ML19351E168
| ML19351E168 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 08/21/1967 |
| From: | YANKEE ATOMIC ELECTRIC CO. |
| To: | |
| Shared Package | |
| ML19351E167 | List: |
| References | |
| NUDOCS 8011250703 | |
| Download: ML19351E168 (9) | |
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YANKEE NUCLEAR POWER STATION g, \\filf's OPERATION REPORT NO. 79
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l This report covers the operation of the Yankee Atomic Electric 9 Ccmpany plant at Rowe, Massachusetts, for the month of July 1967 At the beginning of the period the plant was operating at approximately 172 MWe.
On July 6 No. 1 main coolant loop was isolated in crder to ascertain the primary to secondary leak rate of No.1
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j steam generator prior to the scheduled shutdown. At 0918 hours0.0106 days <br />0.255 hours <br />0.00152 weeks <br />3.49299e-4 months <br /> July 9 the turbine was taken off the line and the plant shutdown for the purpose of effecting leak repairs to No. 1 and No. 2 steem generators and to replace the thermal barrier gaskets in No. 1 and No. 3 main coolant pumps.
Subsequent to the isolatien of No. 1 loop 100 cc of iodine-131 tracer solution was injected into the loop for primary to seconlary leakage determination. Analysis of water samples during the succeeding twenty-four hour period revealed the No. 1 steam generator leak rate to be 19.6 1 5.2 gpd.
The total system primary
()
to secondary leak rate prior to loop isolation was approximately 300 gpd.
Immediately after plant shutdown preparations for entry into No. 2 steam generator primary side were made.
By July 12 both inlet and outlet side diaphrages had been removed and the secondary side hydrostatically pressurized for tube leak location inspection.
Cnly one leaking tube was found, on the inlet side near the center of the tube sheet. The measured leakage, at a differential pressure of approximately 900 psig, was 268 gpd.
An internal visual inspecticn of the leaking tube was attempted by utilization of a flexible optics barescope.
However, results were inconclusive due to the pccr resolution of the scope.
Vertical location of the leak within the c2be was established, by means of traverse plug measurements, at er slightly abcVe the tube sheet.
Upen completion of inspecticns inlet and outlet ends of the tube were prepared, plugged and O
welded.
Facing of an adjacent inlet tube end was necessitated by an inadvertent arc strike made during the plug welding process.
No abnormalities were detected during the primary side inspection other than the finding of three irradiated sample container baill on the inlet side which were recoved.
Radiation levels encountered I
during the repair were comparable to those found during the previous steam generator repairs in March, approximately 10 to 15 r/hr one foot from the tube sheet.
No.,1 steam generator primary side diaphragms were removed July 13.
No leaks were apparent under secondary side static head precsure.
However, further pressurization to approximately 850 osig revealed one ". weeping" tube, again near the center of the inlet nba sheet.
Determination of the vertical leak location was not side
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attempted una tube preparation, plugging and welding were completed July lb.
During the secondary side inspection two carbon steel vedges were found on the tube sheet. These were ultimately identified 'cy the vendor to be construction vedges used,in the steam generator i
during fabrication.
One sample container bail was found on the primary l
side.
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' Secondary cides of Loth steam generators were successfully hydrostatically tested to approximately 875 psig after water and crud samples vere taken from the top of the tube sheets for chemical analysis. No further primary to secondary leakage was detected. On July 21 filling of the isolated loops was initiated preparatory to plant startup. However, a leak was detected, at primary water static head pressure, at the outlet side diaphragm of No. 1 steam generator.
Pressurization to 500 poig also revealed leakage at the inlet side diaphragm. No leakage was detected on No. 2 steam generator. Upon completion of draining of the loop No.1 steam generator manway i
covers were lowered and the diaphragms inspected. On the outlet side six small seal weld defects, detected by dye-penetrant inspections, were I
ground out arid weld repaired. On the inlet side several small weld defects were also noted. However, grinding and repair welding were ineffectual due to water condensation in the waterbox dripping onto
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drying of the waterbox, preparation of the weld area, and revelding of 3
the veld area. This necessitated complete removal of the diaphragm, the diaphragm. During the process of rewelding difficulty was again encountered with condensation and concomitantly, with cracking of the TIG tack welds holding the diaphragm in place prior to completion of the root pass. The diaphragm was again removed, the surfaces reprepared, and the diaphragm root pass completed in 9 continuous work effort.
The final weld passes and dye-penetrant inspections were completed July 25 r'
Immediately thereafter the manway covers were replaced and loop hydro-static tests to 900 psig successfully completed. Subsequent main coolant
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system hydrostatic tests to 2000 psig were also completed with no leakage detected.
Concurrent with the steam generator work effort No. 1 and No. 3 main coolant pumps were removed from the primary system for maintenance.
No. 1 pump was removed from the loop immediately after it was drained
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July 10.
By July 19 lapping 'of the thermal barrier gasket flanges had
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been completed, the pump reassembled and installed in the loop,and breakaway torque determined. Removal of No. 3 main coolant pump from the loop was accomplished with considertole difficulty July 15 This pump had been originally insta] led with assentially zero clearance at the mating surfaces.
By July 20 the main and thermal barrier gasket flange surfaces had been lapped, the mating surface clearance opened up, and the pump reassembled and installed in the loop. The following day power connections were made and breakaway torque determined.
Prior to plant shutdown the turbine geherator exciter commutator condition had deteriorated to such a degree that a daily inspection and replacement of brushes was necessitated.
Subsequent to taking the generator off the line and during turbine coactdown inspection of the commutator revealed it to be burned to such an extent as to preclude j
honing in place. The commutator was shipped off site for repair July 12 and returned July 17 Upon completion of final cleanup of the j
mica undercutting the exciter was reassembled and ready for cperation July 20.
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By 2125 hours0.0246 days <br />0.59 hours <br />0.00351 weeks <br />8.085625e-4 months <br /> July 25 all primary loops had been filled, vapor container integrity had been established, and plant heatup initiated.
Criticality was achieved at 0137 hours0.00159 days <br />0.0381 hours <br />2.265212e-4 weeks <br />5.21285e-5 months <br /> July 26 and by 10h8 hours the generator was phased on the line. A plant load of approximately 80 MWe was maintained until 1826 hours0.0211 days <br />0.507 hours <br />0.00302 weeks <br />6.94793e-4 months <br /> at which time the turbine was taken off the line for test of the overspeed trip. Upon successful completion of the test the generator was again phased and a plant load of 600 MWt attained shortly thereafter. Throughout the remainder of the period the load varied between 176 MWe and 178 MWe as circulating water inlet temperature varied between 460F and 52 F.
The fourth. Core VI air charge to the vapor container was initiated July 29 and will be terminated when the total weight of dry in the vapor container is approximately 66,000 lbs.
Plant Chutdowns
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Shutdown No. 90 6-5 7-9-67 Scheduled shutdown for steam to generator leak repairs. Total 7-26-67 outage time: 409 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.
Plant Maintenance The following is a list of major plant maintenance items performed by the plant staff during the month of July,1967 Y
l.
Seats and disc were replaced in the 2" bleed line orifice valve.
2.
The 75 ton vapor container polar crane cable was replaced.
3 No.
1, 2 and 3 feedwater heaters were hydrostatically tested and two tubes and four tubes were plugged in No. 2 and No. 3 I.
heaters respectively.
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4.
The circulating water and condensate sides of the main condenser were inspected. Four tubes were plugged.
5 The left-hand turbine throttle valve, which failed to close on plant shutdown, was disassembled, inspected and cleaned of baron deposits.
6.
The 448 breaker which failed to remain closed when operated was repaired.
7 During the shutdown numerous primary and secondary system valves were inspected and repacked.
Instrumentation and Control The following is a list of the major instrumentation and control maintenance items performed by the plant staff during the month of July,1967
_4_
l.
The new low range loop fill pressure transmitter was groomed and tested.
2.
No. 1 feedwater flow transmitter was cleaned and calibrated.
3.
The condenser hot well level controller was repaired and calibrated.
h.
The steam generator high level alarm set points were reset to 2h ft. from 27 ft.
5 The main coolant loop temperature channels and T-average auctioneer were recalibrated.
6.
Various repairs were made to the in-core flux vire system.
Reactor Plant Performance
(
)
Prior to plant shutdown, core reactivity depletion was normal at approximately 0 70% AK/K per 1000 MWtD/MTU. Following reactor startup July 26 a just critical all rods out boron concentration was obtained.
Core excess reactivity was in good correlation with the reactivity follow data.
During the previous plant shutdown in May, for condenser eleaning and operator training, No. 10 control rod stuck six inches 7 \\
(
)
from the fully inserted position while being driven in the "in"
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direction. This occurred on four separate occasions but at the same elevation. Each time the rod dropped freely when the stationary gripper coils were de-energized or operated normally when the pulldown coil was utilized.
However, the complete history of the rod and related components was reviewed in an effort to determine the cause and signif-icance of the sticking. As a result of this review it was concluded j'~}
that the problem did not represent a safety hazard and could possibly
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be due to a crud build up in the operating mechanism.
The mechanism will be flushed during the next refueling.
Chemistry Prior to plant shutdown the main coolant boron concentration decreased from 509 ppm to h94 ppm.
On July 9 the system was borated to shutdown concentration, lh65 ppm. At the end of the report period the boron concentration was hh5 ppm.
On July 10 the pH of the main coolant system increased from 5 00 to 6.42 due to the presence of approximately 12.8 ppm of ammonia.
Hydrazine used for oxygen scavenging had apparently leaked past isolation valves to the suction side of the charging pumps. On July 23 hydrazine was injected into the system to maintain low oxygen concentrations during loop fill operations tuuiplant heat up.
Uninten-tionally, an over addition was made which resulted in a primary system ammonia concentration of 70 ppm on July 2h. The concentration was reduced to 9 2 ppm the same day, by cation bed ion exchange, and to 0.21 ppm by July 28.
Main coolant crud levels during this varied between
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h.68 ppm and 80.5 ppm. At the end of the period the level was 0.35 ppm.
After plant startup the average main coolant iodine-131 specific activity was 1.97 x 10-5 pc/ml; I-131/I-133 atomic ratio was 0.58.
The average tritium specific activity decreased to 8.02 x 10-1 pc/ml from 2.16 pc/ml as a result of primary system dilutions made during the startup.
)
l A main coolant crud sample collected on July 31 had the l
following radiochemical analyses dpm/mg crud:
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l Cr-51 Hf-181 Mn-Sh Fe-59 i
6 6
2.h8 x 106 5
2.4h x 10 1.99 x 10 2.59 x 10 co-58 co-60 Ag 110 M
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2.00 x lo 5.28 x 10 4.01 x 105 j
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A main coolant gas samnle also collected on July 31 had the i
following radiochemical analyses:
ue/cc gas l
Xe-133 Xe-135 Ar-bl
-3
-3
-2 3.72 x 10 h.h3 x 10 2 59 x 10
,e Health and Safety
.)
It was reported in Operation Report No. 76, for April 1967, that the inadvertent gas release which occurred on April 4 was comprised of 32.2 uc of beta-gamma activity and 60 5 me of tritium as a gas.
This should be changed to read that the release was comprised of 34.2 me of beta-gamma activity and 60.5 me of tritium as a gas.
r ~s During July the waste disposal liquid releases totaled
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128,000 gallons containing 2.38 me of gross beta-gamma activity, and hh.3h curies of tritium. Gaseous vaste releases during the same period totaled 89.59 me of gross beta-gnmma activity. An additional 6.046 curies of tritium as a vapor was purged from the vapor container during the plant shutdown.
Secondary plant water discharged during the period consisted of 175,000 gallons containing a total of 28.2 pc of gross beta-gamma activity and 29.5 curies of tritium.
Radiation exposure doses for Yankee plant personnel and NEPSCo. personnel, as measured by film badge, for the month of July,1967 were:
Plant Personnel Average accumulated exposure dose 625 mrem Maximum accumulated exposure dose 1871 mrem Service Company Personnel Average accumulated exposure dose 1087 mrem Maximum accumulated exposure dose 1529 mrem
. (
Design Changes An addition to the turbine throttle valve closure scram circuit was installed. This addition consists of a parallel circuit through micro switches operated upon closure of the turbine contrcl valves. The circuit provides a redundancy to the existing channel and vill initiate a reactor scram on closure of the control valves should either throttle valve stick in the open position.
Plant Operations Attached is a summary of plant operating statistics and a plot of daily average load for the month of July,1967 Correction c
The Plant Operating Factor (to Date) and Reactor Plant
( '
Availability (to Date) figures for the months of February through June,1967 should be corrected to read as follows:
Plant Operating Factor (%)
Reactor Plant Availability (%)
February 71.43 82.46 March 71.19 82.18
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April 71 58 32.41 May 71.95 82.61 June 72.32 83.82
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I YANKEE ATOMIC EIETRIC COMPANY -- OPERATING
SUMMARY
JULY 1967 EIETRICAL 10 NTH YEAR TO D&TE Gross Generation WH Sh,300,200 715,130,h00 7,077,590,900 Sta. Service (While Gen. Incl. Losses)
WH 3,420,h39 43,035,h61 473,058,283 Net Output WH 50,879,761 672,094,939 6,604,532,617 Station Service 6.30 6.02 6.68 Sta. Service (While Not Gen. Incl. Iosses)
WH 423,950 933,217 24,728,684 Ave. Gen. For Ibnth (Thh Hours)
W 72,984 Ave. Gen. Running (334.20 Hours)
W 162,h78 PIANT PERFORMANCE Net Plant. Efficiency 27.h8 28.50 28.L7 Net Plant Heat Rate Bru/WH 12419 11975 11987 7
Plant Operating Factor 41.h8 77.26 71.89 Reactor Plant Availability 46.19 86.25 82.36 NUCLEAR glfrH CORE VI TOTAL Hours Critical HRS 343.68 5729.05 49,454.73 Times Scrammed 0
2 54 Burmp Core Average ND/IEU 371.35 6209.86 Region Average WD/MTU A (INNER) 371.510 624h.h10 23,016.91 B (MIDDLE) hh6.250 Th37.41h 15,112 70 C (OUTER) 296.403 4977.409 h977.41
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