reduction in the PCS. The operator could terminate this pressure reduction by closing the PORV block valves.

Thermal Margin Monitor: This discrepancy involved a lack of four channel cable separation for cables connected to the input of the TMMs. All four channels of upper and lower nuclear power inputs to the TMM were routed to remote data processors through a single cable. The upper and lower nuclear power signals are used in the TMM to aenerate an axial shape imbalance (ASI) signal. This ASI signal is then used to generate a variable PCS low pressure trip setpoint for

NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION (8-831 . APPROVED OM8 NO. 3160*

0104 EXPIRES: 8/31/86 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME (11 DOCKET NUMBER 121 LER NUMBER 131 PAGE (41 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant 0 5 0 0 0 2 5 5 9 4 - 00 8 - 0 0 5 OF 0 8 input into the RPS. Failure in the common cable carrying signals for all four channels.would have .

resulted in erroneous calculation of ASI and generation of an incorrect low pressure trip setpoint.

The TMM however, also generates a constant minimum low pressure trip value and selects the higher of the ASI biased v~lue or the minimum value. Therefore faults in the cable would have resulted in a default to the constant low pressure trip setpoint and not a complete loss of low pressure trip capability. -

Inverter Cable Separation: This deficiency, identified on March 30, 1994, involved a lack of power cable separation from inverters to RPS and ESF instrument loops. Cables for the "right" and "left" channels were installed in the same cable trays rather than separated. .

The RPS is designed as a deenergize-to-trip system. Postulated failures of the cables (short, open or ground) sharing a common raceway would have resulted in a loss of power to the system. This loss of power would deenerg1ze the associated RPS channel resulting in the one ..

channel failing to a trip condition. If both cables faulted, the two out of four trip logic of the RPS, would have been s~tisfied, resulting in a reactor trip. ..

The ESF detection circuits are designed deenergize to act~ate whereas the actuation circuits (two .

  • out of four logic) are designed energize to actuate. Postulated failures of the cables (short, operi .

or ground) sharing a common raceway vyould result in a loss of*power to.the system. If both cables faulted, two of the four detection relays would drop out, providing inputs to both "left"

- and "right" channel actuation circuits. As one of the faulted cables also powers one channel of actuation circuits, only one channel of required safeguards equipment would have been actuatep.

Subcooled Margin Monitors: On April 9, 1994, the Subcooled Margin Monitors (SMM) were

  • declared inoperable when it was found that this Class 1E system was powered from the same fuse as the non-Class 1 E feedwater control solenoid valves. Loss of the SMM would be obvious j to the operator as the digital display would be dark. In a case where both SMMs are lost, plant
  • procedures require that the operator manually calculate subcooling margin using pressure and

. temperature curves o_r steam tables. . . * .. . * * *. .

Reactor Protection S~stem: This deficiency involved a 120-volt AC outlet being connected to .

one channel of the R S without adequate electrical isolation. A fault in equipment connected to the 120-volt power outlet could have resulted in losing *power to one channel of the RPS. Each

  • of the four RPS channels is designed to trip on loss of power. This fault could have resulted in

. tripping one-channel, leaving the RPS in a one out of three tripping scheme. As the 120-volt

  • *outlet was only connected to one channel of the RPS, this lack of isolation is not considered,to **..<

. . : ,.be safety significant. . * . ..

Auxiliary Feedwater: This discrepancy involves a lack of electrical isolation between non-Class 1E instrumentation in the main feedwater system and Class 1E auxiliary feedwater instrumentation. -

For the "Left" channel circuitry, a fault in the non-Class 1E components would result in a loss of 1 of 2 auctioneered DC power supplies which provide auxiliary feedwater flow control and

  • indication. The remaining auctioneered power supply would remain available and auxiliary feedwater control and indication would not be affected. Two backup redundant AFW flow

.' ~<:)*

. .., . NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION

.

  • 1&-83) APPROVED OMB NO. 3160*

0104 EXPIRES: 8/31/86 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME 11 l DOCKET NUMBER 12) LER NUMBER 131 PAGE 14)

SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant 0500025594-008-0 0 6 OF 0 8 indicators (one per steam generator) would, however, lose power and be unavailable. Forthe "Right" .channel circuitry, *a fault in the non-Class 1E components would result in a loss of flow control and indication to both steam generators. The flow control valves in this train of AFW would fail open assuring that a supply of feedwater was available for removing heat from the steam generators in the event that AFW co<;>ling was req~ired. The operator would rely on steam generator level to control AFW flow by cycling the AFW pumps as necessary.

Condensate Storage Tank Level: This discrepancy involves a lack of electrical .isolation between non-Class 1E instrumentation and Class 1E condensate storage tank level instrumentation. A fault in either of the two non-Class 1E indication loops could result in a loss of tank level

  • monitoring loop LT-2021. A redundant tank level monitoring loop, LT-2022~ would have .been .

available to provide control room operators with an indication of Condensate Storage Tank level.

Reactor Protection System Tem~erature Protection and Thermal Margin Monitor: This * *

  • discrepancy involves a .lack of e ectrical isolation between the non-Class 1E source range audible countrate amplifier and Class 1E temperature monitoring equipment. A fault in the no*n..:c1ass 1E audible count rate drawer could cause a loss of the Class 1E RPS temperature protection cha~nel "D". This would result in the los.s of th~t channel's inputs to the Subcoole~ Margin_ ..

Monitors (SMMs) and one channel of Variable High Power (VHP) and-Thermal Margin/Low .

Pressure (TM/LP) trips. With the loss of the "D" channel inputs to the SMMs the operator would receive an annunciator alarm. However, the SMM would continue to function using redundant

.temperature inputs from other sources. The loss of the "D" channel of TM/LPNHP trips would also be alarmed in the control room, "D" channel could be placed in the bypass condition, and

  • the resultant two out of three tripf?ing logic would be used. It has been concluded that, .even .. ,.

with the fault, the (RPS) would still have been capable of performing its safety function. .

  • Inverter output: Class 1E inverter output breakers were used as isolation devices between Class 1E and non:--Class 1E circuits on all four 120 vac preferred power inverters. Due to the current limiting nature of inverters, short circuits on the non-Class 1E loads have the potential to reduce voltage below the manufacturer's minimum requirements for the equipment being fed from the .

inverters for a period of between 8 and 25 seconds. A short circuit on one of the unfused non:..

Class 1E inverters would result in a trip of one channel of the reactor protection system .. The remaining three inverters would remain available to power vital instrumentation. The affected inverter's output voltage would recover in 8 to 25 seconds. . * *.

  • Core Exit Thermocouples: Palisades has 16 core exit thermocouples (CETs) which provide .

operators information on primary coolant conditions during accident conditions. These .CETs . .. *. *

  • -were found connected to a non-Class 1E data logger computer. A fault on the non-Class"1 E *data .. *
  • logger computer could potentially render all of these thermocouples inoperable. Although it is
  • considered unlikely that a single fault would affect all .16 circuits, other temperature indications including hot and cold leg temperatures would still have been available. These temperature indicators in conjunction with the reactor vessel level monitors and SMMs would provide the operator with sufficient information to monitor for potential inadequate core cooling. The plant

. requested, and received approval for, a temporary deviation from the commitment to remove the ***"' *

  • 16 CETs from the data logger on June 1, 1994. The CETs will, however, be disconnected from

..the non-class 1E datalogger during the 1995 refueling outage. * * *

. ., . .,r---------------'I NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION.19-831 APPROVEO OMS NO. 3160-0104

~PIRES: 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 0 5 0 0 0 2 5 5 9. 4 - 0 0 8 -C 0 0 7 OF 0 8

  • Subcooled Marcin Monitor Isolators: This discrepancy involved electrical signal isolators in the
  • primary.. coolant system temperature monitoring loops. No documentation was available for these isolators demonstrating their ability to prevent a fault on the output side of the device.

from degrading below an acceptable level for the circuit connected to the device input. These isolators are used for two applications. First is isolation of two temperature channels which feed the SMMs. An electrical fault in one of these channels or the SMM could result in a reactor trip if- two of the High Power trips or two of the TM/LP trips were actuated. In the event the reactor" did not trip because of erroneous indication, the control room would have quickly noted the problem given the high visibility of the Var*iable High Power Trip instrumentation. The second

  • application of these isolators is to isolate non-class 1E instrumentation used for reactor control.

A fault in control circuitry could propagate to the safety channelcircuitry.<One channel of the

  • instrumentation would be disabled. A reactor trip could riot result but any temperature error would be quickly noted due to the high visibility of the instrumentation in the control room.

Although no qualification tests were available for these electricaf isolators, they are similar in design to other isolators (transformer coupled) which have been successfully qualified. It is believed that if these isolators had been tested they would have been shown to be. acceptable for their application. * * *

.* *:Main Steam lsol~tion Val'(es: This discrepancy involv~s a lack-of'electrical isolation between
  • the Class 1E main steam 1solat1on valve (MSIV) actuation solenoid valves and non-Class 1 E
  • equipment including the atmospheric dump valve and turbine bypass valve control circuitry. A fault in the non-Class 1 E circuitry could have resulted in blowing fuses. which provide power to
  • the MSIV solenoids. These solenoids are energize to actuate and operate valves to remove air .

from the MSIV operators to allow them to close. There are two redundant MSIV isolation .

control circuits and each of those circuits provides output signals to close both valves. Thus, *

  • even if the fuses were blown in one of the circuits, the redundant circuit would have remained -

available to actuate both MSIVs if required. The control povver schemes for the MSIVs contain power available lights located in the control room. Had the MSIV fuses blown, the .control. .

  • power lights woufd have extinguished.
  • This would have been noted by the control room operators during their routine rounds in the control room. . * .*.

Corrective Actions:

To provide higher quality designs, a number of enhancements to the plant's design change program have taken place in recent years. In the early .1990s, modification procedures*were revised to more clearly identify separation and isolation requirements. By 1993, engineering guidelines had been developed to identify specific approaches to implementing effectiv.e_channel .

separation and Class 1 E to non-Class 1 E isolation in the field. These guidelines are now * . **-

'**' referenced in the plant modification procedures. . .

  • . Prior to 1994 the plant's modification process was revised to require a multi-disciplinary group

-.-'. * , review of all safety-related design changes just prior to their release for installation. _*

NRC Form 366A . U.S. NUCLEAR REGULATORY COMMISSION 19-83) APPROVED OMB NO. 3160-0104

    • LICENSEE EVENT REPORT (LERI TEXT CONTINUATION EXPIRES: 8/31 /86 FACILITY NAME 11 l DOCKET NUMBER 12) LER NUMBER 131 PAGE 14)

SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant Q 5 Q Q Q 2 5 5 9 4 - Q Q 8 - Q 1* Q 8 . OF Q 8 During the recent maintenance outage an overall review of channel separation and Class lE-10 ...

non-Class 1E isolation was conducted; As part of this review, composite connection.diagrams for preferred AC power circuits were developed .. Prior to startup from that outage, all identified separation and isolation deviations were corrected with the exception of the Core Exit Thermocouples which will be corrected during the 1995 refueling outage. A request for .a

  • deviation to allow the CETs to remain in place was granted by the NRC on June 1, 1994.

Training of plant personnel regarding the Class 1 E to non-Class 1 E isolation and associated design guidelines and bases will be conducted as part of technical staff training.

Previous Occurrences:

LER 94-008.

LER 93-006 Jj,***.

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