ML19351E127
| ML19351E127 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 11/27/1963 |
| From: | YANKEE ATOMIC ELECTRIC CO. |
| To: | |
| References | |
| NUDOCS 8011250644 | |
| Download: ML19351E127 (13) | |
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YANKEE NUCIIAR POWER STATION g
EIS $10 #C4 OPERATION REPORT NO. 3lt
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For the month of
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YANKEE ATOMIC EIICTRIC COMPANY Boswn Massachusotts November 27, 1963 L
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This report covers the operation of the Yankee Atomic Electric Company plant at Rowe, Massachusetts for the month of October 1963.
At the begired.ng of the reporting period the plant was in the coM, borated condition as Core II - Core III refueling cperations continued.
As discussed in the Operation Report for September 1963, in service damage had occurred to both high and low flux specimen homers contained within the reactor vessel. Of the eight high flux specimen holders, on 4 four could be retrieved from the core baffle. Both low flux specimen holders were broken off from their respective support plugs and could not be removed from the annulus between the thermal shield and vessel wall. Subsequent investigations were made early in October to ascertain the extent of further damage. The results of the inspection program and its consequent effect on future plant operations can be found in the Reactor Plant Performance section of this report.
On Octobe. 10, the Core III component handling program was g
complete. Twenty-tw e hafnium absorber sections and two inconel clad Ag-In-Cd control rodu w re installed in the core. Four new 3.h% enriched fuel assemblies in the center, 36 new h.1% enriched fuel assemblies around
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the periphery plus 36 3.h% enriched spent Core II fuel assemblies comprise the Core III loading pattern.
In early 1963, the two in-core instrumentation thimbles damaged x during the Core I - Core II refueling were shipped to the manufacturer for c
j metallurgical inspection. Following examination the manufacturer recoamended the installation of stainless tubular inserts in the instrumented fuel assemblies to limit wear the thimbles caused by rubbing against spacer ferrules in their respecti.s assemblies.
During October 1963, seven inserts with expanded type holders were added to new fuel installed in the instrumented quadrant.. The remaining ten instrumented assemblics in the o
quadrant are spent Core II fuel and consequently the installation of (j inserts was accomplished underwater. Spring clip type inserts were added to these assemblies. Three additional new fuel assemblies, one in each h
of the remaining three quadrants are also equipped with inserts.
On October 10, an inspection of the west source vane was made with underwater viewing equipment following which the vane was transferred to the fuel pit. At some future date the vane will be shipped to the manufacturer for further metallographic study. Also on this date, the high and low flux :pecimen holes in the core baffle and core barrel were fitted with plugs to limit bypass flow through the core.
Approximately three days were required to complete the installation of core internals following whien the cavity was drained and the vessol head placed in positic,. The stainless liner of the cavity was again dece ednated by an outside contracting service.
On October 19, the main coolant system was filled following which
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venting was accomplished on the main coolant pumps, control rod pressure
, housings and the pressurizer. Thereafter the main coolant system was
" coM leak tested at 2h50 psig. The only leak in the system was a nanway gasket on the pressurizer which was repaired L.,
i* ~htening.
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. e m On October 23, all control rods were cold drop tested from the fully withdrawn position of 90 6/8 inches. Drop times on some rods were significantly shorter than data obtained previously and an investigation as to the cause was begun. Expected drap times were recorded after additional venting of the control rod pressure housings had taken place.
The reactor was brought critical on October 23, following which cold physics data was obtained. Thereafter, the main coolant system was brought to temperature using both pump heat and reactor heat.
All control rods were again drop tested, this time in the hot condition. However, during further banked rod physics testing, No. 20 control rod failed to move in Trom the 79 7/8 inch position while all other rods in the group moved satisfactorily. Attempts to insert the rod using x
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the pull down coils were unsuccessful and consequently the main coolant g
system was cooled down, depressurized and vented.
No. 20 rod travel housing W
was removed from the vessel head for preMmhnmy evaluation of the cause of rod hang up,the inspection shouing the difficulties to be within the vessel and not the drive mechanism.
On Octot "- 30, the reacter vessel head was again removed from the shield tank cavity. Approximately three days were required to prepare the shield tank cavity for flooding and remove the vessel head. A Lignificant improvement in stud removal was realized, being attributed to the different plating and thread lubricant used. The original set of studs were silver plated causing considerable delays due to galling in both the Core I and Core II head removal operation. A new set of studs had been installed initially for Core III, having a Parkerized thread treatment. These new studs were removed with a minimum of effort requiring only 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> to loosen and 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> for complets removal to a storage rack. Previously, stud removal cperations required come 3 days to complete.
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Direct visual inspection of No. 20 control rod chowed that the end of a stainless steel rubbing strap had curled out and away from the vane surface. Subsequent investigation traced the hung strap to a combination of problems in the rubbing strap and guide block design. The gap between respective straps is approximately.250 inchas coinciding directly with the thickness of the unchamfered guide blocks on the upper core support plats, and at certain rod positions the gap is opposite the unchamfered top edge of the guide block.
No. 20 rod being located in an area of maWmn crossflow in the core was forced up against the guide block.
As the rod was inserted, the strap caught on the top of the guide block, and consequently the strap curled outward causing hang up.
To prevent a recurrence of the incident, it was decided to remove all rods from the core and Md additional chamfering to the ends of the rubbing ctraps since no guide block correcticn is possible. The twenty-two hafnium rods were removed from the core individually and had their rubbing 7 straps chamfered. Since the control rods had ceen very little neutron J flux, the radiation levels encountered during grinding were tolerable.
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While disengaging No. 20 absorber section from the drive train, one of the four fingers on the bottom latch of the control rod drive shaft fell to the floor of the shield tank cavity. The design of the system is such that the fingers on the drive shaft are held in place by a pin which is in turn tack welded at both ends to a shoulder on the drive shaft coupling. Failure of the weld caused the pin to work itself free and separate from the drive shaft. Whether the loose finger and missing pin contributed to the hang up of Rod No. 20 rubbing strap is not known.
Thereafter, all drive shafts were examined as they were removed from the shield tank cavity. A second pin had freed itself from the drive shaft on Rod 18, while further investigations showed that approximately 25%
of the welds had failed.
To effect repairs a temporary lead shield was V) set up in the vapor container to permit withdrawal of the drive shaft to the charging floor and all pins were full penetration welded, around their h
complete circumference. Due to their'sise, it has been concluded that the two missing pins within the primary system will not hinder reactor operations.
During the plant cooldown on October 25, the inner 0-ring seal on the reactor vessel flange developed a leak. A simLlar failure had occurred during the initial cooldown at the beginning of the refueling shutdown. It is now felt that thermal expansion effects during changes in f
system temperature were the cause. This conclusion was reached following
-m LJ a hold in the plant cooldown to allow the vessel head temperature to approach that of the vessel body. Approximately two hours after the seal had failed, the tell tale leak off valve between the inner and outer 0-ring was opened. No leakage was evidenced across the inner seal. Consequently, revised heatup'and cooldown operational procedureswill be established to limit the differential temperature at the vessel flange.
nU At the end of the reporting period the plant was in the cold, g
borated condition as repair operations continued.
W Plant Shutdowns Shutdown No. 62-2-lh A continuation of the Core II -
Cere III refueling shutdown.
Plant Maintenance Following is a summary of major activities carried out by plant maintenance personnel during the month of October:
1.
Repairs and modifications to the in-core instrumentation were completed during the month.
2.
No. 3 and No. h gland seals were insp oted.
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3 The installation of
. _; new safety valves on the main steam lines was completed.
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Insulation work in the vapor container was completed.
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- 5. An ion exchange unit was charged with resin and placed in v
service.
6.
Valve packi.g in the vapor container was completed during the month.
7.
No. 3 steam generator was inspected.
8.
All four steam generators were hydrostatically tested.
9.
No. 3 feedwater heater was hydrostatically tested and found defective.
10.
All motor operated valves in the vapor container had their stems inspected.
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- 11. No. 1 and No. 2 heater drain pumps were inspected.
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Megger testing was completed on all rod drive cables.
- 13. The station service transformers were inspected.
Ih. Mtscellaneous secondary side steam and condensate valves were repacked.
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- 15. Modifications to the air removal system an the circulating water discharge line were completed during the month.
- 16. Modifications to the turbine moisture removal system were completed during the month.
17 Both turbine throttle valves were inspected and repairs made
- u; to broken poppet valves.
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- 18. The four servo motors on the turbine control valves were tested and adjusted for operation.
Chemistry Until October 15, the phield tank cavity water specific activity ranged between 2.0 and 2.8 x 10-4 Jac/ml. Following installation of the reactor vessel head and initiation of testing the average main coolant specific activity rose to 2.2 x 10-2 pc/ml.
Main coolant boron concentration wao kept at approximately 1600 ppm until October 18 when it was lowered to 1500 ppm at the onset of low power physics testing. Following cooldown of the main coolant system the boron concentration was again increased to 1600 ppm and remained there throughout the balance of the reporting period.
Early in the period the Core II control rods were encapsulated in
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i 2 a storage can in the spent fuel pit. Thereafter, through mixed bed puri-fication, the spent fuel pit water specific activity continually decreased during the month. At the end of the reporting period the specific activity had been reduced to 9.h x 10-h pc/ml from a previous high of 3 7 x 10-3 ;1c/ml.
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Following replacement of the vessel head the main coolant oxygen levels were reduced to a non-detectable value. Oxygen was removed from the system by establishing a hydrogen blanket on the low pressure surge tank and reacting the dissolved hydrogen with oxygen in the ganna flux from the spent fuel. The reaction took place with the main coolant at ambient temperature. The previous normal use of Hydrazine was unnecessary.
Following the cold control rod drop tests the main coolant crud increased from 0.20 ppm to 23 ppm.
Reactor Plant Performance Continuous count rate and periodic 1/M shutdown measurements were obtained during interchange of fuel assemblies. At no time during the
. refueling sequence was the core shutdown margin less than 12% 6 K/E.
During the month a further search was made to determine the g
location of the damaged low flux specimen holders. The base of each holder was originally set in a basket which was in turn welded to the thermal shield. Subsequent investigations with underwater viewing equip-ment, binoculars, and feeler tools confirmed the following:
Southeast - Originally contained specimen holder. The specimen is still in the basket but the tubular holder has broken off and is folded into a V shape, being f
lodged between the vessel wall and thermal shield.
Southwest No specimen holder was installed in this location.
The basket assembly is in place.
Northwest - Originally contained specimen holder. The specimen and holder could not be located. It was also I
noted that the basket had separated from the h
thermal shield.
Northeast - No specimen holder was installed in this location.
Tha location of the basket could not be determined.
After a thorough investigation of the problems associated with the loss of both high and low flux specimen holders, it has been concluded that future operations of the reactor vessel and its internals will not be impaired. Their position within the core baffle and core barrel respectively is such that movement of the pieces to other locations within the vessel is unlikely.
Discussions on this topic were held with the primary system designer, reactor vessel manufacturer and the A.E.C.
The in-core instrumentation eggerate was inspected with underwater viewing equipment. As discussed previously, wear, induced by contact with ferrules on the fuel assemblies, was found on some thimbles. The amount of wear varied over the length, being essentially surface rubs at the top
( ~. of each thinble, while at the bot'.om a definite wear pattern, som 12 - 15
' mils in depth was noted. This is as expected, since the thimbles are fixed at the top, but being free to move at the bottom, do undergo some
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v lateral movement due to water flow. The installation of spacer tubes in j
the fuel will essentially eliminate any further wear on the thimbles.
An inspection of the west source vane showed it to be in excellent mechanical condition. All bolts and tubes were intact and tight. However, to permit further mmhtion, the vane was transferred to the spent fuel pit and a new source was installed at the west positim in the core.
The Core III physics startup test program began on October 22 with cold drop testing of all control rods. All 2h rods were dropped at least once from the fully withdrawn positis of 90 6/8 inches. The average drop time recohled was 1.h2 seconds being $a good accord with that data measured previously.
On October 23, the first attempt to reach criticality at 1660 ppm ron, 2000F main coolant temperature, and all rods at 90 0/8 inches was h;
unsuccessful. After boron dilution to 1550 ppm, criticality was achieved 1
with Groups 2, 3, h, 5, 6 and 7 at 90 0/8 inches and Group 1 at hh 2/8 inches.
Initial heatup of the main coolant system to 250 F was accomplished through pump heat only during which temperature coefficient data was obtained. From 2500F to 5000F, reactor power was used during which hourly i
just critical data were measured. From 5000F to $300F, temperature r oofficient and rof worth da,ta were obtained.
V Control rod group l through 5 Stere drop tested onn from 90 6/8 inches with the reactor at operating pressure and temperature. At that time, all drop times appeared normal. However, shortly thereafter, during subsequent banked rod testing, the hang up of No. 20 control rod wa; noted.
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At the end of the month, ana3,ysis of Core III data for rod wwth, g
"temperaturo coefficient, and pressure coefficient was incomplete. The W
results will be reported in a future Operation Report.
Turbine Plant Perfornance At the end of the reporting period all modifications to the turbine moisture removal system were essentially complete. A description of the modifications can be found in the Operatim Report for September 1%3.
Future higher power operations necessitated an uprating of the ccpacity,of the four feedwater regulators. A description of these modifi-cctions can be found in the September 1%3 Operation Report.. During the month, one inch air operated bypass valves were installed around each of the regulators to permit mere positive,:ontrol at low flows.
No. 3 and h gland seals on the low pressure turbine were inspected, ev1dence of water cu,tting being found on both seals. Both are
.am seals having as a supply a tap from the main steam piping ahead of a throttle valves. The problem has been referred to the turbine manufacturer for his recommendations.
e-Future plant operations at highw power levels required that higher current capacity bushings be installed on the main transformer.
This work was accomplished during October following which the bushings were successfully Doble tested.
No. 3 feedwater heater developed a tube side leak during hydro-testing, and consequent 4 the shell was removed to permit inspection of the tube sheet. Inspection showed a number of tubec had failed in an area where the tubes pass through a support plate within the bundle, the failure being attributed to vibration of the tube bundle. It is not readily apparent whetherthe vibration is induced due to flow within the heater or that a resonant condition with some other plant component has been established.
During the month, a shell side inspection of No. 3 steam generator
,o was made. No adverse conditions or areas of concern were found.
Instrumentation and Control During the refueling outage a number of changes and modifications were made to the nuclear instrumentation. Among them are the addition of a scram sequence panel, a high power level alarm on power range channels 3, h and 5, power range coarse gain switching on channels 3, h, 5, 6, 7, 8 and recalibration of main coolant temperature channels to new ranges.
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The scram sequence panel was installed on the FN cabinet to provide indication of the first scram signal to reach the scram amplifiers.
To identify more closely any irregularities in the power range channels, high power level alarms have been installed on channels 3, h and 5.
The circuitry is identical to that of the alarms existing on channels 6, 7 and 8.
All power range, level alarns are now set at 10h%.
Previously, coarse gain adjusting on each of the power range h
channels was performed by the Instrumentation and Control group.
Switches to provide coarse adjustment of the gain on each channel have been added to the rear of each of the six power range panels and will now be under administrative control to be operated at power by shift supervisory personnel.
The ranges of the narrow range main coolant temperature channels and the Tavg. channel hava been changed in anticipation of operation at higher power levels. The new ranges are as follows:
0 Tc 510 - 560 F Th h65 - 5350F 507.5 - 537 5. F Tavg.
A fail safe lamp test panel has been added to the main control board. This circuit provides a means of testing the fail safe lamps periodically, and will eliminate the possibility of hating a fail safe alarm without knowing which circuit ha3 the power loss.
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. Health and Safety During the month of October 182 drums of solid radioactive vaste, containing approximately 326 m, were~ prepared.
119 drais containing a total activity of approximately 290 m were shipped from the site. In addition, an outside contracting service prepared and removed from the site $7 drums and 2 packages (13 cu. ft each) containing a total activity of approxin tely 300 me, it being the residue from the second decontamination of the shield tank cavity liner.
On October 7, an underwater light used in the spent fuel pit was removed to the machine shop for repairs. This resulted in contamination levels of 1000 - 20,000 dpm/ft2 in a local area of the machine shop floor.
The affected area was reped off and normal cleanup procedures instituted.
Radiation levels measured after drnining of the secondary side m
of No. 3 steam generator were 120 nr/hr inside the manhole, and 8 r/hr
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4 inside the hand hole openings. Internally, a radiation level of 800 mr/hr h
was measured at the feedwater ring. Contamination on the secondary side 2
of the steam generator was generally less than 200 dpm/ft.
The following contamination and radiation levels were measured on underwater viewing equipment that remained immersed in the shield tank cavity throughout the refueling shutdown: Periscope, 3 x 10k dpm/ft2 and 5 - 10 mr/hr; lights, 8 x 103 dpm/ft2 and 10 - 20 mr/hr; light cords, 6 x 10h dpm/3 running feet.
Radiation levels measured on the waste disposal evaporator ion exchanger housing were 70 mr/hr contact and 5 mr/hr at one meter.
Due to its proxinity to the nuclear auxiliary operator's desk, a concrete brick cave was constructed around the ion exchanger unit reducing radiation levels to 0.8 mr/hr contact outside of the shielding.
On October 2h, a steam leak was discovered at the packing gland g
of a main coolant stop. valve in No. 2 loop. All personnel making entrance into the loop were required to wear plastic coveralls over cotton coveralls and full face mask with gas cannister. Air samples showed the airborne particulate activity to be 1.1 x 10-9 pc/cc in No. 2 loop and 1.5 x 10-9 31c/cc on the charging floor. Following the repairs to the packing gland, the requirement for respiratory protective equipment was lifted.
An air sample taken from the incinerator stack during burning of combustible waste indicated an airborne activity of 8.7 x 10-9 pc/cc of air sampled. The principle isotopes were identified as Ag-110m and Co-58. All burning was suspended pending investigation of the filtering system which later showed the particulate filters to be burned through.
New filters were installed.
While preparing the shield tank cavity for flooding on October 30, airborne activity b:th in the cavity agd on the charging floor reached mwi mums of 9.9 x 10-9 m/cc and 1.6 x 10 7 mc/cc during use of impact tools for tightening dcwn seal ring studs. The activity resulted when scrapings from the seal ring flanges became airborne in the exhaust air from the impact tcols. The principle isotope iden"..ted was Co-58.
Respirators were worn by all personnel entering ' 2e vapor container during this period.
1 Radiation levels under the reactor vessel head and at the moat as the head was lifted to 3 feet showed 1700 r/hr and 250 cAu as compared to 8 r/hr and $50 mr/hr during removal of the head at the beginning of the refueling shutdown in September.
Radiation levels on the control rods, which were reA7ed from the core for modifications to the rubbing straps, were 10 - 30 r/hr at one inch on the vanes and top adapter, and 300 - 500 e /hr at one inch on the lower one' foot section ~f the absorber. During gihMg of the straps, o
the lower section was covered with flexible lead shielding reducing the radiation level on contact with the shielding to 50 mr/hr.
Prior to grinding, the rods were decontaminated causing contamination levels of a 10h dpm/ft2 to be reduced by a factor of 5 to 10.
c, Contact radiation levels measured on the dashpot sections of the h
control rod drive shafts removed from the core averaged approximately 5 r/hr. Some dashpots who had seen longer service in the core measured as high as 35 r/hr.
Iead shielding was suspended in front of the drive shafts to limit exposurs while repairs wore made to the support pins of the latch fingers.
Personnel exposur or Yankee plant personnel as masured by film badge for the month of October 1963 were x
Average for all station personnel
$32 e
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Maximn individual exposure 1180 mr
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Personnel exposure fcr outside contracting personnel employed during the shutdown as neasured by film badge for the month of October 1%3 1
were Average for all contractor personnel
$87 mr
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Maximum individual exposure 980 mr
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The average exposure of the combined work force was $h8 mr.
Design Change _s 1.
Four one inch air operated bypass valves were installed around the feedwater regulators to permit more positive control of feedwater to the steam generatorsat low plant loads.
2 Core III will be a three region core consisting of a center section of new 3.h% enriched fuel, a middle ring of spent 3.h% enriched fuel ani an outer ring of new h.1% enriched fuel. The spent assemblies within the middle ring were originally part of the outer ring during Core II operation.
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The change was made primarily to achieve a higher discharge burnup within the fuel and also to achieve a more even distribution of burnup among respective assemblies.
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o yC Authorization for this design change was requested in Proposed Change No. 36, submitted on June 7, 1963.
A.E.C. approval was granted on September 13, 1963.
3.
Vibration snubbers, or dampeners, have been attached to the main steam piping both interior and exterior to the vapor container. The locations of the snubbers were selected by an outside consulting service who had measured main steam line movement while the plant was operating at various power levels.
14. In anticipation of operation at 185 rte, higher current capacity bushings were installed on the main transformer.
5.
Repeated operational difficulties with the vacuum priming m
system on the circu' sting water discharge piping led to a
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complete modification of the air removal system. The new g
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system is comprised of a 12 inch pipe mounted on the w
discharge piping for some 75 feet of its length. At selected points the dircharge pipe is vented to the 12 inch pipe and thence to an air removal pump mounted on the turbine hall floor.
6.
Reinforcing struts have been added to the discharge piping
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of the high pressure casing of the turbine. The strengthening c
is required due to the anticipation of operation at higher power levels.
Plant Ooerations Attached is a su mary of plant operation statistics for the month of October 1963, and a plot of dailv average plant load for the same
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period.
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YANKEE ATOMIC EIECTRIC COMPANY - OPERATING SUNHAff ELECTRICAL MONTH YEAR TO DATE Gross Generation KWH 83h,6h6,000 2,536,118,000 Sta. Service (While Gen. Incl. Losses)
KW 56,538,h82 387,295,0h9 Net Generation KW 778,107,518 2,3h8,822,951 Station Service 6.77 7 38 Sta. Service (While Not Gen. I' '1. Losses)
KWH 822,h75 2,h63,313 16,h32,151 Ave. Gen. For Month (72C HRS.>
W 0
Ave. Gen. Running
( o HRS.)
W 0
PLANT PERFORMANCE Net Plant Efficiency 28.39 Net Plant Heat Rate I'tu/KWH 12,021 Ibs. Steam / Net KWH U
Circulating Water Inlet Temp.
Maximum F
Mi n4,mm oF Plant Operating Factor 69.56 65.03 NUCIEAR MONTH CORE III TO DATE Times Critical 1
1 307 Hours Critical HRS 30 98 30.98 21,58h.09 Times Scrammed 0
0 38 Equivalent Reactor Hours @ $h0 MWt HRS 15,203.3 Average Burnup of Core MWD /mtU Control Rod Position at Month End 0
Equilibrium at 0 Nt 150 F Tavg.
Group 1 Rods out-inches O
Group 2 0
Group 3 0
Group h 0
Group 5 0
Group 6 0
Group 7 0
0 0
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o YANKEE ATOMIC ELECTRIC COMPANY DAILY AVERAGE LOAD for OCTOBER 1%3 150 -
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8 109 -
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(a) Shutdoan No. 62-2 1h i
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5 10 15 20 25 30 j
4 DAYS 3
0