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Report on Cable Failures - 1968
	ML13205A074
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Site:	San Onofre
Issue date:	07/24/2013
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SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 1 REPORT ON CABLE FAILURES--1968

SAN ONOFRE NUCLEAR GENERATING STATION UNIT 1 REPORT ON CABLE FAILURES -- 1968 SOUTHERN CALIFORNIA EDISON COMPANY SAN DIEGO GAS & ELECTRIC COMPANY

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SAN ONOFRE NUClEAR GENERATING STATION UNIT 1 ,

REPORT ON CABIE FAILURES - 1968 INDEX Secti on 1 SUtv'MARY 2 SOOUENCE OF EVENTS 3 INVF..STIGATIVE ORGANIZATION 4 SAFEI'Y EVALUATION AND CORRECTIVE ACTION 4.1 Safety Evalua tion of Operat ions During the Cable Failure Incident Cl 4.2 Ana lys is to Verify Electrical Separation Requirements of Equiprrent 4.3 Fire Fighting Eva luation

4. 4 Fire and Smoke Detection and Alarm Syste m

4. 5 Operating -Sh utdown Procedures 5 ELECTRICAL SYSTEM INVESTIGATION AND CORRECTIVE ACTION 5.1 Cable Fail ure and Correctiv-e Action 5.2 Testing Results 5.3 Cable Tra,y Loa ding 5.!1 Inspection of Cables and Trays 6 STARr- UP PRCGRAM 7 APPENDIX

SECTION 1 SUfv'iMARY 1.1. 0 PURPOSE

'fuis report was prepared to inform the Atanic Energy Carnnission of two incidents at the San Onofre Nucl ear Generating Station Unit 1: a cable failure adjacent to containment penetration EPC4 which occurred on February 7, 1968 ," and a cable failure in the No. 2 480- volt switchgear roan on March 12, 1968 .

After extensive investigations by the Southern california Edison Company, NUS Corporation, Westinghouse El ectric Corporation, and the Bechtel Corporation, the findings as well as the detailed analysis and safety evaluation leadifb t o these findings are present ed in the body of this report . Also included is a detailed description of the incidents and extensive action taken to avoid a recurrence.

It has been concluded that the most probable mechanism leading to both incidents is traceable to a common cause , thermally overloaded 480-volt conductors . For t his reason, this summary and the r eport which follows concerns itself primaril y vvith the f1a.rch 12 incident.

1.1.1 DESCRIPTI ON OF 'IHE mCIDENTS A. February 7: 1968 At 4:45 p.m. on February 7, 1968 , while operating at 380 M\<Je (net ),

several alarms were annunciated in the control room and a loud noise was heard from the plant area. Immediately thereafter , a fire was observed. in the cables leading to sphere penetration EPC4. 'Ihe fire was promptly extinguished. D..le to concern for contairnnent integrity , unit load reduction was initiated at 4 :50 p.m. and the reactor and turbine tripped by 5:10p .m., with reactor cooldown initiated ~t 5: 25 p .m.

The subsequent inspection revealed that the outer bu~<head of the penetration had been forced ~~ the canister shell . Also ,

the 65 cabl es leading to this penetration , outside of the sphere, had been damaged by fire . Eleven cables leading to penetration EPC9 , located directl y above EPC4 , were also slightly damaged . Six of the male connectors of the EPCLI canister were discovered pulled out of the inside bull<head . Inside the sphere all cables at both penetrations v1ere undamaged .

I t was noted that of the cables leading to this penetration ,

forty-five serve pressurizer heaters which had been energized continuously for 96 hours0.00111 days 0.0267 hours 1.587302e-4 weeks 3.6528e-5 months prior to the incident . During the shutdo\\'11 following the incident , there were no operational difficulties experienced. A subsequent r eview of circuits

1 -2 disab l ed by the fire indicated that t he ability to maintain a saf e shutdown was not impaired . An investigation was immediately initiated to establish the cause of the fire .

During the course of investigations and t hennal loading tests of a similar penetration (vJPC7) fol lowing the FebruarY 7, 1968 incident , it had been concluded that the thennal overloading of the cab l es was due prtmarily to restricted ventilation with the

\'leat her protective cowling at the cable entry to the penetration .

Since tests indicated that the cable temperature was well within the manufacturers rating with the cowling removed , it was decided to operate without the cowling until an outage that was planned for April . During the outage, improved cowlings

\vere to be installed and the remaining pressurizer heater cables would be replaced with larger conductors .

The f ailed pressurizer heater cab l es leading to EPC4 were replaced with l arger size conductors , the penetration canister was repaired, and the unit was returned to service on February 19, 1968 . It appeared that the failure was due to a localized problem and it was not suspected that a similar cable failure vias irrminent else-where i n the plant . However, the investigating gr-oup continued its work to determine the exact cause of f ailure . Based on subsequent information, it is recognized that the thermal over-l oading of these conductors was a general condition due to their sizing and was not restricted to l ocalized heating in the penetration cowling.

B. March 12, 1968 On March 12 , 1968 , at 12 : 25 a .m. while operating at 38o ~-1ide (net),

smoke was observed corning fran t he No. 2 480- volt switchgear room . It was determined that the smoke was due to a fire confined to cab l e tray sections 39C3 , 39C4 , and 39C5 in this room .

After appraisal of equipnent conditions in t he l\To . 2 480-volt swi tchgear roam and of the problems associated with the No . 2 480-volt bus and control room intelligence , the reactor was manuall y tripped at 12: 34 a .m . During the course of the fire ,

f eeder cables from the diesel gener a t or to the No . 2 48o- volt bus in tray 39C5 \*Jere burned and grounded. 'lhis circuit was cleared by relaying the entire No . 2 480- volt bus .

In accordance with station fire protection procedures , assistance was requested f'rom the Marine Corps fire fighting unit . Station personnel proceeded to fight the fire with portable equipment and, t ogether with the Marine Corps unit, extinguished the fire by 1:00 a . m. By this time , other s tation supervisory personnel had arrived at the site .

1-3 Actions to pr oceed with the cool down were initiated at 1 :10 a.m. , March 12 . 'Ihe Atanic Energy Comnission Canpliance Inspector was not ified of the incident at 2 : 50 a .m. and was informed that the plant was b eing brought to cold shutdown conditions . ;

Becaus e power had been l ost to t he Boric Acid Injection Pump, it was decided that boron would be injected as necessary through the use of the Bor ic Acid Transfer Pump. Also , a Primary Pl ant Makeup Pump was oper ated t o maintain proper reactor cool ant water inventor y . At approximately 5 :00a.m.,

t he cooldown was stopped when the Chemical Technician reported that the boron concentration was being reduced rather than incr eased . An assessment \<laS then made by the Plant Eilgineer (SRO) and i t was conc l uded that a shutdown margin in excess of

1. 0% 6 KIK was available . (Subsequent calculations indicated t hat the minimum amotu1t of shutdown reached during the incident was 2. 8% 6 K/K . )

At that t ime , l ack of boration was attributed t o the higher than normal vol ume control tank pressure exceeding the discharge capabil ity of the transfer pumps . Subsequent investigations ,

however, have established the actual cause as blockage of transfer pump now due to accumulation of boric acid crystals .

DJring the cooldown higher than normal pressures were noted i n t he volume control tank and radwaste systems .

Boration was then accomplished by manually closing the volume control tank outl et valve and by gravity feed fran the refueling water storage tank to the s uction of the charging pumps . 'There-after, cooldmm proceeded without any further boron injection probl ems .

'Ihe fire v.ras confined to three overhead cable trays stacked one above the other in the No . 2 switchgear room . 'Ihe cables in these trays were badly burned for a length of 15 feet . 'There wer e 185 electr ical circuits in these trays including the leads from the pressurizer heaters . 'Ihe fire was of such a l:i.mi ted nature that there was no overheating to the grating and beams or t he air intake located 38 inches above the trays .

'lhe plant equipnent is arranged such that the major redtu1dant equipment in the plant is duplicated on the No . 1 and No . 2 48o- volt buses with some additional duplication and misce llaneous l oads on a third bus . For this reason , although the No . 2 bus was deenergized , the redtu1dant equipnent on the No . 1 bus was available for service.

'Ihe No . 2 48o- volt bus was cleared of f aulted cables and reenergized by 9 : 45 a.m. and tmdamaged equipnent such as the boric acid heaters and heat tracing were returned to service from this source . IJ.he cooldo\m was completed at 10:00 p .m.

tllarch 12 , 1968.

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1.1. 2 INVESTIGATIVE ORGAN~ZATION As a result of t he March 12 incident, three principal Task Forces

\'tere organized to perform the following:

Ccnduct a safety review and recorrrnend corrective measures .

Investigate the cause of the failure and reconmend corrective action.

Restore the unit to a proper operating condition.

All recommendations by the Task Forces whether of a mechanical, electrical or operational nature, have been presented for approval by the On-Site Safety Review Comnittee,by the Nuclear Safety Audit and Review Committee and the Safety Control Board .

'lhe appl icable sections in the San Onofre Unit 1 Final Engineering Report and Safety Analysis , will be revised, as required, to reflect t he equipment modifications which resulted from this i nvestigation .

1.1 . 3 SAFETY EVALUATI ON A!'.JD CORRECTIVE ACTION A. 'lhe principal responsibilities of the Task Force to Conduct a Safety Review and Recommend Corrective Measures were:

1. A post-incident reconstruction of events and operational difficulties .

2. Recommendations to prevent or minimize the recurrence and consequences of a future similar failure.

3. As part of Item 2 above, analysis and recornrrendations as to t he degree of physical separation of e l ectrical circuits in order to rreet the objectives of (1) minimum conse quences and (2) assured safe shutdown .

B. A surrrna.ry of specifi-: areas of review, the conclusions reached, and the action taken by this Task Force are as follows:

1. Pl ant Des i gn Items

a. During the March 12, 1968 incident, redundancy of plant equipment proved adequate to bring the reactor to a safe shutdown condition. However, analyses have been made to investigat e the safety irrplications of the

.J cable failure and to demonstrate that the required redundancy exists to accomp lish a safe shutdown and to minimize t he consequences of another similar incident .

Cable has been relocated as necessary to meet this objective.

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b. 'Ihe amount of inoperative equiprrent could have been reduced if provisions had exist ed for sepal~ation of the faulted diesel feeder from the No . 2 480-volt bus . To i.ll"l)rove bus isol ation, pcrwer circuit breakers have been installed in the feeder cables to the 480-volt buses. ,

c. 'Ihe Volume Control , Flash, and Waste Gas Surge Tanks were overpressurized due to inoper ative equipment and to insufficient relieving capacity for conditions of this incident . 'Ihe integrity of the tanks has been verified by measurement, hydrotests, dye penetrant checks, and ultrasonic inspection . 'Ihese investigations have been confi!"l'red by a Consul tant Metallurgist. To prevent further overpressurization, relief valves sized to accommodate the maximum flow of 180 gpm have been installed .

d. Flooding of the Flash Tank resulted when the Flash Tank bypass valve remained in t he normal rather than the bypass position coupled with loss of poNer to the Flash Tank discharge pumps . To guard against undue over-pressurization modificati ons have been made such that the Flash Tank bypass valve fails bypassing the Fl ash Tank on loss of power or air.

e. Other operating difficulties experienced during cooldown will be prevented in the future by the addition of a magnetic flowrreter , with control room indication, in the boric acid transfer pump discharge line.

2. Operating Procedures

a. Reactor trip and hot shutdown were performed without diffi-culty .

The decision to initiate a cold shutdown was appropriately based on the uncertainties regarding the conti nued avail-ability of equipment and the knowledge that significant pl ant repairs would have to be implemented .

In this instance, there was improper operator- action since the applicable station operating instructions, which require boration of the reactor coolant system prior to initating the cooldown, were not followed .

Plant conditions did not indicate that such an acti on was necessary.

Dilution of the boron resulted due to (1) not berating the reactor coolant system to the cold shutdown condition prior to initiating the cooldown , (2) insufficient follow-up with respect to verifying that boration was actually t aking place by a boron analysis and boric acid storage tank level checl<:s .

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b. 'Ihe inadvertant boron dilution of the Reactor Coolant System was detected in sufficient time to maintain a minim.un shutdown margin of 2 . 8% .6 K/K . 'Ihe equipment necessary for the reactor cooldown -'as avail able and was either automatically or manually operable.

c. Additional ope rator training has been conducted to stress the irrportance of (1) adher ing to normal and emergency operating instructi on , and (2) p l acing sufficient emphasis on the evaluation and assessment of plant condition prior to initiating a cold shutdovm .

d. 'Ihe operational instructions have been ampl ified t o assure that the cooldOim will not be initiated prior t o verification of the appropriate boron concentration and all operating personnel will be trained to take a boron sample for analysis .

1.1.4 EillCI'RICAL SYSTE1'~ INVESTIGATION AND OORRECTIVE A~TION A. 'Ihe investigation of the cable tray fai l ures was conducted by the Task For ce to Investigate Cause and RecoJ'I'll'rend Action . 'Ihe work of this corrrrni ttee was supplerented i n the area of cable and tray inspect ion by the Task Force to Restore the Unit to Service. 'lhe group investigat ed the following areas:

1. Review of the conductor insulation requirements, sizing criteria , and specific sizing of individual conductor s .

2. Revlew of the prote ction scheJres associated with individual circuits .

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3. Review of cable tray physical and thermal l oading desigp limits to assure that there is no thermal overloading.

4. Inspection and testing of cabl es obtained from the circuits invol ved in the fai l ure .

5, Inspection of all cab l es i n t r ay systems throughout the pl ant for any evidence of distress.

6. Sirrulati on testing of tray sections involving the same con-ductors in similar configuration and with the same loading;s as t he t r ay section in which the failure occurred .

7. 'Ihermal analysis and tests of various cable configurations.

8. Analysis and simulation tests relat ing t o the cable failure incident adjacent to containment penetration EPC4 which occurred on February 7, 1968 .

1-7 B. 'fue extent and thorougtmess of the investigation lead to the following conclusions:

1. 'Ihe No . 6 AWG wire used for the 45 pressurizer heater leads was thermally overloaded for the conditions of tray 39C3.

2. Tray 39C3 was heavily filled to a leve l above the side rails which impeded heat dissi pation and caused heavy pressures on the l ower cables with possibl e def ormation of the cable materials .

3. 'fue combination of the above conditions which caused the conductors to operate above their 90°C insulation rating increases their susceptibility to insulation fail~~ with ti.me . Coupled with rrechanical dC!l'ffige to the insulation ,

the susceptibility i s further increased .

4. 'fue previous cable fail ure adjacent to containrrent pene-tration EPC4 involved simil ar No . 6 AWG conductors serving the pressurizer heaters , but which were fed from a different source and tray system . 'Ihe cab l es entered the penetration through a weather protective cowling where ventilation was restricted. This resulted in conductor t emperatures exceeding 90°C. 'Ihe lack of support to prevent conductors from beari ng heavily against each other contributed to the cable failure .

5. 'Ihe rost probabl e cause for each of the two cable failures was thermally overloaded pressurizer heater cables coupled with heavy mechanical loading or ~ resulting in a phase-to- phase fault co~dition between two cables of separate circuits .

6. Lack of concurrent three phase cl earing permitted low level fault current to continue tc flm'l and resulted in addi-tional faults and heat generation in the tray .

C. Corrective work and modificati ons resulting from the investi gation are as follows :

1. 'Ihe No. 6 A\vG wires in the pressurizer heater circuits have been replaced with No . 4 AWG wires in three-conductor cables.

Each group of 15, three- conductor cabl es has been located in a ne\v separate tray .

2. To reduce the number of circuits carried by each 480- volt penetration and to provide for increased conduct or sizes ,

a portion of the pressurizer heater circuits have been relocated to two additional penetrations .

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3. 'Ihree-phase tripping devices to replace the fuse-switch devices have been installed on all 48o-volt power circuits to provide positive three phase clearing of a -circuit in the event of a fault on one phase or an intercircuit fault condition.

4. Cable tray thermal and physical l oading has been further reduced so that no thermal overloading exists in any of the cable trays throughout the plant, by the installation of new trays, selective relocation of existing circuits and increase in s ize of certain conductors *

5. Cable repairs and revisions have been made throughout the plant as recommended by experienced Southern California Edison teams inspecting the electrical systems throughout the plant.

1.1.5 Sl'ARI'-UP PRCGRAM The Task Force to Restore the unit to a proper operating condition, in addition to inspecting the cables in the tray systems throughout the plant are doing the foll owing:

A. To verify that the new cable for the three damaged trays is installed properly and the recommendations of the investigative carmittee are followed, a qualified quality assurance team consisting of Southern California Edison and Bechtel experienced t echnical personnel is inspecting all repairs and modifications .

B. All repairs a."ld modifications will be thoroughly checked, first, by appropriate electrical testing to demonstrate that the installation is correct and that the various components and systems affected by the incident are in proper working order and function as originally designed.

C. The verification and start-up activities will be coordinated by the Station Chief and his operating staff. All operations will be performed as prescribed by the applicable Operating Instructions and Start-Up Procedure Manuals which are being

used as a guide for developing testing procedures .

D. In order to verify that cabl e locations are within p.,.--oper oper-ating l imits on return-to-service , temperatures will be measured at sixty-eight points . Forty- eight points will be recorded continuously on rrultipoint strip chart recorders and twenty additional l ocations v.rill be monitored by means of capillary bulb type temperature indicators . High te11perature alanns will be uti lized in conjunction with these points.

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1.6 CONCLUSION

S Based an the analysis and evaluation described in this report, it is concluded that the actions taken provide f or: (1) substantially increased assurance against cable tray failures, (2) earlier detection and quick response to a fire, ( 3) a smooth safe shutdovm with a minimum of operational difficulties in the event of a similar incident , and

( 4) minimum conseque nces arising from. an incident involving cable trays.

'Iherefore, based upon the extent and thorougtmess of the investigations conducted, the conservatism incorporated in the modifications, and upon completion of the start-up test program presented in Section 6 of this report, the plant can be returned to normal operation with a high degree of confidence in its operational safety.

SECTION 2 SEQUENCE OF EVEN'IS 2 .1. 0 PENETRATION FAILURE A. Int roduction On February 7, 1968, whJ_le Unit 1 was operating at 380 MWe (net),

penetration EPC4 failed as a result of a cab l e failure .

'lhe fire , observed in the cabl e tray l eading t o t he penetrat ion was extinguished and a rea ctor trip and cooldown was i nit iated .

This report describes the events during t his i n ci dent.

B. Sequence of Events Irnrrediately Before , During and After t he Cab l e Failure A detail ed description of events regarding this incident f ollows :

Tine Event Prior to Core depletion tes t s were in progress , and all Incident pressurizer heater s had been on for 96 hours0.00111 days 0.0267 hours 1.587302e-4 weeks 3.6528e-5 months .

4: 45 p.m. "Pressurizer high l eve l-heaters on" initi ated .

Heat e rs f ailed to core on . Actual pressurizer l evel normal.

4 :45+ p.m. 480-volt bus ground alarm initiated . 100% ground on No . 1 480-volt bus .

4: 46 p. m. A l oud noise heard in control room . Lighting f luctuated in control room .

4: 47 p . m. Security Officer repor ted a loud noi s e and fire at Sout heast s i de of sphere . Heating and ventil ating a.1.ann initiated.

4 :47 p . m. Trans f erred No . 1 480-volt bus t o No . 3 480- volt bus. Ground indicati ons on No . 1 and No . 3 480- volt buses. Transferred 480-volt bus es ba ck to normal . \t/at ch Engtneer and PEO i nvesti gat ion reve aled fire at EPC LI sphere penetr at i on . Fighting fire with Ansul and 002 exti nguis h ers . Fire under control.

4 :50 p. m. Opened 480-vol t circuit breakers t o i s ol ate ground .

Ground c l eared when Group C pressurizer heater breaker was opened . Started dropping l oad to remove unit from line .

2- 2 Time Event 5:05p.m. Unit load at 20% - control rods on manual,control.

Transferred No . lA and No . lB 4 kV buses to C trans fonrer .

5: 10 p . m. Tripped reactor/turbine by pushbutton . Visual inspection made inside sphere for evidence of

.f'lre . No damage found.

5:17p.m. ORMS channel Rl212 on monitor.

5 : 25 p.m. Stopped reactor coolant pllJll)S A and C. Started cooldown of main coolant system.

C. Extent of Damage The inspection revealed that the outer bulkhead of penetr ation EPC4 had been forced fran the canister shell . Also the 65 cabl es leading to this penetration, outside of the sphere, had been damaged by .f'lre . Eleven cables l eading to penetr ati on EPC9, which is l ocated directly above EPC4 , were also slight ly damaged by the .f'lre outside the sphere . Six of the male connectors of EPC4 canister were found pull ed out of the inside bulkhead . Inside the sphere all cables and connectors at both penetrations were un~d .

2 .1 . 1 CABlE TRAY FAILURE A. Introduction

<h March 12 , 1968, while Unit 1 v1as operating at 380 MWe (net),

.a cable f ailure in cab l e traJ 39C3 occurred and the resultant fire which took pl ace in the No . 2 480- volt switchgear room led to tripping the reactor at 12:34 a . m. 'll'.is .f'lre resulted in significant damage t o conductors in three cable trays . '!his incident complicated reactor cooldown.

B. Sequence of Events Irrurediatel y Before , During , and After the Gable Failure A detailed description of events regarding this incident follows :

Time Event Prior to Watch En~neer and Pl ant Equipment Oper ator were Incident in the 220 kV switchyard. Another Plant flluiprrent Operator was in the controlled area inspecting equipment . 'Ihe Control and Assistant Control Operators were in the control room.

2-3 T.1.rre Event 12:21 a.m. "Intake Structure Hi Level" alann initiated.

Ass i stant Control Operator dispatched to ~the Intake Structure.

12:21+ a.m. "'480- volt System Ground', ' Station D. C. Bus Ground or Low Voltage ' , ' Hydraulic Stop Gate Trouble' " alarrrs initiate d. Control Operator i dentified a 90% ground on No. 2 480- volt bus and checked equipment fed off this bus in an effort to locate and clear the ground .

12 : 22 a.m. "Sphere Heating and Ventilating System Trouble" alarm initiated.

12 :22+ a.m. Control Operator called and ordered t he Plant Equiprrent Operator i n the controlled area to return to the control room.

12:23 a.m. Assistant Control Operator reported fran the Intake Structure. Found no reason for the "Intake Structure Hi Level" alann.

12:24 a.m. Watch Engineer informed of trouble in the plant.

12 :25 a.m. Lost annunciator panels for turbine- generator first out, auxiliary, and electrical boards .

12 :25+ a.m. Assistant Control Oper ator observed smoke in the No. 2 480-volt switchgear room and notified the Control Oper ator by phone . Unable to enter the No . 2 480-volt switchgear room due to the smoke .

12:25+ a . m. Plant Equipment Operator dispatched from the control room to he l p the Assistant Control Oper ator .

12:27+ a.m. Oper ators observed blue arcing above the east door winda# of No . 2 480-volt switchgear room.

12.:28+ a .m. Operators returned to the control room to report on trouble .

12:31+ a.m. Watch Engineer arrived at No . 2 480- vol t switchgear room.

12 : 32 a . m. Watch Engineer observed fire in three cab l e trays abov-e the east door .

C' 12:33 a . m. Watch Engineer returned to the control room .

12 :34 a.m. Reactor tripped.

2-4 Tirre Event 12 : 35 a .m. Assistance requested from Marine Corps Fire I::epartrrent .

12:35 a.m. No. 2 480-volt bus cleared by overcurrent relay operations

12:36 a.m. Notifi ed the Dispatcher of tmit trip. Watch Engineer and Operators fighting fire.

12:37 a.m. Performed operations to shutdown the unit, transfer auxiliary equipment and to 12:55 a .m. restart the reactor coolant pumps.

12:45 a.m. Marine Corps Fire I::epartrrent arrived .

12 :56 a.m. Fire purrps would not start. Started gasoline engine driven Screen Wash Pump (backup errergency fire pump) and opened intertie between salt water and fire main systems.

1:00 a.m. Fire declared extinguished.

After the fire was extinguished an evaluation of conditions indicated a plant cooldown should be started . 'Ihe following are some of the significant events that took place :

(Reference should be made to the attached chart of operating pararreters . )

Time Event 1 :10 a . m. Transferred steam dump control from automatic to pressure control. Reactor Coolant System temperature at 540°F. Began preliminary operations to cooldown .

2: 15 a.m. Operated the North Boric Acid Transfer Pump for ten minutes . Started taking hourly Eerie Acid Tank temperature readings .

2 : 30 a .m. Radiation Chemical- Technician called in.

2:35 a .m. Started the steam driven Auxiliary Feedwater Pump.

Feeding the Steam Generators . Reactor Coolant System temperature 510°F.

2:45 a . m. Comrn:mced cooldown.

2:50 a . m. AEC Compliance Inspector notified by Station Chief .

3:00 a .m. Operated the North Boric Acid Transfer Pump for t en minutes .

2-5 Time Event 3:50 a.m. Padiation Chemical-Technician in the plant.

~ :00 a.m. Feduced cooldc:Mn rate and closed steam dtl!Jl) to condenser.

~: 30 a. m. Peactor coolant system boron sarrple obtained.

5:00 a.m. Reactor Coolant System boron concentration deter-mined to be 1638 ppm. Stopped system cooldown at

~~0°F and 870 psig .

5:00 a.m. O'larging Purrp suction transferred to the Refueling Water Storage Tank. Opened rr.ov llOOB and D.

5:10 a.m. Reactor Coolant sample boron concentration was 1562 ppm.

5:20 a.m. O'larging Ptmp suction transferred from the Volwre Control Tank . Closed iVDV llOOC . Reactor Coolant System temperature 435°F and pressure 860 psig.

6:~0 a.m. Reactor coolant sample boron concentration at 1734 ppm.

7:12 a.m. Reactor coolant sarrple boron concentration at 1835 ppm.

7:~5 a.m. North Boric Acid Transfer Purrp in service ,.lith 12% boric acid solution being added to reactor coolant system.

8:~0 a.m. Reactor coolant system cooldOim resUired . System temperature at 400°F and 1200 psig.

9:45 a.m. No . 2 480-volt bus reenergized.

C. Extent of D:llnage The damage attributed to the cable failure consisted of the follO\'/ing:

(1) 185 electrical circuits lying in cable trays 39C3 , 39C4, and 39C5 in the No. 2 480-volt room. 'Ihese circuits were totally burned for 15 feet . Approximately 175,000 lineal feet of conductor will be required to replace these circuits.

(2) Section of cable trays 39C3, 39C4, and 39C5 were warped from the heat .

(3) Eighteen (18) control transforners were damaged in m:>tor control center No. 2.

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( 4) 'Ihe knife S\.'fitches in the pressurizer heater cabinet were found wel ded together.

(5) Heating and Ventilating Annunciator Panel burned out.

(6) Smoke damage occurred to the following: ;

(a) Motor control center No. 2.

(b) 480-volt switchgear Nos. 2 and 3.

(c) Lil'}lting switchgear.

(d) Pressurizer heater cabinet.

(e) Spent Fuel Building supply for casing and plenum.

(f) Colunns, grating, and walls in the No . 2 480-volt room.

SAN ONOFRE NUCLEAR GE NE RATI NG STAT ION REACT OR PARAME T ERS FOL L OWING S HUT DOWN DUE TO CABLE FAILURE ON MA RCH 12, 19 6 8 575

-~TR I P @l 0 0 3 4 550

\...- ~

52 5 500

~ ;

4 75

"" ~ ......__

4 50 4 25 4 00 I'- L OO P "A" COLD L EG T E MP (

F)

__.--- T RI P @ 0034 2000

""' \_

1750

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1500 r-...

P RESSURIZER PRESSURE (PSIG )

/

1250 10 0 0 ""\ ....__---

.L 7 50 "

(SWITCHED POWER RECORDER SOURCE RANGE 5

~

r

(.)

4

-.......... r-

.... 3 0

X 2

- SOURCE RANGE COUNT RATE (CPS)

(C H- 1202 )

2200 r BORON CONCE NT RATION ( PPM) 2 100 TRIP (Q) 0034 I

2000 I BORATING WITH*PJ NO. TRANSFE R PP I 1900 I TRANSFERED CHG PP SUCTION TO REFUELING WATER TK- \

J;

-~VI l OB a D OPE N 1800

/

1700

~~~PBF~*RT~tN~;~: - ~ i--- \ /

I -~ 4 /

1600 K~

RAN B. A . T RANSFE R PUMP FOR 10 MI NS ~ PROBABLE MINIMUM Ca DU E TO DELAY TIM E FROM SAM PL E TO MEASUREMENT 1500

~ TRIP @I 0034 0

2 PROBABLE MINIMUM SHUTDOWN DUE

!.-< ~TO DELAY TIME IN BORON ME ASUREMENT 3

"""' i"-.

4 5

6 7

L.---

""' ~

~PERCENT SHUTDOWN- (% )

2300 2400 0 10 0 0200 0 300 0 4 00 0 50 0 0 60 0 0700 080 0 0900 T I ME

SECTI<N 3 INVESTIGATIVE OOGANIZATIOO 3.1. 0 PURP03E

'Ihree principal Task Forces were organized to ass~ that (1)' a thorough investigation of the incident would be accomplished , and (2) to initiate corrective acticn required to prevent possible recurrence. 'The respcnsibilities of the Task Forces were to accomplish the following:

A. Conduct a safety review of the incident and recoiTITEnd corrective measures.

B. To in~ stigate the cause of the failure and recCII'Ilrend corrective action.

C. To restore the tnit to a prcper operating conditicn.

3.1.1 DrSCUSSION

'Ihe findings, conclt.5ions and all recCil'llrendaticns resulting from the investigaticns of these Task Forces were submitted for review and approval to the follCMing corrnrd. ttees :

A. Ch-Site Safety Review Carrnittee B. Nuclear Safety Audit and Review Carmittee C. 'The Safety Ccntrol Board

'lhere was a thorough discussion of all reconrnendations st.Dmttted to each of these Canm1. ttees prior to their approval and imple~rentation of the recommended corrective actions .

A chart outlining the Investigative Organization is attached. Also attached is a chart outlining the Nuclear Safety Conrn1 ttees .

INVESTIGATIVE ORGANIZATION SAN ONOFRE NUCLEAR GENERATING STATION CABLE FAILURE INCIDENT- MARCH 12, 1968 I I SUPERINTENDENT OF STEAM GENERATION

- I TASK FORCE TO INVESTIGATE CAUSE TASK FORCE TO CONDUCT A SAFETY REVIEW TASK FORCE TO RES1DRE AND RECOMMEND CORRECTIVE ACTION AND RECOMMEND CORRECTIVE MEASURES UNIT TO SERVICE CHAIRMAN CHAIRMAN CHAIRMAN ASSOCIATE CHIEF ELECTRICAL ENGINEER CHIEF STEAM GENERATION ENGINEER SUPERVISOR OF STEAM OPERATION UNDERGROUND RESEARCH a DEVELOPMENT MECHANICAL ENGINEER lNG STEAM GENERATION SUBSTATION STEAM GENERATION SDG a E REPRESENTATIVE S~._AM GENERATI ON WESTINGHOUS E REPRESENTATIVE MECHANICAL ENGINEERING ELECTRICAL ENGINEERING NUS REPRESENTATIVE CONSTRUCTION ENGINEERING CUSTOM ER SERVICE STAFF BECHTEL REPRESENTATIVE BECHTEL REPRESENTATIVE APPARATUS SYSTEM OPERATI ON BECHTEL REPR ESENTATIVE WESTINGHO.JSE REPRESENTATIVE

SOUTHERN CAUFORNIA EDISON COM PANY NUCLEAR SAFETY ORGANIZATION FOR SAN ONO FRE NUCLEAR GENERATING STATI ON ATOMIC ENERGY CO MMISSION NUCLEAR SAFET Y CONTROL BOARD VI CE PRESIDENT !ENGINEERING)

V I CE PR ESIDENT (POWER SUPPLY)

V ICE PRESIDENT (ELECT RIC) - SOG a E FREQUENCY

INFORMALLY, AS REQUIRED NUCLEAR PHYSICS CONSULTANT

( SHALL ATTE N D A LL MEEnNGS)

N UCLEA R SAFETY AUDIT AND R EVIEW COMMITEE ROTAT IN G CHAIR MANSHIP MANAGER OF POWE R SUPPLY DEPARTMENT STAFF MEMBERS* MANAGER OF EN GINEERING DEPA RTMENT WESTINGHOUSE ON-SITE]

MECHANICAL EN GR. COMMITTEE ME MBERS*

F UEL SUPERVI SOR ELECTRICAL ENGR . SUPERI NTENDENT OF STEAM GENE RATI ON CONTROLS ENGR. (SHA L L ATTEND CHIEF MECHANICAL ENGINEER CH EMICAL E NGR. A LL MEETINGS)

(RAOIAnON PROTECTION ) CH IEF STEAM GENER ATION ENGINEER SUPERVISOR OF STEAM OPERATION SUPERVI SING MECH AN IC AL ENGINEER SUPERVISING PLANT EN G INEER- SDG a E ADDITIONAL CONSULTANTS FREQUENCY* QUARTERLY , AND A S REQU IRED AS REQUIRED TO VER IFY A.'iD EXPEDIT E CRITICAL DECISIONS SUCH AS RADI ATI ON PROTECTIOII SYSTEM INSPECTION .

AND l iATER IALS ETC.

ON -SITE SAFETY R EVIEW COMMITTEE QIAJRMAH* Sl:r.TI ON CH IEF CO MMITTEE MEMBERS PLANT SUPERVISORY STAFF.

LIASON REPRESE NTATIVE- SDG a E FREQUE NCY loiON THLY. AHD AS REQUIR ED SAN ONOFRE STAT ION CHIEF RE SPONSIBILITIES ON-SITE SAFETY REVIEW COM MITTEE NUCLEAR SAFETY AUDIT AND IIEVIEW CO MUIT TEE HJCI..EAR SAFETY CONTROL BOARD ANALYlE INSTANCE S WHEN TECHNICAL SPECIACA - I. REVIEW AND EVAWATE TECHNICAL SPECIFICATION I. FORMALLY SUBMIT SAFETY ANALYSIS REPORT T O T IONS HAVE BEEN VIOLATED.

VIOLAT IONS, TAKE APPROPRI ATE ACTION. AEC IF A TECH. SPEC . IS VIOLATED.

2 SUBMIT A FIRST HAND FACTUAL REPORT TO THE 2.. ANALYZE RECO MMENDED CHANGES TO TECH . SPECS. 2 . REV I EW A ND APP ROVE RECO MMENDED CHANGES TO AUDIT COMMIITEE IF A TECH NICAL SPECIACATIO N AH D PR!:PAR E A REPORT TO THE CONTROL BOARD TECH. SPECS.

HAS BEEN VIOL ATED IF TH E RECO MI.I ENOATIOHS ARE ACCEPTED 3 . SUeMI T PROPOSED CHANGES TO T ECH SPECS TO

3. DE T ECT POTE NTI AL SAFETY HAZARDS BY A NAlYSIS 3 REVIEW AN D APPROVE PROPOSED EQUIPMENT RE- AEC FOR C ONCURRE!ICE OF PLAN T ACT MTIES PLA CEI.IENTOR U ODI FICATIONS AND PROPOSED 4 . MAINTAIN MANAGE MEN T CONTROL WITH R ESPECT 4 REVIEW ALL PLANT PROCEDURES AND CHANGES SYSTEM CHANGES DOCUMENTREASONSFOf< CHANGE TO NUCLEAR SAFE T Y IN COMPA NY OPERATIONS T HERETO . AND WHETH ER IT INVOLVES AN " UNREVIEWED SAFE-

~ REVIE W ALL PLANT AD NOR MALITIES TY QU ESTI ON * .

e RECOMMEND MODiriCATIONS ro TECH Sl'f:CS. 4 . IN !nATE ITS OWN RECOMMEND.m<INSON CHANGES 7 f'REPARE REPORTS R[ QUES TEO I Y THE CHIAR MAN T O TECH . SPECS.

OF THE AUDT COMMI TTfE . l'i. INITIATE OPERATIONAL IMPROVEMENTS TO PLANT SAFETY WITHIN THE SCOPE OF THE TECH SPECS

6. !!£VIEW AND EVALUATE PLANT SAFETY DURING A BNORMAL PLANT CONDrriO NS.

T. P CRFORM PERIODI C AUDIT OF Oll(RAriON EOUI~CNT PEHFOR MA N CE. LOOS AN D PftOC EOURES.

SECTION4 SAFETY EVALUATION AND CORRECTIVE ACTION 4.1 SAFETY EVALUATION OF OPERATIONS DURING WE CABlE FAILURE lliCIDENT

4. 2 ANALYSIS TO VERIFY ElECTRICAL SEPARATION REQUIRFMENTS OF EQUIP!'>1ENT

4. 3 FIRE FIGHTlliG EVALUATION

4. 4 FIRE AND SMOKE DETECriOO AND ALARM SYSTEM 4.5 OPERATING- SHUTDOWN PROCEDURES

SECI'ION 4 SAFEI'Y EVALUATION AND CORRECTIVE AGriCN

4. 1 SAFETY EVALUATION OF OPERATIONS DURING THE CABIE FAILURE INCIDENT

4. 1. 0 PURroSE

'lhe f oll owing analysis is made to review the significance of t he cable failure of March 12, 1968, including subsequent operation and inoperable equipnent as they relate to plant safety . This analysis , which begins with the first observati on of trouble , was made in order to detennine the probl ems that developed and their effect on the ability to safely shut down the reactor.

A detailed sequence of events, from the time the first indication of an operating difficulty was received in the Control Roan , is given in Section 2 of this Report .

4. 1.1 REVIE\v OF INCIDENT A. Equipnent Operability As a result of the cable failure, the reactor v1as tripped and placed in a hot shutdown condition. Power and/or e l ectrical controls associated with the following plant equipnent were damaged as a r esult of the fire .

1. Stack Discharge Fan A- 22

2. Residual Heat Removal Loop Suction Valve , MOV 814

3. Residual Heat Removal Loop Discharge Valve, rtCV 834

4. Component Cooling vlater Heat Exchanger Outlet Valve (Top) , 1\DV 720A

5. South Primary Plant ~1ake-up Water Pt.mp

6. Power lost to the folla-~ing Annunciator Panels :

a. Turbine Generator First Out Panel

b. Electrical Panel

c. Auxiliary Panel

4- 2 In addition, the follCMing equipnent which is part of t he plant engineered safeguards were electrically inoperative as a r esult of damaged cables :

1. Safety Injection Recirculation Valves , MOV ' s 357 and 358

2. West Recirculation Pump and Dischat>ge Valve , MOV 866B 3* Electric Auxiliary Feedwater Pump

4. Safety Injection Train Valves , West Train MOV' s 85lB, 852B, 853B and 854B

5. Refueling Water Storage Tank Outlet Valve , MOV 883 (nonnally open)

. 6. Seal Water Injection Pre-Filter Bypass Valve , MOV 18

7. Refuel ing Water Pump Discharge Valve to Recirculation System, MOV 880 Safeguard equipment l ocated on other plant buses was operabl e throughout the incident.

Also, f eeder cables from the Diesel Generator to the No . 2 480-volt bus were burned and, as a result, developed phase-to-phase faults . Since the breakers associated with these feeders are located at the Diesel Ge nerator which is remote f'rom the No. 2 480-volt bus, clearing of this circuit cou~d only be accomplished by de-energizing the entire No . 2 480-volt bus . Since this bus had to be de-energized ,

considerably more equipnent became inoperable than would have been the case if breakers had been installed at the 480-volt bus . However, both diesels renained a\a.ilable for service to the No . 1 and No . 3 480- volt buses . Breakers will be added to the 480- volt buse s to prevent a recurrence of this problem (refer to the Equipnent Addition and IV1odif'ications .Subsection for detailed discussion).

'Ihe follm'ling is a list of equipnent that became inoperative due to the loss of the No . 2 480-volt bus rather than directly due to fire damage:

1. Battery Charger Set B

2. South Salt Water Cooling Pump

3. South Refueling Water Pump (G- 27S) c 4. West Residual Heat Removal Pump

5. South Transfer Pump

4-3

6. Boric Acid Injection Punp

7. Test Pump

8. Boric Acid Storage Tank Heaters

9. Boric Acid System Heat Tracing 10 . South Primary Pl ant Make- up Pump

11. Waste Gas Compressor

12. Flash Tank Bypass Valve , CV- 101 13 . East and West Flash Tank Discharge Pumps

14. Center Component Cooling Water Pump

15. Reactor Cavity Cooling Fan A-9S

16. Stack Discharge Fan A-24

17. Motor-Operated Valves

a. Refue l ing Water Stor age Tank Valve , rtDV llOOD

b. Volt.mle Control Tank Outl e t Valve , fiDV l l OOC

c. West Residual Heat Exchanger Inlet Valve , MOV 822B

d. Component Cooling Water Heat Exchanger Outl et Valve (Bottom) , MOV 720B

\\hen the No . 2 480- vol t bus was restored to service at 9 : 45 a .m., March 12 , all equipnent \'lith the exception of that with damaged cables was again available f or service .

All redundant components of plant equipnent required either f or a safe shutdown or safeguard purposes were unaffected and available at all times during the incident, with the exception of the Heat Tracing , and the Boric Acid Storage Tank Heaters .

B. Cold Shutdown Operations After the reactor was tripped and the fire was extinguished ,

an evaluation of plant conditions indicated that a reactor system cooldown should be started . Actions to proceed

,.,ith the cooldown were initiated at 1 :10 a .m. f*1arch 12 .

4-4 As a re*s ult of the loss of the No. 2 Motor Control Center, the Boric Acid Injection Pump was inoperable . 'lhis pump is normally used for borating the primary coolant since metering is provided and preselected amounts of boron can be injected to obtain the desired concentration. Since this pump was not available, it was decided that poron would be injected for a cold shutdown condition through the use of the North Boric Acid Transfer Pump . 'lhis pwnp was operated for two ten-minute periods during the cooldown in order to increase the boron concentration approximately LIOO ppm in the Reactor Coolant System . Sufficient quantities of demineralized water were also added to the Reactor Coolant System to make up for system shrinkage as the cooldown proceeded .

The Chemical Technician arrived on site and a primary coolant sample was taken at 4:30 a.m. 'lhe results indicated that

. the required boration was not being accomplished and the cooldown was immediately suspended.

Upon determining that boric acid was not being injected, an alternate rreans of boration was begun using the Refueling Water Storage Tank. Borati on using this tank is accomplished through gravity feed and the closure of MOV llOOC. Because remote operation of MOV llOOC had been l ost as a result of the fire, the valve had to be closed JTL.3.nualJy . Upon closure of this valve, the boron concentration began to increase .

C. Chemical and Volume Control and Radwaste System Operations During the course of the cooldown, water was being injected with a Primary Coolant Makeup Hater Pump into the Volurre Control Tank to maintain the primary coolant water inventory .

When it was determined that boric acid was not being injected through operation of the North Boric Acid Transfer Pump, an assumption was made that this traPsfer pump could not overcome the s~1tly higher than normal pressure (approximately 40 psig) within the Volume Control Tank . At that time an attempt was made to vent the gases in the Volume Control Tank to the Flash Tank in order to loNer this pressure. Venting to the Flash Tank was not effective because the Waste Gas Compressor was inoperable, which resulted in higher than normal pressures in the Radwaste System . It was also not possible to release gases to the stack s ince the Stack Fans (A-22 and A- 24 ) had also l ost their power , and the gas discharge valve (SV-99 )

\-.rhich is interlocked with the operation of these fans would not open.

(

4-5 When the Volume Control Tank Outlet Valve (fv'DV llOOC) was closed in order to utilize borated refueling water, the water level in the Volume Control Tank increased until it reached the level where automatic diversion to the Flash Tank occurred. 'Ihe Flash Tank Discharge Pumps were inoperative and the level of the Flash Tank increased to the point where the Flash Tank Bypass Valve (CV-101) should have diverted, bypassing letdown directly to the Holdup

~anks. However, CV-101 had failed in the normal position as a result of the loss of power and continued directing water into the Flash Tank.

During this period, Vol t.l!TE Control Tank pressure was noted to be above the pressure transmitter range of 100 psig. At this point, the Volume Control 'I'ank as well as the Flash Tank and Waste Gas Surge Tank were water-bound and at pressures above design. To correct this situation the Flash Tank Bypass Valve was manually positioned so that the letdown could flow freely to the Liquid Radwaste holdup tanks.

4.1.2 SAFETY EVALUATION A. Initial Operator Action

'lhe first indication relative to safety , resulting from the cable failure of March 12, was a ground alarm on the No. 2 480-volt bus. This bus is required for reactor criticality by Technical Specification 3. 7. Four minutes later, the Turbine Generator First-Out , Electrical and Auxiliary Annunciator s failed . Nine minutes after the annunciator failures the reactor was tripped, and one minute later after tripping the reactor the No . 2 bus relayed.

The loss of any plant annunciation is of operational concern, and, depending upon the degree to which annunciators are lost and what other plant intelligence may be avail alJle , may influence operator judgment such that he manually trips the reactor .

It should be noted that at all t imes during the cable failure all plant vital instrumentation, as well as reactor plant annunciation, r emained in service and available for operator surveillance; that is, although same annunciation had been lost , Control Roan r ecorders and other inst.r-t.m:entation monitored by annunciators were displayed in a normal manner to the reactor operator at all times during the cable failure and ensuing fire.

B. Reactor Trip t o Hot Shutdovm Conditions Technical Specification 3.7 requires a plant shutdown if c.

~

the No. 2 480-volt bus cannot be restored to normal service.

When the No. 2 bus was grounded and loss of anmmciation occurred, the reactor and turbine generator were manually tripped . 'lhe trip was initiated and t he pl ant shut dmm.

All equipment necessary to place the plant in a hot shutdown condition was available and functioned properly.

c. Cold Shutdown Qperations An assessment of the situation resulted in the decision to initiate a cold shutdown which was appropriat e .

'lhis assessment was based on the uncertainties regarding the continued availability of equipment and the knc:Mledge that s~ficant pl ant repairs would have to be implemented.

During the course of the cooldown operating personnel believed that more than sufficient boric acid had been added to the Reactor Coolant System for the cold shutdown

. Xenon-free condition . 'lhe first boron sample was obtained at 4: 30 a .m. and the analysis completed at 5:00 a .m. This indicated that the coolant concentrati on had been reduced to 1,638 ppm (from an initial level of approximatel y 1, 911 ppm) and t he cooldovm was :irrnnediately suspended . Plant conditions at this time were 440°F, and 870 psig , and a conservative calculation at that time indicat ed a shutdown margin in excess of 1% ~ K/K.

A sample taken at 5:10 a .m. showed a further reduction in boron concentration t o the minimum value of 1,562 ppm.

This further dilution was the result of making up to the reactor cool ant system between 4 : 30 a.m. to 5:00a.m.

when cooldown was stopped. During the entire dil ution period source range instrumentation was monitored and the count r ate was noted as not increasing. Shortly thereafter rtt:N llOOC \'las manually closed and boration was initiated fran the Refueling Water Storage Tank . Each sample analyzed there-after indicated successi vely higher values of boron.

Subsequent calculations indicate that at the minimum boron concentrati on (1,562 ppm) the shutdown margin was 2. 8% AK/K (see Appendix)

Subsequently investigations have established the actual cause as blockage of transfer pump flow due to sol idification of boric acid. It was not recognized at the times the Transfer Pump was operated that little or no boric acid was actually pumped and with the addition of demineralized water to maintain reactor coolant inventory , dilution of the Primary Coolant System resulted .

14-7 To proVide more positive indication of successful boration when enploying the boric acid transfer pumps ,

a flow meter has been installed in the Boric Acid Transfer Pt.nnp discharge line , redundancy has been provided in the heat tracing , the Boric Acid Storage Tank Heaters now have separate power suppl ies and pc:Mer cable routing, and an additional line s ection has been traced and insulated (refer to Equip-ment Addition and Modificati ons Subsection f or detailed discussion) .

Existing Operating Instructions stipulate that (1) prior to initiating a cold shutdown, boration to the Xenon- free cold shutdm~ condition should be accomplished, and (2) verification of the baron concentration in the Reactor Cooling System is to be made by chemical analysis and observation of a decrease in the Boric Acid Storage Tanlc l evel.

Once this is accanplished, the instructions permit the operator to proceed with the cooldown.

In this instance, there was improper operator action since the applicable station operating instructions ,

which require boration of the reactor coolant system prior to initiating the cooldown, were not followed .

Plant conditions did not indicate that such an action was necessary. Boron dilution resulted from (1) not berating the reactor coolant system to the cold shut-down condition prior to initiatiP~ the cooldown , (2) insufficient follm1- up with respect to verifying that boration was actually taking place by a boron analysis and boric acid storage tank level checks .

A munber of corrective measures regarding operating procedures which are outlined in the Summary of Corrective Action have been taken to avoid a recurrence of this situation .

D. Engineered Safeguards As noted above, although sane canponents in the safety Inj ection, Sphere Spray , and Recirculation Systems were inoperable as a result of the fire, at least one redundant component of all affected equipnent in each of these systems remaJ.ned operable during the cable failure and subsequent fire . Each of these systems would have been capable at all times of perfonning 1 ts design safety function .

0 In addition, both on-site Diesel Generators were available throughout the subject cable failure and could have been used, if necessary, .in conjunction with 480- volt buses No. 1 and No. 3.

E. Chemical and Volume Control and Radwaste System Operation Dlrr'ing the course of events following the cable failure, the Volt.nne Control Tank, Flash Tank and Y.laste Gas Surge Tank were overpressured due to the inoperability of various pieces of equi:pnent in the Radwaste System. To prevent a future overpressuring of this system, relief valve sizing on the Volume Control and Flash Tanks has been increased and the Flash Tank Bypass Valve (CV- 101) changed so that it fails in a position to bypass the Flash Tank (refer to Equipment Addition section for detailed discussion).

In order to determine the highest pressure obtained in these tanks and the Radwaste System, a series of tests were conducted . Inspection of pressure gauges within the Radwaste System indicated that the low pressure range gauges had became distorted due to excessive pressure. Identical gauges were obtained and subjected to a pressure l evel where similar distortion occurred. 'lhe results of this overpressure testing indicated that the Flash Tank and the Waste Gas Surge Tank had reached a pressure of approximately 125 psig.

As a further check, a 0-100 psig pressure transmitter on the Volume Control Tank was inspected in order to determine the extent of distortion; hoNever, no evidence of deformation was noted on this transmitter . Based on the lmowledge that this instrument would have been damaged at a pressure level of approximately 150 psig, it \'las concluded that this was the maximum pressure to which this tank could have been subjected.

Tb determine the extent of damage, if any , on these three tanks, all were rreasured for comparison with as-built drawings . 'Ihese measurements revealed that no distortion occurred. Further confirmation was obtained by conducting dye-penetrant tests on all tank welds. There appeared to be sane slight degree of distortion or circumferential expansion on the Fl ash Tank, which was attributed to initial fabrication . Measurements of the tanlc shell indicated that this expansion amounted to approximately 0 . 25 inches beyond design dimensions . Ultra-sonic tests in this area were accomplished and verified that this portion of the tank was also sound.

4-9 To reinforce the findings with respect to the inspection of these tanks and in particular the slight distortion noted on the Flash Tank, a Consul tant ~tallurgis t was contacted to obtain an independent opinion. Mr. G. M. Butler, Metallurgical Service Laboratories, submitted a report (see Appendix) which confirms Edison's conclusions that these tanks are suitable for continued service.

4.1.3 EQUIPMENT ADDITIONS AND MODIFICATIONS A. Diesel-Generator Breakers The cable failure incident indicated that additional power breakers installed between the 480-volt buses a."ld the cable leads to the diesel bus will provide greater 480-volt isolating capability and more operating flexibility in case of a feeder cable failure.

Initially one breaker was provided at the diesel-generator end of each of these cable runs.

In the event of a short circuit in the cable between the 480-volt auxiliary buses and the diesel-generator bus, the additional breakers 'l'lill autanatically open to separate the fault .from the auxiliary electric system. 'Ihis increase in fault clearing selectivity will allow short circuits to be cleared in the cable leads without affecting the continuity of service of other auxiliary system elements.

'Iherefore, two Westingtlouse DB-75, 480-volt, 2000 ampere circuit breakers have been installed between the No. 1 and No. 2 480-volt auxiliary buses and the cable runs to the diesel-generator bus. 'Ihe interrupting rating of the DB-75 circuit breaker is sufficient to clear faults from the 480-volt bus. 'Ihese breakers will be controlled at the switchgear \'lith indicating ligtlts and breaker trip alarms in the control room. 'Ihey are interlocked with the existing breaker so that they cannot be closed unless the breaker at the diesel-generator is open.

B. Provide Magnetic Flow Meter In Transfer Purrp Discharge Line In the course of attempting to borate using the Boric Acid Transfer Pumps , it was necessary to rely on changes in Boric Acid Storage

Tank level and chemical analysis of the Primary Coolant to verify that boron was actually being injected.

4-10 In order that a more irrrnediate means of determining the rate of boron injection be available to the operator, a magnetic flow meter has been installed in the Boric Acid Transf~r Pump Discharge Line and recorded on Control Roc:m instrumentation.

c. Provide Backup Heat Tracing on Boric Acid Lines ~

Tests indicate that heat tracing on the Boric Acid Lines i s important for a long tenn po\Jrer l oss . Spare heat tracing is provided aDd has been connected to an alternate power source and arranged so that it will automatically come into service in the event of a failure in the nonnal tracing system.

D. Separate Boric Acid Storage Tank Heaters In order to provide complete redundancy within the Boric Acid Storage Tank Heater circuitry, complete physical separation of the t\'IO heaters and the-l_r power sources is required. fue power source to each heater presently comes from separate motor control centers . Power cables have been routed through separate cable trays. Only one heater is required to be in service at any one time and the necessary instrumentation is provided to cause the second heater to begin operating if required.

E. Installation of Additional Heat Tracing and Insulation In the original station design, no heat tracing nor insulation was provided on the portion of the Boron Injection System Piping between CV- 334 and the suction of the charging pumps.

It was felt that this was not required since normal operating procedures requll'e that this portion of the line be flusl')ed *.

wi th primary water after any boration in order to prevent plugging. However, should improper flushing occur, additional heat tracing and insulation will further reduce the possibility of any plugging. Accordingly, heat tracing on this section of line has been provided.

F. Revision of Relief Valve Sizirig and Point of Release on Fl ash Tank and Volt.nne Control Tank Relief valve sizing on the Volt.nne Control Tank and the Flash Tank has been changed to accollU'Tlodate the maximt.nn possible amount of letdown of 180 gp11 . 'Ihe original design basis for relief valve sizing on .these systen5 provided that these valves would only be required to accollU'Tlodate gases . However,

4-11 as a result of this incident, the relief valve sizing has been increased to accommodate a maximum fluid flow of 180 gpm . In addition , the point of relief valve release fran the Flash Tank has been changed to the suction of t he. Flash Tank Discharge Purrps. 'Ihe relocation of the relieving point will allo11 liquid to be selectively relieved from the Flash Tank in order to m1nim1~ the am::.>unt of gas that would be diverted to the Holdup Tanks during any relief val ve operation. 'Ihe relieving pressure will be approximately 55 psig on the Voll..lm::'! Control Tank and 30 psig on the Flash Tank.

G. Flash Tank Bypass Valve CV-101 During the cable failure, power \vas los t to control valve CV-101. 'Ihe normal funct i on of this valve is to bypass the Flash Tank should a high level occur in this tank . 'Ihe valve was desigr1ed to fail in t he normal position and allow water to continue to enter into the Flash Tank on loss of power. \.Jh.ile this mi.ght no:rrrally be satisfactory, it did not account for the possibility of a concurrent failure of the Flash Tank Ptmps .

resign changes have been developed so that this valve will fail in a posi tior. bypassing the Flash Tank and directing all water to the Holdup Tanks as a further means of protecting the Flash Tank from undue flooding. Failure to this new position will occur on l oss of power or instrument air.

4 .1. 4

SUMMARY

OF CORRECTIVE ACI'I ONS Based an t he above safety evaluation, the following recommenda-tions have been implemented:

1. Provide additional operator training to assure that:

a. 'Ihe importance of adhering to normal and errergency operating instructions is recognized.

b. Sufficient errphasi s i s pl aced on evaluation and assessment of plant conditions prior to initiating a cold shutdown.

2~ AmplifY appropriate operating instructions to assure that t he proper cold shutdown boron concentr ation is verified by actual sample analys is before a plant cooldo:.m i s init i ated .

4-12

3. Train all operating personnel to obtain boron samples.

Sampl es will be obtained and analyzed as required during emergency cc:ndi t icns to affirm proper boron concentraticn.

4. Provide separation with respect to power source, and electrical wiring between redundant components to m1n1muze the consequences should a similar 1ncident, occur.

5. Accorrplish equipnent additions or modifications as outlined in Paragraph 4.1. 3.

ll-13

4. 2 ANALYSIS 'ID VERIFY ELECTRICAL SEPARATION REQUIREMENTS OF EQUIB\1ENT

4. 2 . 0 PURPOSE A study has been made of the el ectrical separation of redundant plant components to determine whether additional separation may be required. 'Ihe requirement for equipment to operate under normal and emergency operational conditions has been considered, as well as i ts relation to other equipment that might perform a similar or redundant function .

'lhe scope of the study includes power sources , and cable tray routing for el ectrical wiring. Complete el ectrical separation for duplicate pieces of important equipment was used as a guide for the study even though in same cases this approach goes beyond existing plant design cr iteria.

4.

2.1 DESCRIPTION

A. The following systems were analyzed to assure that the necessary electrical separation exists for redundant equipment desirabl e for a safe and orderly reactor shutdown under normal and emergency conditions . Recommendations regarding electrical separation were made and implemented for these systems as a result of the analysis.

Chemical and Volume Control System Safety Injection System Air-Conditioning System Residual Heat Removal System Auxiliary Coolant System Circulating Water System Compressed Air Syst~

Reactor Coolant System Miscellaneous Water System B. 'Ihe ana~ysis of the following systems determined that all necessary equipment will perform their safety functions during emergency conditions . No additional action was required.

c

4-14 Containment Isolation Feedwater and Condensate System Steam System C. 'lhe following systems were reviewed even though they do not directl y relate to t he ability to safely shut down the unit .

No. el ectrical separation was found necessary .

Turbine Cycle Vents and Drains Turbine Plant Chemical Feed System Ra.dwaste System Turbine System Turbine Lube Oil System t1Lscellaneous System Turbine Cycle Sampling System Reactor Sampling System Sphere Test System Attached are S1.ID1!Tla.I'ies of the analysis undertaken for each system listed under (A) above and the pl ans that were developed to assure that the necessary degree of electrical separation exists . Detailed analysis of cable tray routing and power source revealed that in certain instances changes were necessary to accomplish the planned separation . These specific changes are l isted at the conclusion of each system analysis .

4*2. 2 CHEFII CAL VOLUI'-1E AI\))) OONTROL SYSTH~

A. System Safety Functions This system is directly associ ated with safe operation of the reactor plant and the capability to shut down and maintain control of the reactor in the shutdown condition.

Its primary safety function is to regulate the concentration of boron in the primary coolant

4-15 B. Separation Requirenents Tb accomplish complete redundancy in all functional areas, separation of electrical leads for each of these components and its backup component must exist . In order ~o provide such separation, verification Nas required that the electrical leads for the following equipment combinations are routed by completely separate paths from the component in question to its power supply.

EQUIR1ENT REQUIRIJ-Kl ELECrRICAL SEPARATION Power Source 1 Power Source 2 Power Source 3 Boric Acid Injection North Boric Acid South Boric Acid Pump Trans fer Punp Transfer Pump MOV- llOOB ~10V-llOOC MOV- llOOD North Charging Pl:mp Test Ptunp South Charging Pump Boric Acid Piping Alternate Boric Heat Tracing Acid Heat Tracing Boric Acid Heater Boric Acid Heater C. Circuitry Revisions The following circuitry reV1s1ons have been accomplished in order to provide the recommended physical separation .

Equipnent Action Taken

l. Boric Acid Electrical leads separated from the South Injection Boric Acid Transfer Pump and the power Pump source relocated to Motor Control Center

. 3.

2. MOV-llOOD, Electrical circuits separated from Refueling ~10V-1100C and power source relocated Water Storage to MCC- 3.

Tank Outlet Valve

3. Test Pump Rerouted control circuit of the Test Pump to provide isolation of Tes t Pump , South Charging Punp , North Charging Pump ,

electrical circuits .

~-16 Equipnent Action Taken It. Boric Acid Rel ocated power supply , rerouted power Stor age Tank cir cuit , and removed transfer swi tch to Heat ers provide isolati on between th~ t wo stor age tank heat er s .

5. fur i c Acid Provided new power source for spare heat Pipi ng Heat tracing elements . Power circuits between Tracing the two heat tracing systems will be physically separated .

4. 2.3 SAFETY INJECTION SYSTN'l A. Syst em Ftmctions The Safety Injection System provides protection against the consequences of reactor coolant blowdown in t he event of rupture of the primary coolant pressure boundary .

The design criteria of the Safety Injection System stipulates its satisf actory oper ation with "second order mechanical equiprrent failures ." Compli ance wi th these criteria i f the Saf ety Inj ection System were called upon i n t he event of a loss- of-coolant accident is de~onstrated in Section 10 of the FERSA.

B. Separation Requirements A coincidental occurrence of a fire and requirement for initial safety injection is not considered credible and s eparation of safety injection circuitry would therefore not be required on that basis .

'Ihe credibility of a pl ant fir e , however , increases as t bne el apses fol lowing an assumed DBA. Accordingly ,

prudent j udgJTJent points to the desirability of having separate control and power circuits to at leas t redundant components of t he spray and recirculation systems .

Since major cable revision work is underway , the scope of el ectrical cabl e separation has been extended to the Safety Injection System.

To accomplish complete redundancy , physical separation of electrical cables for each component and its backup component must exist . The overall system review indicated t he f ol lowing requirements shall be verified .

4- 17 Equipnent Requiri~ Separation From Each Other With Respect to Electrical Wiring Injection:

Power Source 1 Power Source 2 East Safety Injection West Saf-ety Injection funp Pump East Feedwat er Pump West Feedwater Pump MJV 854A MOV 854B fvDV 853A r..-r>v 853B r.DV 852A MOV 852B fvDV 851A r..-r>v 851B Gable Route 1 Cable Route 2 Cable Route 3 I*10V 850A MOV 850B MOV 850C f'.DV 850A, B & C each have two separate power supplies , motor control centers 1 and 2 .

Reci rculation Power Source 1 P0\'1er Source 2 and Spray: North Refuel ing South Refueling Water Pump Water Pump East Recirculation West Recirculation Pump Pump HOV 866A MOV 866B f'.lOV l lOOB tilOV llOOD North Charging Punp South Charging funp r.nv 18 r1ov 19 Pov1er Source 1 Pawer Source 2

Power Source 3 MOV 356 t10V 357 i'IOV 358 C. Circuitry Revisions The followinG circuitry revisions were accomplished in order to provide the planned physical separation .

Equipnent Action Taken

1. Safety Injection Rerouted electrical cables and relocated Recirculation Valve power source to r.JCC-3 to provide f*IOV 358 isolation from ~:ov ' s 356 and 357 .

4-18 Equipnent Action Taken

2. Seal \>later Injection Rerouted electrical circuits to provide Pre-Filter Bypass i s olation between MOV ' s 18 and 19 .

Valve HOV 1 8

3. Grou2 I Rerouted electrical cables to provide i solation between the equipment in East Safety Group I from that in Group II.

Inj ection Pt.nnp East Feedwater Pump MOV-85lA IDV-852A lvDV-853A f-10V- 854A Grou2 II

\'lest Safety Injection Pump West Feedwater Pump MJV- 85lB fYDV-852B MOV- 853B I110V-854B

4. MJV-850A, B & C Rerouted e l ectrical cables to provide isolation of MOV-8~0A ,

MJV- 850B, and I\10V- 850C from each other .

5. East Recirculaticn Rerouted e l ectrical cables to Pump and MOV- 866A i sol ate the East Recirculation Pump and MOV-866A from the West Recirculation Pump and MOV- 866B

6. 'North Refuel ing Rerouted e l ectrical cables to Water Pump isolate the North Refueling Water Pump fran the South Refueling

\vater Punp .

4-19

4. 2 . 4. AIR-CONDTIIONINJ SYSI'Ell A. System Functions The air-conditioning system , although not strictly related t o the capability to shut dovm and maintain control of the reactor in the shutdown condition , is desirable to provide air flow in the following safety- rel ated equipment areas:

1. Stack - For controll ed release of radioactive gaseous \V"astes (Fans A-22 and A- 24) .

2. Reactor Cavity - For cooling of nuclear instrun~ntation (Fans A- 9 and A-98) .

3. Control Rod Drive Space - To limit temoerature of control rod drive operating coils (Fans A- 8 , A- 8S ,

and A- 8SS).

B. Separation Requirements Assure that the electrical supplies to the fan motors in Col umn 1 below are routed separately from those listed in Col umn 2.

Column 1 Col umn 2 A- 22 A- 24 A- 9 A- 9S A- 8 A- 8S A- 8SS separated from items listed in both columns .

C. Circuitry Revisions

'Ihe following circuitry revisions have been accomplished in order to provide the planned physical separation .

Equipnent Action rraken

1. Spent Fuel Building Rerouted electrical circuits Exhaust Fan A- 24 and relocated power supply to f*1CC- l to i solate fran Fan A- 22 .

2. Reactor Cavity Rerouted electrical circuits Cooling Fans to provide isolation between Fans A- 9 and A- 98 .

3. Control Rod Drive Rerouted circuits to isol ate c Space Cooling Fans A-8, A-OS, and A- 8SS from each other.

4-20 4.2.5 RESIDUAL HEAT ID'10VAL SYSTEM A. System Ftmctions The residual heat removal system is normally required for cooling do~m the r eactor coolant system once the pressure and temperature are less than 400 psig and 350°F, respectively.

This is accomplished by the residual heat removal pumps circulating reactor coolant through the residual heat loop and the reactor . Each of the residual heat removal pumps assures that pumping capacity is only partially lost if one pump fails or beccmes inoperative. This system is also required during refueling operations .

B. Separation Requirements The following electrical separation requirements for the residual heat re~oval system shall be verified.

1. Confirm that electrical cables for one residual heat removal pump are physically separated from its com-panion pump.

2. Assure complete physical separation for electrical l eads for the motor operated valves (f"DV 822A and B) on the inlet of the residual heat exchangers .

3. Confirm that the residual heat exchanger cannot be overpressurized due to an inadvertent valve operation by verifying that the electrical wiring is physically separated between i*lOV- 834 and r10V-833 and also between the valve groups i*10V- 813 and iviJV-814 .

C. Circuitry Revisions The following circuitry revisions have been accomplished in order to provide the pl anned physical separation .

Fquipnent Action Taken

1. Residual Heat Removal Rerouted circuits to isol ate Loop Suction Valve t*10V 813 to l'!OV 814 .

2. Residual Heat Removal Rerouted circuits to isolate Loop Discharge Valve rl'DV 833 from MOV 834.

3. Residual Heat Ex-

Rerouted circuits to isolate changer Outlet Valve I"'OV 822A from r.JOV 822B.

4. Residual Heat Removal Rerouted circuits to separate Pump the East and Hest Residual Heat Removal Punps .

ll-21 lJ.2. 6 AUXILIARY COOLANT SYSTEM A. System Functions

'Ihe Auxiliary Coolant System performs functions that , although not relating directly to safety , are important to orderl y operations . One Component Cooling Pump will suppl y cooling for the Residual Heat Removal System, Safety Injection Re-circulation Heat Exchanger and Spent Fuel Pit . Component cooling is generall y required for an orderly plant shutdown ,

and control of the plant after a shutdown.

B. Separation Requirements In order to provide backup in the event of equipnent fai l ure, physical separation of electrical l eads shall be verified between each of the three Component Cooling Pumps.

C. Circuitry Revisions The foll~'ling circuitry revisions have been accomplished in order to provide the planned physical separation .

Equipment Action Taken North Component Cooling Rerouted the e l ectrical circuits Hater Punp to provide separation of the three component cooling water pumps .

4. 2 . 7 CffiCULATING WATER SYSI'El\1 A. System Functions

'Ihe Circulating \tJater System provides the source of cooling

f or the Auxiliary Coolant System. 'Therefore , ccrnponents that interrelated with the Auxiliary Coolant System are also generally required for an orderly plant shutdown and for control of t he plant after a shutdown.

B. Separation Requirements

'IWo Salt Water Cooling Pumps are provided to supply circulating water to the Component Cooling \1/ater Heat Exchangers

One of these tv1o pumps shall be operable at all times and physical separation \vith respect to electrical cables shall be assured.

C. Circuitry Revisions The following circuitry revlslons were accomplished in order to provide the planned physical separation .

~-22 Equipnent Action Taken North Salt Water Cooling Separated electrical circuits Pump to provide i solation of the North and South Salt \>later Cooling Pt.mps

4.2. 8 COfvlPRESSED AIR SYSTEN A. Systffil Functions The compressed air system is designed to supply air for pneumatic instrument operation and control. An emergency compressor and receiver is provided to furnish compressed air for emergency instrument service which is sufficient to accomplish an orderly plant shutdoVIn and maintain control of the plant after shutdown .

The emergency air compressor or one r.Jain compressor can be

rtm fran a diesel generator. Each main canpressor is supplied from a separate 48o volt bus , and the emergency air compressor is supplied from a motor control center.

B. Separation Requirements It shall be verified that the electrical suppl y to the main compressors is physically separate from the electrical supply f or the emergency compressor .

C. Circuitry Revisions

'Ihe following circuitry revisions were accomplished in order to provide the planned physical separation .

Fg,uipnent Action Taken Eirergency Instrument Air Separated the electrical circuits Compressor of the Elrergency Instrument Air Compressor from the other Air Compressor circuits .

4-23

4. 2 . 9 REACTOR OOOLANI' SYSTEM A. System Functions Plant safety associated with the Reactor Coolant~ System is directl y related to the various trips and interlocks initiated by the following instrument channels :

1. Pressurizer Pressure

2. Pressurizer Level

3. Reactor Coolant Flow

4. Reactor Coolant Temperature

5. Nuclear Instrumentation

6. Turbine Auto Stop Oil Pressure

7. Loss of Feedwater B. Separation Requirements All of the Reactor Protection System is of a "de-energize to trip" design. While this is in the safe direction, a loss of power may result in a loss of indication and control which J.s undesirable when proceeding with a pl ant shutdown.

'lherefore assurance shall be made that cables from the inverters to the automatic transfer s\,Jitches are run separately

~ from the source cables for the 37 . 5-kVA transformer to ~aximize the availability of power to the instrument channels . Also, el ectrical wiring has been separated to assure that at least one of all the redundant instrument channels will be available for indication.

C. Circuitry Revisions

'lhe following circuitry revisions were accomplished in order to provide the planned physical separation.

Equipllent Action Taken

Power Supply to Vital Provide separation of inverter Bus l eads from alternate source in cabl e trays.

4. 2 . 10 MISCELLANEOUS WATER SYSTE1'1S A. System Functions This system is not directl y* related to the ability to accomplish a safe pl ant shutdmm or to maintain the plant in a safe shutdown condition . It does supply water to the

4-24 fire system and as such is necessary in the event of a fire.

Both fire pumps, however, have backup from two service \'later pumps and two screen wash pumps , one of which is driven by a gasoline engine .

B. Separation Requirements Physical separation of the electr ical cables to the two fire pumps is not considered necessary ; however, since these cables were damaged by the fire, it is planned that they be physically separated in the course of their renewal .

C. Circuitry Revisions

'Ihe following circuitry reVlslons were accanplished in order to provide the planned physical separation.

Equipnent Action Taken

l. North Service Water Pump Reroute electrical circuits to provide isolation of the North and South Service Water Pumps .

2. West Fire Pt.nnp Reroute electrical circuits to provide isolation of the West and East Fire Pumps .

3. South Primary Plant Reroute electrical circuits to Make-up Water Pump provide isolation of the North and South Primary ~*1ake-up \vater funp circuitry .

4-25

4. 3 FIRE FIGHTTI-IG EVALUATION

4. 3.1 PURPOSE

'lhe purpose of this evaluation is to determine if changes to fire fighting equipnent and/or procedures are required as a result of the experienced gained during the incident.

4.3.2 DISCUSSION

'TI.1 e cable f ailure occurred in a closed room which filled with smoke . Wit h visibility obstructed , detection of the fire source was hindered , thus del aying fire fighting activity .

Operating personnel notified the r~larine Corps Fire .I:epartment as they canbatted the fire with a 150# Ansul and 50# carbon dioxide ext inguishers . 'Ihe fire was temporarily arrested but not contained, since the electrical circuits involved could not immediately be de- energized. 'Ihe 1'1arine Corps fire fighting personnel entered the switchgear room and sprayed water using fog nozzles on t he cable trays . 'Ihis r esponse fran the l'-1arine Corps Fire Department was prompt and in accordance with established station emergency procedures .

Alerting of the Marine Corps Fire .I:epartment was in accordance with established station fire protection procedures . However ,

t he procedure should have provided that the Marine Corps Fire

.I:epartment be alerted as soon as the emergency was determined ,

rather than waiting until a fire is identified.

Rel ationship between the filarine Corps Fire .I:epartment and the San Onofre Huclear Generating Station personnel is one of close liaison. Fire Department personnel f'requentl~* visit the plant to familiarize their personnel with the l ocation of fire fighting apparatus and hydrants . 'Ihey attend the Station ' s Fire Fighting Practice demonstrations . It is intended that this rel ationship will ~ontinue .

4. 3. 3 CORRECTIVE ACTI ON 1.. To assist in rapid detection of future fires, smoke detectors with alarms in the control roan have been installed in various locations to provide early warning.

2. 'Ihe matter of notification of the r*1arine Corps Fire

.I:epartment has been revie\':ed , and the appropriate procedures have been revised to require pranpt notification .

4-26 4.4 FIRE AND SVlOKE IEI'EGri ON AND AI..AR-1 SYSTEM 4.4.0 PURPOSE A fire and smoke detection system is desirable to provide prompt detection and identification of fire and/or smoke in various areas of the plant . 'lhe system will provide the control roan with means to monitor areas of the plant containing equipnent and cabl es required for the operation and control necessary for the safe and orderly shut down of the unit.

4.4.1 DISCUSSION The decision to install a fire and smoke detection system is a part of the overall effort to augment plant fire protection and to improve early detection of an incipient fire condition.

Leading manufacturers of fire and smoke detection systems have demonstrated that the most sensitive and reliable manner to promptly detect fire or smoke is by means of sensing the products of combustion.

A "Pyr-a-larm" fire and smoke detection system, using sensing and alarm equipnent manufactured by Pytronics , Inc. has been installed at San Onofre Nuclear Generating Station .

The sensing element uses the ionization chamber principle wherein products of combustion entering the detector caus e a chaTJge in current flow across the ionization chamber. This change in current Dow is used to operate the trigger electrode of a cold cathode tube, causing it to operate and a ctivate an alarm in the control roan of the plant. Because the detector contains no moving parts , it has proven to be e>..'tremely rel iable in its operation and has been used extensively throughout this continent for the past 12 years .

4.4. 2 CORRECTIVE ACTION The system is designed to detect smoke or fire in separate areas of the plant . The monitored areas of the p.J..ant have been divided into eleven (11) zones as follows :

1. Diesel-generator and motor control center No . 3 area.

2. 416 0-volt switchgear room . .

3. No . 2 and No . 3, 480- volt svritchgear roan .

4-27

4. Inverter and d-e switchboard room and battery roan .

5. 'Ihe cable gathering area below the turbine front s tandard .

6. Control roan area.

7. Corrrrnunications room .

8. Admini str ation Building. ;

9. 220-kV r e l ay house .

10. Reactor auxiliary building .

11. Containment vessel strategic cable areas .

Approximately 110 ionization detectors have been installed to cover the eleven ( 11) zones listed above . Separate armunciation i s provided for each zone to penni t quick identification . '!he detection system f or each zone is completely independent such that short circuits , failure of a detector , or any other type of malfunction in any one zone will not affect the satisfactory operation of the detection system in the other zones . '!he de-tection system is continuously electrically supervised f or power supply 10\.,r voltage , breaks in wiring or grounds. These probl ems will be immediately armunciated in the control roan and identified by zone .

'lhe wiring for t his detection system has been run in a new and separate metal conduit system.

An operating instruction has been written for the fire and smoke detection and alarm systems which set s forth the procedure to be followed by the operators in responding to alarms in the system. 'Ihese procedures consist of directions such as dispatching personnel to the areas , to evaluate the condition and report their findings . In addition, it outlines directions to be fol l owed in the event areas are inaccessible due to a fire , \*lith specific instructions to t ake emergency procedtrres s uch as de-energizing equipnent located in roans and references to applicable fire fighting procedure .

~-28 Q 4. 5 OPERATING-SHUI'IX)WN PROCEDURES

~.5.1 PURPOSE A review has been made of existing Station Operating Instructions and emer~ency s hutdown procedures to d~termine where changes are required as a result of the incident .

4.

5.2 INTRODUCTION

The initial procedures followed by Station personnel during the incident were to determine the cause of the alarms received. Once the source of the alarms was found and it was established that a fire exist ed , a proper attempt was made t o i s olate and clear the ~ 8o-volt bus ground condition . vihen it was determined that the effect of the loss of the No . 2 480-volt bus would result in exceeding a limiting condition of the Technical Specification, the reactor was t r ipped .

4. 5. 3 DISCUSSI ON A. Electrical Fault Cl earing aperating Instructions Operating Instruction S-6 "4160 Volt Feeder Faults 11 describes the procedure f or cl earing e lectrical f aults and is applicable to this incident. 'Ihe operator's actions to clear the fault were in accordance with this procedure and were effective . There fore , no revision to this Operating Instruction is necessary .

B. Fire Fighting Operating Instructions Station Order S-A- 2 , "Fire Protection" describes the responsibilities and fire ~ting procedures to be followed. Experience gained during the fire has been incorporated into the Station Order as follows :

1. 'Ihe procedures to be fol lovled when a fire is in a switchgear roan and involves the safety of personne l or equipnent have been revised . 'Ihe new procedures require the oper ator to promptly call for eme~ency assistance .

2. A new section has been added for procedures to be followed in the event of an alann from the area smoke detector system. These procedures require t he control room operator to dispatch another operator to investigate the area in which the alarm or iginated and determine the problem and action required . These procedures also require the operator to request eme~ency assistance from the proper agency .

4- 29 (perating Instructions S 1, 2 and 3, "Fire Ptnrps and Water Systerrs , Dry Chemical Fire Extinguishers, Carbon Dioxide Fire Extinguishers, 11 have been reviewed and are proper . 'Ihe Control operator responded correctly and pl aced the engine-driven screen wash punp (energency fire punp) into service for fire figt'lting upon loss of the two station electric-driven fire purrps .

C. Shutdown Qperating Instructi ons Operating Instructions S-3-1. 5, 2 . 5 and 5 . 2, "Plant Hot Shutdc:Mn to Cold Conditions," "Cnemical Shim Control and Errergency Boration of the Reactor Coolant System," have been revised to further emphasize the importance that the concentration of boron in the primary system shall be determined by chemical analysis before a cooldown is started . All other applicabl e Operating Instructions have been reviewed and found adequate.

D. Additional Changes

1. A series of check cards have been prepared to aid the operator in his response to emergency situations .

'These cards contain a broad outline of each of the emergency operating instructions listing the major automatic and manual actions that must take place .

'Ihe check cards also contain a reference to the appropriate operating instructions that provide rrore detailed instructions . 'Ihe check cards will be kept in an indexed file on the Control Operator ' s desk

\'.rhere they wil l be readily accessible. By use of the applicable cards, the operator will be able to roni tor the control boards and rmke notes of the events that have or have not occurred and take action accordingly .

2. All operating personnel have been trained to obtain boron sarrples . Sanples will be obtained and analyzed as required during errergency conditions to affirm proper boron concentration.

SECTION 5 ELECTRICAL SYSTEM INVESTIGATION AND CORRECTIVE ACTION 5.1 CABLE FAILURE AND CORRECTIVE ACTION 5.2 TESTING RESULTS 5.3 CABLE TRAY LOADING 5.4 INSPECTION OF CABLES AND TRAYS

SECI'IOO 5 EIECI'RICAL SYSTEM INVESTIGATI ON AND CORREGriVE ACTIO.~

5.1 CABLE FAILURE AND CORRECTIVE ACTI ON 5.1.0 PURPOSE

'Ihe purpose of this analysis is to determine the causes of cable failures f or each of the two incidents that occurred at San Onofre . 'Ihe conclusions are based upon the investi gative work of the Task Force to Investigate Cause and Recommend Corrective Action which included the testing program outlined in Subsection 5. 2 and given in detail in the Appendix. In addition, recommended modifications to electrical equipment to prevent the recurrence of cable failures due to any of these probable causes are presented .

5.1.1 CAUSE OF CABLE FAIT..URE AND RESULTANT FIRE IN CCM'LI.1'n OF PENEI'RATION EPC4 ON FEBRUARY 7, 1968 On February 7, 1968 , a cable failure occurred within t he weather protective cowling of penetration EPC4 on the exterior of the containment .

This penetration had 65 conduct ors r anging in size from No . l/0 AHG to No . 6 A\oJG copper wires. At the time of the failure, the 45 No . 6 AWG conductors supplying the pressurizer heaters had each been loaded at approximately 46 amperes for 96 hours0.00111 days 0.0267 hours 1.587302e-4 weeks 3.6528e-5 months . (See Figure 1 showing Pressurizer Heater Wiring Arrangement. )

'Ihe* oost probabl e cause for the failure in the cowling of EPC4 was the use of No . 6 AWG copper wire in the 45 pressurizer heater cables which were grouped in bundles restricting ventilation. Heating due to power l osses of these conductors under the cowling caused the 90°C rated insulation on these conductors to be subjected to elevated temper atures , which accel erated aging of the insulation.

In'addition, the following two factors could have contributed to the failure:

A. Lack of supports allowed conductors to bear heavily against each other and thus contributing to causing a phase- to- phase fault .

5- 2 B. Developnent of tracking currents and the subsequent flow of fault current between 480-volt pins on the exterior face of the penetration due to moisture .

The exterior face and areas between the conducting pins on these penetra tions were fil led with an RTV (roan temperature vulcanizing) sili con rubber which could have permitted the entrance of moisture , leading to eventual electrical breakdown at the exterior face of the penetrations .

Circuit protection for the pressurizer heaters consisted of fused disconnect S\vitches for the 30 three- phase circuits .

The use of individual fuses to provide for the clearing of faults on three-phase 480-volt circuits which were involved in the fire resulted in single- phase operation as shown on Figure 2 . This permitted law level f ault current to continue to flow causing additional faults and heat generation at the outside face of the penetration .

Heat from the resulting fire travel ed through the pins t o the insi de of the canister. The heat caused the insulating materials inside the canister to decompose ,

f orming gases which generated sufficient pressure to expel the outsi de bulkhead from the canister .

5 . 1. 2 CAUSE OF CABlE FAILURE AND RESULTANr FIRE IN CABlE TRAYS ON MARCH 12, 1968 On March 12, 1968 , a cable fail ure occurred and the resultant fire damaged cable trays 39C3, 39C4, and 39C5 . It is significant to note that, as in t he February 7 incident, all of the pressurizer heaters had also been in service with each of the 45 No . 6 AWG conductors serving these heaters , loaded to approximately 46 amper es . In this case , the heaters had been in service f or approximately nine hours prior to the failure . The pressurizer heater cables were located in the l ower tray (39C3).

'Ihe most probable cause was the use of No . 6 AWG copper wire in ~he 45 pressurizer heater conductors in a heavily fill ed cable tray restricting ventilation . Heating due to the power losses caused these conductors to operate above their 90°C insulation rating, causing accel erated aging.

5- 3 0

The following factors coupled with the overheating could have contributed to the failure:

A. 'Ihe trey was heavily filled to a level above the side rails, causing heavy loading on the lower cables and possible deformation or flow of insulating materials .

This loading or other mechanical damage in combination vrith t hermal overl oading of cables, contributed to a phase-to-phase fault condition between two separate 48o- volt circuits setting the insulation on fire in the tray.

B. Several cable-to-tray ties using No . 12 '.n-1 wire, rather than nylon, were found holding power cable in position in the steel treys . 'Ihese were suspected of possible heating due to transformer action . A wire t i e , which had burned apart, was found at the point of ITDS t severe damage in t r ey 39C3.

c. Defective cab l e .

D. Damage during installation.

'Ihe large initial short circuit cUITent was cleared by the fuses in the faulted phases . HeM ever, the currents in the unaffected phase was below the fuse continuous rating . (See Figure 2 . ) Current was subsequently back f ed through the pressurizer heaters into the short circuited cables, supporting the canbustion of adjacent cable insulation .

Lack of three phase clearing permitted l ow leve l fault current to continue to flow and sustain the fire causing additional faults and heat generation in the trey.

5.1.3 REPLACEMENT CABLE INSULATI ON The existing single-conductor No. 6 AWG butyl rubber insulated neoprene jacketed cables , originally utilized for pressurizer heater circuits , were replaced with tr~e-conductor No . 4 AWG cables rated at 90°C conductor temperature . The three- conductor No. 4 AHG cables are also insulated with butyl and jacketed with neoprene with an overall jacket of polyvinyl chloride.

'lhe butyl rubber ozone resistant ins ulation, with a neoprene jacket, is used external to the sphere for 600-volt power and control circuit cables at San Onofre as well as other CorrqJany installations. 'Ihis canplies with Southern California Edison ~*1aterial Standard No . 225 which is included in the Appendix. Suppliers tmder this standard are limited to a carefully prequalified group .

5-4

'tvulkene" cross-lined polyethylene insulated conductor was selected for use within the sphere due to its radiation resistive properties

In evaluating and selecting the desired cable insulation system, it is normal practice to consider environnental exposure. As in all Southern California Edison applications, the power and control cable provided at San Onofre vras selected on the following bases :

A. Southern california Edison~s experience at other system locations .

B. Experience of other Utility Companies in the United States.

C. Established national standards.

D. Southern California Edison's Specifications .

E. Manufacturer 's specifications and test data.

F. Manufacturer' s reputation.

G. Environmental conditions.

5.1.4 CDRREcriVE ACTION A. 'Ihe existlilg single-conductor No. 6 AWG butyl rubber insulated neoprene jacketed cables, originally utilized for pressurizer heater circuits, were replaced with No. 4 A\vG three-conductor cable. 'lhis will provide for more orderly aiTangement of the cable in the trays, and will tend to keep related conductors in a single-circuit adjacent to each other.

B. 'Ihe remaining damaged power and control cables, which vary in size from 500 MCM to No. 12 A\tJG, were replaced with cable of the same type as that previously installed as specified in Svuthern California Edison Material Standard 225 .

c. rrhree-phase circuit breakers have been used to replace the fused devices as short circuit and overload protection on all 480-volt circuits, including the pressurizer heater circuits. 'Ihis type of breaker has several modes of protection, each of which provides three-phase tripping.

The modes are as follows:

1. Magnetic coil contact openirlg for medium to l ow magnitude fault protection i s used in all breakers.

5-5

2. Thermal e l ement contact opening for overload protection is used in all breakers *

3. Current limiting fuses for high magnitude fault protection have been provided with t he l arger three-phas~ breakers .

'Ihe breakers were tested at the Southern California Edison ' s High Current Testing Facility . 'Ihe t est results indicated the breakers to be highly satis-factory. A copy of the test data on the breakers is

included in the Appendix.

'lhe cl osed , open, or tripped condition of these breakers is indicated by the position of the breaker oper ating handl e. 'Ihis visual indication allows Operating Personnel to verify an abnormal condition on the pressurizer heater and on other 480-volt circuits on their regularly scheduled inspection tours through the plant .

D. 'Ib reduce the number of circuits and the total conductor power losses carried by each 480- volt penetration, and to provide for the increased conductor sizes , four existing canisters are being modified and replaced, and two exi sting spare penetrations are being equipped with new canisters . All 480-volt circuits entering the containment will utilize these modified penetrations . Supports are also being provided at t he penetrations to prevent cables from being directly supported by their terminals .

E. To reduce physical loading in cab l e trays , existing cables are being relocated to new trays as required .

F. 'Ihroughout the plant, cab l e tray thermal loading was reduced by relocating existing circuits to new trays, and by changing conductor sizes where required . 'lhe pr essurizer heater circuits were relocated to new separate trays. (See Subsection 5. 3)

G. All cable in trays was inspected for mechanical or h eating damage . Replacements or repairs were made as required .

(See Subsection 5 . 4.)

H. All TW wire ties were removed from cable trays.

I. Tb prevent the possible entrance of moisture to the f ace of the low voltage power and control penetrations, all existing and new penetrations were equipped with \*Jeatherproof enclosures which completely cover and protect the penetration t erminations . All exterior enclosures Nere provided with thermostatically controlled heaters to 1naintain a temperature above the dewpoint .

5-6 5.

1.5 CONCLUSION

S

'!he most probable corrrnon cause for the two cable failures was overheating of the pressurizer heater cables coupled with rrechanical loading or damage. In addition, other factors have been identified which could have contributed in various degrees to the principal cause of failure . To preclude any future similar incident which could be caused by any of these factors, corrective actions have been performed as outlined in Paragraph 5.1.4.

SAN ONO FRE NUCLEAR GENERATING STATION A 8 c 80A 46. 6 AMPS 80A 46.6 AMPS 80A - 46.6 AMPS 80A 46.6 AMPS 80A 46.6 A MPS 80A 46.6 AMPS 480VOLT PRESSUR IZER HEAT ER CIRCUITS NORMA L OPERAT ION FIGU RE I

80A 46.6 AMPS 46.6AMPS

~ '---

.___ 46.6AMPS PRESSURIZER HEATERS

- l s c2 42.7 AMPS

- DB 480V - 1sc 2 36.6AMPS

- 25 BUS

- ACB lsc0 13.4AMPS FAULT

- l s c2 4

I lsco 13.4 AMPS 36.8AMPS

-lsc2

~ r---

- I set!

43.4AMPS

~

- lsc 2 480 VOLT. PRESS. HEATER CABLE TRAY PENETRATION a SPHERE SW ITCHGEAR DIST CABINET lsc0 = INITIAL SHORT CIRCUIT AFTER CABLE FAILURE lsc 2 = SUBSEQUENT SHORT CIRCUIT CURRENT BACK FED THROUGH HEATERS THE PORTION OF lsct PASSING THROUGH UNBLOWN FUSES IS BELOW FUSE CONT INUOUS RAT ING SI MP L IFIED TH REE- LINE WIRING DIAGRAM OF PRESSURIZER HEATERS FIGURE 2

5-7

5. 2 TESTlliG RESULTS 5.2.0 PURPOSE This section summarizes the tests conducted to evaluate the existing electrical equiprent, cable trays and sPhere penetration . Details of test repor-ts are attached in Section 7, Appendix.

5. 2 .1 TES'IS ON ELECI'RICAL EQUIPMENT AND CABLE TRAYS A. Pressurizer Heater Control Unit The Pressurizer Heater Control unit varies the supply voltage to a portion of the pressurizer heaters.

Operational tests on in-service equipment at San Onofre showed no characteristics detrimental to cables or equiprrent.

B. 'Ihermal Loading Test on Tray 39C3 A cable tray loaded with energized cable similar to the . one involved in the failure at San Onofre was subjected to temperatures similar to the condition at the tirre of the incident. Terrperatures in the cable tray were found to be dependent on such factors as spacing, cable configuration, compaction, thermal loading and ambient t emperature. 'The cable te!ll)erature was fotmd to vary significantly within short distance s for diffe rent cable configurati ons. Cable temperatures as high as 158°F were obtained which exceeded the manufacturer's 90°C rating of the cable insulation .

C. Cable Tray Short Circuit Simulation Test A test '"as perforl'!"ed to determine if a cable fire could be initiated and sustained by a m rnentary short circuit followed by low level current feeding into the fault.

A cable tray was loaded similar to cable tray 39C3 and an intentional phase-to-phase short circuit was initiated between opposite phases of two adjacent three-phase, 480-volt, de lta-connected circuits. After the fUses in the faulted phases had cle ared, t he two phases in each circuit which remaine d ener gi zed, backfed to the f ault througj1 the pressurizer heaters. 'Ihe intense heat created by the s ustained phase-t o-phase arcing, i gni t ed t he cable insulation. Additional electri cal faults followed and t he fi re proceeded at a rapid rate.

'Ihis t est demons trated that a cab l e tray fire could be initiat e d and s ustained in t he manner des cribed above .

5-8 D. Pressurizer Heat er Cable Bundle Overheating Tests A 45-conductor bundle of No . 6 AWG wires was loaded to 48 amperes to approximate the heater current .

Currents for the 30 pressurizer heaters at San Onofre vary between 45 amperes and 48 amperes , depending upon 480-volt bus voltage , length of supply circuits , and variations in individual heaters.

Temperature measurements were obtained with:

1. 'Ihe bundle in air .

2. 'Ihe bundle wrapped in two layers of control cables.

3. 'Ihe bundle insulated with fiberglass.

Temperatures varied from 85°C f or the bundle in air, 135°C wrapped in two l ayers of cables, in excess of 250°C for the bundle insulated with fiberglass. cases 2 and 3 exceeded the manufacturer 's 90°C rating of the cable insulation.

E. Pressurizer Heater Cable Oven Tests Sections of Simplex 600-volt No . 6 copper anhydroprene-xx cable (1965) were subjected to heat in an oven at various temperatures and lengths of time until damaged .

'Ihe appearance of the San Onofre sample shO\Aled jacket deterioration similar to cables subjected to oven temperatures of 170 to 200°C for 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months .

F. Pressurizer Heater Cable - Vol tage Breakdovm Tests Various l engths of No . 6 AWG pressurizer heater cab l es ,

shovving cracked, overheated jackets v1ere overvoltage tested under water. All of the cable samples passed the 10.8-l<V five-minute test, and al l but one cable passed the 41-kV d-e test. 'Ihe nonnal test voltage for this size cable is 25- kV d- e .

G. Pressurizer Heater Cable Test by Simplex on Physical Condition of Insulation Simplex Wire and Cable Company tested samples of pressurizer heater cables obtained from between the point of failure and the s phere and the point of failure and the source . 'Ihese tests indicated that the cable had overheated.

5-9 H. Westinghouse 600-Volt Switchgear

l. Pressurizer Heater - Fused Disconnect Switch Fault interruption tests were made on the original Westinghouse type FDP switch with FRS- 80 dual~

element and KTS-80 current l imiting fuses. The switch performed satisfactorily with KTS current limiting fuses. Fault tests using FRS dual element fuses which were in service at the time of the cable failure caused the sNitch contacts to weld closed.

2. Westinghouse Tripac Circuit Breaker Fault interruption tests on the Tripac T,ype FA, 70-A circuit breaker showed the unit performed very well with no visible distress and very l ittl e contact erosion. 'Ihis device has been installed on all 480-volt circuits and will be utili.zed to replace the Westinghouse type FDP fuse-sv1itch device for the pressurizer heaters .

I. Existing Penetration Cowling - Cabl e Heat Run A bundle of cable, representative of the cable tmder the cowling of Penetration EPC4 or HPC7 was assemb led and l oaded to determine internal temperatures . An actual cowling (vJPC7) , removed from San Onofre, was used. Temperatures up to 109°C were recorded in t he center of the bundle . 'Ihis temperature exceeds the manufacturer's 90°C rating of the cable i nsul ation .

5-10

5. 3 CABlE TRAY LOADING 5.3.0 PURPOSE This section summarizes the investigations performed'to determine the extent of physical overloading and thermal overloading of the tray sections involved in the fire.

'Ihe investigation was elivided into two ll'aj or categories :

A. Tray Physical Loading B. Tray 'Iherrnal Loading L1.mi ts 5.3.1 TRAY PHYSICAL LOADING When the trays were investigated to determine physical loacllng , it was found t hat sore cable trays were filled above t he level of the side rails. As a ~s ult of re-placing and relocating fire damaged cables, relocating redundant circuits, resizing of conductors for circuits, and rennval of power cable resulting from thermal analysis described in Paragraph 5. 3. 2, many of the overfilled tray conditions were corrected. Physical unloading of the remaining trays has been accomplished to reduce the cab le fill to the level of the side rails.

A scale model of t he cable tray system was devel oped to facilitate design of new cable trays used for physical separation and cable tray unloading.

5. 3. 2 TRAY THERMAL LOADING LIMITS The investigation of the thermal overloading included an analysis of the aroount of current carried by each of the conductors in every tray section, the loading criteria to be established and the action to be taken to correct tray overloading.

A. In the inves tigation of therrnal overloading, the full load current of every cable in a tray througtlout the plant (926 tray sections) was compared with the manufacturer's alloNable current ratings for insulated copper conductors and 90°C conductor temperature. Power cables supplied by motor control centers are sized for 125% minimum of load nameplate current r ating.

Cables fed from the 480- volt switchgear are sized to provide 150% minimum of the l oad nameplate current ratings . /my cable not adhering to these minimum cri-teria was replaced or parall e led with another conductor of t he sarre size . A total of 1200 engineering man-hours

5-11 was expended on this circuit and tray thermal loading analysis . 'lhe cables in each tray were considered to be grouped in the rros t adverse thermal arrangement ,

that is, all power conductors tightl y grouped and surrounded by a blanket of control cables. Where groupings were found which could produce calculated conductor temperatures in excess of 90°C , power cables were removed from these trays until the 90°C criteria was met.

The detailed analysis techniques used to determine if temperatures would exceed 90°C in the center of the conductor grouping are presented in the Appendix.

B. Corrective recommendations to provide for a safe thermal loading limit in each tray required determining the following for each existing tray in the plant:

1. The existing tray physical fill.

2. 'lhe ratio of the total area of power and control cable to the total area of power cable.

3. 'lhe t otal power losses generated in the tray.

C. The following criteria were established for the therma.l loading analysis:

1. An average ambient temperature of 30°C, (86°F).

2. 'lhe assumption that control cables consisted of 100% high thermal resistivity butyl.

3. The assumption that normal operat ing conditions prevailed for cable loading and, as a limiting check , the assumption that no diversity existed (all connected load in operation).

In the case of the pressurizer heater circuits, it was assumed that they operated continually.

4. 'Ihe assumption that cables were installed in the most adverse arrangement. For analysis, a circular cross- sectional bundle of cables was assumed for each tray. All loaded power cables were assumed to be at the center of the bundle, with all control cables in the tray pl a ced uniformly around the power cables . ~ these criteria, higher conductor tempera-tures resulted than would be a ctually experienced when the cables wer e spread in a shallow layer across a 24-inch cabl e tray.

5-12

'Ihe maximum conductor t6Tlperature in the actual cable tray con~tion where cables are not arranged in a circular bundle v1ith all heat pro-ducing conductors in the center, but are spread across a 24-inch wide tray, is expected to be sub-stantially less than 90°C as a result of this unloading .

5.3.3 CORRECTIONS AND CONDUCTOR TEl'lPERATURE fvDNI'IORINJ A. New tray thermal loading schedules were developed based on results of a computer analysis which considered all of the above conditions for every cable in every tray. 'Ihe schedules listed 51 circuits in a total of 49 different tray combinations that required relocation to new or unloaded trays to accomplish this thermal unloading.

'Ihe cable tray thermal overloading investigation in-cluded an analysis of the amount of current carried by each of the conductors in every tray section. As a result of this investigation, 42 circuits required the use of larger con:iuctors or installation of conductors in parallel to increase the circuit capability .

Actual maximum conductor temperatures during either start-up or normal operating conditions will be far below the temperatures calculated since the most adverse cable arrangement and operating conditions were assumed.

It was also assUired that total connected load was in service at all times .

B. Temperature monitoring devices have been installed throughout the plant to confirm that conductor t~era tures are below the allowable conductor temperature rat ings permitted by cable manufacturers .

C. An analysis of the 15 three-conductor replacement cables for the pressurizer heater circuits placed in new separate 24- inch cable trays indicates that the maximum conductor temperature is not expected to exceed 50°C in a 30°C ambient .

5-13

5. 4 llJSPECriON OF CABLES AND TRAYS 5.4.1 PURPOSE A detailed inspection of cables in all trays was considered necessary to verifY that the cables remaining in service did not evidence signs of overheating or other physical damage.

Quality assura~ce teams consisting of qualified Southern Edison and Bechtel personnel are following all repair and modification work to assure that specifications are met and good construction practices are followed.

5.4.2 INSPECTION In oroer to perform a detailed examination of the rem::urung station cables, 17 inspection teams were utilized, consisting of qualified and experienced Southern california Edison supervisors and accompanied by contractors' journeyrren. Each team consisted of one Southern California Edison supervisor and one or two journeymen electricians. 'Ihe electricians removed individual cables from the cable tray and the inspector flexed and inspected each cable to determine if prolonged overheating damage or other physical damage existed.

If damage or distress conditions were discovered, the cable or tray was tagged and the location noted on recoro sheets . A team of Southern California Edison engineers then determined whether the cable should be removed or repaired, and, if repaired, how the repairs were to be effected.

All the cables in trays throughout the plant , which involved more than 15,000 lineal feet of cable tray , were inspected and reports from the inspectors were reviewed , evaluated, acted upon, and then filed for reference

An estirra.ted 500 man-days of effort by Electricians, Riggers, and Laborers were required to carry on the inspection assign-ment, and 530 man-days of supervisory work to inspect the cables.

Th~ total cost of the inspection effort is estimated at

$107,000.

5.4.3 RESULTS OF INSPECTION It is very significant that no evldence of da.rrage due to over-heating was found on any of the cables remaining in service .

Evidence of jacket deterioration due to overheating was found on seven pressurizer heater cables after t hey '"'ere removed from the trays.

5-14 Corrections were made to cables where rrechanical damage result-ing from installation was fm.md. Such rrechanical injuries are usually caused by pulling techniques, manner of tying cables, etc. 'Ihe cables provided are protected by a protective jacket for this purpose.

'Ihe results of inspecting the power and control cables througp-out the plant are as follows:

A. No sigflS of cable insulation damage by overheating was found on any of the remaining wire .

B. Nine hundred and ninety-nine cases of damage to cable have been found and corrected as required.

C. Five cases of inproper pulling of 220-kV switchyard control cable were found. 'Ibese cables were replaced.

D. '!he short lug;:; used originally for connecting the 480 volt motor leads in sixty-nine motors were replaced with a more satisfactory and longer lug.

E. 'lliree hundred and thirty-nine 4-kV ternrl.nations were untaped and refinished in accordance with procedures developed and approved by the cable rnmufacturer and by Southern California Edison engineers . '!he jackets on the original 4-kV terminations were irrl:>roperly finished and resulted in corona problems and high noise interference with other sensitive systems .

F. CXle hundred and thirty cases of inproper cable tray installation have been found and corrected.

SECTION 6 STARr-UP PR<XlRAM 6 . 1. 0 PURPOSE Because of the rra.gnitude of repairs and IIDdifications made foll owing the cabl e failure incident, it is necessary to verify that all com-ponents and sys tems affected by the incident are in proper working order and function as originally designed prior to restoring the unit to service.

6.1.1 ORGANIZATION The veri fication and start-up activities will be coordinated by the Station Chl.ef (who holds a current SRO license) and througp his operating staff. Start-up t e ams from the contractors will also assist him with the preparation and execution of the start-up activities. 'Ihe Watch Ebg1.neer for each shift is a qualified Senior Reactor Operator, and will supervise the step-by- step operations during and after the start-up .

'Ihe foll owing corrponents were mcx:lified or repaired and verification of proper operation will be derronstrated:

A. Electric Motor Heaters:

'Ihirteen motor he ater circuits to be proven.

B. Purrping Corrponents:

Reactor Coolant Syst em Drain Tank. Pump G20-B West Sphere Sump Pump West Reheater Pit Sump Pump West Feedwat er Purrp Lube Oil Pump Reactor Ca.vi ty Sump Pump East Sphere Sump Pump East Intake Sump Pump "A" Reactor Coolant Purrp . Lube Oil Pump West Fire Purrp West Recirculation Purrp West Resi dual Heat Removal Pump North Service Wat er Pump West Feed\lfat e r Pump West Fee dwater Pump . Lube Oil Pump .

Refue ling Water Filter Pump Sout h Re fueling Water Pump Auxiliary Feedwater Pump Reactor Cool ant Pump B" Sout h Pr:1.mary Plant Makeup Purrp East Recirculation Pump Turbine Auxi liary Oil Pump Condenser Vacuum Pump

6-2 South Flash Evaporator Feed Pump West Flash ~1aporator Condensate Pump Flash Evaporator Recirculation Pump North Flash Evapor at or Re circulation Pump South Reactor Cavity Dewatering Pump C. Motor Operated Valves:

MOV-822-B M:>V-814 M:>V-834 MJV- 866- B r!'DV-348 MJV-357

'tfiJV-720-A f'DV-852-B f.DV-854-B lvOV- 880 f1DV-853-B rrDV-851- B MOV- 883 M:>V-19 D. Cooling and Ventilating Systems :

Cooling Fan A-5-s Cooling Fan A-6-S Cooling Fan A-7-S Fan A- 3 Fan A-22 Fan A- 23 Auxiliary Cool er Fan No. 1 Auxiliary Cool er Fan No . 2 Sphere Circulat ing Fan A-12 E. Miscellaneous Corrponents:

Main t ransfo!"ller cooling equipment Three (3) power receptacles Center Instrument Air Compressor JVbtor control Center No. 3 supply Dtmb Waiter Pressurizer Heat er Groups "B" and "D" Communications Circuits New ACB & Tripac Breakers 6.1.2 VERIFICATION PROCEDURES Before a component or sys t em is put in service, the following steps will be t aken:

6-3 A. A quality assurance team consisting of Southern California Edison and Bechtel experienced technical personnel are following all repair and mxlification work to assure that specifications are net and good construction practice is achieved.

B. Electric circuitry and canponent and system controls ~w111 be checked as follaxs when required:

1. Control circuitry will be checked and verified.

2. Protective relaying will be verified.

3. Interlocking ci rcuits will be verified.

14. Power circuitry will be verified.

5. Corrponent will be operated separately.

6. System protective and interlocking circuitry will be verified.

7. System control circuitry will be verified.

8. System vdll be operated manually .

9. System will be operated autoiTE.tically.

C. A detailed description of the procedures to be used in putting station back in operation has been prepared as a separate decurrent and is described in t he following pages. 'fue Start-up Procedure Manual is divided into nine sections:

1. Delineation of Work will consist of a general staterrent con-cerning objectives, typical work and equiprrent functions.

2. Administration, Clearance Procedures and Records will discuss general responsibilities for administration , clearance pro-cedures and record keeping.

3. Electrical Testing covers the responsibilities of the various parties and groups involved in electrical test and start-up until optimum operation of the unit is established.

4. Instrurrent Testing and Calibration will outline those instru-rrent tests and calibrations required as equipment is returned to service and reactor start-up is initiated.

5. Sequence of Operations will be a tabulation of order in which equipment affected by the cable failure will be returned to operation.

6: Auxiliary Equipment, this section describes the checks neces-sary before equipment and preliminary operations are started to achieve safe operation . A verification that proper system alignment has been checked, lubrication, cleanliness and adjunct services are available and in service shall be made.

7. Precritical Tests will be outlined and referenced to appli-cable procedures and operating instructions . 'Ihe follow1ng dynamic tests and/or operations shall be perfo:rrred as required by the Technical Specifications and/or before reactor start-up:

6-4 a a. Q:>erate Chemical and Vol\.J're Control System equipment required by 'lechnical Specification 3. 2 .

b. ~rate Safety Injection System equipment required by Technical Specification 3.3.1.

c. Verify that the Safety Injection System and Contain-rrent Spray System will respond pr anptly and pr cperly as required by Technical Specification 4. 2 , I, A and B and I I B. (Foll0\'1 ~rating Instruction S 3.4, Cold (perational Test of the Safety Injectim System and Containrrent Sphere Spray System and ~rating Instruction S.3.3.3, Hot ()perational Test of the Safety Injection System.)

d. Operate the e l ectric drive auxiliary feedwater punp required by 'lechnical Specification 3. 4, (Operating Instruction S-2.13. )

e. Verify operability of Auxiliary Electrical Equiprrent required by 'lechnical Specificatim 3. 7.

f. Test the Einergency Power System required by Technical Specification 4. 4 A and B. Follow ~erating Instructions S-2-11, Diesel Generator 'lest (Heekly Interval) and S-2-12, Diesel Generator Test (Refueling Interval).

g. Test operation of the hydraulic stop gates. Follow

~rating Instructi on S-2-14.

h. Test all Reactor Trip Circuits to ensure that signals are received at the t rip breakers .

i. Test all Turbine Trip Circuits to ensure that signals are received at the trip solenoid.

j . Cooplete sphere penetration leak rate t ests after pene-t rations are installed and before sphere integrity i s required. b

k. After sphere integrity i s established perform a Hydrostatic 'lest of the Peactor Coolant System, follc:w (perating Instruction S-3-1. 8.

l. After the Peactor Coolant System has been heated to operating temperature and pressure per form cootrol rod drop time tests.

8. Sequ=nce of Start- w Operations will incltrle a copy of the react or precritical che ck list, tur'bine -~nerat or pre-operatimal check list and the tnit start- t.p Operating Instruction .

6- 5

9. 'Cab:te 'TertFerature r.bnitoring In order to verifY that cable temperatures throughout the plant are vii thin proper operating 1irnits on return-to-service, temperatures \dll be rreasured at 68 selected l ocations . ,

Initially each temperature sensor wil l be att ached to a cable located near the center of the test tray cross section.

'!he cables at the test locations will be checked periodically througnout the test and the sensors relocated as necessary to assure that the sensor is attached to the cable operating at the highest terrperature in the tray .

'Ihe nanufacturers' allowable conductor terrperature (on a continuous operation basis) for the 600-volt cabl es installed at San Onofre is 90°C .

To assure that the 90°C conductor temperature i s not exceeded, the surface terrperature of the cable nrust be limited to 85°C to allow for an approximate 5°C terrperature drop througp t he electrical insulation of the cable.

'll1e selection of cables to be rronitored will be on the basis of highest expected temperature; however, the recorde r alarm points will 1nitially be set at a value to all0\'1 for the possibility that the point of rreasurenent may produce values sorrewhat less than the ma.x1.mum.

Pecorded terrperatures \Adll be rroni tored tmtil after the Thrlt output reaches 450 MWe gross and records will be retained at San Onofre for reference . Indicated terrperatures will be l ogged once per shift for t wo weeks following return-to-service then once per day for one month and foll~~ing this, once per week until 450 MWe loading is accomplished.

'Ihe above schedule is predicated an satisfactory temperature l evels at the points measured.

Measurerrents \dll be discontinued upon verification that all terrperatures are within design values at ma.x1mum load ratings .

6.

1.3 CONCLUSION

S In order to verifY plant circuitry and system operations after changes have been completed, test tearrs of Edison and contractor forces have been organized . 'Ihese tearrs will coordinate their testing with the operating staff . The operations will be per-famed as prescribed in the applicab l e operati ng Inst ructions and in accordance with the Start-up Procedure Manual which includes all the applicable operating instructions and orders required to accomplish

6-6 0 the work 1n an orderly and safe marmer and it has been prepared as a separate voll..llre. VolUI'I'e I, Start- Up Procedures , San <Xlofre Nuclear Generating Staticn , was used as the basis and guide for preparing the above~entioned Start- Up Plan.

The results of the testing will be tabulated and will be made part of the permanent plant records alcng w1th the 1nitial start-up records .

TESTING COORDINATION FOR RETURNING TO SERVICE SAN ONOFRE NUCLEAR GENERATING STATION 1968 STATION RESPONSIBLE FOR CHIEF OVERALL RETURN TO SERVICE 1

SUPERVISOR RES PONS ISLE FOR PLANT EDISON EDISON PLANT OPERATION COORDINATING OPERATING ENGINEER ENGINEERING---- CONSTRUCTION

'------...----__. EFFORTS WITH TESTING ENGINEER REQUIREMENTS RESPONSIBLE FOR COORDINATING STATION TECHNICAL PERSONNEL EFFORTS WATCH RESPONSIBLE FOR SHIFT 1 ENGINEERS SUPERVISION OF OPERATIONS BECHTEL RESPONSIBLE FOR r----1 WESTINGHOUSE SfART-UP IN SURING REPAIRS ENGINEER 8\'GINEER ARE COMPLETE AND RELEASING CLEARANCES EDISON TEST SUPERVISOR RESPONSIBLE FOR ELECTRICAL TESTING OF REPAIRED CIRCUITS I I jOPERAmRSJ CHEM-RAD RESPONSIBLE PROTECTION FOR CHEMISTRY INSTRUMENT RESPONSIBLE ENGINEER FOR STATION ENGINEER AND RADIATION '-------.------' INSTRUMENT AND PROTECTI ON ELECTRICAL TESTING

'TECHNICIANS TECHNICIANS EDISON TEST PERSONNEL

SEX;TIOH 7 APPENDIX

7. l TEST REPORTS 7 . 1. 0 'Thermal Loading Test on Tray 39C3 7.1.1 Duplication of Sustained Combustion P.esulting Prom Pressurizer Heater Cable Short Circuits - Tray 39C3 7 .1. 2 Existing Penetration Cowling - Cable Heat Run 7 .1.3 New Cable 1'ra.y 'Ihermal Loading Criteria - Heat Rlm

7. 1 . 4 West~jhouse 600-Volt &~itchgear Test 7 . 1. 5 Boric Acid Crystallization Study 7 . 1. 6 Chemical and Volwne Control and Radwaste System Tank Overpressure Investigation (A) Metall urgist Analysis (B) Hydrostatic Test of the Volume Control, Waste Gas Surge and Flash Tanks

7. 2 PREVIOUS DESIGN BASIS FOR C.OBLE SIZING 7 .3 CABLE

7. 3 . 0 f,1aterial Specification No. 225 7 .3 . 1 Simplex 600- Volt Cable Test

7. 4 CABlE TRAY 'IHER!"l.AL LOADING ANALYSIS

7. 5 SHUI'DO'!M f"lAFGIN ANALYSIS A'l' MP.XIJ'1UM DIUJTION 7 .6 D.AJV!.AGED CN3LE TRAY PIC'IURES

7. 7 . DRAHINGS 7 .7.0 Chemical and Volume Control System 7 . 7. 1 Safety I~jection ~;stem 7.7.2 ~adioactive vlaste Disposal Systerns c-- 7. 7 . 3 Additional Cable 'l'ra.y Location (I':Jodel and Drawing )

7 .7.4 Smoke Detection System Location

7 . 1.0 'IHERMAL LOADING 'IEST ON TRAY 39C3 REPORI' OF THE~ LOADING TEST TRAY 39C3 SAN ONOFRE NUCLEAR GENF_RATING STATION PURPOSE The purpose of this test was to determine the maximum temperatures that might develop in tray 39C3 as it was loaded prior to the cabl e failure, under conditions of normal operation, and under the maximum credible CUL"'Tent l oading. A series of tests as outlined below were conducted duri~ May 1968.

DISCUSSION The lists of circuits to be tested under concurrent and maximum credible current operation and the currents at which they were operated were provided by the Bechtel Corporation.

Due to the l arge number and variation of circuit currents , ave~e values of load current were selected for duplication purposes. The levels to which the cil'"'cuits were lo8ne0 for this test a.re as follows:

1. CONCURRENT LOAD Actual Load Test Load No . of Current/ Current/

Conductors Conductor Conductor Circuit and Size (Amps.) (Amps.)

Residual Heat Removal Pump B 3- #1/0 71.0 71.0 Pressurizer Heater Leads 45- #6 46 46 Reactor Control Rod Cooling System 3- #4 48. 5 46 Auto. Transfer Siren 3- #6 20 20 Flash Evaporator Condensate Pump - West 3-#10 18 . 7 20 Fl ash Evaporator Feed Pump - sw 3- #10 18.7 20 Co11!11unications Power Panel 3- #12* 6. 3 20 Sphere Fan A3 3-#8 11 11 Sphere Fan A4 3-#8 11 11

. Reactor Cavity Water Pump 3- #1 2* 12.5 11

Indicates multiconduct.or cable .

1. CONCURRENT LOAD - Cont ' d Actual wad Test wad No. of Current/ Current/

Conductors Conductor Conduct or Circuit and Size (Amps.) (Amps.)

Reheater Sump Pump West 3-#12* 10.2 11 Sphere funp G21E 3-#12* 6.5 7 Reactor Bldg. Fan Al2 3-#12* 6.7 7 Reactor System Drain Tank Pwnp 3-#12* 18.7 4

2. MAXTI1UM CREDIBLE LOAD Fire Pump West 3-#4/0 143 142 Fire Pump East or Power Recpt. 3-#4/0 143 142 Main Transformer Feeder #2 Cooling Equipment 3-#2/0 112.8 113 Residual Heat Removal Pump B 3-#1/0 71 71 Pressurizer Heaters 45-#6 46 46 Reactor Control Rod Mechanism Cooling System 3-#4 48 .5 46 Reactor Cooling Fan ASS 3-#8 35.7 36 Reactor Cooling Fan A6S 3-#8 35.7 36 Reactor Cooling Fan A7S 3-#8 35.7 36 Sphere Cooling and Filtering Fan A3 3-#8 25 25 Sphere Cooling and Filtering Fan A4 3-#8 25 25 Flash Evap . Recirc. Pwnp N\o/ 3-#10 24.5 25 Flash Evap . Recirc . Pump S\v 3-#10 24.5 25 Auto. Transfer Switch (Emerg.

Siren) 3-#6 20 20

Indicates mul t i conductor cable .

2. MAXIMUM CREDIDLE LOAD - Cont 'd

.. Actual Load Test Load No. of Current/ Current/

Conductors Conductor Conductor Circuit and Size (Amos .) (Amps .)

Service Water Pump North 3-#10 19.5 20 Flash Evap. Cond. Pt.rrnp West 3-#10 18.7 20 Flash Evap. Feed Pump SW 3-#10 18.7 20 Communica. Power Dist . Panel 3-#12* 6. 3 20 Refueling Water Filter Pump 3-#12 14 14 Reheater Pit Sump West - G55B 3-#12* 10.2 11 Reactor Bldg. Circ. Fan Al2 3- #12* 6.7 7 Pump G21B Sphere Sump 3-#12* 6.5 7 Lifting Frame 3-#12* 7.0 7

'furbine Lube Oil Transfer Pump 3-#12* 4.5 4 Reactor Cooling System Drain Tank Pump 3-#12* 18.7 4 Air Camp. Motor Heater - KlB 3-#12* .4 1 Aux . Cool . Water Pump Motor Heater 2-#12 .4 1 Motor Heater - G36B 2- #12 .33 1 Motor Heater - Gl4B 2-#12 .57 1 Reactor Cavity Sump Pump 3-#12* 1.7 1 Salt Water Cool. Pump Motor Heater 3-#12* .3 1

Indicates multiconductor cable .

A 15-foot section of cable tray 39C3 containing its complement of wires, including the burned sections, was sent to Edison ' s Shop and Test Division at Alhambra , California. Personnel ~~Edison ' s Apparatus ,

Engineering, Power Supply and Shop and Test Departments emptied tray 39C3

0 wire by wire, recording the description and position of each within the tray.

'Ihree ccmplete cross- sectional unloading profil es were drawn during this procedure . Fran these tray profiles , Profile #3 representing the cross-section six inches from the point of failure and most severe burning was selected as the ~~del to most closely approximate the cable arrangement for the reloading of the tray. A quantity of undamaged cable which ran from the fire area to the switchgear, plus some additional used cable, was sent from San Onofre and used to reload the tray . 'Ihe tray was set on steel supports which made point contact with its bottom.

Cable was l oaded into the tray, wire by wire in accordance with a cable loactlng diagram developed from the selected Profile #3 . Cable lengths used were approximately 40 to 45 feet each to allow splicing and connections away fran the tray area . For the initial test, 23 thermocouples were strategically located in four anticipated hot spot areas in the tray. 'Ihese locations were at 30 inches, 60 inches, 90 inches, and 120 inches from one end of the tray. Additi onal thermocouples were pl aced beneath the tray to record the ambient temperature . A 24- point Esterline Angus chart type tem-perature recorder was used to record the temperature pattern in the tray.

Tb connect cables for current loading and to f acilitate testing, all conductors carrying the same test currents were connected in series by splicing ends beyond the tray, resulting in six energized series circuits for normal (concurrent ) l oading . Current values used were 71A, 46A, 20A, llA, 7A and 4A.

Power was obtained from a three-phase 240- volt fused distribution box, and fed to a 3 kVA , 240-120/240- volt transformer. In the last of the five tests performed , a 10 kVA transforme r '~as used to separately supply the heater cable circuits . In all tests, current control was obt ained by using 240V and 120V variacs , pa.'ler stat s , and trans t ats in cmjunction with loading transformers conne cted to the individual circuits.

A clamp-on ammeter was used for metering load currents. At the primary source a wattmeter was permanently installed measuring total watts to the transformers and loads. Calculati ons were made to determine watts l ost in the cabl es under test .

'lEST 1 - CONCURRENT IDADING For t his test t he lower half of the cabl es i n the tray were tied with

'IW insulated wires while the upper layers were laid in untied .

Ambient temperatures ranged from 22°C to 28°C .

Maximum temperature readings were *obtained at two locations . Recorded t emperatures varied cons i derably between thermocouples at each locat ion.

Readings for each of the two groups of t he rmocouples showing maximum t emperatures were as follo\*ts:

Test 1

'Ihennocou21e No . Temperature~ oc 1 54 )

6 29 ) This group located 60 inches 9 32 ) from load end of tray.

18 73 )

17 33 )

23 39 )

4 38 )

8 30 ) This group located 120 inches 12 32 ) fran end of tray.

14 72 )

13 36 )

21 38 )

T1me to reach the above l evels was 320 minutes . Both ambient and tray thermocouple readings then started to decrease after 320 minutes' elapsed time.

'lEST 2 - CONCURRENT I.DADING For this test all cables were securely bound \*lith 'IW insulated \'lire in order to reduce ventilation. Several thermocouples were relocated within their group location to anticipated areas of hip-) 1 temperature. Two thermo-couples were relocated, one to the center of the pressurizer heater wire bundle at each end outside of tray. At these points fiberglass insulation '"as wrapped about the exposed cables to reduce the heat loss at the tray ends .

'Ihe ambient temperatures varied fran 21 °C to 29°C. Maximum tempera-tures were recorded at two locations.

Watts lost in the test cables were calculated to be 2076 watts .

Watts lost per foot of tray were 52 watts.

Readings for each of the two groups of thermocouples showing maximum temperatures were as follows:

Test 2

'Ihe:rmocouole No.

1 38 )

6 28 ) This group located 60 9 33 ) inches fran end of tray.

18 79 )

Test 2 - Cont'd

'Ihermocouple No. Temperature, °C 17 32 )

23 74 )

4 50 ) 'lhis group located 120 8 29 ) inches fran end of tray.

12 31 )

14 79 )

21 78 )

Time to reach the above levels was 390 minutes.

'!EST 3 - CONCURRENT IDADlliG For this test the ~6 ampere pressurizer heatP.r circuits were operated at 48 amperes . Heat lamps were used to hold the ambient constant at 30°C.

The ambient temperatures varied from 20°C at the beginning to 30°C at the end.

Watts l ost in the test cables were calculated to be 2240 watts. Watts l ost per foot of tray were 56 watts.

Readings for each of the two groups of thermocouples showing max~

temperatures were as follows:

Test 3

'IhermocOUJ2le No. Temperature 2 oc 1 "46 )

6 33 ) This group located 60 9 39 ) inches from end of tray.

18 85 'I 17 37 )

23 80 )

4 53 ) Th1s gro1.1p located 120 8 33 ) inches fran end of tray.

12 35 )

14 86 )

21 85 )

Time to reach the above levels was 1025 minutes.

'IESr 4 - MAXJMtlvt CREDmiE I.DAD For this test additional circuits were energized . CUrrent values used were 142 , 113, 71, 46, 36, 25, 20 , 14, 11, 7, 4 and 1 amps .

~

'Ihe ambient temperatures varied from 24°C to 33°C. Max:imt.m tempera-t ures were recorded at two locations . Heat lamps were used to hold the ambient temperature at 31°C.

Watts l ost in the test cables were calculated to be 3596 watts . Watts l oot per foot of tray were 90 watts.

Readings for each of the t'1'1o groups of thermocouples showing rnaxirm..ml temperatures were as follows:

Test 4

'IhennocouEle No. Temperature~ oc.

1 50 )

6 43 ) This group located 60 9 47 ) inches :f'rcm end of tray.

18 90 )

17 54 23 91 4 56 )

8 48 ) This group located 120 12 47 ) inches from end of tray.

14 87 )

21 93 )

Time to reach the above levels was 390 minutes.

'JEST 5 - MAXTI1U1 CREDffilE I.DAD For this test the 46 ampere pressurizer heater circuit current was raised to 52 amperes. Two additional thermocouples were installed in the hot spot area, one touching a #6 pressurizer heater conductor through a slit in its insulation, the other taped to the surface of the jacket on the same conductor. Current values used were 142, 113, 71, 52, 36, 25, 20, 14, 11 , 7, 4 , and 1 amps

The ambient temperatures varied from 28°C to 33°C. Heat pwnps were used to hold the ambient constant at 33°C .

Watts lost in the t est cables Here 4000 watts . Watts l ost per foot of tray were 100 watts .

Readings for each of the two groups of thermocouples showing maximum readings were as follows:

Test 5

'Ihermocouple No. Temperature l oc.

1 54 )

6 43 )

9 49 ) This group located 60 18 102 ) inches from end of tray.

17 Slt )

23 101 )

25 103 ) Tbuching conductor.

26 102 ) Tbuching jacket.

4 60 )

8 49 ) This group located 120 12 48 ) inches fran end of tray.

llt 97 )

21 102 )

Time to reach the above levels was 330 minutes.

OONCLUSIONS

1. Temperatures in the cable tray were found to depend on a canbination of factors. 'Ihese include cable spacing, con-figuration, compaction, current l oading, number of cables, and ambient temperatures .

2. Temperatures vary radically within short distances in the tray for different cable configurations and compactions.

3. During normal operation, temperatures within this cable tray probably exceeded the manufacturer 's r ating of the cable insulation.

J. L. Cohen Apparatus Engineer

~TC25*

4'\ 15'-o'y- ' L.~s**

r"RAY 39C3

- - '**' .,*

I ',- * * * * * * ,*

12/ 9/ II 7 9 "17 / G 5 120" so" 30" 71E RECORDING TEMPERATURE OF # 6 CONDUCTOR TEST 5 ONLY

- RECORDING TEMPERATURE OF#f JACKET TEST 5 ONLY TRAY SIMULATION TEST- PLAN VIEW SHOWING TH ERMOCOUPLE LOCATIONS FOR TESTS 2 THRU 5 5 - IO- 68

~-=-= -"".. .;. ,--.

THERMAL LOA DING TEST 0 N SIMULATED T RAY 39C3

WIRING DIAGRAM FOR SIMULATION OF TRAY 39C3 MAXIMUM CREDIBLE LOAD 46A, 36A, 25A, 71A, 142A, 11 3A, 20A , II A, 14A, 7A, 4A, lA,

.6 6 ./\. .2 11 ./\... .349 ./\... .0144 ./\... .0114 J'l.. .0095 J\.. .644 ./\. .221 ..1'\. .225 ./\. .655 ..('L .45 ./\. .713 ./\...

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50A I BRE~~ER :

40V 2- -...-.....

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I 240 -24 0/120o~

DCJ IOKVA 24 0- 240 v.

VARIPAC 240V, 9A NOTE:

DOTTED CONNECTIONS MADE UP IN TEST 5 ONLY FOR ISOLATION OF 46A LOADING CIRCU IT.

POWERSTAT 120V, 20A

WIRING DIAGRAM FOR SIMULATION OF TRAY 39C3 CONCURRENT LOADING 46A 7 1A 20A II A 7A 4A

. 66.n .0 144 ... .50 (\ .55 ... .43 "' 0 .45 ,..

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VARIPAC 240V, 9A POWERSTAT 120V, 20A

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0 7 .1.1 DUPIJCATION OF SUSTPJNED COJV!BUSTION RESUVl'ING FROM PRESSURIZER HEA'IER CABlE SHORT CIRCUITS - TRAY 39C3

(

DUPLICATION OF SUSTAINED COMBUSTION RESliT.,TING FROJI PRESSURIZER HEA'ffiR CABIE SHOFIT CIRCUI'IS - TRAY 39C3 PURPOSE OF TEST This test was made to demonstrate that a phase- to-phase fault between opposite phases of two adjacent three- phase 480- volt, delta connected cable circuits is likel,v to result in a cable fire and sustain the fire if each phase is protected by individual fuses rather than by an automatic breaker, which provides three-phase cle~ for a si~le-phase fault .

A cable tray carrying power and control cables with the same configuration as the cables in tra.v 39C3 was utilized for these tests .

Representative pressurizer heater l oads were supplied through the tray from individual FRS-80 fuses connected to a 480- volt three -phase source from the original pressurizer heater switchgear cabinets which had been removed from San Onofre .

M additional test was performed using three- phase ~ircui t breakers to clear a fault in the cable tray .

RFSliT.,TS OF TEST

1. A cable fire was initia t ed afte:r an intentional phase-to-ph ase short circuit was cleared by FRS-80 fuses . 'Ihe fire was sustained because cnly the faulted phase were cl eared by the fuses . 'lhis allowed a current flovT and voltage to develop at the fault by " feedback" from the load due to the two phases remaining energized in each of the two three- phase delta circuits .

The "feedback" current at the fault is limited by the load impedance to a va lue much small er than load current and , consequentl y t he fuse on each remaining energized phase does not clear the circuit . In this particular circuit the "feedback" current is limited to 14 amperes if the faultec'l phases retain ~ood contact after the initial short circuit current or if the short circuit current bla//s the f aulted phases open (the more usual case ), an open circuit "feedback" voltage of 2lJO volts exists. The eable i nsulatlon system near the phase-to- phase fault is carbonized to varyin~ degrees of electrical resistance by the previous short circuit current . Therefore, it is possible to develop, at the phase- to-phase fault, various feedback current and voltap.;e magnitudes within the limits of 240 volts open circuit and 14 amper.::s at full short.

llider the proper ccnditions, small "feedback" l eakage currents develop in the carbonized cabl e insulation over a long period of time .a nd arcing eventuall y occurs between the f a ulted phases.

In an auxiliary test , several trial runs with two short cables demoostrated that sustained arcing was easily obtained . The sustained arcw.g betv:een the cable corductars is siml.lar to the susta1ned arc in arc welding . 'll1e intense temper ature of the sustained phase-to-phase arc starts the cable insulaticn system burning. 'Ihe undamaged energi.zed cables in the tray

surrounding the s ustained arcing starts burning which causes additional electrical faults and more cable fires. Chce sustained arcing is achieved the f1 re proceeds at a rapid rate.

2. 'Ihe two cabl es intentionally short circuited we re burned ~and charred in the short circuit area, but litt l e or no da.rrege occurred to the adj acent cables f'rcrn the short circuit current itself, but rather ~

the continuous f eedback into these circuits.

3. In two test rtm.s, two Westinghouse "Tripac" tmits interrupted satisfac-tori l y all phases of two three-phase circuits having a sil1gle phase-to-phase fault.

CONCLUSICNS

1. 'Ihe voltage and current "feedback" to a previously cleared phase-to-phase f ault of an independently fused, two-circuit, three-phase, delta connected system can cause a fire.

2. 'lhe Westinghouse FDP fused load break switches are not satisfactory for this applicati on for two reasons :

A. 'lhe breaker contactors do not meet the manentary current ratings required.

B. Each phase is independently fused.

MF.THOD OF TEST

'Ihe three 100- kva. , 2400/480- vol t single- phase transformers were camected in del ta and the 480- volt l ow s ide ,.,as connected t o the three- phase buses running down the middle of the two \<lestinghouse FDP fused l oad break switch panels.

Cables were connected as shown in Figure 1. As noted sorre of the cables v1ere energized with the far end taped , some were used to circulate current to heat the cables in t he tray and six three-phase circuits were unde r full load conditions . 'Ihe six circuits were connected to the Rama Resi stance Loading Elements . 'Ihe heat dissipated fran these elements was bl own by fans throug}1 a ttmnel of fire resistant material and canvas to heat the cables in the tra.v to 90° C be fore making short circuit tests.

Instrumentation was installed to record:

A. Each phase voltage at the "Iow side of the transformers.

B. Current i n one phase of t he phase- to-phase fault.

C. "Back f eed" current fran the load to the f ault.

D. Vol tap.;e appearing across the phase-to-phase fault.

An intentional f ault was made between cables No. 424 anrl No . 411 at about the center of the tray run before each test . Several technlques of faulting were tried in an attempt to duplicate actual conditions. Both cables ins ula-tion sys tems were cut awa,v on one side to expose the conductor . Carbonized

particles obtained from heating cable insulation of identical cables were placed between the cables at the bared conductor. 'The cables v1ere ovet'-layed with the carbonized particles of cable insulation in place .

'!Wo Westinghouse "Trlpac" units were installed in place of the FDP fused load break Slrltches in heater circuits No . 1 and No . 2. 'These ,..,ere the two three-phase circuits that contained the phase-to-phase fault . ~ 'Ihe "Tripac" tmit opens all three- phases of a circuit when any type fault occurs . '!Wo tests were made and the "Tripac" tmits operated as expected in both cases .

'Ihe "Tripac" tm1 ts were removed and FDP fused load break switches were wired to heater circuits No . 1 and No . 2. These FDP fused load break switches failed because of insufficient morrentary current rating in the breaker contacts. After this incident, all FDP fused load break switches were removed and each individual circuit was connected to the 480- volt bus through a FRS-80 fuse to complete the test.

Before the final test rtm in the cable tray, leads were extended from cables No . 1424 and No . 411 which were disconnected at the bus end . 'Ihis permitted several demonstrations of how "feedback" current and voltage from the load were able to start "stabilized-arcing" and, consequently, cable insulation fires .

The final short circuit test was made with the intentional phase-to-phase fault made on cables No . 424 and No. 411. The resistance between the fault phases was adjusted to 5000 ohns . The faulted cables vtere placed in the fourth l evel of cables from the top of the tray and the other four three-phase circuits were in close prox:1.mi ty. A thennocouple placed on the outside of one of the f aulted cables indicated the cables and tray in the f ault area had been heated to 85°C just prior to the application of the short circuit. 'Ihe canvas tunnel covering the cable tray was removed . 'Ihe backup breaker on the 2400-volt side wa~ de~nergized and the faulted circuits \'fere connected to the 480-volt bus through fuses . 'Ihe backup breaker was then c l osed and the faulted phases were instantaneously cleared by the fuses. The short circuit current caused sorre noise and arcinP; at the fault, but no sustained fire resulted. However, the "feedback" voltage and current existed, and by movi~ the faulted cables sligtltly a sustained arcing was achieved at the fault. The resulting fire caused multiple elec-t rical faults on surrounding. cables which werE cleared by the FRS- 80 fuses.

After 19 of 54 f\5es had blown the fire \'fas extinguished . 'The fire had spread over an area of several square feet at this tine and would have continued to involve the majority of the cables in the tray .

EQUIPr.ENT liED 1, 'Ihree 100- kva 2400/480-volt single-phase transfonrers .

2. One panel ccntaining 12 three-phase Westinghouse FDP fused load break switches. Che panel containing six three-phase Westin@1ouse FDP fused l oad break switches . 'Ihis equipment was rerroved from the San Cnofre Nuclear Generating Station to Alhambra &lop for this test .

3. A replica of the cables ann cable trav which were destro:ven by fire on l\o1arch 1?, 1968 , at San Onofre Nuclear Generating Station . ~ A repli ca cable tray was 24 inche s wide by 3 inches deep and 1?-1/2 feet lon~ .

'!he material was p;alvanized steel. 'Ihe cable trav was loaded with 234 cables of various sizes as shown on the cable trav profile diagram shown under the cable tray heat rtm _test. 'Ihe cables were of three types:

A. Simplex Butyl insulated with neoprene jacket .

B. General Electric cross-linked polyethlene.

C. Conmunication cables .

4. A R.ama Industrial C011PanY Resistor Assembly and Suoport tyne IH- 6557 .

'!he assembly consis ts of 54 individual hairpin e l errents each rated 5 kva at 480- volts which results in a total load factor of 270 kva at 480-volts. '!he elements are bussed in groups of three in a single phase. '!here are six three-phA.Se circuits.

5. Instrumentation

~tlnneapolis Honeywell Oscillograph Current Trans forrrers Potential Transformers Shunts Amneters

6. Miscellaneous

'Ihree propeller type fans Fire extinguishers Insulating material, canvas and steel ho:rses Heating lamps Loading transformers

'Thermocouples Potentiorreter H. M. Stone Apparatus Engineer

FIGURE 1 WIRE CONNECTIONS FOR ENERGIZED CONDUCTORS CABINET NO. 1

(#l2) ;

Heater No .

A 401 - 429 I 423 B 1IC

f> B 402 - 430 I 42 B #1 c 40~ - 431 I 424 c

(#10) Short A 4o4 - 440 I 411 A 1IC

=116 B 402 - 441 I 414 B c 4o6 - 1JJ.2 I 432 c

(#8)

A 407 - 443 I 41 A 1IC B 408 - 444 I 416 B #3

6 c 409 - 445 I 420 c

(#11)

A 410 I 41 A 1IC

6 B 412 I 4 B #4 c 417 I 4 4 c

( =lr~ )

A 418 I 4 A 1IC B 419 I 4 B #5

6 c 422 I 4 8 c

(=It T)

A 426 361 I 421 A 11c B 427 367 I 4 B f/6 c 428 36~ I l,. 6 c

Q WIRE CONNECTIONS FOR ENERGIZED CONDUCTORS CABINET NO. 2

14 #13 Compartment 75, 45, 48, 8, 103 /A A \* 51, 54, 57, 6o, 138 1/C #12 1/C #12 3/C #12 76, 46, 49, 9z 103 /B B \ 52, z5, 58, 61, 138 &

3/C #12 77, 47, 50, 10, 103 /c c \ 53, 56, 59, 62, 138

16

15 351, 354z 357 /A A \ 63, 66, 69, 72, 102 1/C //12 1/C #f3 352, 355, 358 /B B \ 64z 67, 70, 73, 102 &

3/C #12

~ 353, 356, 359 /C c \ 65, 68, 71, 74, 102 NONE NONE

FUSE CONDITIONS AFTER TEST FIF.E CABINET NO . 1 401, 429 - OK A Phase 423 OK 402, 430 - OK B 425 ;

NG 403, 431 - OK c 424 NG 4o4, 440 - NG A Phase 411 NG 405, 441 - OK B 414 NG 406, 442 - OK c 432 NG 407, 443 - OK A Phase 415 NG 4o8, 444 - OK B 416 NG 409, 445 - OK c 420 NG 410 OK A Phase 413 OK 412 OK B 433 NG 417 OK c 434 NG 418 OK A Phase 439 NG 419 OK B 437 NG 422 OK c 438 UG 426, 361 - OK A Phase 421 OK 427, 367 - NG B 435 NG 428, 363 OK c 436 NG CABINET No. 2 75, 45, ~8, 8, 103 - OK A Phase 51, 54, 57, 6o, 138 NG 76, 46, 49, 9, 103 - OK B 52, 55, 58, 61, 138 NG 77, 47, 50, 10, 103 - OK c 53, 56, 59, 62, 138 OK 351, 354, 357 - OK A Phase 63, 66, 69, 72, 102 OK 352, 355, 358 - OK B 64, 67, 70, 73, 102 OK 353, 356, 359 - OK c 65, 68, 71, 74, 102 OK

POSSIBLE ELECTRICAL CONDITIONS

@ PHASE TO PHASE SHORT

~latts Amps Volts Resist.

Short 0 14 .8 0 0 860 6.0 138.5 23.2 Max. 880 7.2 119 16.6 800 10.0 80 8.0 760 12.. 0 46 3.85 220 14.0 14 1.0 880 7.2 119 16.6 Open 0 0 234 00 Circuit

39C3 CABLE .XRAY SIMULATION PRIOR TO SHORT CIRCUIT TEST SUSTAINED COMBUSTION RE SULTING FROM PRES-SURIZER HEATER CABLE SHORT CIRCUITS RESULTS OF CABLE SHORT CIRCUIT TE ST

7-3/C Nl2 3- 1/C "'a 6-1/C '"'12 15- IIC"'I2 CROSS SECTION OF CABLE TRAY 39C3

7 .1.2 EXISTIHG PENE'I'RATI <l-J CCM:J:NG - CABIE HEAT RUN c

REPORT OF THERMAL LOADING TEST ON CABLE UNDER CO\aJLING FUR CONTAINMENT SPHERE PENErRA.TION EPC4-WPC7 The purpose of this test was to determine the possible maximum temperature within the cowlings mounted on containment sphere penetrations EPC4 and WPC7 .

In order to perform this test, it was necessary to reproduce the physical and electrical conditions as they existed during actual service.

Penetration cowl ings EPC4 and WPC7 were identical with regard to the nunber and size of conductors carried into the aluminum housings * 'Ihe normal load current for WPC7 (which is sli ghtly higher than the EPC4 load current) was used in the simulation.

The Bechtel Corporation provided a cable schedule and current loading values for these penetrations.

The test was conducted in two stages at Edison's Shop and Test facilities at Alhambra, California. Participating in tb..ese tests were representatives of Edison's Apparatus , Engineering, Power Supply, and Shop and Test Departments .

A cable bundle was assembled, consisting of six lengths of 1/c

1/0, six lengths of 1/c #2, and 54 lengths of 1/c #6 butyl insulated, neoprene jacketed control cable. Each piece was approximately 6' in length within the cable bundle. These pieces of cable were connected in series groups in accordance with the current loading schedule provided by Bechtel.

One end of the cable bundle was secured with plastic electrical tape and a thermocouple #19 inserted at the center of the bundle, one inch from the end. 'Ihis end was then packed with 11 Duxseal 11 compound to simul ate the 11RrV 11 silicone rubber compound which was used to seal the penetration face and cable ends against moisture at the San Onofre Nuclear Generating Station.

A second thermocouple #18 was taped t o the top of the cable bundle, one inch fran the end. A third thermocouple #13 \'las t aped to the bottom of the cable bundle at the 90° bend within the cowling .

Other thermocouples used were #3 taped to the top of the cowling,

20 taped to the underside of the cowling, and #1 mounted below the 90° elbow for ambi ent temperature measurement .

A 90° elbow and two straight sections, one non-ventilated and one ventilated, were shipped from San Onofre* to be assembled as complete cowlings for these tests .

A 1/2" thick 't'TOoden plug was inserted at the end of the straight section of the cowling for the tests to simulate the penetration face . The cable burxile was inserted into the cowling touching the plug. Several cables protruded through holes provided in the plug for connection to loading trans-f ormers . 'Ihis test was performed in two parts, the first using the non-ventilated straight section of cowl ing and goo elbow, and the second using t he ventilated straight secti on of cowling and goo el bow.

Power was obtained from a 3-kVA 240- 240/120-volt single-phase distribution transfonner. Fbur individual series circuits in the cable bundle were l oaded as foll ows : 142 A, 71 A, 46 A, and 12 . 5 A. CUrrent control was obtained by use of 240- volt variacs. A clamp-on ammeter was used t o check currents periodically .

For rec01"Cling temperatures an Esterline- Angus chart type temperature recorder was used .

The circuits duplicated for these tests were as follows :

Actual Load Test Load No . & Size CUrrent/Conductor Current/Conductor Circuit of Conductor (Amps . ) ( Amps . )

Recirc . Pump B 3- #1/0 142 142 Resi dual Heat Removal Pump B 3-#1/0 71 71 Pressurizer Heaters 45- #6 46 46 Reactor Control Rod Mech. Cooling System Fan A8S 3-#2 48. 5 46 Fan Al 3-#6 12. 5 12. 5 Fan A3 3-#6 12. 5 12. 5 Emergen-cy Lighting Panel 3- #6 Not Allocated in WPC7 3-#2 RESULTS:

Test #1 - Non-Ventilated Cowling r Maximum t emperatures were as follows:

'fuerm:>couple # Max. Temp . Location 19 Cente r of cable btndle .

18 Tcp of cable bundl e .

13 90° bend in cable.

3 'I'q) Of CCM ling .

20 Bottom of ca~ling .

1 Ambient.

Test #2 - Ventilated Co.ding

'fuermocat.p le # M3.x

Terrp . I.ocaticn 19 l09°C. ~nter of bmdle .

18 85 Top of cable bt.ndle .

13 50 90° bend of cable .

3 50 Top of ccmling.

20 40 Bottom of cowling.

1 28 Arrbient .

I t is concluded that under conditions of high ambient t emperatures exceeding those encountered during these tests, cable temperatures could rise to levels above the cable insulation rating , resulting in damage to the cables .

J . L . Cchcn Apparatus Enginee~

EXI STING PENETRATION COWLING - CABLE HEAT RUN COWLING DIAGRA M SHOWING CONDUCTOR L AYOUT AND THER MOCOUPLE LOCATIONS FOR HEAT RUN TESTS a"

T.C. 3

~;::::;:===:::::~. - - - - ---

CONDUCTORS ARE A CONTINUOUS"'

SERIES LOOP T HROUGH COWLING TO LOADING TRANS. - - - - -...... .,T.C.I3

.~T.C .20

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T.C. I

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TO LOADING TRANS.

ALL CONDUCTORS AT PLUG SEALED WI TH DUCTSEAL WOOD PLUG 1,--Z-----

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50 A.

BREAKER

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3KVA 240-240/120 v.

=Jt2 TRANSTAT

3 VARIAC

4 POWER

6 POWER STAT STAT r--1-----. KN 00 P POWERS TAT 220/20 12.5A 46A ?lA 142A LOAD LOAD LOAD LOAD WIRING DIAGRAM FOR COWLING HEAT RUN TEST

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7 . 1. 3 NE\o/ CABLE TRAY 'lHERMAL LOADH:G CRITERI A -

HEAT RUN

'lEST REPOID' NEW CABlE TRAY THERMAL LOADING PRESSURIZER HEATER CABLE - HEAT RUN PURPOSE A test was cooducted on May 12, 1968 , utilizing a model of the new #4 AWG pressurizer heater cables in their new cable tray configuratic:n. 'lhe purpose of the test was to determine the max1.mun temperature that could be expected tn these cables under normal full load, 46 amps, and overload condition, 52 amps

DISCUSSION l

To simulate conditions to be found at San Onofre Nuclear Generating Station, two 12-foot lengths of 24" x 3" expanded metal, stee l, cable trays and a reel of 3/C #4 AWG 600 volt cc:ntrol cable \'las sent to Edison's Shop and Test facility at AJhambra, California.. 'Ihis material is identical to that presently being installed at San Onofre Nuclear Generating Staticn.

'lhe two lengths of tray were bolted together to form a single 24-foot length which was then motmted on 2-foot high steel horses. Cnly point contact was made between the bottan of the tray and the horses.

'lbe cable used for these tests was supplied by the Okoni te Corrpany. It cc:nsisted of th1"'ee 1/C #4 AWG 600 volt butyl (Okonex) rubber insulated, neoprene (Okoprene) jacketed conductors, cabled together \trith jute fillers, botmd with JT(Ylar tape and jacketed with "Okoseal" poly-vinylchloride compound.

A single length of cable was looped through the tray to form fifteen 40-foot l engths with 24 feet of each in the tray. Including connecting l engths rtmning outside the tray to the por11er supply, the total length of cable was 650 f eet. 'Ihe three cooductors in the cable were connected in series to form a continuous circuit. 'Ihe fifteen parallel lengths were placed within the tray in a sinp-).e layer, starting at the edge of the tray with no separation between cables. 'Ihe cables did not fill the bottom of the 24-inch t~y, leaving 7 inches of exposed tray.

Each end of the tray \<las wrapped vri th fiberglass insulation to limit the heat loss.

Nine, 250-W., equally spaced, heat larnps were directed at the ccncrete floor beneath the tray to maintain a ccnstant ambient temperature in the area.

To m:n1tor t en;>eratures , fourteen thernncouples and an Esterllne-Angus chart type t emperature were installed. 'The locaticn of these thei"TTcouples are as follo~1s :

fl1 - 4'-4" from end of tray.

2 - 8' - 3" fran end of tray .

3, 4, 5, 6, 7, 8- 12' from end of tray .

9 - 16' from end of tray.

10 - 20' - 3" from end of tray .

21 - "Tray Temperattn"e" - 11 ' -10" from end of tray .

22 - Ambient beneath the tray and 12' from the end.

23 - Outside tray beneath fiberglass insulation , 6" from T.C. #1 tray end.

24 - Outside tray beneath fibergl ass, 7" from T.C. #10 tray end.

'nlennocouples 1, 2, 5, 9, and 10 were placed into the center of the middle cable in the layer. 'nle outer PVC jacket was slit to permit entry of each thermocouple and then taped vii th PVC tape .

'nlermocoupl es 3 and 7 were inserted into the center of other cables in a similar manner.

'nlennocoupl es 4, 6, and 8 were taped to the surface of the outer jacket and placed between adjacent cables . 'Thermocouples 23 and 24 \'lere taped to the top of the middle cable beneath the fiberglass ,

outsi de the tray.

Power v.ras suppl ied from a 240 ...volt source through a 240- 240/120 isol ation trans former. For Test 1 a variac and loading transfol"fl'er was used. For Test 2, a transtat was used. A wattmeter, voltmeters, and arnrreters were used to measure power input .

Test #1 -

For this t est a current of 46 an:peres was circulated through the cabl e . 'Ihis provided a total calculated loss of 1086 v1atts in the cable and 25 . 2 \'latts/foot in the tray . Maximum thermocouple readings were :

T. C. #

1 39 Maximum readings were obtained after 270 minutes

Q Test #1 (cont .)

T. C. # Temp. oc 2 41 3 40 4 40 5 40 6 39 7 39 8 39 9 39 10 39 21 26 22 24 23 38 24 44 Test #2 -

After tenn1nating Test #1, Test #2 was iirmediately begun.

For this test the current circul ating through the cable was increased to 52 amperes. '!his provided a total calculated loss of 1404 watts , and 32 . 4 watts per foot of tray. Maximum thermocouple readings were :

T.C. # Terrp. °C 1 44 Maximum readings 2 46 were obtained after 3 44 135 minutes.

4 44 5 44 6 44 7 44 8 44 9 44 10 44 21 28 22 26 23 43 24 46

CC'NCLUSIOOS It \tor'aS cmcluied fran analysis of this data that the 3/C

4 AWG pressurizer heater cables will experience a maximun~ tell'perature rise of approximately 20°C in their new cable tray installatim. 'This temperature rise is well within the terrperature limit of this insulation.

J. L. Cchm Apparatus Engineer c

. . }~ . , 1 I

,').J-1' CABLE S I NS~~LA TING ENDS LLED IN TRAY BEFO RE IN TEST IN PROGRESS ENDS INSULATED

7 .1. 4 vJESTINGHOLSE 600-VOLT SHITCHGEAR TEST ACCEPI'ANCE '!EST - WESTINGHOUSE 600-VOLT SWITCHGEAR TRIPAC 'IYPE FA CIRCUIT BREAKER

SHORr CIRCUIT IN'IERRUPI'ION 'lEST PURPOSE OF 'lEST

'fuis test was conducted on March 23...24, 1968 to verify the acceptability of the Tripac circuit breaker as a substitute for the existing Westingj10use FDP r*used load breaker switches.

'Ihe suitability of three-phase tripping devices was investi-gated in order to develcp a replacement tripping device that would provide positive three-phase clearing of a circuit in the event of a fault en cne phase or on an inter-circuit fault conditicn.

CCNCW3ICNS

'fue Tripac three-phase tripping units perfo~d satisfactorily in all respect s and their installation will provide an i.nprovement in circuit-clearing capability.

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[ TRI-PACbreakers availability: THI-PAC types F through L ;

application The TRI-PAC breaker is essentially an AB De-ion circu it breaker incor porating a current-limiting device which enables it to be used on distribution systems whe re fa ult currents up to 100,000 symmetrical rms amperes are available.

As the n ame implies, it is a TRiple PACkage of protection-(!) time delay the rmal trip, (2) instantaneous magnetic trip, and (3) current limiting pro-tection-combined and coordinated in a single compact and economical d evice.

TRI-PAC breakers are used on low voltage distribution systems when the available fault current is above the interrupting ratings of standard molded case breakers but does not exceed 100,000 symmetrical rms amperes.

Th ey are designed for use in switchboards, control centers, panelboards, combina tion starters, bus duct plug-in units and separate individual enclosures.

In ad dition, they are suitable for application as main breakers and for pro-tection of branch and feeder circuits and connected apparatus. When prop-e rly applied, TRI-PAC breakers may also be used for the back up protection of standard molded case breakers.

- general desig:t.

-

tt f_ d ~eatures

descriptive AD De-ion circuit breakers bulletin 29-150 page 9 1 6 retain a ll fe a tures of standard AB D e -ion circuit coordinated corn-breakers: TRI-PAC breakers are built to th e same exacting mon trip to prevent design standards and by the same methods as conventional West- single phasing: When a inghouse mold ed case circuit breakers. They retain all the current limiter operates, fe atures ol s tandard breakers includi ng: De-ion arc quenchers, the ejected plunger causes non welding silver alloy contacts, common trip and Moldarta instant release ol a com-and / or glass polyester cases. mon tripping bar. All poles are openedsimultaneously, eliminating the possibility z compact, e asy-to-remove current limiter housing:

of single phasing.

Current limiters are contained in a single, compact Moldarta housing. It is fron t r emovable for easy access to current li miters when replacemen t is necessary. Limiters are correctly aligned and held in place by a retaining bar so thai when the housing is pulled out all are disengaged from their receptacles simultane-ously.

-~j positive trip indication: Whe n a breaker trips, the handle always moves to the center "trip" position. In addition, the cause of tripping is indicated in the following ways:

3

If the breaker cannot be reset immediately a lter tripping b ut limiter housing safety interlock: When the limiter housing is removed a safety interlock tr ips the breaker b efore the can be rese t a lter a shor t p eriod it indicates thermal tripping d ue limiter stabs disengage. Therefore, these terminals are never to an overload or high resistance fault.

required to interrupt current. This interlock also prevents closing

If it can be reset immediately a "normal" fault c urrent has been ol the breaker while the limiter housing is r emoved so that it is interrup ted by instantaneous magnetic action.

impossible to come in contact with "live" parts.

II the TRI-PAC cannot be reset, high fault interruption by the current lim iter has taken place.

4 visible disconnecting means : Removal of the limiter housing simultaneously removes the limiters. With the limite rs removed it can be readily observed that the limiter contacts are open and that the circuit is disconnected.

Jl_ plug-in type lim iter texminals: Studs on each c urrent limiter engage "tulip" type connectors in the breaker base.

Since the limiter housing provides perfect alignment this arrange-men t assures positive connection and easy removal olthe limiters.

5 specia lly d esigned curre nt limit-ers: When a high fault current causes one or I

more limiters to function, a spring-loaded plunger is ins tantly e jected from the end of the _.!j easy replacement of limiters : Loosening oltwo screws limiter. The plunger strikes a trip bar which releases a retaining bar in the limiter housing and perm its removal causes the breaker contacts to open the instant of limiters.

the fault occurs.

An extended plunger on ~y limiter indicates, I at a glance, on wh ich phase the fau lt has occur- 10 1 missing limi t er interlock: This interlock, in the limiter red so that testing of limiters is unnecessary. housing, prevents the housing from being replaced unless all Presence of an extended plunger also prevents limiters are in place. Thus accidental single phasing is prevented, relatching ol the breaker. Thus, "good" since the breaker cannot be reclosed when a limiter is missing.

limiters must be used or tl1e breaker cannot be opera ted. These limiters are not ailected by the overloads or normal short circuits cleared choice of three t e r m inal connec tions: TRI-PAC b reakers are by the thermal-magnetic action olthe breaker, available with front connected pressure type terminals, bolted c and unless they have cleared a high fault current, as evidenced by an extended plung er, they may be used without question.

rear-connected mounting studs and plug-in te rminal mounting b locks.

ilccessories: TRI-P/\C breakers accommodate many standard Since theso limite rs are designed lor usa on ly 1\B breake r accessories including: shunt trip, w1dervoltage trip with TRI-P/\C breakers, sale, p1oper coordi* and auxiliary cont(lc!s. Application ol other accessories should nation is assured. be reviewed with Westinghouse.

'lEST 352 - 'lEST DATA Westinghouse 600 Volt Switchgear

'Iri- Pac Type FA 70 A. & Oenter Substation FUsed Disconnect rrype FDP w/ FRS 80 & KTS 80 FUses March 23 & 26, 1968 (2) (2) (3)

Available Available Peak let Total (1) Phase-to-Phase Fault Fault Through Clearing Test Type & Locaticn Voltage Current Current Current Tirre No. of Fault (R>tS Volts) ( Ff.1S Artps ) (Crest Amps) (Crest Amps) (Cycles) Remarks

'IRI-PAC 2 TYPE FA 2 70 A.

Alal 3~ at 300' 475 2900 4160 3540 0. 40 Breaker tripped, fuses did not blow.

Blal ~-4 at 300' 475 2500 3540 3240 0.85 Breaker tripped, fuses did not blow.

C2al !4-0' arcing at 24 ' 475 12,300 17,700 Fault current not of suffi-cient magnitude to measure.

Small wire used for the f ault burned and ~ned t he circuit.

C2a2 II 475 12,300 17,700 7060 0. 47 Breaker tripped, fuses did not blo,..r.

A2al 3~ at 0 ' 475 24,900 33,400 11,200 0. 40 A & C phase fuses blew.

Breaker tripped .

FUSED DISCONNECT z TYPE FDP z 100 A.

WI'rn FRS 80 OOAL ~ FtJ~

A4al ~at 0' 475 24,900 33,400 15,800 All fuses blew but internal (RMS ) 3~ fault started and exten-sively damaged t he swi tch .

New switch obtained for remainde r of t est s .

A4a2 3~ at 300' 475 2900 4120 3830 2.0 'J\.10 fuses blew & switch cont act s wel ded where fuses were blown. 'Ihird fuse not blown but contact badly eroded.

C4al ~4 arcing at 24 ' 475 12,300 17,700 7060 0.5 Both fuses blew, swit ch contacts not. wel ded .

(2)

Available Availab£~) Peak 1~~) Total (1) Phase-to-Phase Fault Fault 'Ihrough Clearing

'!est Type & Locatioo Voltage CUrrent Current Current Tine No . of Fault (FMS Volt s ) ( RMS A!q:>s ) (Crest .Arrps ) (Crest Amps ) (C:tcles) Remarks (Continued )

A4a 3 30' at 0' 475 24,900 33,400 14,550 'IWo fuses blew but internal 30 fault occurred similar to previous t est of sarre rragpi -

tude. Contacts not ~~lded but internal bus destroyed.

f'w switch used f or remainder of test .

FUSED DISOONNECT 1 TYPE FDP 2 100 A.

WITH KTS 80 CURRENT LTI.UTING FUSES A3al 30 at 300' 475 2900 4120 1770 0.10 'IWo fuses b levi.

B3al ~--0 at 300' 475 2500 3540 2060 0 . 10 Both fuses blevl.

C3al ~--0 arcing at 24' 475 12, 300 17,700 2940 0.04 Both fuses blew.

A3a2 3~ at 0' 475 24,900 33 , 400 4120 0 . 05 'IWo fuse s blew .

(1) 'Ihe locaticn of the fault indicates the length of a #4 cable nm between the load terminals of the test revice and the f ault.

(2) '!he avail able fault current is that current which would flow if not interrupted by the tes t breake r of ruse. 'Ihe rreasured current, on JTDst tests, was l ess than the available current due t o current limiting acticn of the breaker or fuse.

(3) 'The peak- let- through current is the maxinrum rreasured current that f lows through the test device. This value can be l ess than the available current due to current limiting acticn of the breaker or fuse .

P. L. Wheeler Assistant Apparatus Engineer

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7 .1. 5 BORIC ACID CRYSTALLIZATION STUDY c

BORIC ACID CRYSJlALLIZATION STUDY At 12:31 a.m., March 12, 1968, a fire in the 480-volt S\dtchgear room at San Onofre Nuclear Generating Station resulted in a power loss to the heat tracing on t he boric acid injection system. At the time of the failure the average temperature of the 1nj ection system was 17'PF.

During this period two unsuccessful attempts were made to 1nj ect boric acid into the reactor coolant system using the North Transfer Punp which <lid not sustain a pov1er loss. 'Ihe attempts \'t'ere made at 2:15 a.m. and 3:00 a.m.

Power was restored to the system at 10:10 a .m. , on the same day. 'Ihe heat tracing system recorder in<licated that the injection system t emperature had decayed in two distinct gi"'ups to temperatures of 1500p and 1200F. Due to the fact that the heat t racing system recorder was not operating during the power loss the t emperature decay rate could not be detennined. It "WaS , therefore, ass lUlled that the decay rate was linear. See attachnent.

Pn inspection of the system revealed that the Boric Acid Storage TaP.k recirculation line located bet\.,reen the tank and CV 333 is inadequately heat t raced.

It was observed that when the system was put on recirculation, a cloud of boric acid crystals ,..,as pumped out of the recirculation line into the storage tank.

'Ihose crystals passed as a cloud through the tank and out the bottom of the tank thus introducing boric acid crystals into the piping system.

'Ihe experiment s conducted in the laboratory were based on the asstunption that at 2:15 a.m. when the first attempt was made to inject boric aci d using t he North Transfer Pt..nnp, boric acid CI"JSt als had already formed in the system restrict -

ing the transfer pump suction. 'Iherefore, the experiments were conducted \'lith boric acid crystals present in the s ystem. Ho\*Tever it does mt s eem possible that the system would cool sufficiently in the 1-314 hour period between the power failure and t he first attempt to inject boric acid to cause the restriction.

'lhe scure basic laboratory setup that was used in the previous boric acid crystallization study \'las used in this study but with two rrodifications . First ,

the pwnp discharged to the top of the ten-foot vel"t;ical stand of pipe and second, a one-inch I.D. plastic pipe wa.s ins erted at the discharge line to the stainles s steel drum fran the tl:ro-inch I.D. pipe.

As a result of the experiments conducted the following observations \*lere made:

A. Boric acid crystals in the stagnant system that is near its saturation point do not tend to <lissolve. If heat is lost on that sys tem, these crystals becane the sites at which the precipitati on of t he boric acid in the system is initiated.

'lhis condition can be related to t he boric acid crystals which originate in the Boric Acid Storage Tank recirculation line and are 1nj ected. into the system whenever the system is G recirculated

B. '!he application of heat by means of heat tracing to a system where boric acid crystals have fonned on the walls of the piping in that system results in the boric acid crystals breaking awey from the walls of the piping and going into suspension. If the liquid in the system is then ptmtped, the crystals are carried along with the liquid until they come up against a restriction in the systan. At this point they begin to accumulate, gradually shutting off the flow through the restriction.

This occurred in the laboratory at both t he pump suction and at the :point where the system piping \vas reduced from two-inch I.D. to one-inch I.D. 'llie capacity of the punp used in the experiment was two gpn. Had a pt.nnp with a capacity equivalent to the transfer pump's, 45 gpn, been used the overall effect of the migration and packing would have been greatly magnified.

It is noted that before the North Transfer Pump became operable it was necessary to flush the pump suction . '!here fore, the application of the above observation to the existing systen is obvious.

llie following conclusions are made based on laboratory observations and t he inspection of the boric acid injection system.

A. Due to the cold Boric Acid Storage Tank recirculation line, boric acid crystals are probably present in the system at all t1mes .

B. In a system where boric acid crystals have fonned as a result of the loss of heat on that system, the reapplication of heat to the system will result in the crystals going into suspension .

c. Boric acid crystals in suspension vdll migrate with the now of the fluid in that system.

D. A restriction in the system will result in the accumulation of boric acid crystals at the point of the restriction.

E. 'fue inadvertent injection of boric acid crystalti into a system introduces crystal gre>>rth sites in the system in the event that heat on the system is lost.

It is not readily apparent how the transfer pump suction ~ms plugged in the short time bet\'; een the l oss of power and the time the North Transfer Pump was operated. However, if it is asslUT!ed that boric acid crystals were

already present in the suction line followed by a loss of heat tracing, the possibility of rapid crystal deposition exists even though the temperature of the line was above 1500F.

~

'Ihe laboratory experiments have den:onstrated the severe pacldng ten-dency of the boric acid crystals once they begin to fonn in a pipe. 'Ihus, if crystals are present in a line the chance of plugging is very high.

R. D. Britt Chemical Engineer

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7 .1. 6A OIEMICAL AND VOLUf.'E OONTROL AND RADWAS'JE SYSTEM TANK OVERPRESSURE INVESTIGATIQ'J - METALLURGIST ANALYSIS

LOS ANGEl METALLURGICAL SERVICE LABORATORIES SAN DIEG division of TESTING ENGINEERS, INC. OAK L AN[

11009 S. N ORW ALK BLVD. S ANTA FE SPRINGS, CA LIF. 90670 SAN JOSE 12131 723-85 41 a 941-3291 Date: 4-19 -68 P.O. No . T-7747 Lab . No . 18145 SOUTHERN CALIF ORNIA EDISON CO.

Div ision Chemi ca l Section P .0. Box 392 Redondo Beach, Cal iforn ia 90277 Attn: Mr. R. D. Br itt REP-QRT ON THREE OVERSTRESSED VES SELS IN SAN ONOFR E NUCL EAR STAT ION INTROD UCT I ON On Apri l 2, 1968 , at the req uest of Mr. R. D. Britt, an exam in at ion was made of a fl as h tank, a waste gas s urge ta nk, and a volume contro l tank at San Onof r e to dete rmine whet he r possib l e me tallurgical damag e had been caus ed by ove rst re ssing to an est imated 125 psi as the result of a powe r failure.

Mr. R. M. Bani ste r, ass istant engin ee r, assisted in the examinati on .

Mr . Ha ns Ottoson , stat i on chief, and Mr. J. C. Haynes , chi ef eng in eer ,

we re al so contacted .

1

FLASH TAN K Per s pe ci fication book: Le ngt h 10 1 6 11 , O. D. 4 1 0 11 ; wal l thic 1<ness of dished heads and of shell 0 . 140 11

Materi a l 304 S/S. Per namep l ate, tes t ed to 69 ps i . Ori ent at ion ver tical.

Thi s tank showed s l ight bulg ing . Thi s was mos t easi l y seen at a c ir cumfe r -

enti a l we l d about 2/3 of the way up the tank . The we ld me tal, be ing thicke r, had no~ ex panded as much (if a t a ll) as the adjacent meta l above and be l ow the we ld. Simil a r const raint against expans ion was caused by a ho rizontal pipe nea~ the t o p, be low which bulging coul d be seen , and by a l arge man -

ho l e on t he s ide near the top .

No measurements of the tan k dime ns i ons after ove rst ress ing \-Je re ava i l ab l e .

Therefo re , the tank was carefull y ex am ined. Obse rva t ions an d ch ecks of the di s t or ti on of t ank wa ll s indi cated that a t no point was bulgin g beyond origina l di mens ions g reate r than one -quarter of an inch.

MSL # 18145 Page 2 - cont.

EffECT OF BULGING Bulging, or circumferential expansion, results in plastic flow of the metal shell, whi ch c auses both wa ll th in ning and cold working of the metal. An es timate of the amount of circumferential expansion or stretch of the shell allows judgment as to the effect of such stretch .

Radial expansion of 0.25 inch corresponds to diamete r increase of 0.5 inch. This in turn corres ponds to a circumfe rential increas e of 1.57 inches.

In this 48 inch diame ter shell (circumference 151 inches), this equals an elongation of slightly over 1% in the shell plate as a result of the over-stress.

The shell meta l, annealed 304 stainless steel, has high ductility and no sha rply-defined el ast ic limit. In conventional tensile t est ing, it will elongate over 40% befo re breaking . During this elongating, it is work-harde ning. Its 11yield point 11 is being increased by this co ld-working .

The effect of a 1% e longation upon the mechanical properties will be sl ight.

The yield point will be slightly rai s ed, so th a t subsequent overpress u re u~

nearly to the level of the first excursion will cause no further bulging .

The wall thic kness will be r educed by about 1% - but this amount, 0.001 4 inch, is within the manufacturing tolerance for the plate .

It is concl uded that the meas ured bulging has had no harmful effect on the gene ra 1 she 11.

Metal immedi ately adjacent to the we ld s may have stretched somewhat more, due to local bending. Suc h loc a l e longation cannot have exceed ed 3%. This is much l ess t han the deforma tion capability of s ound we lds in 304 stainl es s.

SUGGESTED FURTHER EXAMINATION Bec ause of the very s li ght possi bility that local stretching in the we ld s may have caused incipient cracking at or near a weld, non-destructive testing along circumfere ntial we ld s was suggested. Externa l testing by ultras on ic techni ques wa s subsequently performe d. No indications of cracks were repo rte Since no crac ks were revealed by thi s ins pection method, i t is concluded t hat the tank can safe ly be used at pressures up to that to which the overpressure subjected it.

2. WASTE GAS SURG E TANK Per specificat ion book: Length 10 1 7; O.D. 4'6 11 ; wall thickness of she ll and heads 0.375 11

1*1 a t e rial A285C stee l, which is straight carbon stee l .

Pe r namep l ate, tested to 88 l bs. Orientation ve rtical.

Carefu l examin a tion of al 1 s ides di s closed no hint of a bulge, eithe r at the welds or elsewhere.

c

MSL #18145 Page 3 - cont.

CONCLUSION It is concluded this tank, with much heavier walls, was undeformed. There-fore there is no poss ibility of any damage having occurred due to the over-stressing, and no need for further inspection.

3. VOLUME CONTROL TANK Per spec ifi cat ion book and namepl ate : 11 1 7 11 l ong, 5 1 0 11 O.D., heads 0.241 11 thick; shell 0.250 thick. Mat e rial 304 S/S~ Tested to 75 lbs. Ori e nta-tion hori zonta l.

Careful exam inati on di sc los e d no bulging or d isto rtion beyond normal fabri-cation limits . Shell and welds were straight and regular.

CONCLUS ION Same as for waste gas surge tank; no damage and no need for further inspec-t ion.

SUMMARY

The fl as h t ank was bul ged very s lightly, by an amoun~ f ar l ess than its capacity to resist. Because local stretch due to bending at girth welds may have exceeded ove r a ll stretch, non-d estructi ve examination of weld areas was r ecommended . Subsequent ultrason ic inspection was reported to have shown no sus pici ous indic at ions .

Bas ed on our examination and the ultr aso nic t est ing, we conclude th at the flash tank was undam age d and fit for service.

The other two t anks were found to be undamaged and t o have experienced no poss ibilit y of damage .

Metallurgical Engineer Ca lifo rnia Reg. No. 454

7 . 1. 68 rnE!'>'ITCAL AND VOLUJ'IE CCl'J'ffiOL AND RADHASTE SYS'illM TANK OVERPRESSURE INVESTIGATIGJ - HYffiOSTATIC 'lEST OF '1HE VOLUME COJ\TTROL, WAS'IE GJ\S SURGE AND FLASH TANKS c

HYDroSTATIC TEST OF 'IHE CHEMICAL AND VOLtm

. .OONrROL, \t/P.STE GAS SURGE AND FLASH TANKS As a result of the apparent over-pressurization, hydrostatic pres-sure tests were conducted to further affinn that these tanks were suitable for continued service. 'Ihe pressure testing of these tanks was accomplished

.satisfactorily on April 29-30, 1968. No leakage was observed from the tanks.

Results are tabulated as follows:

Test Pressurizing Design

. . Tank Pressure Medium Pressure Cllemi.cal and Volune Control 75 psig Water and Nitrogen 75 psig Flash Tank 30 ps:ig Nitrogen 30 J:X>ig Waste Gas Surge Tank 30 psig Nitrogen 30 psig

7.2 PREVIO'tE rESI GN BASIS roR CABIE SI ZING PREVIOUS DESIGN BASIS FDR CABLE SIZING INTRODUCTION The criteria for \<.'ire and cable size and for detennining electric cable tray l oading used in Southern California Edison pCMer plant' design is established to accomplish the following:

A. Power Wire and Cable Size

1. 'lb carry load currents with conductor temperatures remaining within the limit established by the wire and cable manufacturer to obtain full~..expected cable insulation life .

2. 'lb carry f ault current mtil interrupted by pr:tma.ry protection and have t he conductor t emperature rise retm.in w1thin the manu-facturer's specified t emperature limits.

3. To limit circuit voltage drop to three p:)rcent.

4. To provide a margin for an increased expected wire and cable life .

This is to be accomplished with the conductor t emperature remain-i ng below the manufacturer's established rated temperature for the majority of the generating plant operating t ime .

B. Control Wire Size Cont rol wire to be sized to provide mechanical strength. '!his results in the current carrying capacity of' t he conductors being oversized with respect to actual current which must be carried .

C. Insulation for Wire and Cable

'lhe insulation to meet require~nts of environment and service.

D. Electric Cable Tray Fill The cable tray not to be overfilled with cable. Tray deflection not to exceed 1/360 of' the span. Tray designed to carry 50 potmds per foot of

\'Tire and cable and a 200-potmd live load anywhere alc:ng the span between supports such as \*muld be imposed by a man .

DESIGN GUIDES Design guides and practices which have been enployed to accanplish the requirerrents of the above criteria ~ as follows:

A. Sizing Power Wire and Cabl e

1. Conductor s i ze is established by first multiplying the rated or l oad current by a size increasing factor then select~ a conductor rated by the manufacturer to carry this l arger current . The multiplying factor used is 1-1/2 for loads f ed from switchgear and 1-1/4 for l oads fed f rom motor control centers. The wire and cabl e aJll)acity table used i s from Insulated Power Cable Engineers Association (IPCEA ) f or

'"'hree Circuits 1n a Duct" or Triplex Cables 1n a Circuit."

Incorporated 1n this table are factors to be used for varying conditions of design temperature. 'Ihe design temperature used depends on plant location and on the specific application within the plant. 'Ihe 5-kV power cables supplying power tran the unit and start-up transfonrers t o the lil60-volt switchgear are rated to carry peak start-up load current. This normally exceeds the t ransforner full load rating. In additicn, the cables are placed 1n a single l ayer in the tray with space between cables.

2. Cables also are sized to Ca:rT'J fault current within the manufacturer's 11m1t for total conductor terrperature (usually about 200°C). Tnis requirement, many times, results 1n cables being sized larger than required for current carrying requirernents as stated 1n Sectiar1 A above.

3. Cable conductors are sized to operate with less than three percent voltage drop for full load current operation. This also may result 1n cables being sized larger than required for the current carrying requirements .

4. Increased cable life is expected, as the above f actors provide for wire and cable operating at conductor temperatures less than the max1mum allowed by the manufacturer. Experience gained from previous plants bears out the fact that when these design guides are follor11ed, cables operate at less than rna:x1murn all<:Mable temperatures.

B. Electric Cable Tray Fill Cable tray supports designs are established to meet the tray loading requirements of 50 potmds per foot of wire and cable and of a s in9;le 200-pound live load anywhere along the tray span betweE"n tray supports .

'!he 50-pound per foot of wire or cable is ccnsidered conservative.

(As a meas ure, a heavier cable such as three conductor, 5-kV armored 750 MGr-1 weighs 11. 5 pounds per foot. A more corrmanly used single conductor 4/0 cable w~ighs 0. 85 pound per foot. )

C~ble tray fill is reviewed when the cross sectional area of the cables

. approach 30 percent and is l1rn1 ted to 40 percent when running a l arge varl~ty of cables. 'Ihe reviet'l point is established to equalize loading between trays . Ccmputer programs are to be utilized to control the tray fill.

EXAMPlES OF CABlE SIZING AND APPLICATION IN EXISTil'lJ EDISON PLANTS Each of the foll&ing examples are for existing 480-volt circuits either in motor control centers, or in switchgear.

Cable sizing as to anpacity is taken from IPCEA Table VIII, and Page 309 for 40°C ambi ent and 90°C conductor temperature for 1000 volts.

A. 480-Volt Switchgear Sources L Redondo Generating Station Seal Water Injection Purrp - rated 100 HP, three-phase, 119 amperes full load current.

Cable used - three NO 2/0 copper IPCEA rating - 215 arrperes Calculations - 1.5 X 119 = 180 amps. (well within 215 ampere rating)

2. Redondo Generating Station Main 'furbine Auxiliary Ptmp - rated 150 HP , three-phase, 176 ampere full load current .

Cable used - three NO 4/0 copper IPCEA rating - 287 axrperes Calculations - 1.5 X 176 = 264 amperes (falls within the 287 ampere rating)

B. 480-Volt Motor Control Center Source

1. Redondo Generating Station F\mlace TV BlO"..,er - rated 15 HP , three-phase , 19. 2 aJll)eres full load current.

Cable used - three NO 10 copper IPCEA rating - 40 arrperes Calculations - 1.25 X 19.2 -= 24 ~res (well within the 40 anperes rating )

2. El Segundo Generating Station Air Preheater Rotor Drive Motor - 15 HP, three-phase, na:neplate data - 20 .1 arrperes full load current.

Cable used - three NO 8 copper IPCEA rating - 59 anperes Calculations - 1. 25 X 20.1 = 25 amperes (well within 59 amperes rating )

7.3.0 MATERIAL SPECIFICATION NO . 225 c

SOUTHERN CALIFORNIA EDISON COMPANY LOS ANGELES , CALIFORNIA MATERIAL STANDARD NO . 225- 63 (Revision of M. S. 225- 61)

SPECIFICATION FOR 600-VOLT RUBBER-LIKE- INSULATED CONTROL CABLES c

J anuary 10, 1963

1 - 1 MATERIAL STANDARD NO. 225 - 63 (Revision of M.S . 225-61 )

SPECIFICATI ON FOR 600- VOLT RUBBER- LIKE- INSULATED CONTROL CABLES PART 1.00 INTRODUCTI ON 1.01 I NTENT 1.01.01 I t is the intent o f the Southern California Edison Company to obtain appar atus which meets al l of the requirements set forth in th e paragraphs wh ich he r einafter follow.

1.02 I NSTRUCTI ONS TO BIDDERS

1. 02.01 As noted elsewher e , this Specification (M . S .

No . 225-62) i s the revision of Material Stand ard No. 225 -61 .

Bidders are advised to r ead this Specification (M . S. No . 225- 62) in it s e n tirety .

1.02. 02 Whereve r used in this Specification the word 11 Edison 11 shall mean the So uthern California Edison Company, and the word " Manufacturer" shall mean the successful bidder on this Specification . The word "apparatus " is used herein to include apparatus , equipment, mate r ials , supplies , or whatsoever may be purchased hereunder with al l the usual and appropriate fittings, attachments, appurtenances , and appliances .

1.02. 03 Arrows shown on the r ight of the pages which make up this Specification are for Edison ' s use when preparing a Quotation Request . Insofar as the Manuf actur e r is concerned ,

the arrows in no way a l ter the meaning or intent of any paragraph or portion thereof; therefore , they shall in no way reli eve the Manufacturer of his obli gations .

1~02 . 04 Bidders shall quote on 600- volt rubber- like -

insulated cont r o l cables which may b e r equired by Edison exact ly as specified herein . Th e general and technical require -

ments of the cables are set forth in Part 3 . 00 of this Specificatiol 1.02 . 05 Paragraph 2 . 03 . 03 .c of this Specification does not app l y .

1 . 02.0 6 Addit i onal ins tructions to Bid ders , if any ,

wil l be specifi ed in the Quotation Request .

2 - 1 PART 2 .00 CONTRACT CONDITIONS 2.01 CHANGES IN SPECIFICATIONS 2.01.01 No changes shall be made in this Specification or referenced Edi s on Specifications unles s authorized by Edison through its Purchasing Agent . Should any conflict prevail between this Specification (or referen ced Edi son Specifications) and the Manufacturer 's Proposal, this Specification (or referenced Edison Specifications) shall prevail. Edison shall have the ri ght to make r eason able changes at any time to the aforesaid Spe cifications including drawings which are a part thereof or made a part thereof by r eason of the changes. Should such change s increase or decrease the amount due or in the time required for performance , an equitable adjustment will be made .

2. 02 COHPLIANCE WITH CODES AND STATUTES 2.02.01 The Manufacturer's Apparatus shall comply ~rith the applicable requirements of all statutes, ordinances~ codes, and standards of legally constituted authorities having jurisdiction . The Manufacturer shall obt ain certificates of compliance where required.

2. 0 3 WORKMANSHIP AND MATERIAL 2.03.01 The intent of this Specification is to secure for Edison Apparatus of firs t class workmanship in all respects . All components shall be manufactured , fabricated, assembled, and finished with ~rorkmanship of the highest quality throughout, and in accordance with the best recognized correct practice.

2 . 03.02 All materials shall be new, of first class C:'lality, and suitable for the conditions specified.

2.03 . 03 Unless specified elsewhere in this Specification:

a. All materials used in the manufacture of the Apparatus shall conform to the latest standard of the American Society for Testing and Materials.

b. All electrical design, materials, tests, and con-struction shall conform to the latest applicable standards of the United States of America Standards Institute (formerly American Standards Association),

the Institute of Electrical and Electronics Engineers ,

and the National Electrical Manufacturers Associ ation, unless specifically excepted by this Specification .

In case of conflicting requirements of these standards, they shall apply in the sequence that they are here listed.

2- 2

c. All struct ural s teel design shall conform to the l atest standards of the American Institute of Steel Construction, Inc.

2.03.04 If the Manufacturer has any reason for deviating from the above standards, he shall state in his Quotation exactly the nature- of the chan ge and his reasons for making the change.

2.03.05 The finished product shall be complete in all respects and shall fully conform to the description thereof set forth in this Specification and in the covering Purchase Order.

2.04 INSTALLATION 2.04.01 Said Apparatus will be installed by and at the expense of Edison unless otherwise specified in the Quotation Request .

2. 05 INSPECTION, TESTS , AND EXPEDITING 2.05.01 Edison shall be allowed access to the Manufacturer's shops and also to those of the Manufacture r's suppliers to inspect the Apparatus and workmanship, to 'rltness tests, and to obt ain other desir ed information .

Inspectors representing Edison shall be given every facility to inspect the work during all stages of manufacture, testing, and shipment .

2. 05.02 Inspection of the Apparatus may be at the Manufacturer's shops and/or those of his supplie rs, or upon r a ceipt at destination at the option of Edison. Inspection by Edison at the aforesaid shops will not be made except on special request by Edison 1 s Purchasing Agent . The "'ai ving of inspection thereof shall in no way relieve the Manufacturer of the responsi-bility of fUrnishing Apparatus according to this Speci f ication .

2.05.03 The Manufacturer shall inform Edison of the progress of the work and shall give Edison ampl e advance notice of the appropriate times for inspections and/or tests. Specified tests will be approved and may be supervised by Edison.

2.05 . 04 When specific inspections and/o~ tests are required, the work on the Apparatus involved shall not proceed beyond that point until Edison has made or waived such inspections and tests.

2 .05.05 If performance tests are to be made in the field, they are to be made at. times and unde r conditions to be mutually agreed upon by Edison and the Manufacturer .

2. 05 . 06 Certified copies of all performance tests shall be furnished to Edison.

2 . 05.07 The Manufacturer shall furnish to Edison , if so r e que sted and at no additional cost , shop and mill reports whe n spe cified.

2 . 05.08 The costs of all tests made in the shops are to be borne by the Manufacturer .

?- 3 2.06 ACCEPTANCE 2 . 06.01 Edison shall not be deemed to have accepted the Apparatus until i t has made sufficient tests to enable it to determine that the Apparatus meets all of the requirements of said Specifications . Such tests shall be made within six (6) months from the date the Apparatus is completely installed ready for use . The conditions of any tests shall be mutually a~reed upon and the Manu-factu rer shall be notified of and may be represented at all tests that may be made. If inspection and/or tests show the Apparatus or any part thereof not t o be as represented and/or contracted for, Edison may refUse to accept it ,

but the Manufacturer shall have a reasonable time within whi ch to correct the Apparatus at his own expense .

2. 07 WARRANTY 2.07.01 Manufacturer warrants that the Apnaratus and all parts thereof t o be delivered hereunder shall be of the kind and quality described he~ein and shall perform in the manner specified in Snecifications and no other warranty, except of title, shall be implied . If any failure to comply with said Specifications appears within the period of one (1) year from the date of the commencement of use of the Apparatus but not later than eighteen ( 18) months from date of deli very, Edison shall notify the Hanufacturer thereof immediately, and the Manufacturer shall there upon correct without delay and at his own expense the defect or defects by r epai ring the defective part or parts or by supplying a non-defective replacement thereof, but, if the Anparatus i s installed or its installation supervised by the Manufacturer, the aforesaid period shall run for one (1) year from the date of completion of installation and acceptance provided same is not unreasonably del ayed by Edison . In the event the Manufacturer shall correct any detect as herein above provided, then with respect to the Apparatus corrected the aforesaid period shall run for one (1) year from the date of completion of installation of such correction and acceptance thereof provided same is not unreasonably delayed by Edison .

The liability of Manufacturer ( except on warranty of title and on the liability r especting patents herein set forth) arisin~ out of the suppiying of sai d Apparatus or its use vhether on warranties or otherwise, shall not in any case exceed the cost of correcting defects in the Apparatus as above set forth and upon the expiration of said one (1) year, all such l iability shall termi-nate .

2.08 PATENTS 2.08.01 The Manufacturer shall, at his own expense, defend all suits or proceedings instituted against Edison, its officers, agents, or employees, based upon any claim that the Anparatus or any part or use thereof constitutes an i nfringement of any patent of the United States covering the Apparatus ,

any part thereof or the process intended to be perforrred thereby and will pay any and all awards of damages assessed against Edison, its officers , agents, or employees, in any such claim, suit or -proceedings, and uill indemnify and c save harmles s Edison against any l osses , expenses (other than expenses of Edison ' s own Law Department), and/or damages resulting from any such claim, suit or proceedings and/or incurred in obe dience* to a decree resulting from any such claim, suit or proceeding, or pursuant to a compromise thereof approved

2 - 4 by the Manufacturer, provided that Edison , promptly upon service of process upon it, gives to the Manufacturer notice in writing, or by telegraph, o f the institution of such suit or proceeding , and permits the Manufacture r, throu~h counsel chosen by it, and satisfactory to Edison, to defend the same, and p,ives the Manufacturer all needed information, assistance and authority to enable the Manufacturer so to do . If in any such suit, a temporary~restraining order, or preliminary injunction be granted , the Manufacturer will make every reasonabl effort, by giving a satis factory bond, or otherwise to secure the suspension of such restraining order or temporary injunction . If, in any such suit, the Apparatus, or any part thereof, or the nrocess perfor med thereby, be held to constitute an infringement, and its use be permanently enjoine d, the Manu-facturer will at once make every reasonable effort to secure for Edison a license, authorizing the con~lnued use of the Apparatus, or of such part or process. If the Manufacturer be unable to secure such license within a reason -

able time, it will, at its own expense, and without impairing performance re quirements, either replace the Apparatus vith non - infringing Apparatus, or modifY the Apparatus or the process performed thereby to avoid infringement.

If unable to do either of the above things, the Manufacturer will r emove the Apparatus and refund the money paid therefor, in addition to indemnifYing and saving harmless Edison , as aforesaid .

2.09 RIGHT TO USE WORK REQUIRING CORRECTION 2.09.01 If, after the Apparatus has been installed it is discovered that it or part thereof may require correction as herein elsewhere ~rovided , Edison shall nevertheless have the right to use such Apparatus until such time as i t is convenient to Edison th at such Apparatus be r emoved from s e rvice for corre ctio 2.10 SHIPMENT, PACKING , AND PIECE MARKING 2.10.01 The Apparatus shall be shipped in assembled units insofar as is consistent with good shipping practice.

2 .10.02 The Apparatus shall be carefully packed for shinment and loaded on the cars or docks at the Manufacturer 's plant re ady for shipment. Machined and other unpainted surfaces shall be fully protected from i mpact and weather damage . All openings int o the Apparatus shall be carefUlly ~lugge d or covered so as to be fully protected against weather damage. All costs of packin~,

loadin g , and blocking are to be borne by the Manufacturer .

2.10.03 When items must be dis assembled for shipment they shall be match-marked. All units and their containers shall be piece-marked and shall show th~

Purchase Order number. Whe n specified, they shall show the Edison Material Standard number.

2.11 RISKS 2.11. 01 The Manufacturer shall not be held responsible or liable for any loss , damage , detention , or delay caused by fire or strike, civil or milit ary authority, or insurrection or riot, or any other cause which is unavoidable o r beyond his reas onable control, or in any event for conse~uential dam~e s .

2 - 5 2 .12 INSURANCE 2 .12 .01 In order t o permit Edison , afte r the Apparatus has been delivered to t he Carrie r F . O. B. as aforesaid, to maintain upon such Apparatus or part thereof sufficient ins urance to protect Edison ' s interest the~ein, the Manu-facturer agrees i mmedi ately to inform Edison's Traffic Department of each shi p-ment, giving detailed information as to car numbers, etc., and of the value of each such carload and shipment to e nable Edison to maintain such ins uran ce.

2 .13 TITLE 2 .13. 01 The title to the Apparatus he re in specified shall pass at the actual point of shipment at the time such Apparatus shall be delivered by th e Manufacturer to the Ca rrier for transportation as herein elsewhere spe cified .

3 - 1 MATERIAL STANDARD NO. 225-63 (Revision of M. S . 225-61)

SPECI FICATION FOR 600-VOLT RUBBER-LIKE- INSULATED CONTROL CAB~ES PART 3 . 00 GENERAL AND TECHNICAL REQUIREMENTS 3.01 SCOPE 3 . 01 . 01 Specifi ed herein are the general and techni cal requirements of the 600 - volt rubber- like-insulat e d single -

conductor and mu lti-c o nductor control cables which may be r equired by Edison. The cable s shall be insulat e d, jacketed, cabled, and covered, a nd they shall be suitable for operation under the service conditions specified below.

3.02 SERVICE CONDITIONS 3 . 02 . 01 The control cables furnished under this Speci-f i cation shall be suitable for installation in und erground ducts and conduits , cable trenches, trays and racks, underground structures, terminals in buildings, and any outdoor app l ication .

I f the cable i s intended for direct burial or a e ri a l service i t will be so stated in the Quotation Requ e st .

3 . 02 . 02 The control cables shall*be suitable for operating both in wet and dry locations and in installations with alternat e ly wet and dry conditions .

3 . 02 . 03 Atmospheric ozone concentrations up to a maximum o f one ( 1 ) ppm for ext e nded periods during the year may be p resent i n the areas where these cables will be installed .

3 . 02.04 Operating voltages will be control and s u p p ly volta&es of not more than 600 volts either a-c or d-e.

3.03 R§FERENCE SPECIFICATIONS 3.03 . 01 The finished cable and its components shall conform as a minimum requireme nt with the following industry specifica-tions and standards, unless otherwise specifi ed herein:

a. I nsulated Power Cable Engineers Association

( IPCEA ) Standard S- 19-81 (Third Ed i tio n ) .

This is also NEMA Publication No . WC 3-1959 ,

Rub be r- Insulated Wire and Cab l e fo r the Transmission and Distribution of Elec trical Energy.

3 - 2 3.03.01 (Co nt inued )

b. Ame ri can Society fo r Testing Materials (ASTM)

St andards D- 574 - 59T . Insulated Wire a nd Cables ,

Ozone- Resistant Type Insulation ; D- 752-6 0 ,

Heavy Duty Neop r ene Sheath fo r Wire and Cable ;

D- 1352- 60 , Ozone- Re sisting Butyl' Rubbe r Insulat ion f or Wire and Cable .

3 . 04 CONFORMANCE TO APPROVED MANUFACTURERS ' PRO DUCT SPECIFICATION 3 . 04 . 01 The cab l e purchase d under this Specification shall b e insulated , jacketed , and assembled in accordance wi th the r espective Manufacturer ' s recommendation insofar as i t is consistent wi th this Specification . The f oll owing paragr aphs which pertain t o each respective Manufacturer are a part of this Specification f o r t hat r espective Manufacture r and l ist the approved product f or u se i n this Specifi cation . The Manufact ure r shall not ify Edison of any r e - issue or cha n ge in the referenced product speci-fi cation .

3.0 4. 02 Oil- Base Insulated Control Cables :

a. Keri te Product Specificat io n Reference :

Eng ineer ing Data o n Ke rite Insulated Wires and Cables .

1. Si n g le-co nductor Cables : The conductors of single-c onducto r cables shall be insu-l ated with Kerite insulating compound

. together with tapes and N. S . Neopre ne j acket ; or , insulat ed wit h Kerite insulating c ompound with combined TP -

nyl on braid jacket .

2. Multi- conduct or Cab l es : Each conducto r of multi-conductor cables shall be i nsu-l ate d with Kerite , after which , the i nsul ated c onductors shall be cabled t oget h e r with jute fillers and the assembly c overe d e ithe r with a N. S . Neoprene j acket or a combine d TP- ny lon braid jacket .

b. Okonite Product Specification Refer ence :

Okonit e Bullet in 1085 , dated 1954 .

1. Sin gle-conducto r Cables : The conductors of single-conductor cables shall be insu-l at ed with Okolite insulating compound wi th a bonde d Okoprene jacket .

2. Multi - conductor Cables : Each conductor of multi- conductor cable s shall be insulated wi t h Okolite wit~ a bonded Okoprene jacket ,

Part c of this Paragraph has b een delet ed (Rome Product Specification ).

3 - 3 3.04.02 (Continued) after which , the insulated and jacketed conduc tors shall be cabled together with rub ber- like fillers and the assembly covered with an Okop rene j a~ket .

3.04.03 But yl - Base Insulated Control Cables:

a. Anaconda Product Refe rence Specification:

GP CS 147-4 dated July 1958 , and GP CS 20 6 -1, dat ed May 1 959 .

1. Single - conductor Cables : The conductors of single - conductor cables shal l be insulat ed with Anaconda low- voltage Butyl insulating compound with a heavy duty black Ne op rene jacket (IPCEA Standard S-19-81, Paragraph 4.13.3).

2. Multi-conductor Cables : Each conductor of multi - conductor cables shall be insulated with Anaconda l ow- voltage Butyl insulating compound with a heavy dut y bl ack Neopre ne jacke t (IPCEA Standard S-1 9- 81 , Paragraph 4 .1 3 . 3),

after which the insulated and jacketed conductors shall be cabled together with rubber- like fill ers and the assembly covered with a heavy duty black Neoprene jacket (IPCEA Standard S-1 9-81, Parag r aph 4.13.3).

b. Okonite Product Specification Re ference:

Okonite Okonex (Keystone) insulated Cable Bulletin H- 463 , dated August 1 955 .

1. Single- conductor Cables : The conductors of single -conduct or cables shall be insulated with Okonex Butyl insulating compound with bonded Okoprene jacket.

2. Multi- conductor Cables: Each conductor of mu l ti-conductor cables shall be i nsu l ated with Okonex Butyl insulating compound with bonded Okoprene jacket ,

after which th e insulated and jacketed conduc tors shall be cabled toget he r with rubb er- like fill e rs and the assembly covered with an Okoprene j acke t.

3 - 4 3 . 04 . 03 (Continued)

c. Rome Product Specification Reference :

(Rome Power and Control Cables, Specific ation No. ROA- 2 , dated March 1 968

1. Single - conductor Cables : The conductors of single - conductor cables shall be insulated with Rezone - A Butyl insulating compound with Roprene . j acket .

2. Multi- conductor Cables: Each conducto r o f multi - conducto r cables shall be ins u lat ed with Rezone - A Butyl insulating compound with Roprene jacket , afte r which t he insula ted and jacketed conductors s h all be cabled together with rubber- like f illers and the assembly covered with a Ropre ne jacket .

d. Simplex Product Specification Reference :

Spec i fication No . 1 685 - F.

1. Si ngle - condu ctor Cab l es : The conductors of single-conductor cables shal l be i nsulat ed with Simplex Anhydrex XX i nsulatin g compound with a heavy duty ,

b l ack Neoprene j acket (IPCEA Standard S 81 , Par agraph 4 . 13.3) .

2. Multi- conductor Cables: Ea c h conductor of a multi - conduc tor cable shall be insulated with Simplex Anhydrex XX insulating compound with a heavy duty black neoprene jacket, after which the insulated and j acketed conducto r s shall be cabled together with rubbe r - like fill ers and the assembly co vere d with a heavy duty black Neoprene jacket (IPCEA Standard S- 19-81 , Paragraph 4 . 13 . 3 ).

3. 05 INSULATION AND JACKET 3 . a5 . 01 The insulating mater i al shall consi st of high -

qual ity ozone - r es ist ant - type compounds and shall c on form as a minimum requirement to IPCEA Standard S 81, Parts 3 . 14 and 3.15, ASTM Standard D-574 - 59T or D- 1352- 60 .

3 . 05 . 02 The jacket material shall consist o f black neop r ene compound having characteristics that conform, as a minimum requirement , to IPCEA Standard S- 19-81 , Paragraph

4. 13 . 3 , or ASTM Standard D-752- 60 for heavy duty o r other approved materials as referred to in Section 3 . 0LI above .

3 - 5 3.05.03 For cab l es rat ed at 600 volts , the i nsulation and jacket thickness shall be in accordance with I PCEA Standard S 81 , Part 3 , Table 12 (insulat i on), and IPCEA Standard S 81 , Part 4, Tab les 26 and 29 j acket) , except that s i ngle-conductor cab l es , No . 9 AWG and smalle r, shall have a jacket thickness of not less than 30 mils. Howeve r, when specified in t he Quotation Request , sing l e -c o nduct o r cables No . 4/0 AWG and sma lle r shal l have a jacket thickness of not less than 65 mil s .

3.06 FILLERS 3.06.01 Fi lle rs used to s eal o r fill the interstices b etween insulat ed conductors i n multi-c ondu ctor cab l es shall not adhere to the j acket over the individually insulated conductors or to the jacket ove r the cable asse mbly .

3.07 CONDUCTORS 3 .07.01 The Quotat i on Request will specify if the conductors are t o be o f aluminum or soft-annealed copper .

3.07.02 Conductors shall be stranded in accordance with IPCEA Standard S 81 f or Class B concentric-lay strande d condu ctors .

3 . 07 . 03 Each individual strand of a coppe r conducto r shall be coated with lead , lead alloy , o r tin . The tensile ,

e l ectrical , and coating properties of the coated wire shall conform to ASTM Standard B-1 89 -58 or B 58 .

3 .07.04 The individual st r a n ds of a luminum conduc to rs shall be uncoated and shall have tensile and e l ect ric al properties th a t conform to ASTM Standard B- 262-61 for three - quarter hard-drawn part i ally anneale d a luminum wire (EC- 26 or EC - 1 6) .

3.08 I DENTIFICATION 3.08 . 0 1 Each s in g l e - conductor and multi-condu ctor cab l e shal l inco rporate a durable l ife-time i dentificat i on wh ich shows the Manufacturer ' s name , the year of manufacture , and the word s

" 600- volt Control Cable", a ll at interv als not to exceed three f ee t. Either of th e f ollowing methods are acceptab l e :

a. A legible and durab l e life -t ime printe d tap e placed in the conductor st r ands , or under the j acke t of s ingle - conductor cables; or, i n t h e conductor strands or under the overall jac ket of mul ti - condu ctor cab l es .

b. Embossing , engr avi ng , or printing on the surface of the j acke t of single - conductor cab l e s and ove r all jacket of multi - c o ndu ct or cables.

3 - 6 3 .0 8 . 02 No conductor coding , either colo r ed, printed, or otherwise, is required .

3.09 TESTS AND TEST REPORTS 3.09.01 Each coil, reel, or length of insulated conductor that is not to be individually covered with a vulcanized rubber-like jacket shall receive and fully withstand after vulcanization ,

and after i mme rsion in water for at least 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months , the application of alternating current volt age equal to or greater than that stated in IPCEA Standard S-19-81 for the appropriate conductor size applicable to cables with a 600-volt rating and insulated with ozone resistant compound. Any insulated conductor individ-ually co vered with a vulcanized jacket shall be tested as above after vulcanization of the jacket.

3.09.02 The Manufacturer shall submit, in duplicate with each shipment of cable, his conventional test report normally furnished to Edison which shall provide a certified record of test results together with a statement to the effect that the cables meet the requirements of this Specification.

3 . 09.03 When specified in the Quotation Request the Manufacturer shall furnish with each shipment of cable the data called for on the accompanying "Special Data and Test Report Tabulation . " Edison will furnish the forms to be used for this requirement . For all the test data required, it is desired that the sampling conform to IPCEA Standard S 81, Section 6.4 relating to the number of samples for physical tests, except that one sample shall be selected from each o rder in which the total quantity ordered (regardless of conductor size or number of conductors) is between 2 ,0 00 feet and 50,000 feet of cable, and one additional sample for each additional 50,000 feet thereafter.

3 . 09 . 04 Edison reserves the right to make any standard dielectric tests on the cable ; such tests will conform to IPCEA Standard S- 19-81.

3 . 10 _REELING, PACKING, AND SHIPPING 3 . 10.01 Cables shall be shipped on reels and shall be in a single length per reel with both ends securely fastened to the r ee l. Cable shall be properly prot ected to assure delivery without damage during ordinary shipping and handling operations .

3 . 10.02 Both cable ends shall be taped or otherwise sealed to prevent the entrance of moisture.

3 - 7 3.10.03 Ree l s shall be of substantial c onst ruction, o f adequate diameter, and covered o r lagged to provide adequate protection for the c ab le. Care shall be exercised to assure that no nails or foreign objects extend through the covering or lagging which might puncture or pene trate th e c~ble.

3.10.04 All re els shall be plainly marked with the Manufacturer's name , description of the cab l e including size, conductor mate rial, voltage rating, ty pe and thickness o f insulation and jacket, length, gross weight, Edison Purchase Order number, and destination. The reel n u mber shall be shown on the same side as the above information. In addit ion, the foll owing description shall be p lainl y marked on the same side as the above information: 600-Vo lt Contro l Cable.

NOTIFICATION OF CHANGE NO. 1 TO MATERIAL STANDARD NO. 225 - 63 SPECIFICATION FOR 600-VOLT RUBBER-LIKE-INSULATED CONTROL CABLES April 1 8, *1 963 TO: ALL HOLDERS OF MATERIAL STANDARD NO . 225 - 63 , Specification For Rubber-like-insulated Control Cables.

The following change has been approved and is hereby made a part of Material Standard No. 225-63 :

Delete the l ast sentence in Paragraph 3.05 . 03 .

Manager of Purchases FBF:teb Copies to: Apparatus Division list of ho l ders of M. S . 225 - 63

MATERIAL STANDARD NO . 225-63 SPECIFICATION FOR Q 600-VOLT RUBBER-LIKE-INSULATED CONTROL CABLES DATE SOUTHERN CALIFORNIA EDISON COMPANY SPECIAL DATA AND TEST REPO RT TABULATION PHYSICAL DATA

1. Volt age Rating

2. No. of Conductors

3. Overall Diameter of Finished Cable

4. Weight PerM Feet of Finished Cable

5. Wire -

Size No. of Strands Material Coating (For Copper) -

Mark One Lead or Lead Alloy, Approx . & Lead Tinned Yes

6. Insulation -

Chemical or Type Name IPCEA Designa tion Manufacturer' s Trade Name Insulation Thickness 1* Jacket -

Chemical or Trade Name IPCEA Designa tion Manufacture r' s Trade Name Jacket Thickness Ove r Ins ula te d Conduct or Jacke t Thickness Over Comple ted As s embly --*- _ ___:._ --- --- ---

MATERIAL STANDARD NO . 225 - 63 SPECIFICATION FOR .

600 - VOLT RUBBER- LIKE-INSULATED CONTROL CABLE SOUTHERN CALIFORN IA EDISON COMPANY SPECIAL DATA AND TEST REPORT TABULATION PHYSICAL CHARACTERISTICS GENERAL Testing Methods, etc ., shall conform to the applicable portions of the latest r evision of IPCEA Standard S 81, Sections 3 , 4, and 6 .

INSULATION J ACKET ORIGINAL

1. Tensile Strengt h , psi

2. Elongation at Ruptur e , in % ( 2 " gau ge)

3. Permanent Set , i n I nches

4. Tensile Stress at 200% Elongation , psi AFTER AGING

5. Oxygen Press ure or Air Press ure Heat Test Tensile Strength , in % of Origi nal Elongation at Rupture, in % of Original Tensile Stress at 200% Elongation , psi

6. Air Oven Test Tensil e Strength , i n % of Origi nal Elongations at Rupture, in % o f Original Tensile Stress at 200% Elongat i on , ps i

7. Ozone Resistance Test (Indi cate any Effect)*

8. Old Immersion Tes t Tensile Strength , in % of Original El ongation at Rupture , in % o f Original

A complete description from the supplie r as t o method of test and calculations is a r equirement he r e in .

MATERIAL STANDARD NO . 225- 63 SPECIFICATI ON FOR 600-VOLT RUBBER-LIKE-INSULATED CONTROL CABLE SOUTHERN CALIFORNIA EDISON COMPANY SPEC IAL DATA AND TEST REPORT TABULATI ON ELECTRI CAL CHARACTERI STI CS , I NSULATION GENERAL Test i ng methods , etc ., shall confor m t o the applicable portions of the latest r evi sion of IP CEA Standard S-1 9 - 81, Sections 3, 4, and 6. *

1. Fina l Factory a -c Test Value , kv Duration Min. ---------------Te st

2. Final Factory d- e Test Value , kv _______________Test Duration Min .

3. Short-Time Dielectric Strength Test Breakdown Voltage , kv Withhold Time During Last Step ______________~Min.

(Refer to IPCEA Standard S-1 9 - 81 , Section 6 .5)

4. Insulat ion Resistance

5. Ac celerated Water Absorptio n*

( Refer to IPCEA Standa rd S 81 , Section 6 . 9)

Power Factor Meas ure ment at 80v/mjl SIC 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months ____________________%

7 days --------------------~%

14 day~ . . . . . _____________________%

Stability Factor ______________________________________%

A c omplete d esc riptio n from th e supplier as to method of test and calculations is a r e quirement here in .

7 . 3.1. SI MPlEX 600-VOLT CABlE TEST PHOENIX

SEA TTLE

HONOLULU LOS ANGELES SAN FRANCISCO GAR NETT YOUNG & COMPANY SUBSIDIARY OF SIMPLEX WIRE & CABLE co.REC£1 \fED 2901 E. VAL VERDE COURT , COMPTON, CAL IF ORN I A 9022 1 TELEPHONE: *2 1 3 ) 774 - 3170 T ELEX: 67 - 21!7 MAR 2 9 1958

.. APPARATUS DEPT.

March 27, 1968 Mr. Jack Cohan Southern California Edison Company Post Office Box 351 Los Angeles, California 90053

Subject:

Test Data Samples Control Cable San Onofre Generating Pl ant

Dear Mr. Cohan:

Please find attached copies of Mr. M. J. Koulopoulos s telexes of March 25 and 1 26, 1968, in regards to tests made on the tv10 samples of l/C #6 AWG copper Anhydrex XX Insulation (butyl) neoprene jacket 600 volt cable from job site.

Should you desire additional information or further test data, please advise .

Very truly yours, GARNETT YOUNG AND COMPANY

~~-

Sales Manager MJL:jo R epresenting SIM PL EX WIR E & CABLE CO. S. 1'1 . COU CH CO .. IN C. ACM E ELECTRIC CORP. CH ASE -SIIAWMU T CO.

CAMBR IDG E. MASS. QUINCY. MASS CUBA. N EW YORK N r\VR II OYPnDT U6 C::C::

SCAOOIDSANGE SCADS CAMB 3 MARCH 25 , 1968 LOS ANGElES TIME 1610 FSr M.J. LUMPKIN RE SAN Q\lOFRE : SAMPIE NO . 1 r:rENTIFIED AS BErnEEN FIRE AND SHERE .

NO. 2 AS BETIJEEN FIRE AND SOURCE . PHYSICAlS INDICA'lE BarH SAMPIES SUBJEC'I'ED TO OVERHEATING roiDITirn. NO . 2 MUCH v!ORSE 'lliAN NO . 1.

INSULATICN CN rorH SPJI!PLES m'ILL LOOKS OK.

SAMPIE INSULATION SPEC JACKET SPEC 1 EI.ONG. 450% 350 225% 300 TENSilE 950 PSI 600 2460 PSI 1800 2 ELONG . 354 142 TENSilE 795 2300

oo'lli SAMPlES PASSED U.L. HORIZONrAL FLAME 'lEST. GAS FLA.~ APPLIED 30 SEC 'mEN REMOVED . FLAME EXTJNGUISHED TIIMEDIATELY. CHARRED AREA GWNED 4 MINUI'ES .

OO'IH SAMPLES HEATED 'ID 200 C BY CURRENT LOADJ:::m. BURNER APPLIED ONE MINurE. LOAD AND BURNER RErvOVER AFrER ONE MINUTE . 3 1/2 lliCH PROPAGATION 1 MmUI'E 25 SEOONDS BURNING TIME .

M. J. KOUIDPOUI.CS MK (This teletype rressage has been retyped to permit reproductioo. )

MARCH 26 ATIN M LUMPKJN RE SAN ONOFRE INSULATICN UNDER CRACKED NEOP HAD ELONGATION 287% AND 825 PSI TENSilE. RESULTS INDICA'IE INSUlATION CNLY VERY SLIGHI'LY EFFECTED BY HEAT . TESr ON CNE FOOl' SArifi'IE REMOVED FROM TRAY DAt-tA.GED BY FIRE AS FDLUJ\.vS :

lliSULATION 325% Er.mGATION AND 755 'IENSIIE. JACKET 100% EI.CNGATICN AND 2140 PSI TENSilE . INSULATION IS NORr1AL. JACKET VERY DEFIN-ITELY SHOWED HEAT AGING .

M.J. 1<0UI.OPOULOS SCAOO CAMS 2 SCADSLOSANGL

('Jhis teletype message has been retyped to permit reprcxiuction.)

TABULATION OF 'lEST RESULTS OF PHYSICAL PROPERTIES OF SIMPLEX CABLE lliSULATICW & JACKETS San Onofre Sanpl es New Cable

1 #2 Test Report Simplex Spec.

Insulation Ten . str. psi 950 psi 795 psi 1003 osi 600 psi Insulation Elong . % 450 % 354 % 525 % 350 %

Jacket Ten. Str. psi 2460 psi 2300 psi 2470 psi 1800 psi J acket Elang. % 225 % 142 % 425 % 300 %

NCYIE: Sanple #1 ran from fire area to sphere.

Sample #2 ran from switchgear to fire area, and is in worse condition than #1.

7. 4 CABIE TRAY 'lliERMAL LOADTIW ANALYSIS

ANALYSIS OF CABLE TRAY THERMAL I.DADING PURPOSE In this appendix the method is explained which was used in the thermal investigation of the cable trays. Using the rnethods developed bela.-1, it is possible to insure that the cables througtl-out the plant will operate below their r ecommended maximum temperature under normal plant operating conditions.

mrRODUCI'ION The placement of various power and control cables in the cabl e trays can be best described as random. An analysis of the infinite combinations of cable placement in a cable tray is impossible; therefore, a configcr>ation was chosen which represented the very worst possibl e arrangement of cables in a tray. 'Ihis arrangernent is one of all the power cables in the tray grouped in a tight circular bundle and the remaining control cables bundled tightly over the power cables.

'Ihus, if the configuration described above can operate at the normal operating terrperature recommended by the manufacturer, we are assured that the specific cable tray will be thermally safe.

ANALYTICAL APPROACH Once the worst possible thermal arrangement has been established, the task is to determine the maximum temperature within the bundle for a given arrbient air terrperature. ReferTing to Figure 1, it is seen that three temperature differences must be evaluated, and the sum of the temperature differences is added to the ambient t emperature to aTTive at the maximum temperature in the center of the power and control cable bunch. fue method of calculating the temperature gradient through each rnedium is explained in detail in the follovling paragraphs .

'Ihe terrperature gradient tiu:'Ough the power cable bundle ( 'IP) can be calculated using the equation for the temperature drop in a cylinder which is generating heat uniformly througtlout its volt.nre. Holman [1] gives the equation. *

- ~ =~ (1)

P ~K

Where temperature gradient from axis of cylinder to outside surface .

. = heat generated per unit volume .

q R = radius of cylinder .

K* = thermal conductivity of the material.

CONTROL CABLE LAYER TIGHT BUNDLE OF POWER CABLE TAMBIENT FIGURE I - CABLE TRAY CONFIGURATION REFLECTING THE MOST SEVERE THERMAL CONDITIONS POSSIBLE.

&tuation (1) can be expressed in terns of the heat generated per unit length by making the substitution q =

1rR~

to get qp Tp = (2) where q = heat generated per unit length.

p = thermal resistivity of material.

It is seen from equation (2) that the tenperature gradient through a bundle of power cables, each generating uniform heat, i s independent of the bundle diameter if the heat loss is expressed in heat per unit length.

In applying this equation to the condition of a nonhomo-geneouB mixture of power cables , the heat loss must be reasonably uniform over the bundle cross section. If one or two cables have a sigrrl.ficantly high heat output corrpared with the other cables, some appreciable error can result.

'lhe terrperature gradient through the control cable bundle (ll'I]:) is calcul ated by using the familiar fonn of Fourier's heat flow equation in polar coordinates, namely (3) where llTL = temperature gradient from the inside of the l ayer to the outside of the layer .

q = total heat per unit l ength flowing through the layer.

p = thermal resistivity of the l ayer material.

D = outer diameter of the l ayer .

d = inside diameter of the l ayer.

In the above equation it has *been assumed that there i s no air flow through the bundle of power and control cable and that all heat is transferred by means of conduction . 'Ihis may or may not reflect the act ual aver~ field conditions, but it certainly is the most realistically severe restriction which can be placed on a cable tray configuration.

'llle terrperature gradient of the overall bundle in air ( 6TA) is obtained from a consideration of both radiation and con-vection principles . 'Ihe t errperature gradient produced by a fl ov1 of heat from the bundle surface is determined by proportioning the amount of heat which flows due to convec-tion and the amount due to radiation.

Considering first the heat which flows due to convection, the basic equation is used (4) where qc = heat per unit foot transferred by convection.

h = heat transfer coefficient.

A = bundle surface area per unit length.

6 TA = resulting temperature gradient bet'\'leen the bundle surface and ambient air.

McAdan:s - gives the empirical approximation to evaluate the heat transfer coefficient (h) of horizontal cylinders in air as

= .2~~A)l/

4 h (5) where 6TA = the temperature gradient between the bt.lndle surface and ambient air in °F.

D = diameter of the cylinder in feet.

'Ihe units of h are e).:p~ssed in BIU/(hr-ft2- °F). Equation (5) is from the work of many invest i gators and its average deviation is considered to be about + 10 percent . The equivalent form of

[5] in watts/(ft2-°C) is -

(6) where 6T is in °C D is in inches A simplified form of the Stefan-Boltzmann equation is used to evaluate t he heat radiated from a cable bundle qr = LlcrAe:(Tavg) 3~TA (7) where qr = heat per unit l ength radiated from the bundle .

a = Stefan-Boltznann constant.

- 1.!-

Tavg = average absolute temperature of the bundle surface and the surroundings .

ATA = t errper ature gradient between the bundle surface and the surroundings . ;

'Ihe above approximate equation i s very accurate for the small temperature differ ence encountered in power cable applications .

Equations (1.!) and (7) are used together , using the fact that the sum of the heat transferred by convection and radiati on i s exactly equal to the heat generated in the power cables under steady state conditions . Writing the above in equation f orm we get ,

q = . 3A (l)l/1.!

O) llTA5/4 + 1.! o Ae (303 + ll~A )3 llTA (8)

'Ihe only unknown in equation ( 8) for a given set of physical conditions i s llTA, and the manual solution to equation (8)

for llTA is best a:one using graphical rrethods .

Finally, the actual temperature in the c*e nter of the bundle i s obtained by surrming !lT po-wer, !lT layers, llT air, and the ambient air t emperature .

'Ihis terrperature i s the highest possible temperature whi ch can be realized in a cable bundle which is tight enough to prevent any air no.., through the bundl e . If any of the heat i s carried out of the bundle by moving air instead of by conduction alone , the temperature calculated using this method will be higher than actually realized. But from a different point of vie'", one is assured that if a cabl e tray meets the recommended oper ating temperature under the conditions imposed above , it will operate at a safe temperature under any condi-tions which migtlt prevail in a cable tray.

B. Proof of Most Severe Condition

'!he case of all the cables being bunched in concentric circles is established as the most severe condition possible . This is verified from a sorrewhat intuitive approach .

Pract ice has shown that it can be expected that great est t emperatures are produced when several heat sources are brought together instead of spreading them out . 'Ihis is because the heat is confined to a smaller area and therefore is more intense, and highest terrperatures are expected from more intense heat sources . 'Ihe way to rra.ke a given arrx:>unt of heat most intense i s to confine the heat in the smallest area, which is in the shape of a Circle. 'Ihus, the analyti cal investigation has been carried out on circular arrangements of cables .

C. 'Ihermal Analysis of a Given Tray A systerratic approach was taken to analyze each cable tray .

A step-by-step analysis of each tray proceeded as follows:

1. I:etermine the I 2 R loss generated 1n the tray for each cable using the electrical resistance at the normal operating temperature of the cable.

2. Sum the 1nd1vidual heat losses to get the total heat loss for the tray .

3. r:etermine the cross section area of each pa11er and control cable and add the individual areas to get a total area, 1n square inches, of both po\.ver cable and the* area of control cable.

4. 'Ihe above data is supplied to the computer which uses the equations developed earlier to compute the maximum possible terrperature in the ass~d bundle configuration.

5. If the terrperature is too higjl, rem::>ve heat sources and the associated area fran the tray and rerun the data until satisfactory temperatures are reached .

J. Stolpe Assistant Undergrotmd Engineer TJndergromd Research and Development D1 visicn

TRAY 'IHERMAL ANALYSIS INITIAL INSTAILA.TION SWI'ICI-iXEAR ROOM ll1Q. 1 04-26-68

'mAY vr DPl QC RC TC DP2 Qr RT Tr 60AC01 34.600 12 .. 400 32.000 1.670 112 .. 591 12.900 39.600 1.638 129.624 60AQ05 31. 000 25-.300 68.400 1.107 131.233 27. 000 76.000 . 1.072 135.556 60AR02 29.500 6.300 49.200 2.164 190 . 380 6.300 49.200 2.164 190.380 60AR05 31.000 27.300 68.000 1.066 123.913 28.700 73.000 1.039 125.746 60AS05 31.000 25.000 68.000 1.114 131.724 26.600 73.000 1.080 132 .985 60AV03 31.700 8. 300 29.000 1.954 117 .438 8.300 29.000 1.954 117.438 60AW02 36.700 18.200 58.600 1.420 153.635 18.900 58.800 1.393 151.150 60AW05 37.400 19.300 30.600 1.392 94.048 24.300 38 .100 1.241 97-777 REVISED INSTALLATION SWITCHGEAR llJ(lJI NO. 1 TRAY vr DPl ~ RC TC DP2 qr RI' 'IT 60AC01 30.200

7.200 14.000 2.048 74.862 8.200 22.500 1.919 97.429 60AC";.X.)5 31.000 13.300 17.800 1.527 *72'~931 15.000 25.200 1.438 . 86.159 60AR02 34.100 0.900 1.200 5.175 37.186 0.900 1. 200 5.175 37.186 60AR05 31 .000 15.300 18.100 1.423 70 . 322: 16.700 23 .200 1.362 78.593 60AS05 . 31.000 13.000 17 .400 ~.544 72.515 14. 600 22.400 1.457 80.904 60AV03 32.000 8.000 19.000 2.000 88.982. ~.000 19.000 2.000 88.982 60AW02 31.300 12 .800 10.600 1.564 56.657 13. 500 10.800 1.523 56.392 60AW05 39 .000 21.000. 25.000 1. 363 81.061 26.000 32 .000 1.225 85.946 LIDEND: \ .

Dr - P;rea (sq. :1n.) of total cable bundle.

DPl - Area (sq. in.) of po;1er cable bundle - maximum operating load.

Q8 - r2R (watts/ft. ) heat loss - maxirm.ml operating load.

RC - Ratio of diameters - total cable bundle to power cable bundle (max. oper.)

r:oc - Temperature (OC) center conductor of pa.ver cable btmdle (max. oper.)

DP2 - Area (sa . in. ) of power cable bundle total connected load.

qr - r2R (watt/ft.) heat loss - total connected load operating ..

R1' - Ratio of diameters - total cable btmdle to power cable bundle (tot. conn.)

Tl' - Temperature (OC) center conductor of pmter cable bundle (toto conn.)

Q REFERENCE LIST FOR APPENDIX 7. 4

1. Holman, J . P. , "Heat Transfer," McGraw-Hill Book Co. , 1963, pp . 23- 26.

2. McAdams, W. H. , "Heat Transmission," McGraw-Hill Book Co., 1942, p . 241.

3. Neher, J. H. and McGrath, M. H., 'The Ca~culation of the Temperature Rise and L:>ad Gapability of Cable* Systems, AIEE TRANSACTIONS, Vol . 76, Part III, 1957, pp . 752-772 .

7. 5 SHUI'OOWN MARGIN ANALYSIS AT MAXIMUM DILUriON

smJI'I.X)\VN MARGIN ANALYSIS AT MAXIMUM DTI..lJriON -

CABLE FAILURE INCIDEN!' OF MARCH 12 , 1968

'Ibe minimum shutdown margin occurred at approximately~ 5:10 a.m .

on March 12, 1968 . Tne shutdown calculated at the min1mum measured boron concentration of 1562 ppm *was 2 . 8%. 'Ibe method of calculation was based on reactor conditions immediatel y prior to the reactor trip as compared to the reactor conditions at the minimum boron concentration following the reactor trip .

Equilibrium Xenon hac not been reached at the time of the reactor trip; therefore, xenon concentration calculations were made based on the reactor power for the previous three days . 'Ihese calculations showed that the equil ibrium xenon was worth 1802 pcm at the time of trip and increased an additional 680 pcrn by 5:10 a.m .

'Ibe power coefficient contributed 1350 pcm at the time of t rip .

Since the reactor coolant temperature was reduced to 450°F at 5:10 a .m. , the integral rod worth corresponding to this temperature 'fJas used.

'Ibe low power physics total integral rod worth was 5500 pcm @ 150°F and 6800 pcm @ 535°F. Assuming a linear rod ~orth between the two temperatures gives a total rod worth of 6400 pcm at 450°F. A value of 6360 pcm was used since Control Group II was partially inserted at the time of the trip .

Differential boron worth curves showed the boron worth at an average of 8. 2 pcm/ppn. Considering a boron change of 349 ppn, the reactivity change was calculated at 2862 pcm.

'Ibe reactivity associated with the temperature change was neglected since the temperature coefficient is very nearly zero.

Sunmary of Calculations Xenon -680 pcm Rods - 6360 pcm Power +1350 pcm Boron +2862 pcm Temperature Opcm ShUtdown @ 5:10 a .m. - 2838 pcrn A. J. Girardi Thermonuclear Engineer

7. 6 DAMAGED CABlE TRAY PI cruRES c

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ML13205A074

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1.6 CONCLUSION

SUMMARY

2.1 DESCRIPTION

5.2 INTRODUCTION

1.5 CONCLUSION

1.3 CONCLUSION

SUMMARY

Subject:

Dear Mr. Cohan:

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ML13205A074

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1.6 CONCLUSION

SUMMARY

2.1 DESCRIPTION

5.2 INTRODUCTION

1.5 CONCLUSION

1.3 CONCLUSION

SUMMARY

Subject:

Dear Mr. Cohan:

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