ML19351E020
| ML19351E020 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 10/26/1965 |
| From: | YANKEE ATOMIC ELECTRIC CO. |
| To: | |
| References | |
| NUDOCS 8011250439 | |
| Download: ML19351E020 (13) | |
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YANKEE NUCLEAR POWD1 STATION OPHtATION REPORT NO. 57 For the month of SEPTEMBBt 1965 O
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YANKEE ATOMIC ELECTRIC COMPANY N' i~~~ ' :1
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c This report covers the operation of the Yankee Atomic Electric Company plant at Rowe, Massachusetts for the month of September 1965.
At the start of the period, the scheduled refueling shutdown s
was still in progress with effort being made to examine the snap joints of the remaining control rods for proper alignment prior to lif ting the core barrel assembly. Rods one and two, in the center of the core, were found to be partially unlatched. Coincidently, it was planned to replace these hafnium poison section rods witn stainless clad Ag-In-Cd sections at this refueling.
These two rods were sent to the spent fuel pit for storage pending a detailed inspection of the remaining 22 control rods.
T;te three remaining neutron sources were removed to the spent fuel pit.
Examination of the north source vane, which, like the failed west source vane, is bolted, revealed that at least one capscrew had failed. The decision was then made to not use any bolted sources of this type in future cores, but rather to use the newer design which is of all welded construction.
The core barrel assembly lif t was accomplished after some f
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difficulties were overcome.
Close design tolerances of the lifting fixture led to interference with parts of the barrel and vessel and required the loosening and modifying of the fixture.
The lift itself went smoothly despite the fact the barrel had to be rotated half way out
'o allow clearance to the vessel nozzles. The barrel assembly was left in the northwest corner of the shield tank cavity, suspended from the large hook of the polar crane. With the barrel assembly removed, only the
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thermal shield remained in the vessel and access to the bottom of the
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vessel was possible.
The activity in the shield tank cavity area caused cloudy conditions to exist in the cavity water. As water clarity improved, the vessel bottom became visible, which facilitated the removal of foreign material.
The inventory of missing material is still being compiled and will be reported later. The objects missing are all small and consist mainly of a few irradiation specimens from the failed capsule.
The following is a list of material which has been recovered from the vessel and its internals, exclusive of fuel:
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i 13 - charpy V-notch specimens 1 - tensile specimen 3 - tensile specimen filler blocks 2 - V-notch specimen filler blocks 2 - west source vane tube sections 90" long 1 - west source vane tube section 23" long, with two capscrews 1 - piece specimen wrapper, h" long 1 - piece lower section of NW specimen basket,1" sq. x h' long, perforated 1 - piece 3/h" od stainless tube, SE specimen holder 6' 8" long, 11 bend 26" from one end 1 - piece 3/h" od stainless tube, SE specimen holder, ends worn such that upper side is 28" long and lower side only 20" long 1 - 15/8" dia. capscrew, head and shank of thermal shield capscrew 1
3" dia. disc. - thermal shield capscrew " keeper" 1 - 3/8" dia. x 1/2" long threaded stock - portion of bolt which held NW specimen basket to thermal shield v
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. g-c D) 1/2" dia. x 11/2" long capscrew - shroud tube lower spider
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1 (control' rod #17) 1 neutron activation specimen capsule, lA" od. x 51A" long -
end cap was missing and capsule was empty.
- 1. - drive shaf t finger pin - 3/8" dia. x 1" long (known to be missing since Core II-III refueling)
It is significant to note that no material. foreign to the reactor system was found in the vessel or its associated parts.
With the retrieval of a portion of a failed thermal shield capscrew and capscrew " keeper", a detailed inspection of the thermal shield was begun.
The thermal shield is made up of four segments and was assembled in place in the vessel because its diameter is larger than that of the vessel opening. There are four rows of thirteen capscrews each holding the segments together. The thermal shield rests on eight support legs (two per segment) attached to the vessel inner wall. The inspection revealed that the upper end of two joints and the lower end of three joints had parted and lef t a gap of up.to 3/8" between adjacent segments. This indicated that some capscrews in at least three joints had failed. The hole where the capscrew was missing was located in the southeast joint fif th from the top.
Westinghouse designed and built a device to remotely cut the
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capscrew " keepers" and remove the capscrews. This device arrived at
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the site on the 23rd, and after much effort to fit the device to the thermal s./
shield, the top four " keepers" in the SE joint and the top five in the NW joint were cut.
Problems existed in alignment and not all the cuts were centered on their " Keepers" and, as a result, not all of them came free.
The four in the SE joint were removed along with four fractured capscrews.
In the NW joint only one " keeper" was removed. The capscrew head hex fractured when attempts'were made to unscrew it. While working on this capscrew, the " keeper" over the capscrew above fell out and was retrieved.
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ere r e=a te 'e tisat =a pre e=t >== re to complete the repair without looking at anymore capscrews.
The repair will consist of four clamp devices which will clamp the joints in proper alignment.
The mode of joint failure has not yet been determined; however, the machining and removal operation shows that both fractured and whole capscrews exist in the joints with the SE joint most likely to have all
. its capscrews fractured. Westinghouse has tentatively determined that the capscrew examined, failed by cyclic tension.
By examination of the spacer pins on the thermal shield and wear pads on the vessel, it is believed that even in the unbolted condition the thermal shield segments do not vibrate with ~any significant amplitude.
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An inspection of the annulus between the thermal shield and the vessel wall, where the four low flux specimen baskets were located, showed that several of the upper basket support straps had broken off. The northwest basket had. broken loose, fallen to the bottom of the ' vessel and was broken up by the water flow action. This basket contained a specimen
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holder capsule which also broke open scattering the specimens in the y
vessel bottom. The northeast basket, which was empty, had broken loose and dropped, but was held captive by the lower edge of the thermal shield.
It was purposely broken into two pieces and removed. The southeast basket which contained a specimen holder capsule had broken loose at the top but was still held by the bottom bolt into the thermal shield. The specimen holder was retrieved intact and will be sent away for analysis. At the end of the period, the basket defied all efforts at its removal and efforts were being made to drill the bolt out.
The southwest basket, which is empty, is still in place with no apparent damage. A decision will be made on its final disposition.
The baskets have made wear marks in the stainless cladding of the vessel bottom but the depth is negligible. There are, however, two small areas where the clad is worn through in the northwest quadrae, of the bottom caused by pieces of foreign material rubbing on the clad.
d Photographs and impressions have been made of this area to aid in the analysis of the failure. The total area of this failure has been measured at about two sq. in. This breach of the clad has been reviewed by Westinghouse and consultants and no unusual problems could be foreseen which would restrict plant operation.
During this time, personnel from Westinghouse dye penetrant O
checked the upper gusset welds and ultrasonically checked main barrel welds (V) of the lower core support barrel with no defects being found.
The four high flux specimen holders, which had broken loose some time during Core II operstion were retrieved.
These specimen holders, like the low flux specimen holders, were installed during the core I-II refueling. During the core II-III refueling, four of the high flux specimen holders were removed, but the other four had broken loose from the plugs from which the/ were suspended in the annulus betueen the core t
i baffle and core barrel. The irradiation history of these specimens is V
uncertain and the merit of laboratory analysis has not been ruled upon.
The spent fuel assembly, A-8, which had seen service in cores I, II and IV, and nad reached an average burnup of 30,136 fwd /IffU, was shipped in the single element spent fuel cask to Westinghouse.
Because a capscrew was found which could have come from the shroud tube tie plate, the shroud tube spi __ was inspected. A capscrew was found missing from rod li shroud tube where it attaches to the tie plate. An underwater wrench was fabricated to check the torque on the capscrews on the shroud tube tie plate. These capscrews are held captive by crimped locking devices and these locking devices must be broken to rotate the capscrews. Only enough torque was applied to the capscrews to assure that the locking device nas intact and that the capscrew hadn't backed out.
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j Plant Shutdowns v
Shutdown No. 79-h-8 8/9/65 continuation of the scheduled Core IV-V refueling shutdown i
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'f Plant Maintenance Following is a summary of major activities carried out by the plant.uintenance staff, augmented by personnel of the New England Power j.
Service Company:
1.
Set the cams on the control rod drives.
2.
Repaired a leak on No.1 charging pump.
3.
Plugged 18 tube ends (9 leaking tubes) in No. 3 feedwater heater.
h.. Cut valves CH-MOV-526 and $27 from the bleed line for the 3
installation of new seats and wedges and reinstalled same.
5 Completed' the low pressure main coolant vent header.
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Seal welded the two canopy seals on the repaired pressurizer solenoid relief valve, preseure tested it with nitrogen and welded the valve in place.
7 Silver soldered all heater end connectors in the pressurizer.
8.
Pulled cable for MOV-512 which will be located at the bleed line sample point in the vapor container.
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9 Repacked: both main gate valves, the bypass valve and the four shutdown cooling valves, all in loop h; and, bypass valre, safety injection valve and charging valve in loop 1.
10.
Repacked all the capped stem angle valves in the vapor container.
- 11. Replaced the mechanical seals on the safety injection system's purification pump.
- 12. Installed a filter in the ion exchange pit for cavity water filtering.
- 13. A new pressurizer vent root valve, PRV-602, was installed.
Ih. No. 1 purification pump was removed and disassembled. The rotor seal can was found worn through and a new rotor assembly was placed on order.
15 New springs were installed and the seats and discs were
. lapped in on the two pressurizer safety valves while the factory service man was present.
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- 16. Renewed a leaking mandoor gasket on the safety injection
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tank.
i 17.- Cold readings were recorded for the primary system piping
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- 18. The seats and discs of the eight original safety valves L'
from the steam generators were lapped.
- 19. A new return line for the sample system modification was run from the sample cubicle to the low pressure surge tank.
20.
A remote operated wrench was designed and fabricated to install the bolt in the lower shroud tube and also to check the torque on the other bolts.
21.
Relocated the control for the lower lock valve in the fuel chuto from the lower end of the fuel chute to the enclosed lower eptrance to the vapor container elevator.
22.
Support plates for the steam generator feedwater distributor ring supports were fabricated.
AU 23 A water meter is being installed in the charging pumps suction line. The pumps relief line is being re.ucated to the upstream side of the meter.
The following is a description of the maintenance work performed on the turbo-generator unit:
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The high pressure turbine pedestal was moved on its slides by means of hydraulic jacks. The forces requirod were higher than expected
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and the pedestal was jacked up to inspect the slides. Indication of poor 1
- ication and minor galling was evidente Holes were drilled and more grease fittings were installed. After lubrication, the pedestal was set in place. One third. > former force is now required to move the pedestal.
The inside surfaces of both turbines were wire brushed and a
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protective coating was painted on.
The high pressure turbine rotor and blade rings were sand blasted with aluminum oxide. The steam cuts on the blade rings were filled with stainless weld deposit and ground to shape. New seal and chill strips were installed on the blade rings.
The f aces of the turbine casings were stoned.
All the blades in the seventh row, both ends, of the low pressure rotor have now been restellited.
The replacements for one end, two 90 el s acd one h50 ell have 0
been welded in place on the high pressure M AJ m # 2 extraction line. This was done because of steam erosion of the car *
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Both turbine throttle valves were inspected era relapped.
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At the end of the period, the high pressure turbine blade x
rings and cover had been fitted and the bearings and rotor were being assembled and the seals were being checked out.
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Chemistry As reported last month, the antimony concentration in the shield tank cavity water after the failed source was detected was less than 1 x 10-0 pc/mly or essentially, there were no broken tubes.
On September 2, antimony was found in samples at a level of 1 x 10-h ic/ml. This level gradually increased. to 3 x 10-h 1c/ml on J
J September 7 The reason for this slow buildup in activity is that there was no anion excha. ge in the purification system, and, no antimony was being removed. -It is presently believed that in order to. validly detect soluble antimony in water, the chemistry conditions must be oxygenated, possibly borated, and with a temperature higher than 200 F.
Based on these findings, one or more of the source tubes has leaked antimony, although no obvious breaks were detected when the pieces were retrieved.
The crud level of the shield tank cavity water decreased from 1.0 ppm at the start of the period to 0.13 ppm at the end. The specific activity ref ected this' decrease, going from h x 10-3 pc/ml at the start to 3 5 x 10- J1c/ml at the end of the period.
The liquid scintillation spectrometer system arrived at the
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plant and was installed. Tritium analys'es now are being performed at the
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Tritium determinations on secondary water samplos taken before shutdown what the leaking No. 3 steam generator was shutdown, indicate a 2.7 gal / day primary to secondary leak rate. This data confirms previous analysis. based upon iodine that indicated a 2.0 gal / day leak rate.
(See Operation Report No. $$).
e.1 analysis of the spent fuel pit water was as follows:
pH $.2 gross activity (less tritium) 2.8 x 10-3 pc /ml conductivity 2.0 p-mhos boron 15h ppm Reactor Plant Performance Completed the visual inspection of all Core IV fuel assemblies.
Nine fuel assemblies _to te ce-cycled in Core V were found to have foreign mcterial contained within them. Another assembly scheduled to be recycled was found to have two loose adjacent spacer ferrules in the outside row.
These ferrules have slid down and now rest on the bottom end plate of the fuel assembly. A decision is forthcoming on the disposition of this assembly.
' p The inventory of foreign material remved from Core IV fuel in f
h addition to that already removed from the vessel is:
1.
A piece of the side of a specimen basket about 6" long with the welded strap attached.
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Several pieces of wire, assumed to be partial and complete
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lif ting bails from the specimen hole plugs.
3.
Several pieces of stainless of various shapes and sizes assumed to_ pieces of the specimen wrapper.
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Three V-notch specimea, 0.h" square x 2" long.
After inspection, all the fuel assemblies to be re-cycled in Core V were given an underwater jet spray to remove the crud deposits and loosely attached foreign objects. All foreign objects were removed except a small piece which still remains in Assembly B-291.
The results of the inspection of the three sources in the spent fuel pit are as follows:
North Source - A bolted source. Tube surface conditions appeared O
8eed witu heav7 dePesite of cred-it 1e t e=e bolt was believed to be sheared, with the top sections of at least the first two of the four rows of tubes loose.
East Source - A welded source. Tube surface conditions were good with only minor surface imperfections
[]1 noted, and only a light deposit of crud. All welds appeared sound end in excellent condition.
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South Source - A bolted source. Tube surface conditions appeared good with heavy deposits of crud.
All bolts appeared tight and intact.
A detailed inspection was made on the two hafnium control rod poison sections that are in the spent fuel pit. These are A63 and A75 which were in core positions 1 and 2.
These positions are in -the center e
of the core and were half of the controlling rod group which saw much stepping action during Core IV.
Mi.nor surface scratches and guide block stepping wear of little depth were observed on both absorbers. The "breakjoint" was inspected in detail and no wear or deformation was observed.
An umbrella type in-core instrumentation spacer thimble was installed in Core IV fuel assembly A-167, whi.ch is scheduled to be re-cycled in position F-5 in Core V.
Turbine Plant Performance Calculations are being made to determine the effects on performance which will be caused by plugging the failed tubes in #2 feedwater heater.
Investigations seem to-indicate that reductions in'overall plant performance which occur' shortly after plant startups from refuelings,.may
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be caused by the failure of a gasket in the #3 feedwater heater which
-s allows feedwater to bypass the heater. The design of the heater is such that after a'few thermal cycles, the gasket fails internally and some feedwater can flow from inlet side to-outlet side without passing through the heater. The investigation is. continuing in an attempt.to see if this situation can be corrected.
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Instrumentation and Control V
Following is a summary of major activities carried out by the plant Instrumentation and Control staff during September Calibrated the following primary plant instruments:
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four main coolant loop flow channels ut coolant pressure detector Narrow and wide range pressurizer level channels Pressurizer pressure channel Number 1 main coolant pump bearing temperature Loop fill pressure channel The process recorder Calibrated the following major secondary plant instruments:
O The four steam generators narrow and wide range level channels v
The four steam generators steam flow meters The four steam generators feedwater control systems The condenser level transmitter and low level controller Installed new dials and locks on the powe~ range gain controls Checked the operation of the fail-safe relays on the primary
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l Installed a new, spare vapor container penetration in blister 6E
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Repaired the primary vent stack radiation monitor Relocated the low pressure alarm switch for the instrument air header supply inside the main control board Checked the coaxial cables to thimble 3 in an attempt to determine the source of trouble in #h power range channel Started installation of a new vapor container temperature indicator on the front of the main control board, turbine-n generator end V
Installed a float switch in the shield tank cavity to warn of high water level Assembled and tested two new in-core instrumentation post tubing adapters It was determined that both channels k and 8 in thimble 3 have short circuits in their high voltage cables.
It is assumed that refueling water ha: leaked into the dry box and flooded the thimble.
Instrumentation Changes The location of some of the vapor container atmosphere temperature detectors have been changed and one more point has been added to give a total of ten points plus a test point. The eleven points will read on a singl Indicator, through a multipoint switch, on the front of the main' s
control board.
The purpose of this change was to be better able to
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calculata the average temperature within the vapor container when performing
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)_ the continuous vapor container leakage monitoring. The location of the Nd ten points are: the four loops; north hemisphere, high and low; south hemisphere, high and low; charging floor; and the pressurizer compartment.
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Health and Safety During the month of September 1965, the following solid radio-active wastes were shipped off site for disposal:
1.
A shipment consisting of two $ ton concrete casks, one with a drum containing a filter used for waste liquid purification, total activity 1.2 curies; the second, a drum containing the shield tank cavity filter, total activity 1.h curies.
2.
Seven drums containing a total activity of 38.1 millicuries.
59,h2h gallons of liquid waste containing a gross beta-gamma adivity (less tritium) of 0.1h millicuries and 87.2 curies of tritium were discharged during September. Gaseous waste containing a total activity of 2.96 curies of tritium was discharged during the same period.
(From vapor container purge via primary vent stack).
O" In addition to the above waste shipments and releases, the following shipments of radioactive materials were made to Westinghouse:
1.
Some of the pieces retrieved from the bottom of the reactor.
Sent to Westinghouse for analysis their cask and carrier.
Estimated total activity,11 curies 7-]
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Four thermal shield screw heads and neutron detector
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capsule. Sent to Westinghouse via their cask and carrier.
Estimated total activity, 8.6 curies.
3.
One spent fuel assembly (A-8). Sent to Westinghouse via their single spent fuel element cask. The calculated total activity was 2 megacuries. The maximum radiation levels on contact and at three meters were 28 mr/hr and p
3 mr/hr respectively.
U Control rod drive shafts #2 and #10 were removed from the shield tank cavity for inspection. Radiation levels of the shafts from the cap end to within three feet of the dashpot were 130 to 300 mr/hr at 1".
The maximum levels on the dashpote were 70 r/hr at 1" from #10 and 90 r/hr at 1" from #2.
Guide tube #6 was raised to the charging floor level and the radiation levels at 1" were; 2 r/hr at the top, 7 r/hr two feet down, 10 r/hr four feet down, and 15 r/hr at the bottom.
Tr.e filter capsule used for shield tank cavity clean-up was removed and the radiation levels were 7.5 r/hr raximum contact with the side and 2 r/hr contact with the top.
A Tritium concentration in the shield tank cavity water was
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0.1-0.2 uc/ml. The airborne concentration in the general charging floor 3
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area was 2.5 x 10-7 uc/cc. Several samples of the vapor container atmosphere were collected using evacuated chambers and sent to outside laboratories for analysis. These direct measurements have confirmed those obtained from
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. 9 liquid scintillation counting of condensed water vapor and calculation of the airborne tritium concentration based on the room temperature and relative humidity.
Radiation levels from the core barrel assembly vary, depending upon the water level of the shield tank cavity. With the water level at its highest, about 2" of water cover the upper flange and the radiation levels are; 130 mr/hr 1 foot above the flange, 100 mr/hr 3 feet above the flange and general area 70 to lh0 mr/hr. With the water level down (during the inspection), about 19" of the barrel flange was exposed and the radiation levels were: 600-800 mr/hr 1" above the flange, 5-7 r/hr 1" from the gussets, 30r r/hr 3 feet above the flange, and general area, 170-2h0 mr/hr.
During the electrical work on the fuel chute lower lock valve, the radiation levels were; 200-500 mr/hr general area, 500 mr/hr contact valve, 3.5 r/hr contact chute at wall penetration, and 10 r/hr contact 3
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manual drain valve.
Yankee plant personnel radiation exposures as measured by film badge for tht, month of September 1965 were:
Yankee Personnel
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s Average h$2 mrem
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Maximum individual exposure 960 mrem x
N.E. Power Service Company Personnel Average 390 mrem Maximum individual exposure 890 mrem Plant Operations
('s Attached is a summary of plant operation statistics for the x'
month of September 1965 1
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w YANKEE ATOMIC ELECTRIC COMPANY -- OPERATING SUKMY SEFfE:Et 1%$
MONTH YEAR IO LA~ O ELECTRICAL Gross Generation WH 0
826,833,000 h,789,9h9,200 Sta. Service (While Gen. Incl. Losses)
WH 0
$h,h99,983 33h,162,092 Net Generation WH 0
772,333,017 h,h55,787,108 Station Service 0
6.59 6.98 Sta. Service (While Not Gen. Incl. Iosses)
WH 370,h?6 1,266,375 21,06h,826
. Ave. Gen. For Month E
O Ave. Gen. Running W
0 PIANP PERFORMANCE Net Plant Efficiency 0
28.08 Net Plant Heat Rate Btu /WH 12 l$h U
Lbs. Steam / Net WH d.01 Circulating Water Inlet Temp.
0FNot in Service Maximum 0F
)M ni nnim Plant Operating Factor 0
69 99 69 32 Reactor Plant Availability 0
82 33 81 77 10 NTH CORE IV TO DATE 1
NUCLEAR 0
32 3$7 Times Critical HHS 0
8160.27 35,960 96 Hours Critical 0
h9 Times Scrammed Equivalent Reactor Hours @ 600 Wt HRS 0
72h8.h1 26,159 0b WD/mtU Average Burnup of Core 1.
Control Rod Position at Month Ebd REDION MONTH TOTAL BUrHJUP Equilibrium at Group A Rods out-inches INNER Group B MIDDLE Group C OUPER Group D E-6 Borun N 2000 1.
Shutdown for Refueling
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D YANKEE ATOMIC ELECTRIC COMPANY DAILY AVERAGE LCAD for SEPTEMBH1 1965 150 -
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U 3
100 -
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W 50 -
D G
o Plant Shutdown - Continuation of Shutdown No. 79-h-8 0
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