Induced nuclear reactions: processes – systems – and elements – Reactor protection or damage prevention – Pressure suppression and relief
Reexamination Certificate
2000-03-30
2001-12-25
Carone, Michael J. (Department: 3641)
Induced nuclear reactions: processes, systems, and elements
Reactor protection or damage prevention
Pressure suppression and relief
C376S277000, C376S298000
Reexamination Certificate
active
06333956
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention lies within the field of safety devices for nuclear power plants. The invention relates to a blow-off device for live steam from a nuclear power plant, in which the blow-off device is in communication with at least one live-steam line of the nuclear power plant. The invention also relates to a method of blowing off live steam from a live-steam line of a nuclear power plant.
In a nuclear power plant, steam generated in a reactor pressure vessel or in a steam generator is directed through a live-steam line to a turbine. The reactor pressure vessel and the steam generator are accommodated in a reactor building, which has a safety container surrounded by a protective casing. The turbine is located in a turbine building situated outside the reactor building. A line opening into the atmosphere branches off from the live-steam line upstream of a first stop fitting, as seen in the flow direction. Adjoining that line is a line section with a blow-off control valve and a blow-off stop valve, as well as a section with a safety valve, which is connected in parallel with those valves. The line sections that are connected in parallel open out in a common blow-out line. The blow-out line, possibly together with blow-out lines belonging to other steam generators of the nuclear power plant, leads into a muffler or sound absorber, which has an outlet opening to the atmosphere.
The live-steam line as well as a feedwater line pass through both the safety container and the protective casing of the reactor building. Barriers between a primary circuit leading through the reactor pressure vessel and the atmosphere are therefore valve cones of the safety valve and of the blow-off stop valve and, in the case of a pressurized water reactor, also heating tubes of the steam generator, which separate the primary circuit from a secondary circuit.
In the case of a pressurized water reactor, the steam generated in the steam generator is non-radioactive in normal operation. In the event of a serious incident, damage could occur to the heating tubes in the steam generator, even if that is highly unlikely. As a result, radioactive substances would pass out of the primary circuit of the pressurized water reactor into the live-steam line. In that case, the valve cones of the safety valve and of the blow-off stop valve, together with valve seats, would form a barrier between the primary circuit and the atmosphere.
Even though the technology of valve cones and valve seats has been and is being constantly improved, 100% tightness of the seats cannot be guaranteed, since the possibility of foreign bodies or contaminants being located on the valve seat cannot be ruled out, especially if blow-off has been effected beforehand through the affected valves under the conditions of a serious incident.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a blow-off device for live steam from a nuclear power plant which prevents an escape of radioactive substances into the atmosphere even if inadequate tightness of a safety valve or a blow-off stop valve is assumed, and a method of blowing off live steam from a nuclear power plant which enables live steam contaminated by radioactivity to be blown off from a line of the nuclear power plant without radioactive pollution of the atmosphere if an incident occurs in the nuclear power plant, in which the device and the method overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type.
With the foregoing and other objects in view there is provided, in accordance with the invention, a blow-off device for live steam from at least one live-steam line of a nuclear power plant, comprising a blow-off line for the live steam, the blow-off line in communication with the at least one live-steam line and opening into the atmosphere; a filter disposed in the blow-off line for filtering radioactive substances; and a non-liquid activity holdback agent embedded in the filter. The filter effect may be based on physical or chemical as well as biological principles.
With the blow-off device according to the invention, radioactive substances can be removed from the live steam which has passed, for example, a safety valve or a blow-off stop valve that is not closing perfectly. The filtered live steam can then be blown off into the atmosphere without radioactive pollution of the latter. The same applies to such live steam which, for example when a blow-off stop valve is opened, in particular in order to bring about a pressure balance, is to be deliberately blown off into the atmosphere.
The blow-off line may be formed, for example, by a line which branches off from a line section through which the live steam passes into the atmosphere in normal operation. The branching line, that is the blow-off line, may be provided, for example, with a stop device and is opened, for example, in the event of an incident. It preferably has a fixed filter, so that very long filter sections can be realized in an advantageous manner.
In accordance with another feature of the invention, there is provided a muffler or sound absorber, for example, associated with the filter, the muffler or sound absorber including an inlet opening and a first outlet opening. The combination of the muffler or sound absorber with the filter in one structural unit permits a cost-effective, reliable and simple type of construction of the blow-off device in an advantageous manner.
In accordance with a further feature of the invention, the filter is at least partly integrated in a housing of the muffler or sound absorber. As a result, the construction of the blow-off device including a filter and a muffler or sound absorber is further simplified.
In accordance with an added feature of the invention, the filter is surrounded by a receptacle having a feed opening which can be closed. This results in it being advantageously possible to wet the filter with live steam only in a demand case (e.g. an incident) and to shield it, with the feed opening closed, in normal operation from the live steam to be blown off. In particular, the blow-off line can be closed by closing the feed opening.
In accordance with an additional feature of the invention, the first outlet opening can be closed and the inlet opening can be connected through a filter to a second outlet opening of the muffler or sound absorber. As a result, the live steam can advantageously be blown off into the atmosphere in normal operation through the first outlet opening and in the demand case through the blow-off line containing the filter and through the second outlet opening.
The blow-out lines of the power plant, for example, which are connected to the safety valve or the blow-off stop valve, open into the inlet opening.
In accordance with yet another feature of the invention, there is provided a slide which is movable inside the muffler or sound absorber along an axis and through the use of which the first outlet opening can be closed and/or on which the filter is disposed.
For safety reasons, the movement of the slide is preferably exclusively linear (rectilinear) and not curved or angular. The slide generally refers to a movable, preferably guided system part of the blow-off device. The designation “slide”, for example, therefore also stands for a rider, a carriage, a rolling body or a sliding body. In particular the construction in which the first outlet opening can be closed by the slide and in which the filter is disposed on the slide results in the advantage that both the first outlet opening is closed and the filter is positioned at the desired location in the blow-off line, which is cleared, for example after opening of the feed opening, by a single movement of the slide.
In accordance with yet a further feature of the invention, the axis of the blow-off device is preferably essentially vertical. As a result, the blow-off device is especially suitable for such muffler or sound absorbers in which the live steam is blown off upward.
In accord
Bittermann Dietmar
Laurer Erwin
Model Jurgen
Carone Michael J.
Greenberg Laurence A.
Keith Jack
Lerner Herbert L.
Siemens Aktiengesellschaft
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