ML19351E150
| ML19351E150 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 05/22/1963 |
| From: | YANKEE ATOMIC ELECTRIC CO. |
| To: | |
| References | |
| NUDOCS 8011250669 | |
| Download: ML19351E150 (9) | |
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YANKEE NUCLEAR PodER STATION OPERATION REPORT NO. 28 For the month of o
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APRIL 1963
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tS This report covers the operation of the Yankee Atomic Electric a
Company plant at Rowe, Massachusetts for the month of April 1963 On April 1 at a load of 170 Mi, No. h turbine control valve was found to be sticking in the near full open position thereby forcing a plant shutdown. While lowering load on the machine, No. 3 control valve also gave evidence of sticking. The binding in both valves was found to be between the servo motor stem and its guide bushing. The stems were cleaned and polished and replacement brass bushings with increased clearance were installed. A similar repair on control valves No. 1 and No. 2 has operated satisfactorily since 1960.
With repairs to the servo motors completed, the plant was returned to the line and load was raised to 150 Mi.
On April h, full power operation of 170 M1 was resumed.
On April 7 pond elevation dropped sufficiently to permit air
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intake by the circulating water pumps. The consequent loss of discharge siphon resulted in plant load being reduced t.o 168 Mi.
On April 10 a reactor scram from full power of 168 Mi was experienced. Control panel memory lights indicated that the scrat was caused by low neutron flux which could have originated from a dropped control rod. In an effort to determine the actual cause of the scram, the reactor was returned to low power critical condition by programmed
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rod withdrawal. Each rod was exercised individually and the nuclear channels monitored in order to check latch integrity and rod drive action. All rods except No. 20 performed normally.
Slippage of Rod No. 20 was noted on both the position indicating lamps and the vapor container sound system. Extensive electrical checks of the rod drive coils indicated that they were in good condition. Visicorder traces of Rod No. 20 were compared to those of others with only miner discrepancies noted.
It was concluded that the control rod drive diffical t,y could m/
have been caused by insufficient coil current in the stationary gripper coils. Early in 1961 the voltage imposed on these coils was reduced to 50 volts from 120 volts in order to minimize the continuous heat input and operating temperatures. At that time a dropped rod occurrence was experienced and the reduced voltage was increased to 65 volts.
During the ensuing two years it is quite possible that circuit resistance on the particular drive had increased to the paint where 65 volts is no longer sufficient to provide adequate holding power in the stationary gripper coil. Accordingly, voltage on group 6 (rods 17 through 2h) stationary grippers has been increased to 75 volts. All aspects of subsequent operation have been checked and found normal.
On April 11 the turbine was phased on the line and plant electrical output reached 150 Mi.
On April 17 the vapor container sound system, the relative humidity indicator and t.he air particulate monitor indicated the presence J
of a leak in Na. 1 compartment. The plant was taken off the line, main coolant pressure reduced, and No. 1 loop isolated.
Inspection showed
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.-the leak to be at a socket. weld coupling downstream of the root valve -
-in the loop flow detector instrument line. The area was ground out and rewelded.
During'the outage, No. 3 Boiler Feed Pump was tagged out for
_ lubrication. While '.evering the air. circuit breaker back into operating
- position, an iron casting on the ACB levering in device was fractured.
Since'it was necessary to de-energize the bus section to repair the ACB, No. h main coolant pump had to be shut down as it is fed from the same bus. This'resulted in a spurious reactor scram.
The scram was caused by leakage current from scram bistables which were blocked out at the time by the permissive relay.. The bistables on the main coolant. pressure and pressurizer pressure scram ware conducting due to the actual low main coolant pressure of'1500 psi. The tripping of No. h' main coolant pump, with low flow already indicated on No. 1 loop, caused the flow scram bistable to contribute sufficient additional
.h leakage ~to cause the scram. New bistable diodes will be installed at the next refueling.-
The turbine was phased on the line and plant electrical output was raised to 169 W 'on April 19 For the remainder of the period plant load was held to approx -
imately 168 - 169 W gross. Several attempt's were made to regain the.
circulating water discharge siphon using t % temporary vacuum pump, however,'
none were completely successful.
During April, three Core I spent asschlies were ' shipped for inspection and examination off site under an A.E.C. contract.
Ten new fuel assemblies were delivered to the plant in April.
A total of 5h new fuel assemblies are now in storage at the site.
Plant Shutdowra Shutdown No. 57-2-9 h/1-h/2/63-A 21.8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> shutdown for maintenance to Nos. 3 and h turbine control valves.
Shutdown No. 58-2-10 h/10-h/11/63 A 21.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> shutdown resulting
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from a reactor scram.
Shutdown-No. 59-2-11 h/17/63 A 9 hour1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> ~ shutdown for repairs to a leaking flow indicator line in No. 1 loop.
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, Reactor Scrams
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1 Scram No. 3h-2-h-h/10/63 An automatic roactor scram from a power level of $h0 Et. The reactor scrammed due to low neutron flux apparently-resulting from a dropped control rod.
ScramNo.l35-2f
.h/17/63 A spurious reactor scram from a.
power level of < 1 Nt, The reactor scrammed due:to current leakage of low flow bistable diodes.
. Maintenance Following'is a summary of ms!
w.? 'ities carried out by plant maintenance personnel &n-ig; Apri,a 1.
No. - 3 Se2TLv Water iW "as dismantled for inspection.
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- 2.. The cooling watw suppu to the service air compressor was modified ts rovide improved. temperature control during operation.
3 A new lon exchange unit was piaced in service.
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Packing was added to.No.1 charging pump.
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The control rod drive shaft starage rack was rebuilt.
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A faulty contactor connection of No. 1 group pressurizer heater was repaired.
Chemistry
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Throughout the period main coolant oxygen levels were below the
~U point of detection.
After the shutdown on April 1 average main coolant specific activity rose to 1 3'x 10-1 #c/ml.. For the remainder of the period the specific activity ranged between '. 5 and 8.1 x 10-2 pe/ni, Main coolant Iodine-131 concentration varied between 13 and 1.8 x 10~3 pc/ml throughout the period.
A typical main coolant crud analysis made during the period indicated:
Fe - 59 1.h x 1 dpm/mg Ag' - 110 1.6 x 10 dpm/mg Co - 60 9.5 x 10 dpm/mg co --58
$.2 x 1 dpm/mg-O-.
cr - 51 8.6 x 1
.dpm/mg Mn - 5h 6.3 x 10 dpm/mg 4
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The results of-a typical. main coolant gas analysis are. as follows:
Xe - 135.
2.h x 10-1 pc/cc Ie --133 2.h8 ~
pc/cc Kr '85m 1 3 x 10-1 pc/cc.
A ' - h1 1.2 pc/cc Reactor Plant Performance Core reactivity changes were followed closely during the shut-downs of April 1 and April 10. - Data has indicated no unexplained reactivity loss
-as a result of either shutdown.
Correspondingly, commencing April 20 the core exhibited.a period of lower than normal burnup. On April 29, the core began losing reactivity at a higher than normal rate, however,-the reactivity condition Q
had not reached the expected. burn-up curve at the end of the reporting C/
period.
The following were determined by means of in-core instrumentation measurements at a power level of $h0 Wt, control rod groups 6, 3,1,' h and 5 at 88 7/8 and group 2 at 66'0/8.
Fq 30
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20 F6 T*
Minimum QNDB ratio = 2.5 Power coefficient data as measured with peak senon poisoning during the April 17 startup indicated the following:
A P =
-0 76 x 10-h AP
@ $ st bQ W L-Turbine Plant Performance-During the period main steam line vibration data were measured at a power level of 170'W. This data completes the present series and is now being analyzed in an effort -to determine the source of the observed vibrations in the system.
Plant electrical output was reduced slightly commencing April 7 due to the loss of the circulating water system discharge siphon.
Continued efforts to regain the siphon utilizing the recently installed vacuum pump were unsuccessful. Further modification to'the temporary.
vacuum pump, 'as reported in the March 1963 Operation Report,. are now being made.
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4 At a plant load of 170 W, No. 3 Boiler Feed Pump was found to have a 3 mil vibration at the bearing housing. During the April 10 shutdown, alignment of the pump and motor was measured and found to be in accord with the manufacturer's recommendation. The pump will be dismantled for internal inspection at the next scheduled shutdown.
Further study of feedwater heater terminal difference performance has indicated that Nos. 1 and 3 heaters are now operating within their design range.
However, No. 2 feedwater heater continues to exceed its design terminal temperature difference by a factor of two. It is now felt that the excessive terminal difference is due to flooding of the bottom portion of No. 2 heater. A more detailed description of the most recent modifications made to the heaters can be found in the March 1963, Operation Report No. 27 Plant calorimetric data and routine secondary plant performance data were taken and analyzed during the month.
Health and Safety Liquid waste with a total activity 0.66 me was discharged from the plant during April. Oaseous waste containing an estimated 200 me was discharged during the same period. At all times the concentration of waste products discharged from the site was well below the maximum permissible.
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During April 33 drums of radioactive waste contai-ing a total activity of 33 me were prepared.
52 drums of solid radioactive waste containing a total activity of 96 me were shipped from the site during the same period.
Sodium cyanide decontamination of tools used during Core 1 refueling continued during the period. Three separate item from the control rod drive storage rack were decontaminated. Radiation levels on stainless steel pieces were reduced from 150 - 200 mr/h-to less than 1 mr/hr. Other pieces, of aluminum, showed levels of h00 mr/hr before decontamination and h0 mr/hr after decontamination.
Levels measured on a lifting fixture utilized during refueling werereducedfrom100mr/hrto75mg/hr. Contamination levels were reduced from 20,000 - 60,000 dpm/ft before decontamination to 2
approximately 1000 dpm/ft after decontamination.
It is theorized that the poor reduction of radiation levels on the lifting fixture ?as the result of having used a grinding operation en the fixture which imbedded radioactive silver particles.
Three Core I spent assemblies were shipped off site for examination under an A.E.C. contract. Average radiation levels as measured on the cask prior to each shipment were 2 - 3 mc/hr.
2 Contamination levels averaged 2000 - 3000 dpm/ft,
Personnel exposure for Yankee plant personnel as measured by dosimeters for the month of March 1963 were:
Average for all station personnel 7h
=
Mar % m individual exposure h00
=
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- b. Continuous monitoring of off site airborne activity during April indicated levels consistent with pre-operational values.
Design Changes The fuel. chute dewatering circuit was modified to permit the discharge valve to open prior to startup of the dewatering pump.
Previously, the purp would reach operating speed prior to complete opening of the discharge valve thereby resulting ir. water surges down-stream of the valve, Plant Operations Attached is a surmary of plant operation statistics for the month of April 1963, and a plot of daily average plant load for the came period.
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YANKEE ATOMIC EIECTRIC COMPANY - OPERATING SUfMARY APRIL 1%3 EIECTRICAL MONTH YEAR TO DATE Gross Generation KWH 108,818,900 h35,798,800 2,137,270,800 Sta. Service (While Gen. Incl. Iosses)
KWH 6,693,352 27,228,107 157,98h,67h Net Generation KWH 102,125,5h8 h08,570,693 1,979,286,126 Station Service 6.15 6.25 7 39 Sta. Service (While Not Gen. Incl. Losses)
KWH 36h,263 960,791 1h,929,629 Ave. Gen. For Month. (719 IBS)
N 151,3h8 Ave. Gen. Running (665.6 IBS)
KW 163,h90 PIANT PERPGtMANCE Net Plant Efficiency 29.21 29 3h Net Plant Heat Rate Btu /KWH 11,683 11,632 w
Ibs. Steam / Net KWH 1h.06 13.82 i
Circulating Water Inlet Temp.
Maximum F
ho Minimum F
32 Plant @ rating Factor 90.06 89.58 66.92 NUCIEAR MONTH CORE II TO DATE Times Critical 2
35 297 5 fours Critical HRS 707 53
$307.h2 18,55h.85
~ Times Scranned 2
5 35 Equivalent Reactor Hours @ $h0 MWt HRS 6h7 5 h790.2 12,707 3 Average Burnup of Core MWD /mtU 700.g 3181 9 Control Rod Position at Month End 0 Equilibrium at
$h0 Mit, $13 F Tavg.
Group 1 Rods out-inches 88 7/8 1
Group 2 66 6/8 i
Group 3 88 7/8 Group h 88 7/8 Group 5 88 7/8 Group 6 88 7/8
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