ML19351E001
| ML19351E001 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 10/19/1962 |
| From: | YANKEE ATOMIC ELECTRIC CO. |
| To: | |
| References | |
| NUDOCS 8011250392 | |
| Download: ML19351E001 (11) | |
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YAMEE NUCLEAR POWER STATION OPERATION REPORT NO. 21 For the month of SEPTEMBER 1962 l
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Submitted by YANKEE ATOMIC EIECTRIC COMPAIH Boston Massachusetts October 19, 1962-i j
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This report covers the operation of the Yankee Atemic Electric Company plant at Rowe, Massachusetts for the month of September 1962.
At the beginning of the nonth the final phase of the refueling shutdown was in progress as the reactor head was bolted in place. On September 5th, all primary systems having been readied, a hydrostatic test was conducted.
Leakage from a plugged flux wire thimble was detected during the test and the test was terminated. As reported in the August,1962 Operation Report, two damaged flux wire thimbles had been cut off at a point just above the core and removed. To maintain integrity of the primary system both thimbles were plugged at an external location just above the seal cap of the in-core instrumentation penetration. Because of the leakage which appeared at one plug during the hydrostatic test, the plug was mmoved and an internal inspection of the upper end of the thimble was nade. The o
inspection disclosed a number of small cracks and localized internal
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deterioration of the metal in an area approxinately 1/2 to 2 inches above the plug adapter. Accordingly, a decision was made to cap off temporarily the entire flux wire penetration containing the damaged thimbles with a pressure tight cap. While this action rendered one half of the in-core flux wire thimbles inoperative temporarily, the remaining eleven thimbles were not affected.
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The Atomic Energy Coruaission was notified of the condition and on v
Septenber 11, granted a 30 day authorization to operate the reactor at power with the renaining eleven flux wire positions. On September lh, a formal change proposal was submitted to the commission to permit operation of the reactor with eleven flux wire positions over the life of Core II.
On September 8, the hydrostatic test was repeated under a test pressure of approximately 2500 psi with satisfactory results.
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At this time final preparations were being nade for operation with Core II. Control rod drive electrical connections were nade, vent-ilating ducts were reinstalled and a general cleanup of the interior of the vapor container was carried out.
On September 12 at 2:h0 P.M., the initial criticality of Core II was achieved with control rod groups 6,3 and 1 fully withdrawn and group hat 262/8 inches. The main coolant boron concentration at the time was 1200 ppm with a main coolant temperature of 255 F.
Following crit-
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icality-a series of Core II low power physics tests began.
On September 13, during the course of the physics test program, control rod No. 9 in rod group h failed to move from a fully withdrawn position. Several attempts were made to insert the rod including scramming v
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e a q, the reactor. When conventional nethods of moving the rod failed, the rod drive pressure housing was tapped with a plastic mallet and resulted in freeing the rod. No. 9 rod once again was withdrawn to 90 inches (fully withdrawn) and once again hung up at that position. Iq;ain, only by striking the pressure housing was the rod freed. Further investigation disclosed that rod motion was normal and uninpeded from 0 to at least 88 1/8 inches but that rod hang-up would occur when the rod was fully withdrawn. Visicorder traces also disclosed abnormal operation during the final outward step of the rod. At this time the Atomic Energy Comission was informed of the sticking of No. 9 control rod.
In the brief period while the pr' mary system was at full pressure and at operatind temperature, difficulty in closing the pressurizer solenoid spray valve was encountered.
It became evident than on-line repair of the spray valve would be virtually impossible since an isolation valve failed to hold sufficiently tight to allow the repair. As a result,
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a decision was made to cool and depressurize the prinary system to repair the spray valve and at the sane time to pernit investigating more thoroughly
's the difficulty with No. 9 control rod.
On September lh, the plant was in a cold, borated and depressurized condition and efforts were concentrated on removing and repairing the solenoid spray valve and examining the No. 9 control rod drive.
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Removal of the control rod drive housing and inspection of the drivo disclosed signs of interference on a locking cap at the upper end of the drive shaft. The locking cap is a backup or secondary means for eliminating relative motion and wear between the drive shaft and drive linkage and is a newly incorporated feature of the Core II control rod drives. Since its function was not essential to the reliability of the drive, it was removed from the drive shaft.
Following the repair of the spray valve and control rod drive, m
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the primary system was brought to temperaturs and pressure. No. 9 control rod showed no evidence of hanging up or sticking. However, further spray valve problems developed and on September 18, it became necessary to cool and depressurize the primary system again.
After removing and seal welding the bonnet, the spray valve was reinstalled in an upright position as against its previous stem-down position. A new isolation valve was also installed -- a cracked seat having been found in the original valve.
Erratic stepping action in the operation of six control rods was noted during low power physics testing.
The tendency to misstep occurred within six inches of the fully insertedposition.
"'he rods in question moved freely when the reactor was scrammed and moved readily in the O to 6 inch region when actuated by their respective pull down coils. Changes
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.in cam. settings were made on the two rod group programmers which included the six misstepping rods while the reactor was shut down for valve repairs.
On September 20, the primary system was restored to pressure and temperature and the reactor was brought critical. With low power physics testing still in progress sparations were made to return to power operation by gradually reducing the main coolant boron concentration and checking out the secondary plant systems and equipment.
On September 21 at 12:0h P.M. the turbogenerator was phased to the line and electrical power production was resumed. However, at.h:08 P.M.
on the same day, erratic turbine control valve operation necessitated removing the turbine from the line. Subsequently, metal chips were found in the No. h control valve' servo motor. After cleaning the servo motor thoroughly the unit was rephased on September 23.
Further turbine trouble developed on September 2h, when it was O'
noted that the turbine governor was not controlling properly. On September 25, the unit was taken off the line to investigate the cause of the governor difficulty.'
Dismantling of the turbine governor disclosed the presence of r
metal chips similar to those found previously in the No. h control valve servo motor. Since it was evident that metal chips were present in the
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control system and-apparently were being transported by the control oil, a decision was made to flush and back-flush the complete ? turbine control system.
On September 27 at 11:09 P.M. the unit was returned to the line with the turbine governing system functioning properly Plant load was increased to 125 MWe on September 28 and to lh7 MWe on September 29.
O Plant Shutdowns Shutdown No. h8 $/18/62 to 9/21/62 - a 3028 hour0.035 days <br />0.841 hours <br />0.00501 weeks <br />0.00115 months <br /> shutdown for reactor refuelir.g.
Shutdown No. h9-2 9/21/62 to 9/23/62 - a $5 hor / shutdown resulting from tusoine control valve malfunction.
Shutdown No. 50-2-2 9/25/62 to 9/27/62 - a h8.7 hour8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> shutdown resulting
.from turbine governor malfunction.
Shutdown No. 51-2-3 9/28/62 - a h hour shutdown for turbine governor adjustment.
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OJ Reactor Scrams
- Scram Ho.'31-2-1 9/12/62 -.an automatic reactor scram from.a power level of less than 1 IWt. The reactor scrammed on a high start-up rate.as a: result of a manual voltage change on the channels from 200 to 300 Scram No. 32-2-2 9/22/62 - an automatic reactor scram from a power level of less than 1 MWt. The reactor scrammed on 4
a faultyhigh start up rate signal resulting from checking of detector currents.
Maintenance Following is a summary of major activities carried out by plant 4
maintenance personnel during September.
i 1.
Completed cleaning of reactor stud holes.
2.
Positioned and tensioned all the reactor vessel head closure 4
studs.
I 3.
Cut off eleven flux wire thimbles in ' northeast core instru-mentation column. Nine thimbles were plugged and the two
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defective thimbles were left unplugged. A pressure tight cap was seal welded to the top of the column to maintain the integrity of the primary system.
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Removed temporary shielding and equipment from the shield tank cavity.
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- 5. Reconnected control rod drive electrical cables and rein-stalled ventilating ducts.
O 6.
Removed and later replaced No. 9 control rod drive housing for drive inspection.
7.
Replacalloop side pressurizer spray line isolation valve which failed to provide tight shut'off.
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8.
Removed No. 9 control rod drive locking cap.
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- 9.. Removed, inspected and repositioned the pressurizer spray valve.
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- 10. Changed cam settinga on control rod groups h and 6 and adjusted ~ brakes.
- 11. Started installation of.No. 3 safety injection pump.
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Installed new bearing in No. 1 shutdown cooling punp.
13._ Replaced control rod drive coil on rod No. 2h due to a grounded coil.
Ih. Plugged two leaking tubes in No. 1 turbine lube oil cooler.
- 15. Overhauled No.1 instrunont air compressor.
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- 16. Removed metal chips from turbine control valve servo motors.
- 17. Flushed. turbine control oil lines.
Chemistry Main coolant oxygen levels remained low throughout the month with concentrations ranging from 0.005 to 0.20 ppm. The main coolant specific activity was approximately b x 10-3 pc/ml at the beginning of the period and increased to 3.5 x 10-2 pc/ml shortly after power generation commenced.
Boron concentrations varied during September reflecting the temperature condition of the primary coolant. At the beginning of the period with the plant in a cold state, boron concentrations in the order of
- Q 1200 ppm were required. Changes in concentration were effected as necessary durirg the physics testing. Deboration of the system for power operation proceeded smoothly with the anion exchanger performing well.
Turbine Plant Performance Feedwater heater terminal temperature difference data were taken j
at a load of 125 MWo. The results indicated improved performance as a result of the heater modifications but also indicated that a deviation h
between actual and design terminal difference still exists, particularly
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in the case of No. 2 heater, t
Reactor Plant Performance 4
Low power physics testing was carried out on Core II following a
the new core criticality. While detailed analysis of the test data has not yet been completed, the following observations were made.
1.
The boron concentration required to maintain the reactor critical with all control rods withdrawn is approximately 100 ppm lower on Core II than on Core I.
2.
The critical control rod position at low boron concentrations-
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coupled with control rod worth measurenents indicate that reactivity shutdown will all control rods ibily inserted is essentially the same on Core II as it was on Core I.
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3 A generator load cycling test indicated no significant reactivity effect resulting from the initial load cycling of the clant.
- h. The xenon power coefficient data obtained on Core II startup
'is lower.than that obtained by load cycling at equilibrium xenon during the Core I, 6000 hour0.0694 days <br />1.667 hours <br />0.00992 weeks <br />0.00228 months <br /> test series. This confirms the end of life tests on Core I which indicated that the moderator temperature coefficient was strongly dependent upon core xenon concentrations.
Rod drop checks were made on all control rods (including No. 9 rod after removal of its locking cap). All rod drop times were within the prescribed limits.
Health and Safety Liquid waste with a total activity of 0.35 millicuries was discharged from the plant during September. One hundred four drums of solid waste containing 2h6 millicuries were shipped for off-site disposal while 76 barrels of solid waste containing h0h millicuries were drummed.
At all times the concentration of waste products discharged or shipped from the site was well below the maximum pernissible.
Q No gaseous waste was discharged from the plant during September.
At the beginning of the period wit /1 the final phase of the in the shield tank refueling operation in progress, air-borne activity /cc.
cavity ranged normally from 1 x 10-10 to A temporary increaseinair-borneactivityto1x10gx10-9pc Atc/cc was detected during the venting of control rod drive housings and venting of the pressurizer and main coolant pumps.
.h Radiation levels in the shield tank cavity after removal of one inch thick lead sheet from the floor of the cavity were:
General cavity area 350-700mr/hr Over neutron shield blocks 100-250mr/hr 3 feet above reactor head insulation 100-200mr/hr Top of control' rod drive and catwalk area 70-150mr/hr General area radiation levels on the charging floor prior to the reactor criticality were 0.5 to 5 mr/hr and h0-50 mr/hr over the edge of the shield tank cavity. Contamination on the charging floor ranged from 2
3,000 to 30,000 dpm/f t,
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Q Radiation levels measured near the surface of the upper. core i
supportbarrelliftingfixturewereontheorderofh00to1500mr/hr.
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-Smcarable contamination was in the vicinity of 107 dpm/ft.
Radiation levels encountered during the removal of No. 9 controlrodwerereducedfrom600mr/hrto150mr/hrbytheadditionof lead shielding around adjacent rod drive housings. The locking cap removed from No. 9 drive had a measured radiation level of.700 mr/hr at the top end of the cap.
Removal of the pressurizer spray valve was carried out in an areawitharadiationlevelof20to60mr/hr.
The following contact radiation levels ware measured during September with the plant in a cold, borated, depressurized conditions Location Radiation Level on Contact Shutdown Cooling Pump 115 Safety Injection Pumps 0.3 '
No. 1 Purification-Pump Tail Pipe 205 mi-No. 2 Purification Pump Tail Pipe 500mr/hr Low Pressure Surge Tank Bottom 7 r/hr.
Inlet to Low Pressure Surge Tank 225mr/hr Q
No. 1 Charging Pump
'h2mr/hr i
No. 2 Charging Pump 10mr/hr No. 3 Charging Pump 29mr/hr No. 1 Main Coolant Pump 3 to 20 mr/hr No. 1 Loop Check Valve 30 mr/hr No. 2 Loop Main Piping 30to105mr/hr No. h Loop Stop Valve 25 mr/hr No, b Loop By-Pass Valve 35mr/le Pressurizer Shell 1.5mr/hr O
rreeeurizer S rer tine 6 to 50mr/hr P
Activity Dilution Decay Tank 5CO to 850 mr/hr
< Solid Waste Drum Storage Area 30to100mr/hr
- General Area Level.
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Personnel exposures as measured by film badges for the period May 1 to September 15 were as follows:
Average for all station personnel and temporary service company personnel assigned to the potentially contaminated area - - - - - - - - - 1820 mr.
Maximum individual exposure - - - - - - - - - 3630 mr.
While the refueling shutdown did not start until May 18, the above exposures for all practical purposes represent those incurred during the refueling operation.
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Design Changes The following minor changes in plant design were completed in September:-
1.
A net KWe indicator was connected and placed in service.
The new indicator is mounted above the operating bench-board in the control room and displays the plant net electrical output.
2.
As described elsewhere in the report danage to two flux wire thimbles and a subsequent leakage question resulted in a decision to cut off nine additional thimbles and cap the entire eleven wire penetration. While this renders eleven flux wire positions temporarily inoperative, it in no way affects the renaining eleven flux wire thimbles which enter ry the reactor vessel through a separate penetration.
U The internal condition observed in the thimbles at a point above the plug adapters made it necessary to consider a nodification to the thimbles in the remaining flux wire penetration. In order to make certain that the tubing above the plug adapter for the remaining eleven thimbles was of sound naterial, a new connector tube sheet was
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designed, fabricated and installed which provides for the
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removal and replacement of all tubing in the zone of indi-cated deterioration.
Ca September 11, the A.E.C. granted a 30 day authorization to operate the reactor with the aforementioned modifications.
On September lb, Proposed Change No. 29 was submitted to the A.E.C. covering the modifications in detail.
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Changes in Operating Procedure Operating Instruction $0h0:1 was revised and reissued during September to reflect the change in the nuclear instrumentation system resulting from the installation of additional power range scram circtitry on the three compensated ionization chamber outputs.
The system revision was reported in Operation Report No. 20 and is in accordance with Proposed Change No. 23 submitted on May 9, 1962, and approved by the A.E.C. on August 23, 1962.
In Plant Training Three sponsor company engineers were in residence at the plant for the duration of the Core II low power physics tests.
Plant Operaticns a
Attached is a summary of plant operation statistics for the month of September 1962, and a plot of daily average plant load for the same period.
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TANKEE ATOMIC ELECI3 TIC COMPANY - OPERATIE SUTJRY SE?fElGER 1962 ELECTRICAL MONTH TEAR TO DA'fE Gross Generation M
13,398,600 382,572,500 1,3h3,919,800 Sta. Service (While Gen. Incl. Losses)
M 1,0h3,037 31,071,386 108,603,h68 Net Generation M
12,355,763 351,501,11h 1,235,316,332 Station Service 7.78 8.12 S.C6 Sta. Service (While Not Gen. Incl. Losses)
^M 1,7hh,605 3,83h,096 13,925,81h Ave. Gen.
For Month (720 HIG.
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g 18,609 Ave. Gen.
Running (108.2 HRS.)
g 123,63h PLANT PERFORMANCE Net Plant Efficiency 28.99 28.79 y
Not Plant Heat Rate Btu / M 11,773 11,855 Lbs. Steam / Net KYH 13.71 1h.0h Circulating Water Inlet Temp.
Maximum or h5 Minimum oF h3 Plant Operating Facter 5
12.21 38.h3 56.21
'!UCLEAR
}DfMI CORE II TO DATE 27 27 289 Times Critical Hours Criticai HRS 280.52 280.52 13,527.95 2
2 32 Times Scramened Equivalent Reactor Hours 8 h85 Wt HRS 87.9 87.9 8716.h Average Burnup of Core WD/mtU 85.h 85.h Control Rod Position et Month End Equilibrium at Ih7 We Group 1 Rods out-inches O
Group 2 90 m
Group 3 15 Group h 90 3roup 5 0
Group 6 90 1
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YANEL ATOMIC ELETRIC CWANY DAILY AVERAGE LOAD for SEIEER 1962 150 -
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g (d) 8 100 -
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(a) Shutdown llo.h8 4
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(d), Shutdown No.51 0
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10 15 20 25 30 g
DAYS.