Twenty years of experience in handling sodium in experimental sodium facilities

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1 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.

2 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

Availability/Capacity Factor (%) -----> Three Stage Nuclear Power Program 95 90 85 80 75 70 65 69 72 67 75 71 79 75 84 80

4 - under construction Scaling to 700 MWe Gestation period being reduced 10 more planned LWRs 2 BWRs operating 2 PWRs

commissioning high power potential Stage - III Thorium Based Reactors 30 kwth KAMINI- operating 300 MWe AHWR- under

3 Availability/Capacity Factor (%) -----> Three Stage Nuclear Power Program 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 PFBRunder 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

4 Fast Breeder Test Reactor 13.5 MWe Flow Diagram of FBTR

5 Prototype Fast Breeder Reactor Flow Diagram of PFBR 5

6 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 Component Testing Absorber Rod Drive Mechanism Fuel Handling Equipments Heat Transfer Studies in LCTR Failed Fuel Location Module Thermal Hydraulic Studies Sub-Assembly Test Loop Ganga Water Loop 1/4 th Reactor Assembly Model (SAMRAT) Pool Hydraulics Loop Components & Instruments Developed Sodium Centrifugal Pumps Electromagnetic Pumps Electromagnetic Flowmeters Sodium Instruments such as level probes, leak detectors, Ultrasonic under sodium scanner

7 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

8 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

9 Large Component Test Rig 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 m 3 /h. Material of construction is Austenitic Stainless steel, grade 316.

10 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

detecting sodium leaks in Main vessel, safety

Experiments in LCTR Permanent Magnet Flow

various locations in PFBR Extended Spark Plug

in main and safety vessels of PFBR Sodium

sodium leak in PFBR Mutual Inductance type

sodium level measurement in various sodium

11 1) In-sodium Sensors developed for PFBR Mutual Inductance type Leak Detector for detecting sodium leaks in Main vessel, safety vessel and double wall pipes of PFBR Major Experiments in LCTR Permanent Magnet Flow Meter for measuring sodium flow rate at various locations in PFBR Extended Spark Plug type Leak Detector for detecting sodium leak in main and safety vessels of PFBR Sodium Aerosol Detector for area monitoring of sodium leak in PFBR Mutual Inductance type discrete and continuous level probes for sodium level measurement in various sodium capacities of PFBR Eddy Current Flow Meter to measure primary discharge flow in PFBR

Major Experiments in LCTR 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.

12 Major Experiments in LCTR 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 3) Testing and Qualification of Under Sodium

High temperature piezoelectric transducers developed for viewing

each of Side Viewing and Downward Viewing Transducers.

13 Major Experiments in LCTR 3) Testing and Qualification of Under Sodium Ultrasonic Scanner of PFBR. 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. (d) Qualification testing of transducers in water and in sodium, Validation in radioactive environment. A reference target inside the reactor for proper alignment of scanner. (b) Protrusion of a subassembly (a) (c) (a) Methodology (b)transducer holder (c) Experimental setup (d) USUSS

Functional tests carried out: Torque measurement, Straightness of travel measurement, Verification of inter seal leak

14 Major Experiments in LCTR 4) Performance Evaluation of Shutdown Systems of PFBR 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 Lower part storage vessels Upper parts in storage room

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

15 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. Major Experiments in LCTR 5) Testing of Inclined Fuel Transfer Machine Testing was carried in air and sodium at two phases primary and secondary IFTM assembly

Major Experiments in LCTR 6) Testing of Electromagnetic

through ALIP Sodium Submersible ALIP DC Conduction Pump

s left hand rule EM pump types DC conduction pump AC

Performance validation of pumps carried out by testing

During sodium testing of ALIP Head Vs Flow, Input power

16 Major Experiments in LCTR 6) Testing of Electromagnetic Pumps Reflux Annular Linear Induction Pump (ALIP) Once through ALIP Sodium Submersible ALIP DC Conduction Pump 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.

Other Sodium Test Facilities SILVERINA LOOP DSRDM magnet testing Transfer arm bearing testing SID performance

an elevation of 19 m from the Test Vessel. A Chimney for inducing the natural draft connected to AHX.

17 Other Sodium Test Facilities SILVERINA LOOP 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. SADHANA LOOP 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. SOWART Self wastage studies were carried out at different steam leak rates in the range of 10-50mg/s Model Cold Trap Testing

Other Sodium Test Facilities SGTF BI-METALLIC LOOP 16,000 h of exposure Mod. 9 Cr.

on material specimens in sodium Qualification of Wire type leak detectors layout

LEENA LOOP Experimental data utilised for FBR SG design Total operating hours 6000.

IN-SODIUM TEST FACILITY LCF and Creep fatigue interaction studies on Mod 9Cr-1Mo

18 Other Sodium Test Facilities SGTF 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 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. LEENA LOOP Experimental data utilised for FBR SG design Total operating hours Development of acoustic leak detection system Flow Induced Vibration of SG tubes IN-SODIUM TEST FACILITY LCF and Creep fatigue interaction studies on Mod 9Cr-1Mo and 316 LN materials & weld joints at C. Creep rupture tests on 316 LN Tribology, thermal striping and fretting and wear studies on material specimens

Major Experiments in other facilities Experiments on Adjacent tube wastage

Estimation of SG heat transfer area margin Flow Induced Vibration studies of SG

Integrated Plugging Indicator Development & Testing of in-sodium and cover gas

19 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 (b) (a) (a) Impingement wastage test section (b) Model SG SGTF (c) Integrated cold trap (c)

Sodium Facility For Component Testing (SFCT) A new sodium loop at

Material of construction is SS 316LN. Sodium inventory is 6 tonnes.

capacity EM pump for testing at high flows.

Objectives Testing and calibration of medium length MI type

In-sodium testing of small and medium size reactor components which are

20 Sodium Facility For Component Testing (SFCT) A new sodium loop at Engineering Hall-I The facility is commissioned in January Material of construction is SS 316LN. Sodium inventory is 6 tonnes. 50 m 3/ h capacity EM pump for heating and cooling circuit 170 m 3 /h capacity EM pump for testing at high flows. 220 kw heater capacity, designed for operation up to 600 C. 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. 20

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

21 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. 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 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

22 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-dioxide, 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.

23 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 m 3 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.

24 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

25 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

26 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.

27 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

28 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.

29 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.

30 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.

EXPERIMENTAL FACILITIES FOR PERFORMANCE EVALUATION OF FAST REACTOR COMPONENTS

EXPERIMENTAL FACILITIES FOR PERFORMANCE EVALUATION OF FAST REACTOR COMPONENTS *S. Chandramouli, V.A.Suresh Kumar, M.Shanmugavel, G.Vijayakumar, V.Vinod, I.B. Noushad, B.Babu, G.Padma Kumar, B.K.Nashine