Post on 02-Jan-2016
description
HATCH UNIT 1CONDENSER HOTWELL DAMAGE
& LONG CYCLE CLEANUP VALVE LEAKAGE
FORCED OUTAGES JAN 2013 & OCT 2013
1A MAIN CONDENSER HOTWELL2012 REFUELING OUTAGE
Divider wall section broken
1A MAIN CONDENSER HOTWELL2012 REFUELING OUTAGE
1A MAIN CONDENSER HOTWELL2012 REFUELING OUTAGE
False bottom cracks on Southeast corner tube sheet supports (8)
1A MAIN CONDENSER HOTWELL2012 REFUELING OUTAGE
Divider wall separated from hotwell floor False Bottom topside
1A MAIN CONDENSER HOTWELL2012 REFUELING OUTAGE
Cyclic fatigue due to large variations in circwater temperatures
Condenser design deficienciesCorrective actions:
Repair to previous condition System Engineer to identify condenser design deficiencies
and initiate design changes
INITIAL CAUSE DETERMINATION
Banging sounds identified from 1A HotwellSame general area as previous damaged areaODMI created, evaluated to most likely be an FME
issue (Grating)Sounds only heard when operating at or near 100%
power
JUNE 2012
Unit 1 Forced shutdown due to high conductivityCondenser tube rupture, circwater entered the
hotwell24 hours before planned Unit 2 refueling outage
FEBRUARY 2013
1A HOTWELL DAMAGE
1A HOTWELL DAMAGEFEBRUARY 2013
FALSE BOTTOM DAMAGE
TUBE RUPTURE
No PMs on hotwell level transmitters“A” transmitter crosstied to 1B hotwellLevel recorder displayed 1B hotwell level twice1A hotwell level maintained too highLong cycle cleanup valve leakby
CAUSE DETERMINATION
1A Hotwell72”+
1B Hotwell~40”
HOTWELL LEVEL
1N21F165 valveOpen during startup onlyShort cycles condensate/feedwater from the
condenser hotwell, through the condensate demins, through all FWHs, then back to the condenser hotwell
Also used during low power operations for RWL control
LONG CYCLE CLEANUP
1N21F16514” CCI DRAG VALVE
LONG CYCLE CLEANUP FLOWPATH
F romC ondB oo s te rP um pD is ch
AO
Feedwater (~350 degrees, 1000 psi) short cycled back to hotwell
Drains below hotwell false bottom (under water)Result:
Flashing of feedwater within hotwell Water hammer inside hotwell
1N21F165 LEAK BY EFFECTS
“A” level transmitter valved back to 1A hotwellTransmitters recalibrated1A hotwell level loweredStopple valve plug considered, but rejected
~75 REM dose projectionAugust & September, patches placed on valve body
due to external leakage
MARCH – OCTOBER 2013
External leakage exceeded the capacity of the conbay floor drain sumps
Shutdown required as flooding neared the 3” setpoint to trip circwater pumps
VALVE BODY BLOWOUT
~1” THOUGH BODY HOLE2” VALVE BODY
REPAIRS7” X 7” X 2” PLATE
Inadequate valve designNo PMs (installed mid 1990’s)Leaking upstream valves Inadequate thermal performance monitoring
No temperature indication downstream of 1N21F165
CAUSES
Since 2007, both Unit 1 RFPT RPMs were noted to have increased by about 150 RPMs Indications of feedwater being short cycled to the hotwell. RPMS
increased to maintain RWL Thermal performance trends of upstream 1N21F027A/B
valves were not fully understood, and were not acted upon Indicated leakby from those valves
PMs on 1N21F027A/B moved out of 2012 refueling outage with little technical justifi cation
Inadequate ACD from 2012 condenser damage Incorrect assessment of June 2012 banging noises in ODMI No action taken from increasing off gas fl owrates, as
recommended in the ODMI Possibility of external valve leakage not identifi ed, despite
similar occurrences in similar applications
MISSED OPPORTUNITIES
Need PMs on all high energy source drains to condensers FWH high level dump valves Feed Pump min flow valves Long cycle Cleanup valves
Thermal Performance monitoring Permanent thermocouples Heat gun
UT thickness measurements for suspect valvesHotwell level
False bottom impacts PMs for Level Controls
LESSONS LEARNED
QUESTIONS?