Reactor system with a lead-cooled fast reactor

Abstract

Steam generators are in the form of tubular heat exchangers in which molten lead coolant flows within the pipes, while the water-steam flows in a space between the pipes, the steam generators are arranged in separate boxes and communicate with the reactor cavity by means of circulation conduits for raising and discharging the lead coolant, the steam generators and most of the circulation conduits and are arranged higher than the level of the lead coolant within the reactor cavity, and the circulation pumps are arranged within the reactor cavity on the circulation conduits and for raising the hot lead coolant, and a technical means is provided for ensuring natural circulation of the lead coolant through the reactor core when the circulation pumps are switched off. The specific volume of lead coolant per unit of power of the reactor is reduced and the safety of the reactor is increased.

Claims

1. A reactor system, comprising a reactor cavity, separate boxes, and main circulation conduits extending between the reactor cavity and the separate boxes, the reactor cavity having an upper cover and a shell-ring dividing a downcomer section and a riser section of a lead coolant circulation circuit within the reactor cavity, and disposed within the reactor cavity are a reactor having a reactor core, lead coolant having a lead coolant level in the riser and downcomer sections, and main circulation pumps for the lead coolant, and disposed within the separate boxes are steam generators, wherein the lead coolant circulates through the steam generators within pipes and water-steam circulates through the steam generators in spaces between the pipes of the steam generators, and the steam generators are arranged in the separate boxes higher than the lead coolant level of the riser and downcomer sections, the steam generators are in communication with the reactor cavity via the main circulation conduits, the main circulation pumps are mounted within the reactor cavity on the main circulation conduits to pump the lead coolant from the riser section into a top of the steam generators and through the pipes of the steam generators, and the main circulation conduits return the lead coolant discharged from the pipes of the steam generators and from a bottom of the steam generators into the downcomer section, and a device is arranged within the reactor cavity for lead coolant natural circulation through the reactor core in case the main circulation pumps are switched off, and said device has the form of holes made in the shell-ring within the reactor cavity, and a means for minimizing coolant flow through said holes when the system operates under normal operating conditions, wherein said means for minimizing coolant flow comprises auxiliary pumps and conduits in communication with the holes in the shell-ring and the auxiliary pumps being configured to provide back pressure at the holes minimizing coolant flow through the holes when the system operates under normal operating conditions.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a reactor system scheme according to the present invention.

(2) FIG. 2 is a scheme of the first embodiment of a device minimizing coolant flow in a system under normal operating conditions via holes provided for intrinsic coolant circulation when circulation pumps are switched off.

(3) FIG. 3 is a scheme of the second embodiment of a device minimizing coolant flow in a system under normal operating conditions via holes provided for intrinsic coolant circulation when circulation pumps are switched off.

EMBODIMENTS OF THE INVENTION

(4) A reactor system comprises a reactor cavity (1) with an upper cover (2), an arranged within the cavity (1) reactor (3) having an active zone (4), steam generators (5) arranged within separate boxes (6), circulation pumps (7), circulation conduits (8) and (9), and actuating mechanism systems and devices for reactor for starting up, operating and emergency shutting down (not shown on the scheme). The steam generators (5) made in the form of tubular heat exchangers are communicated with the reactor cavity (1) by means of circulation conduits for rising (8) and discharging (9) lead coolant (10) and are arranged higher than the coolant cold level (11). Impellers of the circulation pumps (7) are mounted within the reactor cavity (1) below the lead coolant (10) hot level (12).

(5) The steam generators (5) are made so that the lead coolant flows within the steam generator pipes from top to bottom. Secondary circuit water flows into a steam generator through a lower pipe (28), and steam is discharged via an upper pipe (27).

(6) According to the particular embodiment, the system comprises a technical means for lead coolant intrinsic circulation through the active zone (4) when the circulation pumps (7) are switched off. This means can be made, for example, in the form of through-holes (13) made in a shell-ring (14) dividing a riser (15) and downcomer (16) sections of the lead coolant circulation circuit within the reactor cavity (1).

(7) The device minimizing lead coolant flow also can be made (FIG. 3) as an auxiliary pump (18) pumping the coolant out of the riser section (15) into the downcomer section (16) of the coolant circulation circuit within the reactor cavity (1).

(8) Each steam generator (5) has a steam discharge device (19) for steam discharge when the coolant temperature rises higher than the allowed level, and a steam discharge device (20) for steam discharge out of the box (6) into the atmosphere. A gaseous chamber (21) of the reactor cavity (1) and gaseous chambers (22) of the steam generator (5) boxes (6) are separated from each other by a sealed device (23).

(9) Lead coolant circulation within the primary circuit of the reactor system is performed as follows. The coolant by means of the circulation pumps (7) is pumped out of the reactor riser section (15) via rising circulation conduits (8) into the top portion of the steam generator (5), then via the discharge circulation conduits (9) it flows into the downcomer section (16) of the lead coolant circulation circuit within the reactor cavity (1). This coolant from the downcomer circulation section (16) flows into the active zone (4) where it is heated in the result of contact with fuel element surfaces. After that, the coolant is transferred to the circulation pumps (7), thus closing the circulation circuit under normal system operating conditions.

(10) The amount of lead coolant within the reactor cavity (1) and steam generators (5) is calculated so that in the case of circulation conduits (8) and (9) depressurization or steam generator tightness failure the lead coolant level inside the reactor cavity (1) would still be sufficient for cooling the active zone (4) by means of intrinsic circulation.

(11) Once the circulation pumps (7) switched off, the coolant is completely discharged from the steam generators (5) into the downcomer section (16) of the coolant circulation circuit within the reactor cavity (1), flows into the active zone (4) and next into the riser section (15) of the circulation circuit. In addition, the difference between cold (11) and hot (12) coolant levels is reduced and the coolant flows from the riser section (15) of the circulation circuit into the downcomer section (16) via the through-holes (13) made in the shell-ring (14), thus closing under emergency conditions the lead coolant (10) intrinsic circulation circuit.

(12) In order to compensate flowing the coolant via the holes (13) under normal operating conditions, can be used a device (FIG. 2) in the form of a bypass (17) connecting the riser section of the circulation conduit (8) with the riser section (15) of the circulation circuit via holes (24) and with the downcomer section (16) of the circulation circuit via the holes (13). When the circulation pump (7) is under operation, the major part of coolant flow rate via the holes (24) made in the bypass (17) conduit enters the section (15), and the smaller part of this flow rate is distributed into the downcomer section (16) of the circulation circuit via the holes (13). When the circulation pumps (7) are switched off and cold (11) and hot (12) levels are equalized, coolant intrinsic circulation establishes.

(13) The device for coolant flow compensation, shown in FIG. 3, can be made as an auxiliary pump (18) and a conduit (25) connecting the riser (15) and downcomer (16) sections of the coolant circulation circuit via the holes (13). When the pump (18) is under operation, the pressure inside the conduit (25) increases, thus preventing the coolant to flow from the downcomer section (16) into the riser section (15) of the circulation circuit. Pumps (18) can comprise flyweights which contribute to coolant intrinsic circulation when the circulation pumps (7) are switched off.

(14) The semi-integral structure of the system and arranging inverse steam generators (5) higher than the lead coolant level present in the cavity (1) allows the lead coolant to be fully discharged into the reactor, thus protecting the system from coolant freezing in the case of accidents accompanied with secondary circuit steam conduit ruptures, and significantly facilitating deposit washing out in the steam generator pipes.

(15) The use in a reactor system of the inverse steam generators (5) can greatly increase the reliability thereof, since in this case steam generator pipes (26) are subjected to external pressure of secondary circuit coolant (water-steam). Also, in the case of an emergency lead coolant temperature rise upstream the steam generators (5), the pipes lose their stability and instead of being damaged (which is the case for direct heat exchangers) they collapse, thus merely completely preventing active coolant (10) flowing out the circuit boundaries and entering water-steam into the lead coolant circulation circuit. The steam generators (5) are provided with active and passive steam discharge devices which limit the accident effects and exclude the risk of environmental release of nuclear substances.

INDUSTRIAL APPLICATION

(16) In this way, the practical use of the inventive design of the reactor system will significantly reduce the amount of lead coolant and increase the reliability and safety of the reactor system under normal operating conditions and in the case of emergency.