CS244384B1 - Model of pipe end to tube plate of inverted steam generator - Google Patents

Abstract

In the case of the model of the tube end in the tube sheet of an inverted steam generator according to the solution ee, steam is experimentally injected through the injection device 4 of the injection hole, which is located in the tube sheet into the groove, β that is, at the weld point of the heat exchanger tube - tube sheet. In the first case, an insert with a cap is inserted into the heat exchanger tube so that the cap covers the weld of the tube with the tube sheet and the insert limits the relatively small volume of sodium between the heat exchanger tube and the insert, and in the second case, the same solution is used imitating a leak failure of the weld of the heat exchanger tube - tube sheet, but without the use of an insert. The solution can be used primarily by manufacturers of steam generators with sodium coolant.

Description

(54)

SÝKORA JOSEP log .; CASTLE HELENA ing .;

VARVAŇOVSKÁ JARMILA, BRNO; HOUČEK VLADIMÍR, SLAPANICE

Model of the end of the tube to the tube sheet of the inverted steam generator

In the case of the tube termination model of the inverted steam generator according to the solution ee, the steam is injected experimentally by means of an injection orifice injector 4, which is located in the tube sheet into a groove, β, just at the weld location. In the first case, the insert with the lid is inserted into the heat exchange tube so that the lid overlaps the tube weld with the tube sheet and the insert encloses a relatively small volume of sodium between the heat exchange tube and the insert. but without the use of a liner · The solution can be used primarily by the manufacturer of steam generators with a sodium heat carrier.

244 384

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Nuclear power plants with a fast reactor with a sodium heat carrier are designed and built as a three-circuit. In the primary circuit, the active liquid metal flows, in the secondary circuit the inactive liquid metal flows, and in the tertiary circuit water, respectively. steam. A heat exchanger - a steam generator - is inserted between the secondary and tertiary circuit.

Currently, so-called direct steam generators are in operation, where sodium flows in the inter-tube space and water respectively. steam inside the heat exchange tubes and an inverted steam generator in which sodium flows inside the heat exchange tubes and water respectively. steam in the inter-tube space. The advantage of the inverted steam generator over the direct generator is in its increased safety in so-called emergency situations.

In the event of a failure of the heat transfer tube, which separates the inactive liquid metal from water or water. steam, the higher pressure steam penetrates inside the heat exchange tube in which the lower pressure sodium flows. The subsequent chemical reaction occurs in a relatively small volume of sodium.

They are currently designing, designing and experimentally verifying models of the inverted steam generator. The proposed inverted steam generators are U, L, J *, £, C, straight, and other. Sodium flows inside smooth heat exchange tubes, which are anchored into the tube sheets. Water or water flows in the inter-tube space. steam. Proposed steam generators are of cell, macrocell and housing design. In the inverted steam generator, the anchoring area of the tubes to the tube sheet is least favorable in terms of the likelihood of leakage of the heat transfer tube separating the heat transfer media and subsequent sodium-water reaction. In the case of failure of the heat exchange tube in the area of anchoring into the tube sheet or in the case of a weld joint failure of the heat exchange tube - tube sheet, water or resp. steam into the space in front of the tube sheet where the relatively larger volume is filled with sodium. In these cases, the chemical reaction of Na - HgO occurs in a relatively larger volume, which can lead to more extensive damage to the steam generator pressure system.

In order to increase the safety in the area of tube ending into the tube sheet, an inverted steam generator with an insert is proposed, which is inserted into the heat transfer tube and led into the tube sheet space where it is fixedly connected to the tube 2 244 384 by a forge. The proposed solution assumes that the liner will have a favorable character for the safety and durability of the steam generator, in the event of a leakage of the heat exchange tube in the area of anchoring of the tube into the tube sheet, respectively. failure of tightness of the weld heat pipe - tube sheet, water or steam will penetrate into a small volume of sodium. The chemical exothermic reaction of the heat transfer media in this case has a qualitatively more favorable character and consequences than in the case of the chemical reaction of the heat transfer media in a relatively larger volume of sodium in the inter-tube space. However, it is opposed to this advantage that in the case of using a liner in the heat exchange tube of an inverted steam generator, the time to detect any leakage by means of chemical resp. Physical methods and possible further leakage may have a negative effect on the consequences of the failure than would be the case with an inverted steam generator without an insert.

The above-mentioned disadvantages can be overcome by experimental examination on the tube end of the inverted steam generator according to the invention, where steam is experimentally injected through an injection device and injection port located in the tube sheet into a groove in the location of the heat transfer tube-tube sheet weld. This groove results in a tubular space. In one case, a liner with a lid is inserted into the heat exchange tube such that the lid overlaps the weld of the tube exchange tube and the liner delimits a relatively small volume of sodium between the heat exchange tube with the liner. In the latter case, the same solution imitating the leak tightness of the heat exchanger tube-tube sheet is used, but without the use of an insert.

The advantage of the device according to the invention is to ensure the same model conditions as with a real steam generator, as the welding technology of the tube and tube plate, the design and the material are maintained. The groove in the heat exchange tube at the weld location is drilled, resp. performed by electro-spark method.

The injection device is located on the tube plate and can be operated manually or remotely. In the inverted steam generator tube termination model, heat exchanger tubes are not surrounded by water or tubing. steam, but air of the environment respectively. inert gas, which is enclosed in a protective jacket.

An exemplary embodiment of the inverted steam generator tubesheet end model of the invention is shown in the drawing.

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In the experimental verification, steam injection is carried out under the same boundary conditions on the model with and without the insert as with the actual steam generator. By analyzing the measurement results and final metallographic analysis, it is possible to decide on the justification of using an insert into an inverted steam generator as a significant element of increasing safety in the area of anchoring of heat exchange tubes to the tube sheet.

Fig. 1 depicts the model of the end plate of an inverted steam generator without an insert. The supply of sodium 12 is provided to the tubesheet space X, from where it is distributed to the heat exchange tubes X, which are anchored to the tubesheet 2 and the collector Water or the water collector. the steam 16 is fed to the injection device 2 via the injection water inlet 6 ^and is introduced through the injection orifice into the groove χ, which is provided on the heat exchange tube χ and results in the tubular space 1. The thermocouple 11 is continuously measured at the location opposite the groove χ and at the collector 13. The sodium flow 12 in the individual heat exchange tubes χ is measured with a flow meter 15.

Fig. 2 shows the ending pattern of an inverted steam generator with an insert. Sodium 12 is supplied to the tubesheet space X from where it is distributed to the heat exchange tubes χ, which are anchored to the tubesheet 2 and the collector 11. The weld 10 of the heat exchange tube 4 with the tube sheet 2 and in the lid 6 are holes 11 for the flow of sodium 12. the steam 17 is fed to the injection device 2 through the injection water supply 6 ^and is introduced through the injection opening 4 into a groove χ which is provided on the heat exchange tube X and opens into the space between the insert 8 with the lid 6 and the heat exchange tube χ. The temperature of sodium 12 in the tubesheet space X, in the region of the anticipated chemical reaction at the location opposite to the groove χ and in the collector 11 is continuously measured by a thermocouple 14. The flow rate of sodium 12 in the individual heat exchange tubes X is measured by a flowmeter 15.

Claims (2)

OBJECT OF THE INVENTION 244 384 1. An end-of-pipe tube model of an inverted sodium heat transfer steam generator comprising heat exchange tubes anchored to the tube sheet and a water injection device; characterized in that a groove (3) is provided on the heat exchange tube (1) at its anchorage point in the tube plate (2), which is connected to the injection port (4), the injection device (5) and the injection water supply (δ); opens into the tubular space (7). 2. The end tube model of the inverted steam generator according to claim 1, wherein an insert (8) with a lid (9) is inserted inside the heat exchange tube (1) so that the lid (9) overlaps the weld (10) of the heat exchange tube. (1) with a tube sheet (2) and in the lid (9) there are holes (11) for sodium flow (12), the injection water (6) being introduced into the groove (3) and opening into the space between the insert (8) with the lid (9Ϊ and heat exchange tube (1)).