IR 05000220/1989023
| ML17056A386 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 10/23/1989 |
| From: | Anderson C, Julio Lara, Woodard C NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| Shared Package | |
| ML17056A385 | List: |
| References | |
| 50-220-89-23, NUDOCS 8911060157 | |
| Download: ML17056A386 (22) | |
Text
U.S.
NUCLEAR REGULATORY COMMISSION
REGION I
Report No.
50-220/89-23 Docket No.
50-220 License No.
OPR-63 Licensee:
Nia ara Mohawk Power Cor oration 301 Plainfield Road S racuse New York 13212 Facility Name:
Nine Mile Point Unit 1 Inspection At:
Salina Meadows Cor orate Office Inspection Conducted:
Au ust 28 Se tember
1989 Inspectors:
C H. Woodard, Reactor Engineer, PSS/EB o-2 $.9 date Approved by:
J.
F. Lara, ea tor Engineer, PSS/EB C. J.
Anderson, hief, Plant Systems Section, EB, OR o -2 date date Ins ection Summar:
Ins ection on Au ust 28
-.
Se tember
1989 Ins ection Re ort No. 50-220/89-23 d:
fl5VO df<<i i
d deficiencies including battery equalizatton voltage concerns and excessive system vol tage drops.
Results:
Six unresolved items were identified requiring 1) review of the safety evaluation of the modification to reduce the number of battery cells, 2)'review of the available voltage at the ERVs to ensure operability, 3) review of the testing of dc circuit breakers, 4) battery charging MG set corrective actions, 5) Power Board ll, 12, 16 and 17 corrective actions, and 6)
EDG 102 and 103 Vdc corrective actions.
89110601~7 89102'DR ADGCK 05000220
Details 1.0 Persons Contacted 1. 1 Nia ara Mohawk Power Cor oration NMPC G. Brownell, Regulatory Compliance
"B. Faubert, Lead Electrical Engineer
"C. Fischer, Supervisor, Electrical Maintenance G. Gresock, Manager, Nuclear Engineering
- D. Jakubowski, Electrical Engineer
- M. Mosier, Lead Engineer-Safety Analysis
"R. Skow, Sr. Electrical Engineer
"D. Wolniak, Asst. Project Designer-Licensing 1.2 U.S. Nuclea~
Re viator Commission NRC B. Cook, Senior Resident Inspector
"Denotes those present at the exit meeting.
2.0
~Per ose The purpose of this inspection was to review the licensee actions taken to resolve concerns identified in the licensee's Restart Action Plan (RAP).
These concerns pertain to Specific Issue 12, "Motor Generator Set Battery Chargers" and Specific Issue 18,
"125 VOC System Concerns."
Specific Issue 12 pertains to the safety reclassification of the motor generator (MG) set battery chargers to safety related.
Specific Issue
pertains to various dc system concerns identified during a licensee system evaluation.
These concerns include low battery equalizing voltages thereby requiring a reduction of battery cells and excessive voltage drops on several circuits which subsequently required cable replacements.
3.0 Batter Char in Motor Generator Sets The two battery charging MG sets originally were classified in the FSAR and treated as safety-related.
However, a
CFR 50 Appendix B review conducted during 1983 incorrectly reclassified the MG sets as non-safety related.
Then on June 13, 1988 in accordance with 10 CFR 50.72/50.73, the licensee notified the NRC (LER 88-13) of their discovery that the 125 Vdc system was not in compliance with the safety-related requirements of the FSAR as a consequence of the 1983 reclassification.
Initial corrective actions involved declaring the associated 125 Vdc systems inoperable and reclassifying the MG sets as safety-related.
This item, including the required corrective actions, is detailed in the Niagara Mohawk Nine Mile Point Unit 1 Restart Action Plan as Specific Issue 12 - Motor Generator Battery Charger The inspector reviewed the licensee actions taken to re qualify the MG sets as safety-related as detailed in Non-Conformance Reports (NCR) 1-88-0115 and 1-88-016 and in Engineering Report ER1611171.
These actions included the following.
Tabulation of all maintenance and modifications performed (including parts replacements)
since January 1983.
Determination of whether replacements and added components were procured as safety-related.
Determination that replacement and added components meet safety-related qualification requirements either as procured, by replacing with a qualified component, qualification testing or by qualification analyses.
Determination that replacement or added components were installed. in a manner meeting
CFR 50 Appendix B safety-related requirement.
Determination of whether any performed maintenance work activities have degraded quality.
Determination of the seismic qualification impact of maintenance, modification and replacement.
During'he time frame from January 1983 until June 1988, during which the MG sets were not treated as safety related, there were a total of twenty four wor k request actions which involved component replacements and two modifications which covered the addition/replacement of eleven component parts for each of the two MG sets.
During this same time frame there were fifteen work requests which did not involve component addition or replacements.
In both the NCRs and the Engineering Report, each of the maintenance/
modification/replacement actions are addressed including the action taken to ensure qualification.
For commercial items which were procured as replacement or modification parts, the licensee qualified these items in accordance with an extensive commercial dedication program (This program was previously reviewed extensively and reported in NRC Inspection Report 50-220/88-07).
Several items qualified in accordance with this program were reviewed.
These included the MG set bearings, voltage regulator, a
potentiometer, and a relay.
These qualification evaluations are detailed in the licensee's performance Requirements Evaluation Form Reports 1117, 1542, 1547 and 962 respectively.
Other items whose qualifications included tests were the generator shaft and bearings.
Items qualified by engineering evaluation included a control transformer and a transistor.
Seismic qualification of the replacement or additional components was addressed for each component to ensure its meeting the seismic criteria
required for this equipment.
Components addressed included the control transformer motor control switch, and rectifier parts.
No deficiencies were observed in the licensee's MG set requalificaiton program.
The inspector confirmed the licensee's status of all of the corrective actions and verifications committed to for this item in the licensee's restart action plan as follows:
Item No.
Corrective Action Status 12.A.l Complete Appendix B reclassfication of MG set as Safety-Related.
Update the Q-List Complete 12.A.2 Involved personnel lessons learned documentation and verification Complete 12.A. 3 12.A.4 Cross disciplinary review of system and major component level determinati ons to ensure qualification.
Document in a report Qhich is verified and accepted by responsible mangers Investigate components installed since 1983 and maintenance work to determine if 10CFR50 qualification requirements were met.
Correct nonconforming items by dedication or replacement.
Document in a report verified and accepted by responsible managers'omplete except for administrative documentation and upper management approval.
Complete except for upper manage-ment reviews of corrective actions and approval of the report.
12.B.1 Prepare a Design Report which provides the design bases for the battery chargers.
Verify that the documents are complete, filed and retrievable.
Design report being revised to incorporate MG set coverage.
Upper management approval of the completed documents and their retriev-ability required.
12.B.2 Update the FSAR and other configuration documents Internal Licensing Change Notice in-cluding program for FSAR updates complete.
This specific aetio'n item will be complete when the actions noted in the status above for items 12.A.3, 12.A.4, and 12.B. 1 are completed, These items constitute an unresolved item pending licensee completing the above actions and NRC review of these actions (89-23-01).
4.0
~125 Vd S
During an evaluation of the 125 Vdc system to document the system design bases, the licensee -identified various design deficiencies.
The inspectors reviewed these deficiencies and evaluated the proposed modifications to resolve the findings.
These deficiencies and inspector observations are documented below.
4.1 125 Vdc Batter E ualization Volta e In 1983 the licensee replaced the 60-cell 125 Vdc lead-antimony type cell batteries with lead-calcium cells.
Following replacement, the licensee observed premature aging of the battery banks and attributed the root cause to the inability to properly maintain the batteries in accordance with manufacturer recommendations.
Specifically, the batteries were not being subjected to a periodic equalizing charge voltage sufficient to meet the vendor's (C&D Power Systems)
recom-mended equalization voltage of 140-143 Vdc, 2.33 - 2.38 Volt per cell (VPC).
The licensee is presently subjecting the battery to an equali-zation voltage of 137.5 V (2.29 VPC).
Increasing the system equalizing voltage to 140-143 V is undesireable since this higher system voltage could result in exceeding the recommended design voltage of much of the 125 Vdc electrical equipment.
To resolve the insufficient equaliz-
'ing voltage, the licensee proposed to reduce the number of battery cells from 60 to 59.
Reducing the number of cells to 59 will enable each individual cell to be charged to 2.33 VPC as recommended by the manufacturer.
To evaluate the adequacy of the proposed modification to reduce the number of battery cells, the licensee formed a multi-disciplinary team to evaluate and document the design bases for the 125 Vdc system.
In order to determine the ability to reduce the number of cells, the licensee performed calculations 125 VDC-BATT 11-ES and 125 VDC-BATT12-ES to determine the minimum required ampere-hour rating of a 60, 59 and 58 cell battery based upon the FSAR case
"b" duty cycle based on a
Results of these calcula-tions provided information to determine if by reducing the number of cells, the minimum required ampere-hour for various duty cycles could still be provided.
In addition to these calculations, the licensee contracted outside consultants to perform similar computerized calculations for both cases of 60 and 59 cells.
The NRC inspectors reviewed the battery capacity calculations to evaluate the adequacy of the proposed modification.
In the calculations, the licensee used a design margin factor of 1.0 which corresponds to no margin in the dc system design whereby no future loads on the battery could be added.
In addition, based on these calculations the licensee intends to increase the minimum acceptable battery capacity to 90K, as well as implement controls to maintain
the battery room temperature at a minimum of 65~F, to ensure adequate battery capacity.
The licensee intends to perform a battery capacity test in September 1989 to establish new baseline data.
Although the licensee has completed battery sizing calculations, the modification safety evaluation taking into account the results of the contracted calculation is presently in the revision process'herefore, this issue is considered an unresolved item pending NRC review of the safety evaluation addressing the adequacy of the battery capacity and other design considerations such as environ-mental controls and the design margin in the battery sizing (50-220/89"23-02).
During the review of the battery sizing calculations, the inspectors noted that the assumed MOV starting inrush and full load currents were taken from MOVAT data.
These currents, however, may not be accurate during design bases events and in fact may be higher due to design differential pressures across the valves.
However, based on observed conservative assumptions included in the calculations, the inspectors concluded that these assumed currents would not significantly change the calculation results.
Within the scope of this review, no other deficiencies were identified.
4.2 Excessive Volta e Dro s
As documented in a previous NRC inspection report (50-220/89-01),
the licensee notified the NRC of a potential design deficiency in the 125 Vdc electrical distribution system.
The licensee reported that the design of some safety related 125 Vdc power/control cables was inadequate which could cause the distribution system to be inoperable.
During this inspection, the inspectors reviewed the licensee's actions taken in response to the identified'eficiencies.
4.2.1 Power Boards ll
16 and
The licensee's evaluation/analyses of the cable replacements needed to correct the excessive voltage drops, safety evaluation and the modification to perform the work were extensively reviewed and previously reported in NRC Inspection Report 50-220/89-01.
The modification had been completed at that time except for the termination of the replacement cables.
The installation was further modified by the licensee to stagger MG set starting times in order to avoid the larger voltage drop which would occur with simultaneous starting.
The inspector verified the installation complete except for a few terminations of power feeders at boards 11 and 12.
A review of the MG set starting circuit calibration procedures verified the staggered starting times.
No deficiencies were observed in these modifi-cations.
However, the following items are required to complete this restart issue:
~
Completion and verification of the installation
~
SORC final approvals
~
Documentation revisions to reflect as-built conditions These items constitute an unresolved item pending licensee completion of the above actions and NRC review of these actions (89-23-03).
Emer enc Diesel Generators EOG 102 103 and Cross Ties Modification 85-092 includes replacement of the 125 Vdc control power feeders from Battery Boards 11 and 12 to Emergency Diesel Generator (EDG) Control Panels 102 and 103 respectively.
The existing cable with a single
¹2AWG conductor per pole is replaced by a cable having two ¹4/0 AWG conductors per pole.
A review was made of the licensee's calculations
¹125 Vdc-D.G.
102/103-LF/VO Rev 1 which provides the basis for the replace-ments.
A walkdown inspection confirmed the modification.
No deficiencies were noted.
Initially this modification also included the replacement of 125 Vdc cross tie cables between EOG 102 and EOG 103 control panels with larger cables.
However, upon further evaluation, the licensee suspended this replacement.
The basis for the suspension was that cross ties with the additional conductor sizing would only be needed in the event of loss of an EOG control power feeder coincident with both an Appendix R fire event and available battery board voltage less than 108 Vdc.
The licensee concluded that for this unlikely, event a temporary stored cable could be installed with properly trained personnel.
The following items are needed to complete this work:
~
Completion and approval of analysis to justify not replacing the cross tie cables
~
Verification of the installation
~
SORC final approvals
~
Documentation revisions to reflect as-built conditions These items constitute an unresolved item pending licensee completion of the above actions and NRC review of these actions (89"23"04)
~
MOV Terminal Volta e In response to NRC Information Notice 88-72, "Inadequacies in the Design of DC Motor Operated Valves" and the licensee's dc system evaluation, studies were performed to determine if
sufficient terminal voltage was available at MOV terminals to ensure the motors will be able to produce the necessary torque to allow valve operation during design bases events.
In performing these calculations, the licensee assumed a
degraded dc system voltage of 105 Vdc at the battery terminals.
Results of the calculations indicated that for MOV 33-04 the minimum required voltage at its terminals was 48.92 volts.
However, the calculations also indicated that only 45.6 volts were available.
The licensee proceeded to replace the No.
feeder cable from the valve board to MOV 33-04 with No. 4/0 AWG cable.
Revised calculations indicated 91.46 volts available at the MOV terminals.
This voltage is sufficient to allow the motor to produce the necessary torque.
Calculations for other MOVs indicated that sufficient voltage was available at the individual terminals.
DC Circuit Breakers While the MOV voltage adequacy calcultations were being performed, the licensee identified the need to replace th~ existing 100 A
feeder breaker for Valve Board 12 with the existing 225 A alter-nate feeder breaker for Valve Board 11.
This modification would allow feeding the larger'oads on board 12 with the larger breaker.
The inspectors reviewed the associated calculations to evaluate the adequacy and impact of the circuit breaker switch.
The modification (85-092)
had not been completed at the conclu-sion of this inspection.
No deficiencies were identified with respect to the replacement of the feeder breakers.
However, a
concern was raised to the licensee pertaining to the preventive maintenance testing of the dc circuit breakers.
During review of the associated circuit breaker coordination curves, the inspector observed that complete coordination could not be veri-fied between the battery and valve boards.
Therefore, the inspector requested that the licensee provide information per-taining to the testing of the dc breakers.
The licensee was unable to provide any evidence documenting the testing of these circuit breakers to demonstrate their trip characteristics.
The consequences of circuit breakers not operating within their required operating bands could result in the loss of a dc bus upstream of the breaker.
The NMP 1 Technical specification Section 6.8. 1 requires that written procedures be established and implemented that meet the requirements of ANSI N18.7-1972 Sections 5. 1 and 5.3 and Appendix A of RG 1.33.
ANSI N18.7 Section 5.3.6 requires that procedures be provided for periodic calibration and testing of safety related plant instruments such as alarm devices, sensors and protective circuit At the conclusion of the inspection, the licensee was not certain if any of the dc circuit breakers had ever been tested since their installation.
This item is unresolved pending NRC review of licensee's evidence that the dc breakers have been properly tested (50-220/89-23-05).
Solenoid 0 crated Valve SOV Volta e Results of dc system calculations indicated that the expected voltage at the SOV circuit is approximately 100 Vdc due to voltage drops within each SOV circuit.
Licensee review of the NMP
EQ Master List indicates that the only ASCO dc SOVs which must change state in a worst case high temperature steam environ-ment are 206 series solenoid valves.
206 series solenoids are qualified based on testing at 76 Vdc (ASCO Test Report AQR-67368).
Therefore, the licensee determined that the existir g cables supply adequate voltage to the SOVs.
No deficiencies were identified.
Electromatic Primar Safet Relief Valves There are six 125 Vdc solenoid pilot-operated primary safety relief valves.
The licensee conducted a calculation and analysis for the power supply of these valves.
As a result, the licensee identified the need to provide higher voltage to the valve pilot solenoids to ensure valve operation, To correct this deficiency, the licensee pulled additional cables for these valves; however, the inspector found that the cabling had not been terminated in the feeder powerboards.
The inspector reviewed the modification package and that the following items still need to be completed:
~
Additional engineering analyses.
and tests to demonstrate the adequacy of the supply voltage at the valve solenoid terminals with the new cables.
~
Completion and verification of the installation.
~
SORC final approvals
~
Documentation revisions to reflect as built conditions.
Because of the uncertainties remaining and the initial concern for the adequacy of voltage to operate the primary safety relief valves this issue remains as unresolved (50-220/89-23-06).
5.0 Unresolved Items Unresolved items are matters for which more information is required in order to ascertain whether they are acceptable, violations, or deviations.
Unresolved items are discussed in Sections 3.0, 4. 1, 4.2, 1, 4.2.2, 4.2.4 and 4.2.6 of thi s report.
6.0 Exit Interview At the conclusion of the inspection on September 1,
1989 the inspectors met with the licensee representatives denoted in Section 1.0.
The inspectors summarized the scope and findings of the inspection at that time No written material was provided to the licensee by the inspector Attachment A
Documents Reviewed Safety Evaluation 89-011,
"125 Vdc System Cable Replacement for MOV 33-04" (MOD 85"092)
Design Evaluation Report (dated 2-21-89),
"125 Vdc Station Battery Replacement/Cell Reduction" Calculation 125 Vdc - VB11-CF/VD, "125 Vdc System Re-design (M.O.Valves)"
Calculation 125 Vdc - VB12-LF/VD, "125 Vdc System, Re-design (M.O.Valves)"
Licensing Document Change Notice (LDCN) U-N35
~
Nuclear Design Procedure ND-130, "Design Input", Rev.
Sargent
& Lundy Engineers Calculation No. NIMO-BATT-6, Rev. 0,
"125 Vdc System Study".
Document Change Request 2 N1-85-092LS-181,
"125 Vdc System Redesign (MOVs)"
Design transmittal construction; Mod. Control No. Nl-85-092 LF174,"
125Vdc System Redesign" Calculations 125 Vdc-BATTll-ES and 125 Vdc-BATT 12-ES, "Battery ¹11 sizing" and "Battery ¹12 Sizing" Calculation 125 VDC-TEN-4-LF/VD, "125 Vdc system re-design; ERV analysis" guality Work Procedure,
"125 Vdc System Redesign/MOV33-04" Mod Package 85-092,
"125 Vdc System Redesign PB
& 12" Internal Correspondence,
"Degraded Grid Voltage-ASCO DC Powered Solenoid Valves" Procedure No. Nl-SOP-5,
"115 KV Power Failure",
Rev.
12SVdc One-line Diagrams Engineering Report on Reclassification of Motor Generator Sets 161 and 171 To Safety-Related Status, ER 161/171, Rev.
1.