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IAEA Workshop on Challenges for Coolants in Fast Neutron Spectrum system:
Chemistry and materials
Twenty years of experience in handling sodium in experimental sodium facilities
B. Babu
Scientific Officer ‘H’ and Head – Device Development and Rig Services Division
Indira Gandhi Centre for Atomic Research, Kalpakkam
Department of Atomic Energy, India.
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Presentation layout
• Introduction
• Experimental sodium facilities
• Large component test rig
• Experiments in other sodium facilities
• Sodium loop operation experience
• Operation philosophy
• Impurities in sodium and purification
• Sodium leak detection
• Minor sodium leak incidents
• Sodium fire and extinguishing methods
• Handling of sodium components
• Safety aspects
• Improvements proposed for future facilities
• Summary
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1995-96 1996-97 1997-98 1998-99 1999-00 2000-01 2001-02 2002-03
Av
aila
bilit
y/C
ap
acit
y F
acto
r (%
) --
--->
Stage – I
PHWRs
• 18- operating
• 4 - under construction
• Scaling to 700 MWe
• Gestation period
being reduced
• 10 more planned
LWRs
• 2 BWRs operating
• 2 PWRs operating
Stage - II
Fast Breeder Reactors
• 40 MWth FBTR - Operating
Technology Objectives
realised
• 500 MWe PFBR-
under commissioning
• high power potential
Stage - III
Thorium Based Reactors
• 30 kWth KAMINI- operating
• 300 MWe AHWR- under
regulatory examination
• power potential Very
large.
• Availability of accelerator
driven neutron sources can
convert Thorium on a large
scale
Three Stage Nuclear Power Program
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13.5 MWe
Fast Breeder Test Reactor
Flow Diagram of FBTR
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5
Prototype Fast Breeder Reactor
Flow Diagram of PFBR
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Engineering R & D in Support of PFBR
IGCAR is actively involved in development of Fast reactor technology
Design validation, testing and qualification of various components of FBRs
is achieved through experiments in sodium or water using scaled down
models.
In-sodium experiments are carried out in the different sodium facilities of
IGCAR
Major Sodium Facilities
Large Component Test Facility (LCTR)
Sodium – Water Reaction Test Facility
SILVERINA Sodium Loop
In-Sodium Test Facility
Bi-Metallic Sodium Loop
Steam Generator Test Facility
LEENA Test Facility
SADHANA sodium loop
Thermal Hydraulic Studies
Sub-Assembly Test Loop
Ganga – Water Loop
1/4th Reactor Assembly Model
(SAMRAT)
Pool Hydraulics Loop
Component Testing
Absorber Rod Drive Mechanism
Fuel Handling Equipments
Heat Transfer Studies in LCTR
Failed Fuel Location Module
Components & Instruments Developed
Sodium Centrifugal Pumps
Electromagnetic Pumps
Electromagnetic Flowmeters
Sodium Instruments such as
level probes, leak detectors,
Ultrasonic under sodium scanner
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Sodium Facilities In IGCAR
• Large Component Test Rig: Sodium inventory -100 tonnes
Testing of full scale reactor components
• Sodium Water Reaction Test Facility: Sodium – 10 tonnes
Specifically for sodium water reaction experiment and developmental activities of
hydrogen meters.
• Steam Generator Test Facility – Sodium - 18 tonnes
Testing of Steam Generator model, Regeneration experiment on cold trap
• SADHANA test facility : [LCTR Storage tank]
Testing of simulated model of SGDHR system, DHX, AHX-Type-B
• Thermal Shock Test Facility [SOWART storage tank]
Thermal shock testing of small components
• In Sodium Test Facility [Fatigue Loop and Creep loop] - Sodium - 1 tonne
Material testing
• Bi-Metallic loop - Sodium – 0.5 tonne
Carbon transfer behaviour studies on materials
• SILVERINA sodium loop – Sodium inventory- 1.3 tonnes
Small component test facility
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Large Component Test Rig
• Five test vessels in which
independent test
conditions can be
maintained
• Electro Magnetic Pump
for sodium circulation and
online purification
• Heater Vessel with 200 kW
power immersion heater
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• Commissioned in 1994 – completed more than 20 years of operation
• Cumulative operating hours till date is more than 70,000 h
• Total sodium hold up: 100 tonnes
• Pipe lines and components are provided with surface heaters,
• Sensors
• thermocouples
• wire type leak detectors
• MI type Continuous and Discontinuous level sensors
• Sodium Ionisation detectors.
• PLC based Data Acquisition and Control system is used for monitoring
all the parameters in the control room.
• Maximum operating temperature of the test facility is 550 °C and the
maximum sodium flow rate is 20 m3/h.
• Material of construction is Austenitic Stainless steel, grade 316.
Large Component Test Rig
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Major Experiments in LCTR
Tests/Experiments conducted for PFBR in Sodium
• Development and testing of in-sodium sensors for PFBR
• Calibration of Continuous & Discontinuous Sodium level probes of PFBR
• Testing and Qualification of Under Sodium Ultrasonic Scanner for PFBR.
• Performance testing of Prototype CSRDM
• Performance testing of Prototype DSRDM
• Performance testing of Primary Ramp & Primary Tilting Mechanism of
Inclined Fuel Transfer Machine of PFBR.
• Performance testing of In Vessel Fuel Transfer Machine Transfer arm of
PFBR.
• Testing of Annular Linear Induction Pump, DC Conduction Pump &
Sodium vapor condenser
• Heat transfer and temperature distribution studies in roof slab model and
control plug model of PFBR and studies on effectiveness of cooling circuit
of top shield
• Sub-Assembly wetting and washing
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Mutual Inductance type Leak Detector for detecting sodium leaks in Main vessel, safety
vessel and double wall pipes of PFBR
1) In-sodium Sensors developed for PFBR
Eddy Current Flow Meter to measure primary discharge flow in PFBR
Extended Spark Plug type Leak Detector for detecting
sodium leak in main and safety vessels of PFBR
Mutual Inductance type discrete and continuous level probes for sodium level measurement in various sodium capacities of PFBR
Sodium Aerosol Detector for area monitoring of
sodium leak in PFBR
Permanent Magnet Flow Meter for measuring sodium
flow rate at various locations in PFBR
Major Experiments in LCTR
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2) Calibration of MI type continuous level probe in sodium
• Mutual inductance type Continuous Level Probes for monitoring sodium level in sodium tanks and vessels.
• Probes of active length 6000 mm and total length of 9600 mm.
• During calibration the secondary voltages recorded at constant primary current of 100 mA,
At frequencies from 2 to 4 kHz
Zero level and full level
At temperatures from 200°C to 550°C.
29 nos. each of continuous and discrete probes of PFBR calibrated
Level probe calibration set up erected in TV-1 of LCTR
Major Experiments in LCTR
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• High temperature piezoelectric transducers developed for
viewing protrusion, growth and bowing of the Fuel SA before
Fuel handling
• 4 nos. each of Side Viewing and Downward Viewing
Transducers .
(b)
(c)
(a) Methodology (b)Transducer holder (c) Experimental setup (d) USUSS
(a) Protrusion of a subassembly
• Qualification testing of transducers –
in water and in sodium, Validation in
radioactive environment.
• A reference target inside the reactor
for proper alignment of scanner.
(d)
Major Experiments in LCTR
3) Testing and Qualification of Under Sodium Ultrasonic Scanner of PFBR.
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4) Performance Evaluation of Shutdown Systems of PFBR
Lower part storage vessels Upper parts in storage room
Testing of 3 nos. of DSRDMs and 9 nos. of CSRDMs completed.
Functional tests carried out:
Torque measurement, Straightness of travel measurement, Verification of inter seal
leak tightness, Measurement of Frictional force during translation, Verification of
scram operation & deceleration (CSRDM only), Verification of EM minimum holding
current & response time
Major Experiments in LCTR
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IFTM is for • Transfer of spent fuel subassemblies
from IVTP to EVTP • Loading of fresh subassembly from
EVTP to IVTP The primary side of IFTM consists of • Primary Tilting Mechanism (PTM) • Primary Ramp (PR) • Primary Gate Valve • Shield Plug • PR liner • Rotatable Shielded Leg (RSL) • Hoisting mechanism Secondary side of IFTM consists of • Secondary Gate Valve • Secondary Ramp
• Secondary Tilting mechanism.
• Testing was carried in air and sodium at two phases – primary and secondary
IFTM assembly
Major Experiments in LCTR
5) Testing of Inclined Fuel Transfer Machine
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6) Testing of Electromagnetic Pumps
Reflux Annular Linear Induction Pump (ALIP)
Once through ALIP
DC Conduction Pump
Sodium Submersible ALIP
A.C. Conduction Pump
• EM pumps – Pumping of sodium
• Fleming’s left hand rule
• EM pump types
• DC conduction pump
• AC conduction pump
• Annular Linear Induction pump
• Performance validation of pumps carried out by testing the pump in sodium.
• During sodium testing of ALIP Head Vs Flow, Input power vs. Flow and Efficiency Vs
Flow characteristics are obtained.
• Long term endurance testing also carried out.
Major Experiments in LCTR
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• Self wastage studies
were carried out at
different steam leak
rates in the range of 10-
50mg/s
• Model Cold Trap Testing
SOWART
• SGDHR Scaled down
model
• A Decay Heat
Exchanger
• An Air Heat Exchanger
(AHX) for heat removal
at an elevation of 19 m
from the Test Vessel.
• A Chimney for
inducing the natural
draft connected to AHX.
• Natural Circulation of
sodium was achieved
as per rated conditions.
SADHANA LOOP
Other Sodium Test Facilities
• DSRDM magnet testing
• Transfer arm bearing testing
• SID performance testing
• Eddy current type DSR position
sensor
• Tribological studies on materials
• Sodium aerosol compatibility of
inflatable seal rubber material.
SILVERINA LOOP
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Other Sodium Test Facilities
BI-METALLIC LOOP • 16,000 h of exposure Mod.
9 Cr. 1 Mo. - SS 316 LN
specimens
completed in flowing
sodium
• Self welding experiments on
material specimens in
sodium
LEENA LOOP • Qualification of Wire type leak detectors
layout for PFBR
• Lowest leak simulated is 214 g/h
detected in 50 minutes
• Maximum quantity of sodium leaked
1.3 kg -detected in 6 h (leak rate
222g/h)
• 100 g/h to be detected in 20 h.
SGTF
• Experimental data utilised for
FBR SG design
• Total operating hours 6000.
• Development of acoustic leak
detection system
• Flow Induced Vibration of SG
tubes
• LCF and Creep fatigue interaction
studies on Mod 9Cr-1Mo and 316 LN
materials & weld joints at 550 – 600˚C.
• Creep rupture tests on 316 LN
• Tribology, thermal striping and fretting
and wear studies on material specimens
IN-SODIUM TEST FACILITY
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Major Experiments in other facilities
• Experiments on Adjacent tube wastage studies at different steam leak rates
• SG endurance test at rated conditions
• Estimation of SG heat transfer area margin
• Flow Induced Vibration studies of SG tubes
• Fatigue and creep experiments
• Testing of Integrated Cold trap and Integrated Plugging Indicator
• Development & Testing of in-sodium and cover gas hydrogen meter
(a) Impingement wastage test section
(b) Model SG – SGTF
(c) Integrated cold trap
(a)
(b)
(c)
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A new sodium loop at Engineering Hall-I
The facility is commissioned in January 2017.
Objectives
• Testing and calibration of medium length MI type
continuous/discrete level probes and RADAR level probes.
• In-sodium testing of small and medium size reactor components
which are part of reactor.
• Sodium freezing studies simulating the secondary circuit of
future FBRs.
• Performance testing of different types of EM pumps and
flowmeters.
Sodium Facility For Component Testing (SFCT)
Material of construction is SS 316LN.
Sodium inventory is 6 tonnes.
50 m3/h capacity EM pump for heating and cooling circuit
170 m3/h capacity EM pump for testing at high flows.
220 kW heater capacity, designed for operation up to 600 °C.
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Sodium Technology Complex (upcoming facility)
• Qualification and Testing of CSRDM/CSR and DSRDM/DSR with improved safety features
• Qualification of third shut down system for reactor operations
• Testing of any other lengthy components of FBR-1 and 2. • Under Sodium Ultrasonic Scanning System & Sweep Arm
Scanner, Developmental studies on In Vessel Under
Sodium Examination techniques for in service inspection.
• Maximum Operating Temperature: 550 °C.
• Material of Construction: AISI 316 LN • Three test vessels • 50 m3/h Annular Linear Induction
Pump • Sodium Purification Circuit • Heating & Cooling systems • Interconnecting pipe lines of varying
sizes
• High bay of 40 m length, 21 m width and 43 m height
• Large sodium test facility • Full scale assembling of full scale
reactor components • Air test facility, Sodium cleaning,
chemical cleaning • Dismantling and safe storage of
advanced shut down mechanisms. • 25T & 10T capacity cranes for high
bay • Electrical Power Requirement : 4.8
MW
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Sodium Loop Operation Experience
Operation philosophy
• An established operating sequence followed meticulously.
• Key operational sodium parameters such as the flow, temperature and purity
are monitored and maintained
• Sodium purity maintained at reactor grade by cold trap
• Plugging runs taken weekly to monitor and maintain the oxygen level less
than 2 ppm.
Impurities in sodium & purification
• Impurities (Ca, O, H and C) ingress into sodium from air, moisture, Carbon-di-
oxide, oils, and greases.
• Due to reactive nature of sodium, Oxygen would be present not only as
dissolved oxide, but also as surface coating (solid oxide).
• Even though carbon solubility is low, carbon can be present as dispersed
particulates.
• Periodic sampling of loop sodium is carried out annually/ between test
campaigns using the overflow type sodium sampler
• Impurity levels of oxygen, carbon and trace elements determined by
chemical analysis.
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Sodium Loop Operation Experience
Sodium leak detection
• Liquid sodium reacts violently with air / water.
• It requires a leak tight containment and specialized sensors to detect leak in
the incipient stage itself to ensure safety.
• Leakage of sodium can be detected in multiple ways
• Sodium aerosol detection
• Sodium Ionisation Detector (SID)
• Sodium leak detection
• wire type
• spark plug type
• Mutual Inductance type Leak Detector
• SID detects minute quantity of sodium leak and tests demonstrated that it can
detect 1 mg of sodium per m3 of carrier gas instantaneously.
• Wire type leak sensors detect leak in the pipelines
• Spark plug type leak sensors detect the leak in sodium capacities, bellow
sealed valves and double envelope.
• MILD works on the principle of decrease in mutual inductance between two
coils when sodium surrounds it.
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Sodium Loop Operation Experience
Minor sodium leak incidents
• Incidence of leak in LCTR - less
• Maximum sodium leak was 2.8 kg – from sodium to air heat exchanger due to
failure of a finned tube to tube sheet weld joint.
• Other sodium leaks < 100 g in bellows sealed valves due to stress corrosion
Sodium fire and extinguishing methods
• Sodium fire is characterised by short flame golden yellow in colour and dense
white oxide smoke.
• Sodium oxidizes spontaneously in air, with the evolution of heat. As sodium
temperature increases, the rate of oxidation also increases, resulting in
sodium catching fire.
• Sodium fire extinguished by
• application of dry chemical powder.
• Flooding with Argon or nitrogen to smother the fire. This method is slow
and effective but is difficult in inaccessible areas.
• Blanketing or oxygen starvation
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Sodium Loop Operation Experience
Handling of sodium components
• During introduction and removal of components into Test vessel - positive
pressure and continuous Argon purging are maintained to eliminate the
ingress of atmospheric air into the system.
• Cleaning of sodium exposed components is necessary for reuse of
components and its safe storage.
• Cleaning methods
• involving chemical reactions - dangerous and the resulting phenomena
are complex.
• Alcohol and thermo fluid oil - piping and small components like valves.
• Dry steam along with nitrogen purging
• Jet of water - parts with very simple geometry
• Process of carbon dioxide bubbled through hot water – Large
components
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Safety Aspects
• Operation of the rig is carried out based on approved technical specifications
and by trained manpower.
• Dyke of 0.6 m height provided around the storage tanks in dump pit - to
avoid entry of water into the pit under conditions of inundation
• Dump tanks and all other sodium system components are of helium leak tight
construction
• Floor area and side walls (upto 2m) inside dump pit are steel lined with 5 mm
thick MS plate – to avoid contact / reaction of sodium with concrete
• Accumulation of small quantity of water over long periods under the MS liner
removed using a small pump.
• Water level in the sump is indicated by a level detector and in turn linked to a
level alarm.
• All the test vessels are provided with over flow lines which are linked to dump
tank.
• Covered leak collection trays are provided below test vessels to collect the
leaking sodium and extinguish the fire by passive means.
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Safety Aspects
• All the major capacities like sodium storage tanks and test vessels are
provided with wire type leak detectors.
• Povisions are made to handle two types of fires - sodium metal fire and
conventional fires.
• Proper functioning of all the instrumentation systems, safety inter locks,
dump valves, sodium leak detection system, diesel generator operation, Un
Interrupted Power Supply (UPS) and battery banks are checked periodically
as per operation procedure and technical specifications.
• Any significant event / leak was analysed and corrective action taken.
• All industrial hygiene and safety requirements as stipulated in the Atomic
Energy (factories) rules are complied with during all operations in the sodium
facilities.
• Periodic review / inspection by regulatory bodies
• Preventive / breakdown /surveillance tests were meticulously followed with
approved procedure
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Improvements Proposed For Future Facilities
• Material of construction: AISI 316 LN is better compared to AISI 316.
• Storage tanks: vertical tanks due to easier design, low thermal shocks and
easier supporting.
• Cold trap: Larger capacity for faster purification after experiments
• Operating experience of EM Pumps has been satisfactory and suggested to
use ALIP in future facilities.
• Recommended to have a level probe in the priming vessel for the priming of
the pump
• Failure of 50 % of the heaters in vertical Heater Vessel [HV] had occurred
after 15 years of operation. So a vertical HV with additional heaters with
dished ends will be suitable.
• Alternate dump paths for the large sodium capacities should be provided.
• Mineral Insulated Sheathed heaters shall be used as surface heaters.
• Unbreakable bead type sleeves to be used to avoid spurious leak signals
• At the outlet of the Plugging indicator blower, a smoke detector and sodium
ionization flute pipe for aerosol detection is recommended.
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Improvements Proposed for Future Facilities
• Periodical check of the leak port of bellows sealed valves for any blockage
like foreign particles and cleaning ensures prompt leak signal
• Cleanliness shall be maintained to reduce the probability of blockage of the
SID sampling flute holes and frequent surveillance/ cleaning of the flute pipes
is necessary.
• Mutual Inductance type discrete sensors instead of Resistance Type Level
Probes to be used.
• Air drier unit needs to be utilized in the compressed air circuit to reduce the
moisture carryover to the solenoid actuated pneumatic valves.
• Diesel Generator set shall be positioned at a higher elevation on a pedestal
above FFL to take care of any revision in the DBFL in future.
• Single crane in high bay lead to queuing of the experimental activities. Two
cranes of different load carrying capacities are recommended.
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Summary
• Comprehensive picture of the Sodium facilities in operation and planned at
IGCAR are given
• Large Component Test Rig was operated successfully for more than 20
years without any major incidents.
• PFBR components were tested in sodium, qualified and installed in the
reactor.
• Experiments on R&D for development of sodium technology continuously
pursued for future FBRs
• In-sodium sensors and devices were developed and tested for FBR
applications
• Experience gained during the course of operation of LCTR.
• Experience gained on methods of handling of components for testing in
sodium and effective cleaning thereafter for reuse
• Feedback of the experience provided as input to the design of new sodium
test facility.
• Overall experience in operating the sodium loops at high temperature has
given us the confidence to continue further experiments and design and
commissioning of new sodium facilities.