Indian Experience in Commissioning,
Operation and Safety of Wet type Spent
Fuel Storage Facilities
B Shreekumar and Kailash Agarwal
Fuel Recycle Group
Bhabha Atomic Research centre
INDIA
PHWR FUEL
BUNDLE
URANIUN OXIDE PELLETS
19 PIN CLUSTER
ZIRCALLOY CLAD
AVERAGE BURNUP-7000 MWD/Te
SPENT FUEL STORAGE TRAY
Arrangement of 2x10
fuel trays inside
shipping cask
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SPENT FUEL STORAGE
KEY PLAN - FUEL POOL BULDING
SECTIONAL ELEVATION-POOL BUILDING
Fuel Storage : Important parameters
 Water quality (pH 6.8 to 7.2, Sp Cond 1uS/Cm,
Turbidity < 1 ppm)
 Pool water activity < 185 Bq/ml
 Pool water level > 3.0 m above top most fuel
 Pool water Temp < 45 deg C
CONSIDERATIONS IN DESIGN OF STORAGE
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Layout :
To consider vehicle air locks for entry and exit
of trailer
 Separation of active and in-active services and
equipment
 Maximum utilization of fuel pool area for
storage
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Capacity : Fuel burn up and stacking density
Shielding: Water depth and wall thickness
CONTD.
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Provision for leak detection and collection either
from liner failure or RCC wall failure
Ventilation system : To maintain negative
pressure inside pool area, filtered supply, HEPA in
exhaust side, RCC stack
Pool water polishing system : To keep pool water
activity low and maintain pool water chemistry
Pool water cooling system : To keep pool water
temperature below 45oC
CODES AND GUIDES ON THE SUBJECT
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AERB Safety Guide No.: AERB/ SG /D-24 Design of Fuel
Handling and Storage Systems For Pressurized Heavy
Water Reactors
ANS 57.7 – 1988: Design criteria for an independent spent
fuel storage installation ( water pool type)
IAEA Safety Series No. 116 1994: Design of spent fuel
storage facilities
IAEA Safety Series No. 117 1994: Operation of spent fuel
storage facilities
IAEA Safety Series No. 118 1994: Safety assessment for
spent fuel storage facilities
IAEA Technical Report Series No. 240 1991: Guidebook
on spent fuel storage
SPENT FUEL STORAGE FACILITY
DM
WATER
PLANT
EXHAUST
VENTILATION
SYSTEM
MAKE-UP
POLISHING
UNIT
STACK
BY 75 Te
EOT CRANE
SPENT FUEL
STORAGE POOL
REPROCESSING
CASK FOR
SPENT FUEL
COOLING
WATER SYSTEM
SUPPLY
VENTILATION
SYSTEM
FEATURES PROVIDED IN SFSFs
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OBE design of pool and building structure
Use of HPC with micro-silica and box type water
proofing of walls & raft
Design load - 30 stack of trays
Leak detection & collection system having 50 zones
Infiltration gallery for maintaining water table below
pool raft with 200% stand by pumps on DG
3 mm SS lining on walls, 6 mm on floor and 20mm for
cask seating area
Single failure proof 75 Te EOT crane for cask handling
Mix of regenerated type MBU & disposable Cation
Provision for handling of trays and fuel bundles on
pool bridge on both sides
FEATURES Contd.
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Tray locators to avoid sliding and for automation
Pull-pull ventilation around pool
VFD drives for ventilation fans for better control &
energy saving
A direct viewing facility from control room for cask
loading / unloading operations
On-line monitoring of pool water chemistry
Monitoring of all critical parameters in SFSF control
room and also in nearby reprocessing plant control
room
FEATURES Contd.
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Redundancy in Polishing system, ventilation system,
Cooling system
Waste storage( LLW and ILW) facility and effluent
transfer system
75 Te Crane, cooling system, exhaust fans ,lighting on
class-III supply and HP monitors and critical
instruments on class-II/UPS
URVA
KAIGA-3 & 4.
SS LINING, LEAK DETECTION &
COLLECTION SYSTEM
SFSF, T&K (TAPS-3&4)
INFILTRATION TRENCH
MATERIAL HANDLING SYSTEMS
1) 75/5 Te EOT CRANE
2) 2 Te POOL BRIDGE
3) 10 Te EOT CRANE
SINGLE FAILURE PROOF CRANE
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Failure of any single component in load path shall
not lead to uncontrolled movement of critical load.
Two load paths; each consisting of gear box, rope
drum, brakes and hooks
Seismically designed girders with anti-toppling
lugs and end stoppers
Analysis for swing of load
Galvanized steel core wire rope
VFD drives for smooth control of speeds
POOL BRIDGE
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Rack and Pinion drive
VFD drives for LT,CT and Hoisting
Provision for Tray handling
Provision for Bundle handling
Safety interlocks for safe handling under min
water level
Provision for automation
POLISHING SYSTEM
POOL COOLING SYSTEM
MUCK CLEANING SYSTEM
VENTILATION SYSTEM
SFSF POOL BUILDING VENTILATION
SAFETY ANALYSIS
1. NORMAL OPERATION
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Radiological safety
Liner leakage
Accidental fall of fuel bundles during handling of
trays
Siphoning of fuel pool water
Build up of activity & personnel exposure
Area contamination / Air contamination
Class-IV Power failure
2. OFF-NORMAL CONDITION
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Black-out scenario
Cooling system failure
Ventilation failure
Swing of 75 Te crane holding the load in seismic
event
A storage tray falling on a stack of spent fuel
bundles
Accidental fall of shipping cask in pool
Fall of stack of trays and bundle failure
Accident management plan is in place in the
event of any seismic event.
COMMISSIONING EXPERIENCE
STEP-BY-STEP COMMISSIONING PROCEDURE
• The fuel pool leak tight integrity has been checked
before and after lining.
• The leak detection and collection headers, SS liners
have been 100 % checked for weld integrity by dyepenetrant test and vacuum box tests.
• The fuel handling equipment like 75 tonne and 10
tonne EOT cranes and Pool Bridge have been load
tested after installation.
• The fuel handling devices and tools are tested under
water with simulated loads to meet design intent.
• The ventilation system is checked for flow balancing
and filters bank efficiency.
COMMISSIONING PROCEDURE contd…
• The low level and intermediate level liquid lines for
waste transfer are tested with hydrostatic pressure
and flow checks.
• All the safety equipment and control room
instruments are calibrated and tested in the field
condition prior to start of operation.
• The shipping cask with tractor-trailer, waste transfer
casks and fuel bundle handling operation trials are
carried out to ascertain the crane reaches and
handling equipment compatibility.
• The class –IV power failures and automatic switch
over to class-III power mode are also tested with main
loads.
• The training of operators has been carried out
through classroom lectures and field training during
construction and commissioning phase.
PROBLEMS EXPERIENCED DURING COMMISSIONING
• Early replacement of HEPA filters
accumulation in construction phase
due
to
dust
• Failure of pool bridge shaft due to misalignment of rails
during first few consignments of shipping casks
• Stuck up of cask lid with body in water and it’s remote
retrieval.
Some of the important Operation and Maintenance
activities in Spent Fuel Storage Facility
•Receipt, handling and storage of Spent fuel from PHWR’S
as per the approved check list.
•Monitoring of the fuel pool water level, temperature and
recording in log book.
•Maintaining pool water level.
•Maintaining pool water temperature below 450 C by
Operation of Fuel pool cooling system and recording various
parameters of Primary cooling water pumps, Secondary
cooling water pumps, Heat exchangers and Cooling tower.
•Maintaining pool water activity below 185 Bq/ml by
operation of Pool water polishing system and recording of
various parameters including Pump discharge pressure,
water inlet/out flow rate, DP across Cartridge filter, Cation
cartridge and MBU etc.
Operation Contd…
•Operation of Muck cleaning unit to clean the floor of the fuel
pool.
•Regular sampling and analysis of Pool water, make up
water, Infiltration well water.
•Physical inspection inside leak detection and collection bay
and ensuring no water collection inside.
•Local verification of alarm status in Area gamma monitors
and Continuous air monitors. Spot air sample analysis
around fuel pool. Changing filter papers for all the
Continuous air monitors. Swipe survey taken at various floor
areas and checking of contamination level. Radiation survey
carried out at various areas.
•Monitoring and recording of supply and Exhaust fans status
including Speed, Bearing temperatures, current, Pressure
drop across HEPA and Prefilter banks etc..
Operation Contd…
•Monitoring and recording of low level and medium level
liquid waste levels in the tanks.
•Collection, segregation, packing and transportation of CAT-I
(Mops, Shoe covers, hand gloves etc) , CAT II / CAT III (
Cartridge filter & Cation cartridge of Pool water polishing unit,
HEPA filters of E2 system and muck cleaning filters) solid
wastes to Waste management facility for safe disposal.
•Pumping and disposal of liquid wastes CAT-I & II arising from
active floor drains, cask decontamination wastes, CAT III
(MBU regenerant waste of Polishing unit) through waste
transfer pipelines to waste management facility.
Operation Contd…
•Operation of DM water plant for fuel pool make up and
also for cask decontamination unit.
•Operation of Infiltration well pump and recording the hour
meter readings.
•Surveillance of Various systems including Health Physics
monitors, Pool water level and temperature instruments,
EOT Cranes, DG sets, Battery banks, Public address
system, Exhaust filter bank efficiency, Air receiver pressure
testing , fire fighting system and functional checks of logic
of ventilation system and infiltration system as per the
technical specification.
Major documents Preserved
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DBRs
Preliminary Safety Analysis Report
Design Reports (DRs) for civil design for pool,
building & stack
DRs for piping, cooling system and ventilation system
Safety manual
QA manual
GA drawings
Technical specifications
Commissioning procedures & Commissioning reports
O&M manuals
Emergency preparedness procedures
Fire order