Flow Mixing T-Unit of Reactor Volume Control System

Abstract

Primary circuit auxiliary systems. The invention provides integrity and normal operation of the T-unit, including cases when the unit operates under abnormal conditions. The flow mixing T-unit of reactor volume control system which includes a T-piece connected with two ends to the bypass line carrying the coolant of one temperature, and with the additional opening to the makeup system pipeline carrying the coolant of a different temperature under emergency and an insert which separates the coolant flows of different temperature, the insert is installed upstream the coolant flow in the bypass so that its outer part is located upstream the coolant inlet into the T-unit, and its inner part is cantilevered inside the T-unit and forms a tube with openings in the area of the T-piece. The T-unit is provided with an adapter mounted at its outlet and forming, together with the insert, a coaxial channel for coolant flow.

Claims

1. Flow mixing T-unit of reactor volume control system which includes a T-piece connected with two ends to the bypass line carrying the coolant of one temperature, and with the additional opening to the makeup system pipeline carrying the coolant of a different temperature under emergency and an insert which separates the coolant flows of different temperature: wherein the insert is installed upstream the coolant flow in the bypass so that its outer part is located upstream the coolant inlet into the T-unit, and its inner part is cantilevered inside the T-unit and forms a tube with openings in the area of the T-piece. The T-unit is provided with an adapter mounted at its outlet and forming, together with the insert, a coaxial channel for coolant flow.

2. A T-unit as defined in claim 1, wherein the inner surface of the outer part of the insert is shaped as a reducer.

3. A T-unit as defined in claim 1, wherein the openings in the insert tube are elliptically shaped.

Description

[0029] The drawings show the flow mixing T-unit of reactor volume control system, where

[0030] FIG. 1 shows the unit as an assembly,

[0031] FIG. 2 shows the distribution of the temperature field over the surface of a standard T-unit, and

[0032] FIG. 3 shows the distribution of temperature field over the surface of the T-unit proposed.

[0033] As shown in FIG. 1, the flow mixing T-unit of reactor volume control system comprises a T-piece (1), an insert (2), the outer part (3) of which is connected to the bypass pipeline carrying hot coolant flow (not shown in the drawing), and the inner part (4) is located inside the T-piece and has openings (5). The unit is provided with an adapter (6) mounted between the T-piece (1) and the bypass pipeline for removal of hot coolant (not shown in the drawing). The makeup pipeline (7), which carries cold coolant flow under emergencies, is connected to the additional opening of the T-piece.

[0034] During operation, water is taken from the reactor coolant pipeline, it flows to the regenerative heat exchanger, heats the makeup water; and the makeup water flows to the RCP. If the heat exchanger operates in the normal mode, there will be no problems with the T-unit since the makeup water temperature is comparable with the temperature of water in the bypass and, therefore, no temperature stress is produced.

[0035] In the event of an accident, the makeup water ceases to get heated, and when entering the RCP branch (via the makeup pipeline) it produces a temperature gradient in the heat exchanger and, consequently, creates temperature stresses in the T-piece. In addition, a decrease in the makeup water temperature is also possible in different, not only emergency, operating modes of the reactor plant including loss of power and spurious actuation of the reactor emergency protection system.

[0036] In this case the cold makeup water gets into the T-piece (1) via the makeup pipeline (7) and then to the coaxial channel between the adapter (6) and the insert (4), and after it gets partially mixed with the hot water coming through the reducer of the outer part (3) of the insert (2) from the bypass, gets finally mixed with the flow entering through the openings (5) in the insert (2) tube. This results in rapid heat exchange between the cold makeup water and hot water entering from the bypass, which ensures equalization of temperatures of the flow passing through the T-piece as shown in FIG. 3.

[0037] Therefore, use of the insert 2 in the T-unit ensures mixing of hot and cold coolant without generating significant temperature gradients at the makeup and bypass pipelines connection. In addition, the effect of relatively high temperature gradients falls on the insert (2), the failure of which does not pose such a threat as T-piece (1) destruction and can be easily rectified by replacing the insert (2) with a new one.

[0038] Numerous studies and calculations carried out by the authors have shown (see FIG. 2 and FIG. 3) that the proposed design makes it possible to ensure the integrity and normal operation of the T-unit in case of its abnormal operation due to retention of its integrity by reducing high- and low-frequency temperature fluctuations and related cyclic stresses.