Type Leak Detector Research Articles

Experiments in LEENA facility with modified wire type leak detector layout in large sodium pipelines

Sodium cooled Fast Breeder Reactors (SFRs) are envisaged in the second phase of Indian nuclear power programme. Liquid sodium is used as the coolant in the SFRs due to its favourable nuclear properties and excellent heat transfer properties. Leaks in sodium systems have the potential of being exceptionally hazardous due to the reaction of liquid sodium with oxygen and water vapour in the air. When a sodium leak occurs, the sodium leak rate, the total quantity of sodium leaked and leak detector layout governs the detection time. Other factors to be considered are insulation material packing condition, distance between the leak point and detector, heater layout, pipe geometry, temperature etc. Potential regions of leakage in Fast Breeder Reactor (FBR) sodium circuits are near welds, high stress areas and regions subjected to thermal striping. Early detection of leak is needed for minimizing the quantity of sodium leaked to outside and consequent damages. Three wire type leak detectors (WLDs positioned at 90°, 180° and 270°) working on conductivity principle are used for detecting sodium leak in the large horizontal secondary sodium pipelines of Prototype Fast Breeder Reactor (PFBR). It was found from the upper boundary curve based on LEENA (LEak Experiments in NAtrium) facility experimental results with present PFBR leak detector layout, that a leak rate of 200g/h and above can be detected within 6h. To improve the detection capability, modified leak detector layout was proposed for FBR 800 NB size horizontal secondary circuit pipelines of FBR with seven WLDs positioned at 45°, 90°, 135°, 180°, 225°, 270° and 315° by taking top of pipeline as 0°. It is required to assess the performance of wire type leak detectors along with its layout on large horizontal sodium pipelines and confirm that they are meeting the requirements. LEENA facility was re-commissioned and five sodium leak experiments with modified leak detector layout on large horizontal pipeline were conducted with different sodium leak rates. From the experimental data it was observed that there was considerable reduction in detection time with modified WLD layout. This is due to the reduction in distance between leak point and leak detector (Reduced from 0.63m to 0.31m). From the experiments it was found that a leak rate of 200g/h can be detected in one hour.

Development and deployment of miniature MI type sodium leak detector for FBTR

The energy produced in Fast Breeder Test Reactor (FBTR) is transferred to feed water for generating superheated steam in once-through shell and tube type counter current steam generator (SG). Sodium and water/steam flow in shell and tube side respectively are separated by thin-walls of ferritic steel tubes. Material defects in these tubes can lead to leakage of water/steam into sodium, resulting in sodium water reactions leading to undesirable consequences. Detection of a leak at its inception, therefore, is important for the safe and reliable operation of the reactor. Monitoring hydrogen in sodium, produced during reaction of sodium with the leaked water or steam is a convenient way to accomplish this. Nickel diffuser based instrumentation has been developed for real time detection of steam generator leak of FBTR at Kalpakkam. Though the performance of the system has been satisfactory, the failure of Nickel diffuser cannot be ruled out. This paper deals with the development and deployment of a miniature Mutual Inductance (MI) type leak detector for detection of sodium leak resulting from failure/rupture of the Nickel diffuser tubes in the SG leak detection system in FBTR.

Development of sodium leak detectors for PFBR

The 500MWe Prototype Fast Breeder Reactor (PFBR) is under advanced stage of construction at Kalpakkam near Chennai in India. The wide and high operating temperature, highly chemically active nature of sodium and its reaction with air make the sodium instrumentation complex over the conventional instrumentation. Over the years, traditional instruments such as wire type leak detectors, spark plug type leak detectors were developed and used in different sodium systems. The redundant and diverse leak detection method calls for development of special instrumentation for sodium systems which include sodium ionization (leak) detector for detecting minute sodium leak in addition to those systems based on mutual inductance principle. For detection of sodium leak from reactor Main Vessel (MV), diverse methods are used such as miniature, remotely locatable, Mutual Inductance type Leak Detector(MILD) and specially modified spark plug type leak detector. The design of MILD is suitably modified for detecting leak in double wall pipes and Diverse Safety Rod drive Mechanism (DSRDM). Steam/water leak in steam generator produces hydrogen and leads to high pressure and temperature in the system. Rupture disc is used as a safety device which punctures itself due to sudden pressure rise. To detect the discharge of sodium and its reaction products at the downstream of the rupture disc due to bursting of the rupture disc, cross wire type leak detector has been designed, developed and tested. The selection of the leak detection system depends on the location where leak has to be detected. This paper describes the recent developments carried out in leak detector systems to meet the challenges involved in developing robust sensors for PFBR including miniaturization of leak detectors and the ability to locate or withdraw them remotely through a long guide tube with complex profile.

Performance evaluation of PFBR wire type sodium leak detectors

Wire type leak detectors working on conductivity principle are used for detecting sodium leak in the secondary sodium circuits of fast breeder reactors. It is required to assess the performance of these detectors and confirm that they are meeting the requirements. A test facility by name LEENA was constructed at Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam to test the wire type leak detector lay out by simulating different sodium leak rates. This test facility consists of a sodium dump tank, a test vessel, interconnecting pipelines with valves, micro filter and test section with leak simulators. There are three different test sections in the test set up of length 1000 mm each. These test sections simulate piping of Prototype Fast Breeder Reactor (PFBR) secondary circuit and the wire type leak detector layout in full scale. All test sections are provided with leak simulators. A leak simulator consists of a hole of size one mm drilled in the test section and closed with a tapered pin. The tapered pin position in the hole is adjusted by a screw mechanism and there by the annular gap of flow area is varied for getting different leak rates. Various experiments were conducted to evaluate the performance of the leak detectors by creating different sodium leak rates. This paper deals with the details of wire type leak detector layout for the secondary sodium circuit of PFBR, performance requirement of leak detection system as per codes, description of test facility, experimental procedure, test results of various experiments conducted and details of measurements made on contact resistance of detector after sodium leak. Paper also reviews the experiment conducted in CEA, Cadrache and compares with results of present experimental study.

Assembling, Sodium Bonding, and Bond Testing of EBR-II Fuel Rods

Processing of the EBR-II fuel rods has led to the development of sodium loading, welding, weld inspection, bonding, and bond inspection techniques. Devices such as capacitance discharge welder, pressure type leak detector, impact bonder, and nondestructive eddy current circuitry have been employed. These techniques have been utilized during the manufacturing of the first core loading or have been developed from the experience gained on that production run. The design of the remotely operated fuel reprocessing machinery for the Fuel Cycle Facility in Idaho has been based on these experiences.

A differential pirani type leak-detector with a charcoal trap: Hiroshi Ishii. Electrotechnical Lab., Tokyo, Japan

A differential pirani type leak-detector with a charcoal trap: Hiroshi Ishii. Electrotechnical Lab., Tokyo, Japan

分光分析型洩れ探し器

Preliminary work on a spectral analysis type leak detector is described.The detector consists of a discharge tube, a spectrometer, a photomultiplier and an amplifier. An electrodeless discharge tube which is attached to the vacuum system is operated by a high frequency current of about 100 megacycles modulated by 60 cycles. The emitted light from the discharge tube is dispersed by a constant deviation prism spectrometer and received by a photomultiplier 1P 21. The audio frequency parts of the signals from 1P 21 are amplified and rectified so as to operate a D.C. milliammeter.When each small quantities of air, hydrogen and helium is introduced to the vacuum system through an adjustable leak valve, several peaks corresponding to the spectral lines characteristic of the gases appears in the meter. In the present experiment, the practically detectable leak quantities are about 104mmHg 1/sec for hydrogen and 105mmHg 1/sec for helium.Comparing with the mass spectrometer type leak detector, the new detector has the following features : 1) No need of vacuum system in the detector, 2) Portable and durable constructions, 3) Simple circuit and prompt operation.

大阪大学サイクロンの質量分析計型リーク・デテクターによる洩り探し

As for the mass-Spectrometer type vacuum leak detector, the theory of probe method is virtually applied to, and as a result of the above, it is ascertained that the actual measurement is quite coincident to the theoretical equation of minimum detectable leak flow rate.For tracing any leak Hunting in the Osaka Cyclotron, Shimadzu MS-A type leak detector has been used, and thus in a short time the first Scheduled goal was attained. The leak detector has been attached thereto by means of the backing method, and it proves that the minimum detectable leak flow rate was 1×10-4 lusec.