IR 05000338/1981019
| ML20039C687 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 08/21/1981 |
| From: | Burke D, Dance H, Marlone Davis, Hall B, Robert Lewis, Miller W, Shymlock M, Tillman A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20039C672 | List: |
| References | |
| 50-338-81-19, 50-339-81-16, NUDOCS 8112300042 | |
| Download: ML20039C687 (30) | |
Text
{{#Wiki_filter:,. MATERIAL TRANSMITTED HEREWITH , CONTAINS 2.790.'d) L. S. \\tces 9egLi:oy Corniss'or UNIT 2 TRANSFORMER FAILURE AND FIRE OF JULY 3, 1981 VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION NRC L.! CENSE NOS. NPF-4 AND NPF-7 DOCKET NOS. 50-338 AND 50-339 JULY 3-15, 1981 REPORT NOS. 50-338/81-19 AND 50-339/81-16 - -- _ I Offico of ' Inscection and Enforcement RegionIIl U.S. Nucieer Regulatory Cornmission / **%a e 8112300042 810925
DR ADOCK 05000338 MATERIAL TRANSMITTED HEREWITH o PDR CONTA!NS 2.790(d). . - . _ _- _.
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. . . . s MATERIAL TRANSMITTED HEREWITil CONTAINS 2.790'd) SAFECUARDS INFORMATION ABSTRACT This report contains the results of a special inspection of the B phase main transformer failure and the resulting fire which occurred at the North Anna Nuclear Plant, Unit No. 2, on July 3,1981.
The inspection included a technical evaluation of the event and of the operational response. The technical evaluation concluded that the event did not have an affect on the health and safety of either the public or plant personncl; however, issues were identified with respect to the location of safety-related transformer transmission lines in a potential fire area and to design features relating to oil retention in transformer areas. The evaluation of the operational response identified several issues in the areas of comunications, fire brigade training and additional site areas in need of a fire plan. VEPC0 has taken the initiative to strengthen their capability on these issues to the satisfaction of the NRC. These and identified generic aspects of the event are under review by VEPC0 and the NRC.
SI - ISS s-n / Aof /L _ Copies CopyM Pages 5hin Document is not to be reproduced without specific approval of IE:II MATERIAL TRANSMITTED HEREWITH CONTAINS 2.790(d). . . . MATERIAL TRANSMITTED HEREWITH - - CONTA!NS 2.790'd) SAFEGUAPDS INFORM 5. TION TABLE OF CONTENTS Section Title Page ABSTRACT i LIST OF FIGURES iv 1.
INTRODUCTION
1.1 Purpose and Scope of Inspection
1.2 NRC inspection Personnel
1.3 Licensee Personnel Contacted
2.
SUilftARY OF NRC F0LLOWUP ISSUES
2.1 Violation of Regulatory Requirements
2.2 Failure fiechanism
2.3 Electrical Criteria
2.4 Plant Procedures
2.5 Fire Protection Criteria
2.6 Fire Protection Capability
3.
PLANT DESCRIPTION
4.
DESCRIPTION OF TRANSFORfiER FAILURE AND FIRE
4.1 Initial Plant Conditions
4.2 Event Summary
4.3 Sequence of Events
4.4 Plant Operational Response
4.5 NRC Response
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FIRE PROTECTION REVIEW
5.1 Transformer Fire Protection Features
5.2 Fire Spread
5.3 Fire Fighting Operation
5.4 Summary of Equipment Used
5.5 Training
5.6 Evaluation of Fire Fighting Operations
6.
SECURITY REVIEW
7.
SUMMARY OF CONCLUSIONS
7.1 Event Response
7.2 Fire Fighting Capability
8.
EXIT INTERVIEWS
Security Review Supplement (Exempt from Public Disclosure) iii MATERIAL TRANSMITTED HERWN CONTAINS 2.790(d) SAFEGUARDS INFORMATIO
. , . , ' ' MATERIAL TRANSMITTED HERENITH CONTAINS 2.7Ed) LIST OF FIGURES FIGURE TITLE PAGE NO.
Transformer Lines and Switchyard
2 Electrical Interconnecting Between the Switchyard and Power Station
3 NRC Sketches of Transfomer Arne.gement
4 Fire Hose Layout
5 Looking Toward B Main Transfomer 27.
West End of North Wall of Turbine Building
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INTRODUCTION 1.1 Purpose and Scope of Inspection This was a special inspection conducted during the period of July 3-15, 1981, by an NRC inspection team from Region II, Office of Inspection and Enforcement.
This inspection was performed for the following purposes 1.
To establish a factual recounting of tha significant events surrounding the North Anna Unit 2 main transformer failure and fire of July 3; and 2.
To evaluate the performance of the licensee; including systems, components, and procedures; with respect to this event to develop a basis for corrective action at this and other sites as appropriate.
The inspection involved 93 inspector-hours onsite by a team of seven inspectors. The inspection concentrated in the areas of overall plant response, operator response, communications, fire response, system design, emergency plan adequacy, security plan adequacy, and the adequacy and use of procedures.
Of the eight areas inspected, one violation of NRC requirements was identified.
(Fire brigade training frequency was deficient - paragraph 5.5).
1.2 NRC Inspection Personnel Inspector Inspection Dates D. J. Burke, Senior Resident Inspector 7/3, 9, 10, 13-15/81 H. C. Dance, Section Chief 7/3-4/81 li. J. Davis, Resident Inspector 7/3/81 B. L. Hall, Physical Security Inspector 7/9/81 W. H. !! iller, Fire Protection Engineer 7/6-10/81 M. D. Shymlock, Reactor Inspector 7/3-4/81 A. Tillman, Physical Security Inspector 7/9/81 Approved By B. C. & El'/8/ t-Paul J. EfeTlogg, Chief, Project Branch 2 Date Signed Division of Resident and Reactor Project Inspection MATERIAL TRANSMITTED HEREWITH CONTAINS 2.790(d) MATERIAL TRANSMITTED HEREWITH O ' . CONTAINS 2390(d) SAFEGUARDS INFOR , .
1.3 Licensee Personnel Contacted Virginia Electric and Power Company
- W. R. Cartwright, Station fianager E. W. Harrell, Assistant Station flanager J. W. Ogren, Supervisor Administrative Services R. Sturgill, Shift Technical Advisor J. A. Hanson, Superintendent Technical Services ti. E. Fellows, Staff Assistant D. E. Thomas, Supervisor, Electrical flaintenance L. E. Retzer, Acting Fire flarshall
- E.
H. Davis, Jr., Director Nuclear Security
- C. G. Luffman, Station Security Supervisor
- E. Tracy, Assistant Station Security Supervisor Stone and Webster P. H. Griffin, Lead Advisory Engineer
- Attended all exit interviews
- Attended July 9 exit interview only 2.
SUliMARY 0F NRC FOLLOWUP ISSUES 2.1 Violation of Regulatory Requirements Fire brigade drills were not conducted on the frequency specified in the station Fire Protection Plan. Technical Specification 6.8.1.f requires procedures for implementation of the Station Fire Protection Plan. Of 32 individual fire drills specified for 1980, only 19 were perfonned.
During the first six months of 1981, 14 of 16 drills had been performed (339/81-16-01)'. See paragraph 5.5.
2.2. Failure flechanism Causes of three transformer failures at North Anna Unit 2 since mid November 1980 should be determined to assure that generic concerns have been identified and addressed (339/81-16-02).
See paragraph 4.4.1 of this report.
2.3 Electrical Criteria Additional criteria should be considered for routing of cables, which affect safety systems, over or near potential fire hazards. Electrical separation and/or isolation switchgear should be considered for the preferred power source (339/81-16-03)2 See paragraph 4.4.3.
. ! 'These numbers are provided for NRC tracking.
2These items have been referred to NRC Headquarters for generic consideration.
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MATERIAL TRAfiSMITTED HEREVilTH ' ' ' , CONTAINS 2.790(d) 3 2.4 Plant Procedures 1.
Procedures and training for abnomal conditions should be reviewed to assure that operators have proper guidance on shutdown of systems that may be jeopardized by fires or other disasters (339/81-16-04).
See paragraph 4.4.6.
2.
Action should be taken to instruct station personnel not involved in erargency plan activities, such as fire fighting, to stay clear.
Personnel nu involved in fire fighting activities became observers at the fire scene (339/81-16-05).
3.
Procedures should specify that gas cylinders are to be secured in their storage er use locations (339/81-16-16). See paragraph 4.4.2.
2.5 Fire Protection Criteria 1.
Criteria for placement of transformers and installation of multiple trans-fomers within a cocoon diked area should be reviewed. Transfomers, with oil cooling systems, contribute to the fire load and are more susceptible to damage in the event of a transfomer fault than a transfomer without an oil cooling system (339/81-16-06)2 See paragraphs 5.1 and 5.2.
2.
A fixed fire suppression system should be considered for spare transfomers stored adjacent to turbine or other buildings. An installed and operable fire suppression system may have reduced the damage caused by this fire which spread to the spare transfomer pad.
However, it should be noted that a typical deluge system would be disabled and partially disassembled when the spare transfomer is removed (339/81-16-07)2 See paragraph 5.1.
3.
At least two means of access should be considered for all building roofs which exceed the height of nomal ground ladders. Only one mea..s of access was available to the roof of the turbine building (339/81-16-08)2 See paragraph 5.3.
4.
Fire hose stations should be considered for roofs of buildings which exceed approximately 50 feet in height.
Fire stations were not provided for the roof of the turbine building (339/81-16-09)2 See paragraph 5.3.
2.6 Fire Protection Capability 1.
Fire fighting procedures (pre-fire-plans) should be considered for plant areas which have a fire potential.
Procedures were only provided for safety-related areas of the plant and did not include the transformer area (339/81-16-10)2 See paragraph 4.4.6.
2.
A connunications plan for all responding fire fighting organizations should be considered. The lack of a common radio system presented some problems in directing the fire fighting operations (339/81-16-11)2 See paragraph 5.3.
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3.
Fire brigade motorized apparatus or hose trailers should be considered to permit rapid moveme it of large quantities of fire fighting equipment to the location of the fire.
In this fire, personnel had to move fire hose from several fire hydrant equipment houses to the scene of the fire (339/81-16-12)2 See paragraph 5.3.
4.
A program of training and periodic inspection should be conducted to alert personnel of fire potentials and to assure fire lanes and spaces for fire fighting equipment are maintained. At the time of the fire, there was considerable congestion on the north side of the plant due to the storage of construction supplies, tool and equipment storage trailers and temporary office buildings.
This arrangement hindered responding off site fire departments in positioning their apparatus. (339/81-16-13)2, see paragraph 5.5.
5.
Scope of the current maintenance program of fixed fire protection systems should be eviewed to assure adequate maintenance.
The fire brigade was unable to open one of the fire hydrants. Subsequently, the hydrant was opened by one of the responding off site fire departments (339/81-16-14).
See paragraph 5.3.
6.
The cause of failure for six operations radios utilized by the fire brigade should be pursued and corrected (339/81-16-15). See paragraph 5.4.
3.
PLANT DESCRIPTION , North Anna Units 1 and 2 are located on the :authern shore of Lake Anna in Louisa County, approximately 40 miles northwest of Richmond, Virginia.
The nuclear steam system is a three loop pressurize 6 water system designed by Westinghouse Corpora tion. The balance of the plant was designed and constructed by Virginia Electric and Power Company (VEPCO) and Stone and Webster. The plants are operated by VEPC0 and each has an electrical output of 947 negawatts.
Basic plant layout consists of reactor containments, one for each unit, and common auxiliary, fuel, turbine and service buildings.
North Anna Unit 3 is under construction and is located adjacent to and vest of Unit 2.
Construction of North Anna Unit 4, west of Unit 3, has been discontinued.
North Anna Unit I received a full power license on flovember 26, 1977.
florth Anna Unit 2 received a full power' licensee on August 21, 1980. Con-structica of Unit 3 is slated to be completed in 1989.
The electrical systems consist of a main generator for each unit which supplies power to a high voltage switchyard via its three main (22 kV to 500 kV) trans- - formers as shown on Figure 1.
Unit 1 main generator has a generator output breaker. This modification has not been accomplished on Unit 2.
The station service system consists of station service and reserve station service trans-formers, 4160 V and 480 V switchgear and buses, 480 V motor control centers, MATER!AL TRANSMITTED HEREWITH CONTAmS 2.790'd).. - . -. . . . - - - - --- . - . .. ., E MATERIAL TRANSMITTED HEREW1TH-t - - - . CONTAINS 2.790(d). -
i I ' j 115 V ac vital buses, and 125 V dc batteries and equipment (See FSAR Section 8.3 ' for details). The normal source of station service power is obtained from the - main generator; standby sources serving both units are available from the high voltage substation.
Figure 2 shows that the emergency buses for Unit 1 are supplied by two redundant sources while Unit 2 is normally supplied by the , l reserve station service transformers only. The modification to provide a ' redundant power source to Unit '2 emergency buses is scheduled for the !! arch 1982,
refueling outage.
The emergency buses for each unit can also receive power from E two separate and similar emergency diesel driven generators. The three main I transformers and the three station service transformers for each turbine unit are located along the north wall of the turbine building as shosn on Figure 3.
A spare transformer is normally stored next to the Unit 2 main transformers.
The transformers are separated from each other by concrete fire walls which extend above and beyond each transformer. A similar concrete wall is also , ! provided between the transformers and the turbine building. A wall is not ! provided between the turbine building and the spare main transformer pad as shown on Figure 3 and in the FSAR.
f 4.' DESCRIPTION OF TRANSFORMER FAILURE AND FIRE 4.1 Initial Plant Conditions r Unit 2 was being returned to service following the maintenance outage to replace the C phase main transfomer which had failed on June 19.
The generator was synchronized to the grid at 0719, thus powering the three output transformers.
Gross generator output was being increased slowly and had reached 76.7 MWe.
Reactor power was constant at 17%. The B phase main transformer failed at 0723.
Unit I was operating at 100% power.
, , 4.2 Event Summary ' An internal electrical fault in the Unit 2 B main transformer at 0723 on July 3, 1981, resultea in tripping of the electric generator and the reactor from 17 percent power. The energy generated from the electrical fault ruptured the transformer casing.
Cooling oil flowed from the rupture in the transformer and ' , ' ignited in the transformer area on the west end of the north wall of the turbine building. Unit 1 and 2 containment buildings are located on the opposite side of the turbine building and were not affected.
The plant and three local volunteer fire departments responded. All fires were out by 0845.
The fire shorted the overhead output aluminum bus bars of C reserve station transformer and resulted in the - transformer tripping at 0745. One diesel generator automatically started and supplied power to the Unit 2 emergency bus normally powered by the C reserve station transformer. A reactor safety injection signal was initiated from the existing low-low T average (Tave) coincident with a spurious high steam flow signal. All reactor safety systems functioned as designed. The safety injection signal was reset after two minutes. No personnel injuries occurred.
Radio-activity was not involved in the fire.
Some components were repaired and a replacement transformer was obtained from VEPC0's Surry plant.
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MATERIAL TRANSMITTED HEREWITH ' ' . ' . 00NTAih3 2.790ld) 6 Unit 1 continued to operate during this event.
One emergency bus automatically switched to its alternate power source when C reserve station transformer tripped and the nomal power source was lost, Power was reduced to 33% power (as a precautionary measure) in preparation for shutting down the unit if the fire condition worsened. The fire was quickly brought under control and a Unit 1 shutdown was not required.
VEPC0 classified the event as an Alert condition and implemented their emergency plan. Notifications were made to local, state, and Federal agencies as specified in the North Anna Fire Protection Plan. Three NRC Region II inspectors and a supervisor responded on July 3 to review the event.
4.3 Sequence of Events The following sequence of events of the July 3,1981, Unit 2B main transformer failure and resulting fire was assembled from review of pertinent plant records, logs, and discussions with plant personnel.
Elapsed Time Time (ftin. ) Event 0719-4 Unit 2 generator synchronized 0723
Failure of Unit 2 B main transformer resulted in Turbine Trip / Reactor Trip i 0723
Fire alarm and deluge system actuation on A and B main transformers Fire alarm announced on PA system j Deluge system on C main transfomer manually actuated 0729
Reactor coolant pumps 2B and 2C secured 0729
Initiated Unusual Event condition per Emergency Plan 0731
NRC informed of Unusual Event 0746
Loss of C reserve station transformer resulted in: i Unit 2 Safety injection (low-low Tave coincident with spurious high steam flow) 2J emergency diesel generator auto started and supplied 2J emergency bus Unit 1 1H emergency bus auto transferred to , alternate supply MATERIAL TRANSMITTED HEREWITH CONTAINS 2.790/d) -. - - -...... - - -.... - - - - - -. -. - -
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Elapsed Time Time (flin. ) Event 0748
Initiated Unit I rampdown to 30% power (precautionary action) ) 0750
flineral and Louisa Fire Departments arrived on site.
0750
Initiated Station Alert condition per Emergency Plan 0752
NRC informed of Alert condition 0754
Aligned Unit 1 1H emergency diesel generator to 1H emergency bus (precautionary alignment) 0755
Reestablished Unit 2 letdown, seal leakoff, and shutdown of auxiliary feed to steam generators.
0805
Spotsylvania Fire Department arrived on site.
0810
Comenced Unit 2 cooldown 0830
Main transformer fire extinguished 0833
Unit 1 at 33% power and holding 0845
All fires extinguished 0900
Emergency terminated 4.4 Plant Operational Response 4.4.1 Background on North Anna Transformers The orginally installed main phase transfomers at North Anna were Westinghouse single phase, 60 cycle, Class F0A (forced oil and air cooled) 22 kV/500 kV transformers with Insuldur insulation, and were rated at 330 flVA at 55* C average rise in temperature.
, Three of the Unit 2,1975 vintage Westinghouse main phase transformers at North Anna have failed over the past year.
The A main transformer failed November 29, 1980, due to a high to low side (voltage) fault; the C main tranformer failed on June 19, 1981, due to a high side to ground fault (bushing failure); and the B main transformer failed on July 3,1981, due to an apparent high side :. grnund fault (bushing failure). The licensee is investigating for any conr:e ; node failure (339/81-16-02).
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According to the licensee, subsequent to identifying arcing from the transformer . high side lead to the low side windings of this vintage transformer, Westinghouse recommended increasing the distance between the high voltage cable lead (to the bushing) and the low side transformer windings (normally some 4 to 6 inches), or wrapping additional insulation on the high voltage lead.
Following the C trans-former failure, modifications were completed on B transfomer to accomplish this recomendation.
Each of the main phase transformers contained some 9,280 gallons of oil. The oil is continuously recirculated by small pumps at the base of each-F0A transformer. The pumps operate at a few pounds of pressure to aid the natural circulation of the oil from the transfomer lower area, where the oil cools the transformer windings, to the upper volume of the transformer where the oil flows from the transformer into radiator type coolers with fans, and back to the suction of the pumps.
A nitrogen gas bottle is attached to each transformer to provide a dry, non-explosive regulated cover gas over the oil in the transfomer.
The cover gas is sampled weekly by the station or off site systems personnel to verify the dry, w nonexplosive makeup of the gas.
In addition, the oil in each transfomer is sampled monthly and chromatographically examined to assure that water and gas are not accumulating in the oil to cause degradation of the oil.
Particulates, if ' visible, are also checked.
Cover gas or oil degradation has not been observed in the Unit 2 transformers.
Recently, some copper or bronze shavings were found in the Unit 2 A main phase transformer; the oil was cleaned and the oil pumps replaced to assure the elimination of the presence and source of the metal shavings which appeared to have come from a worn bushing in one of the oil pumps.
The main phase transfomers have a sudden pressure relief (SPR) device and a mechanical relief valve on top of the transformer for protection. The SPR device actuates an alam and initiates transformer deenergization at approximately 11 psig, while the mechanical relief produces an alarm and relieves internal transfomer pressure over 8 psig.
These transfomers are typically designed for vacuum to 10 psig internal pressure, and usually operate with an internal nitrogen blanket of 0.5 to 6.0 psig.
Due to the main phase transformer failures, the licensee now has three different models of single phase, 60 cycle, Class F0a transfomers for Unit 2.
Transformer C (adjacent to the 22 kV/4.16 kV station service transfomers) is a 500 kV/23.8 kV, 277 ftVA at 55 C (avg. rise) Westinghouse unit containing 10,400 gallons of cooling oil. Transformer A (between C and B) is the North Anna standard spare, a 500 kV/22 kV, 330 tiVA at 55 C Westinghouse unit with Insuldur insulation containing 9,280 gallons of cooling oil.
It is a 1974 vintage West-inghouse transformer as are the three installed on Unit 1.
Subsequent to the fire, the damaged B transformer was replaced with a 500 kV/22 kV, 30011VA at 55 C General Electric (GE) transformer (from Surry). The GE unit contains 19,260 gallons of cooling oil This transfomer is physically larger than the damaged transformer it replaced.nd required removal of the separation wall between the B transformer pad and the spare transformer pad. The spare transfomer pad is presently vacant presentin no hazard due to removal of the wall. The licensee stated that a fire protection (FP) evaluation will be MATERIAL. TRANSMITTED HEREWITH r~"NS 2 790'm S4FEGUARDS INFORMATION
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perfomed to assure that the transformer FP auto deluge system, dike, and drainage sumps are adequate for the increased oil capacity of the GE transformer.
The licensee has analyzed and detemined that the C and B replacement trans-formers can be operated to match the output of the A transformer. The spare main , ! phase transformer is nomally stored full of oil.
Each unit also has three station service (SS) transformers which are Westinghouse 60 Cycle, three phase, 22 kV/4160 V,15 f1VA at 55 C, type SL, class OA/FA, which contain 2,375 gallons of cooling oil.
The three reserve station service (RSS) transfomers which supply Unit 1 and 2 normal and emergency busses from off site power are 34.5 kV/4.16 KV transfomers with underground cables to the emergency 4160 V buses and overhead cables and buses to the station service buses.
Approximately one year ago prior to Unit 2 operation, the licensee added the overhead lines from the RSS transfomers to parallel the underground cables due to electrical analyses which indicated that the underground cables may have inadequate heat dissipation during long term use.
In addition, the licensee installed a large breaker on each phase of the main generator output (in the turbine building) of Unit I which permits an off site electrical power source from the 500 kV switchyard through the main phase transformers to the station service transformers following a Unit 1 trip. The main generator output breaker has not been installed on Unit 2; thus when Unit 2 trips, power is lost to the A, B and C station service transformers and the 2A, 28, and 2C buses auto fast transfer to RSS power to supply the reactor coolant pumps and auxiliary equip-ment.
4.4.2 Transformer Fire The high side output lead or bushing from the B main transformer apparently shorted to ground.
The Unit 2 main generator had been placed on line at 0719, less than four minutes before the fault; thus the main phase transformers were still at ambient conditions (oil temperatures, etc.). The internal electrical fault generated energy that caused the B main transformer to rupture along the upper right hand side and severed one of the oil pump discharge pipes at the base of the transformer, spewing oil from both ruptures.
The oil ignited, causing the fire.
Refer to Figure 3 for the transformer and fire ar ea arrangement. The electrical fault (phase to ground) initiated the transformer and generator leads current differential protection system which operates and locks out the station output breakers to the switchyard and de-energizes the main generator. This initiated a turbine trip which caused the reactor trip.
The fire protection transformer deluge system automatically initiated to spray the B and the adjacent A main transformers; C (adjacent to A) deluge system was manually initiated for additional protection. The inspector noted, during his review of control room logs, that the Unit 2 C main transfomer FP deluge system had auto initiated at 1605 on July 8 and at 1247 on July 9,1981.
The licensee stated that inadvertent deluge system actuations had been occurring due to heat MATERIAL. TRANSMITTED HEREWITH c0NTAINS 2.790(d) _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _
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. detector instrumentation anomalies. If any one of the several heat detectors (on each transformer FP system) become erratic and trip, the deluge system is initiated.
Spurious operation of the Unit 2 A main transformer deluge system occurred at 2015 on July 14, 1981, during changeout of the main bushing.
Licensee instrumentation personnel inspected the heat detectors; one detector was replaced.
Following the July 14 deluge, the licensee isolated the Unit 2 transformer deluge systems to enable maintenance work to procccd.
The B main transformer SPR device also operated and alamed. The B main trans-former oil fire caused bottled gas cylinders, such as the nitrogen cover gas bottle attached to the 2 B main transformer and at least two welding gas cylinders in the area, to relieve. Subsequent to the incident, the inspectors observed that three nitrogen cylinders were not securely attached to their res-pective transformers; the cylinder chain was not secure or was missing. The > licensee was informed for correction. Procedural requirements to secure the l cylinders will be evaluated by the inspector (339/81-16-16). The fire also l damaged a small portion of the security fence E-field monitoring system and some soil was washed away along the security fence by fire-fighting water.
, When the overhead C RSS buses became threatened by the fire beneath them, the Unit 2 B and C reactor coolant pumps were secured at 0729 to reduce the station loads. The licensee initiated notification of an Unusual Event per the Emergency Plan. At approximately 0735, the main steam line trip valves were manually closed to inhibit cooldown of the primary system which was at some 540 F l (approximately 3 F below low-low Tave).
I 4.4.3 Reserve Station > Service (RSS) Transformer Fault At 0746, the oil fire under the C reserve station service buses caused a fault or, the 4160 V buses which opened the main supply and feed breakers for the C RSS transformer. When the fault occurred, a momentary undervoltage spike occurred on the 2J emergency bus which is fed by C RSS. The undervoltage spike fed through to the Unit 2 vital buses (2-III and 2-IV) which caused spurious bistable trips and alarms. A few less significant alarms, etc., occurred on Unit 1 H emergency and vital buses (1-1 and 1-11).
Specific Unit 1 and 2 responses are discussed bel ow. The matter of additional criteria for routing of cables which affect safety systems and the need for additional isolating switchgear for the preferred power source is being forwarded to NRC Headquarters for consideration.
(339/81-16-03).
4.4.4 Unit 2 Response to C RSS Fault Immediately prior to the C RSS transformer fault, Unit 2 was in hot shutdown and was supplied elec.;rical power from the RSS transformers.
The C RSS transformer supplies power to emergency buses 2J and 1H. When C RSS was lost, the 2J bus undervoltage relay started the 2J emergency diesel generator (EDG) which re-energized the 2J bus. Several spurious alarms and trips occurred on Unit 2 vital bus 2-III and 2-IV instruments when the C RSS transformer fault occurred, including low steam generator levels, high pressurizer pressures, containment high pressures and high steam line flows. When two out of three high steam line flow instruments actuated on the undervoltage spike, in coincidence with the MATERIAL TRANSMITTED HEREWITH CONTAINS 2.790'd) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _
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actual low-low Tave condition, safety injection (SI) was initiated. The steam lines were isolated when the failsafe logic of the high steam flow instrumentation initiated. The spurious SI started EDG 2H but the output breaker did not close onto the 2H emergency bus; the 2H bus was being supplied with power from B RSS transfomer, its nomal source. The SI was detemined to be spurious and was reset after some two minutes. The engineered safeguards equipment functioned as required.
The irspectors verified that the reactor coolant system (RCS) cooldown was less than 100*F/hr. as required by Technical Specification 3.4.9.1.
11 ode 5 (Cold Shutdown) was achieved on Unit 2 at 1816 hours on July 3.
The 2J emergency bus was reenergized from the C RSS transfomer at 1925 hours, following removal of the damaged overhead cables from the transfomer. The portion of damaged overhead C RSS bus bars and cables being replaced (not spliced) was from the electrical cabinet bus bars to the transfomer yard con-nections.
4.4.5 Unit 1 Response to C RSS Fault Unit I rampdown from full power began at 0748. At approximately 0835, the Unit was stabilized at 33% power when the fires were extinguished, removing the threat of additional RSS (A and B) losses. When C RSS was lost, breakers 15H1 and 15H11 closed af ter two seconds to supply power from B station service to the 1H emergency bus. Although the 1H EDG auto started during the two second loss of power to the 1H bus, it did not close onto 1H to supply power due to the above transfer. As a precaution, the licensee perfomed an operability test on the IJ EDG to verify the diesel generator would start and run as rcquired; no problems were identified.
The undervoltage spike from the C RSS fault was not significant on the Unit 1 electrical systems, although several spurious alams did occur. Several Unit I control rod group deviation fm the bank alarms occurred at 0746, but no actual rod movement or deviations were observed. The reactor coolant pump themal barrier high flow trip valves (TV-CC-116 A, B, C) also closed, isolating the component cooling water flow from the pump themal barriers.
The reactor operator observed the low flow cosdition and subsequently opened the valves to reestablish flow. Although there were no additional alams, the reactor operators stated that a few chemical volume control system controllers (e.g. - volume control tank level, pressurizer level, and/or RCS letdown) shifted from auto to manual at 0746, but were returned to auto before level or letdown deviations occurred.
4.4.6 Procedural Review The inspectors reviewed the plant response in terms of the applicable procedures.
The plant staff responded rapidly to the transfomer failures, reactor trip, safety injection and subsequent cooldown. Actions were in accordance with pro-cedures.
The Emergency Plan was promptly initiated as well as the response to the fire.
It must be recognized that the timing of this event was such that additional plant staff including plant managment was on hand due to the startup scheduled earlier on the shift. Additionally, day shif t personnel were beginning to arrive at the time of the transfomer fault.
Administrative procedures are MATERIA!. TRANSWTTED HEREW1TH CONTAINS 2.7903 MATERIAL TRANSMITTED HEREWITH , . - . CONTAINS 2390@ SAFEGUARDS INFORMAil0 ,
provided for specific faults such as loss of a transfomer, electrical bus or switchyard failure. Potential loss of equipment due to an emergency such as a fire is addressed in a more general procedure. Additional guidance could be provided in the inspector's view. This matter will be pursued by the inspector from a procedural and training point of view (339/81-16-04).
Fire fighting procedures (pre-fire-plans) should be considered for plant areas which I' ave a fire potential.
Procedures were only provided for safety-related areas of the plant and did not include the transformer area. This matter is being forwarded to NRC Headquarters for evaluation of generic applicability (339/81-16-10).
4.4.7 Oil Loss The drainage system beneath the transformer placements is described in Section 5.1.
Due to the quantity of oil spilled from the transfomer and the water used in fire fighting operations, some amount of oil entered the storm sewer and reached Lake Anna.
The inspectors did not review the spill specifically, but were aware of the licensee's efforts to contain and cleanup the spillage.
State authorities were infomed by VEPC0.
4.5 NRC Response The NRC Duty Of ficer was informed of this event by the North Anna Station fianager utilizing the Emergency Notification System at 0731 (EDT) on July 3.
After three minutes, this telephone became inoperable and subsequent communications were by comercial telephone lines.
The cause of the telephone failure was unrelated to this event.
Two NRC resident inspectors arrived on site at 1300 hours on July 3.
A Region II supervisor accompanied by a third inspector arrived on site at 1600 hours on July 3.
On July 6, an NRC fire protection engineer arrived on site to review the fire aspects of the event. Two NRC security inspectors arrived on site July 9.
Additionally, four NRC representatives from Bethesda and a consultant exanined the fire area on July 9.
5.
FIRE PROTECTION REVIEW 5.1 Transformer Fire Protection Features The main and station service transformers for each associated unit are installed within a comon diked area which is arranged to collect oil in the event of a major oil leak or rupture from one of the transformer oil cooling systems. The criteria for this arrangement will be further evaluated by NRC Headquarters (339/81-16-06).
The dike drainage system consists of several feet of crushed stone installed within a concrete curb which extends six inches above grade and the crushed stone. Two inlet structures are provided and are arranged to collect any liquid accumulations in the diked area and discharge this liquid into Lake Anna through the storm cnd sanitary sewer system.
The edge of the fire walls between the transformers is approximately eight feet from the curb of the MATERIAL TRANSMITTED HEREWITH CONTAINS 2390(d) - - . . MATERIAL TRANS"ITTED HEREVilTH . . CONTAINS 2.790@ SAFEGUARDS CiFORMATION
drainage system.
Each transformer, except the spare main transformer, is provided with an automatic deluge water spray extinguishing system. NRC Headquarters will evaluate the need to provide such a system for spare trans-fomers (339/81-16-07). The turbine building wall adjacent to the transfomers is not provided with a fixed water suppression system.
Fire hydrants and equipment houses are installed approximately 250 feet apart around the plant complex and are available for manual fire fighting operations. The deluge systems for the main transformers are designed to discharge approximately 400 gpm at 80 psi. The fire protection water system at the plant is nomally supplied from two 2500 gpa at 143 psi fire pumps. Two 1000 gpm at 125 psi fire pumps are also available from the construction warehouse site.
5.2 Fire Spread Upon rupture of the transfomer oil cooling system and ignition of the oil, the fire was temporarily contained to the area adjacent to the B nain transfomer.
However, the oil soon flowed to the west of B main transfomer where a spare transfomer is nomally stored. The spare tranformer pad was not occupied since there was no operable spare transfomer available at the site. The ourning oil and water flowed to the west and over the drainage system curb due in part to the oil rupture being on the west side of the transformer which resulted in oil being discharged in a westerly direction. Additionally, the fire fighting operations were being directed from the east. Tne large flow of water (approximately 1200 gpm) being discharged from the three transfomer deluge systems also acted to prevent the oil from flowing to the east.
The fire spread vertically from the burning oil at the spare transformer area up the north side of the turbine building to the edge of the turbine building roof burning the wall coating and vertical cable runs on the exterior of the building. See Figure 3 for a visual sketch.
Fire fighting operations prevented further fire spread. Burning oil also flowed over the curb of the diked area and along the security fence between Units 2 and 3.
Some construction materials stored in this area were also damaged by the fire.
5.3 Fire Fighting Operations The fire brigade arrived on the scene at 0725 and due to the size of the fire, the brigade team leader (Scene Leader) requested Security to call the !!ineral and Louisa Fire Departments. The following hose lay sequence may be followed on Figure 4.
Numbers in parenthesis of the write up refer to the hose sequence shown on Figure 2.
Members of the brigade advanced a 2\\-inch hose line (1) from a hydrant north of the Unit 2 turbine building toward the fire but this hose line was not used since the hydrant could not be opened. Subsequently, the hydrant was opened by one of the off site fire departments. The scope of the current maintenance program of fixed fire protection systems should be reviewed to assure adequate maintenance (339/81-16-14).
The brigade then repositioned to the hydrant north of the Unit 1 turbine building and laid 350 feet of 3-and 2h-inch hose (2) toward the fire. When the fire hydrant was opened, the water pressure caused one of the couplings to separate from the hose. The hydrant hose valve was closed and the defective hose replaced. The inspector considered this an isolated incident.
Fire hose for this hose line was taken from several hose MATERIAL TRANSMITTED HEREYllTH CONTA!NS 2.79(Td) (
_ .- -- _-. - .. . - _. .__ __ - - _
. i .' MATERIAL TRANSMITTED *REvilTH ' ' ' ! CONTAINS 2390(d) '
houses in the vicinity of the transformers. Water was first discharged on the fire at 0730. At 0730, the VEPC0 construction fire brigade responded to the fire i with a 1000 gpm pumper and five fire fighters with nine additional brigade members responding later during the fire. The pumper connected to the hydrant
north of the Unit 1 turbine building and a 2 -inch hose line (4) of 350 feet was . ! extended to the fire. While this line was being placed in service, a 1\\-inch i hose line (3) of 250 feet was extended to the fire from a gated connection to the previously laid hose. These lines were placed in service at 0735. At 0730, the
Fire Brigade Scene Leader requested that Security call the Spotsylvania Fire i Department for assistance.
i At 0740, operations fire brigade members were dispatched to the basement and
mezzanine of the turbine building and utilized two (5 & 6) of the 1 -inch interior fire hose stations to extinguish the fire entering the building and to cool the building wall and structural steel supports. At 0745, three plant employees were assigned to the turbine floor and used three (7, 8, & 9) interior ' fire hose stations to cool the turbine building wall and structural steel supports. Approximately five sprinkler heads on the basement and mezzanine levels of the turbine building opened which helped prevent fire damage in these areas.
By 0746, the fire had damaged the power conductors from reserve station service transformer C which tripped the transformer breakers. At 0750, the fire had extended up the turbine building wall to the roof.
Employees dispatched to the roof at 0800 attempted to extinguish the roof fire with portable fire extin-guishers. Fire hose stations are not provided for the roof. NRC Headquarters will evaluate the need for hose stations on the roof of a building which exceeds approximately 50 feet in height (339/81-16-09), and the need for more than one means of roof access on a building of height in excess of a nomal ground ladder (339/81-16-08). At 0815, a 1 -inch fire hose (12) of 450 feet supplied from the VEPC0 fire pumper was extended to the roof and placed in service to extinguish the roof fire.
The need for a fire brigade motorized apparatus or hose trailers to permit rapid movement of large quantities of fire fighting equipment to the location of the fire is being-evaluated by VEPC0. Additionally this item is being forwarded to NRC Headquarters for their evaluation.
In this fire, personnel had to move fire hose from several fire hydrant equipment houses to the scene of the fire (339/81-16-12).
The fire departments from liineral and Louisa arrived on the scene at 0750. The Mineral Department responded with 15 fire fighters and two 750 gpm pumpers which were positioned outside the protected area north of Unit 3.
One pumper connected to a hydrant north of Unit 3 and supplied a 2S-inch hose line (10) which was used to extinguish the fire along the fence between Units 2 and 3.
This line was placed in service at 0755. The other pumper connected to a hydrant north of Unit 4 and laid a relay 3-inch hose to the first Mineral pumper. After extinguishing the ground fire in the vicinity of the fence, the Mineral fire fighters set up a deluge nozzle supplied by a 2 -inch hose (11) from the first pumper and began discharging water on the fire at 0800.
MATERIAL TRANSMITTED HEREWITH CONTAINS 2390(d) _- MATERIAL TRANSMITTED HEREWITH ' ' ' ' ,' CONTAINS 2.790(d) -
The Louisa Fire Department responded with four fire fighters and left their apparatus at the east end of the plant. A deluge nozzle (13) was set up directly in front of the burning wall. This nozzle was supplied by the hydrant north of the Unit 2 turbine building which previously could not be opened by the plant fire brigade.
The deluge nozzle was placed in service at 0820 but was soon taken out of service since it was interfering with the fire fighting operations on the roof of the building and also since the ground fire was practically extinguished.
The Spotsylvania Fire Department arrived at 0805 with a 750 gpm pumper and seven i fire fighters. The Jumper was parked at the east end of the plant and the fire l fighters assisted etler fire fighting personnel.
The fire was under control at 0830 and all fires extinguished at 0845. The site emergency was secured at 0900.
Figures 5 and 6 are copies of photographs taken by VEPC0 personnel.
Comunications between the fire fighting organizations presented some problems during the fi.e.
The plant security and fire brigade personnel and the responding fire departments could not be in radio communication contact with each other since there was not a comon radio frequency for all responding fire organizations. This matter is being referred to NRC Headquarters for further evaluation (339/81-16-11).
Also, six of the operations radios which were used by the fire brigade failed (339/81-16-15). The inspector will followup on this ma tter.
These problems hindered the licensee from establishing a central control post to direct the entire fire fighting operations. However, the availability and use of the station security radio system prevented this from developing into a major problem.
5.4 Summary of Equipment Used A total of approximately 220,000 gallons of water was estimated by the inspector to have been used in combating this fire (deluge systems 130,000 gallons and manual fire fighting operations 90,000 gallons).
In addition to the routine nozzles, master stream appliances, etc., a total of 350 feet of 3-inch,1500 feet of 2 -inch and 1000 feet of 1 -inch fire hose and three fire department pumpers (two 750 gpm and one 1000 gpm) were used in this fire.
Figure 4 indicates the hose layout and sequence of fire fighting operations. The total number of people directly involved in this fire fighting operation was 70, broken down as follows: VEPC0 Operations Fire Brigade
VEPC0 Operations Employees
VEPC0 Construction Fire Brigade
Mineral Fire Department
Louisa Fire Department
Spotsylvania Fire Department
5.5 Training The inspector reviewed the fire brigade training records for 1981 and the fire brigade training drills for 1980 and 1981. The classroom training for 1981 was MATERIAL TRANSMITIED HEREWITH CONTA$S 2,700(d) _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
MATERIAL TRANSMITTED HEREWITH ' '
,' CONTAINS 2.790;d) SAFECUARDS INf0RMAll0N -
in accordance with the licensee's Fire Protection Plan, Section 7.1.
However, the frequency of fire brigade drills for 1980 and 1981 was not in accordance with Section 7.2 of the Fire Protection Plan in that quarterly drills were not conducted for each shif t fire brigade for every quarter of 1980 and 1981.
For 1980, three of the four Security shifts, who provide the majority of the manning for the brigade, did not participate in two quarterly drills and one shift did not participate in one quarterly drill.
In 1981, one of the Security shifts did not participate in one of the quarterly drills. The Operations shifts who provide the fire brigade leaders and other manning also did not participate in a sufficient number of drills.
In 1980, two of the four Operations shifts did not participate in two quarterly drills and two shifts did not participate in one of the quarterly drills.
In 1981, one of the Operations shif ts did not participate in one quarterly drill.
The failure to meet the firc brigade training require-ments is identified as a Violation (339/81-16-01).
A similar training violation was identified in Inspection Report No. 50-338/80-03 for fire brigade drilis conducted in 1979.
A program of training and periodic inspection should be e:aphasized to alert personnel of fire potentials and to assure fire lanes ar.d space for fire fighting equipment are maintained free of obstructions. This item is being forwarded to NRC Headquarters for generic consideratin.
At the time of the fire, thers coas . ' considerable congestion on the north side of the plant due to the stoNge of construction supplies, tool and equipment storage trailers and temporary efGce buildings. This arrangement hindered responding of off site fire deparVcNs in positioning their apparatus (339/81-16-13).
5.6 E_ valuation of Fire Fighting Operations i The initial objective of the fire brigade was to confine the fire to the point of origin and to prevent W sprGad ini.o the turbine building.
Although, the fire did spread from the pow of origin (B main transformer) to the adjacent spare . transformer storage area, due to the large quantity of burning oil Deing discharged fraa the ruptured transformer, the fire did not cause any appreciaule damage to tne interior of the turbine building. The Scene Leader's prompt act%n in requesting assistance from outside forces assured that sufficient parsonnel and fire fighting equipment were available to combat this fire. The fire fighting operations were satisfactory. An initial critique of the event by VEPC0 and NRC identified a number of areas where improvements should be considered.
These are provided in Section 2.0.
6.
SECURITY REVIEW Site security management personnel provided a detailed briefing supported by photographs, of the sequence of events during and after the fire, and the resulting impact on the security of the site.
Review of Security Force documentation and information revealed that imple-mentation of contingency actions during the emergency pre-empted routine Wirity functions. However, the security integrity of the plant was maintained. The details of Security Force actions, enclosed as a Supplement to this report, are considered proprietary information and therefore, exempt from disclosure in MATERIAL TRANSMITTED HEREWITH CONTAINS 2.790(d) SAFEGUARDS INFORMAll011
_ _.. MATERIAL. TRANSMITTED HEREVilTli
- - CONTAINS 2.790(d) SAFEGUARDS thc0Rf/All0N '
, accordance with Section 2.790(d) of the fiRC's " Rules of Practice", Part 2, Title 10, Code of Federal Regulations.
7.
Sult!!ARY OF CONCt.USIONS 7.1 Event Response The event demonstrated the licensee's response capability to a major plant fire.
The fire fighting response and the plant operational response following the tnn2former failure were satisfactory. There were no adverse affects on the hr,ith and safety of either the public or plant personnel.
7.2 Fire Fighting Capability This fire supported the fire fighting capability requirements of NRC Branch Technical Position 9.5.1, Fire Protection Program, Appendix A, Section C.2. for a fire protection water supply of 300,000 gallons and a minimum manual fire hose ,
stream flow rate of 1000 gpm. An estimated 220,000 gallons of water was used for this fire fighting operation. This fire indicated that when a fire extends beyond the capability of fixed fire suppression systems, additional hose stream flow rates may be required. At times, a total of 12 hose streams discharging approximately 2000 gpm were used in this fire fighting operation.
8.0 EXIT INTERVIEWS ' Exit interviews were conducted tr !nform the licensee of preliminary findings at the conclusion of each segment of this inspection.
These meetings were conducted at the North Anna site on July 4, 9,10, and 15 with individuals shown in Section 1.3.
The licensee acknowledged the findings and indicated reviews were ' already underway far most of the items.
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' MATERIAL TRANSMITTED HEREWITH CONTAINS 2.790($ SUPPLEMENT , SECURITY REVIEil SUPPLEMENT NORTH ANNA UNIT 2 TRANSFORMER FAILURE AND FIRE OF JULY 3, 1981 Docket / Report Nos. 50-338/81-19 and 50-339/81-16 MATERIAL TRANSMITTED HEREWITH CONTAINS 2.790'@ SAFEGUARDS INFORMATIO
. ., . , . - MATERIAL TRANSMITTED HEREWITH CONTAINS 2_790',d).
TABLE OF CONTENTS SECURITY REVIEW SUPPLEMENT Section Title Page 1.
SECURITY FORCE ACTIONS
1.1 Detection and Reporting
1.2 On Site Response
2.
0FF SITE RESPONSE
3.
DEGRADATION OF SECURITY EQUIPitENT AND CAPABILITY
4.
COMPENSATORY !1EASURES
5.
ASSESSt1ENT OF INCIDENT IttPACT ON SITE SECURITY
MATERIAL TRANSMITTED HEREVilTH CONTAINS 2.790(d) _ }}