GB2047958A

GB2047958A - Temperature sensors

Info

Publication number: GB2047958A
Application number: GB8009447A
Authority: GB
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1979-04-04
Filing date: 1980-03-20
Publication date: 1980-12-03
Also published as: FR2453473B1; GB2047958B; DE8009380U1; FR2453473A1; DE3013168C2; DE3013168A1

Abstract

A nuclear reactor structure subjected to high and varying temperature is monitored by a pair of temperature transducers embodied therein. The transducers comprise gas filled capsules (1) each having a thermocouple hot junction (5), (19) attached internally to one end wall which is exposed to the environment of the structure. The end wall of one transducer constitutes a diaphragm (2) the temperature perturbations of which are indicative of the surface temperature perturbations of the structure whilst the end wall of the second transducer constitutes a solid barrel (2a) the temperature perturbations of which are indicative of the attentuated temperature perturbations of the mass of the structure. <IMAGE>

Description

SPECIFICATION Nuclear reactor structures This invention relates to nuclear reactor structures.

Nuclear reactor structures, for example the above core structure of a liquid metal cooled fast breeder nuclear reactor, are subjected to high and varying temperatures and it is most desirable to be able to monitor thermal perturbations affecting the structures.

It is an object of the invention therefore to provide in a nuclear reactor structure means for sensing thermal perturbations induced in the structure.

According to the invention a nuclear reactor structure houses a temperature transducer comprising a gas filled capsule having an end wall exposed to the environment of the structure and a thermocouple hot junction attached internally to one end wall thereof, the conductors of the thermocouple extending through the capsule sealingly to penetrate the opposite end wall.

A nuclear reactor structure preferably houses two such transducers, an end wall of a first capsule constituting a diaphragm to which the conductors of the junction are welded whilst an end wall of the second capsule is constituted by a solid barrel and embodies the hot junction. The transducer comprised by the first capsule is capable of detecting thermal perturbations induced in the diaphragm and which are indicative of the thermal perturbations induced in the surface of the structure. The transducer comprised by the second capsule is capable of detecting temperature variations attenuated by a relatively large thermal mass and indicative of attenuated temperature perturbations induced in the mass of the structure.

A nuclear reactor structure embodying the invention is described, by way of example, with reference to the accompanying drawings wherein, Figure 1 is a sectional view of a liquid metal cooled fast breeder nuclear reactor and Figures 2 and 3 are sectional views of temperature transducers.

The construction shown in Figure 1 comprises a fuel assembly 21 submerged in a pool 22 of liquid sodium coolant in a primary vessel 23. The primary vessel is suspended from the roof of a containment vault 24 and there is provided a plurality of coolant pumps 25 and heat exchangers 26 only one of each of the pumps and heat exchangers being shown. The fuel assembly 21 is mounted on a diagrid 27 and housed with the heat exchangers in a core tank 28 whilst the pumps, which deliver coolant to the diagrid, are disposed outside of the core tank. The core or fuel assembly 21 comprises a plurality of sub-assemblies which upstand from the diagrid in closely spaced sideby-side array and is surrounded by a neutron shield 29. Control rods 30 and instrumentation 31 are shown penetrating the roof of the vault and passing down towards the fuel assembly through a core cover structure 32.The core cover structure depends from a rotatable inner plug 33 which is mounted eccentrically in an outer plug 34 rotatable in an aperture in the roof of the vault.

The plug carries a fuelling machine (not shown) which by rotation of the plugs 33, 34 can be arranged to command any fuelling position of the fuelling assembly. The core cover structure 32 carries control rod and instrument guide tubes 35 and provides a hold-down facility for the fuel assembly. During operation of the nuclear reactor the coolant leaving the upper face of the fuel assembly is subject to rapid changes of temperature caused by changes in reactivity in the fuel assembly and because the coolant output from individual sub-assemblies also varies the core cover structure is subject to thermal shocks.

It is therefore desirable to monitor the temperatures of the core cover structure continuously. For this purpose the core cover structure, which is of stainless steel, incorporates temperature transducers of each of the kinds illustrated in Figures 2 and 3.

The transducer shown in Figure 2 comprises a generally cylindrical argon filled capsule 1 of stainless steel having one relatively thin end face or diaphragm 2. A lead 3 of Ni-Cr and one of Ni-Al designated 4, spaced apart at 3mm centres, are welded to the inner surface of the diaphragm to provide a thermocouple hot junction 5 and they extend within stainless steel sheathed mineral insulation 6 sealingly to penetrate the other end face of the capsule by way of a gland 7. The body of the capsule 1 is in two parts 1 a, 1 b, the part la being machined from solid to produce the diaphragm 2 which 0.25 mm thick. The body part 1 b has a flanged extension 8 which houses the gland 7 carrying a gland nut 10.The thermocouple leads 3,4 of the hot junction are insulated by alumina sleeving 11 and connected to corresponding Nl-A1 and Ni-Cr conductors 12, 13 of stainless steel sheathed mineral insulated cable 14. The connections designated 9 are made by twisting and welding the leads and conductors together followed by painting with ceramic insulation. The cable carries an olive 1 5 which cooperates with a seating 1 6 in the gland body to effect a gas type seal. The gland body extends into the capsule and has a transverse end slot which is engaged by a locating tab 1 7 welded to the cable to prevent rotation of the cable when the gland nut is tightened. The capsule is charged with argon during assembly.

The transducer shown in Figure 3 is generally similar to that shown in Figure 1 except that the part 1 a is machined from stainless steel to produce a solid barrel 2a instead of a thin end face. The barrel has 2 bores 1 8 for conducting the sleeved thermocouple leads and are counter bored for housing stainless steel plugs 1 9 to which the ends of the leads are welded. Assembly of the second construction of transducer is similar to that of the first.

The transducers are housed in sockets provided in the core cover structure disposed so that the thermocouple hot junction carrying end faces of the capsules lie flush with the surface of the structure the leads extending to monitoring display instrumentation outside the vault.

Instruments of the first described kind having a thin wall end face monitor the surface temperatures of the core cover structure whilst those of the secondly described kind monitor attenuated thermal variations in the core cover structure.

Claims

1. A nuclear reactor structure housing a temperature transducer characterised in that the transducer comprises at least one gas filled capsule (1) housed within a socket in the structure with one end wall (2) exposed to the environment of the structure and having a thermocouple hot junction (5), (19) attached internally to the one end thereof, the conductors (12), (13) of the thermocouple extending through the capsule sealingly to penetrate the opposite end wall.

2. A nuclear reactor structure according to claim 1 characterised in that the one end wall (2) of the capsule constitutes a diaphragm to which the conductors of the hot junction (5) are welded.

3. A nuclear reactor structure according to claim 1 characterised in that the one end wall (2) is constituted by a solid barrel (2a) and embodies the hot junction (19)

4. A nuclear reactor structure according to claim 1 characterised in that the structure houses a pair of temperature transducers, an end wall of a first capsule constituting a diaphragm to which the conductors of the hot junction are welded whilst an end wall of the second transducer is constituted by a solid barrel and embodies the hot junction.

5. Atemperature measuring instrument substantially as herein before described with reference to Figure 2 of the accompanying drawings.

6. A temperature measuring instrument substantially as herein before described with reference to Figure 3 of the accompanying drawings.