Patent Application
20140072089
1. Field of the Invention
Example embodiments relate generally to nuclear reactors, and more particularly to a method and system for an alternative boiling water nuclear reactor (BWR) containment heat removal. The cooling system may be used to passively cool the suppression pool via natural convection circulation. The system may be particularly beneficial in the event a plant emergency that causes plant electrical power to be disrupted, or normal cooling of the suppression pool to otherwise become impaired. The cooling system may also be used by the suppression pool to supplement the conventional residual heat removal system.
2. Related Art
The pool 2 is conventionally cleaned and cooled by the residual heat removal (RHR) system of the BWR plant. During normal (non-accident) plant conditions, the RHR system can remove water from the suppression pool 2 (using conventional RHR pumps) and send the water through a demineralizer (not shown) to remove impurities and some radioactive isotopes that may be contained in the water. During a plant accident, the RHR system is also designed to remove some of the suppression pool water from the suppression pool 2 and send the water to a heat exchanger (within the RHR system) for cooling.
During a serious plant accident, normal plant electrical power may be disrupted. In particular, the plant may be without normal electrical power to run the conventional RHR system and pumps. If electrical power is disrupted for a lengthy period of time, water in the suppression pool may eventually boil and impair the ability of the suppression pool to condense plant steam and reduce containment pressure.
In a plant emergency, use of the RHR system may cause highly radioactive water (above acceptable design limits) to be transferred between the suppression pool and RHR systems (located outside of primary containment). The transfer of the highly radioactive water between the suppression pool and RHR system may, in and of itself, cause a potential escalation in leakage of harmful radioactive isotopes that may escape the suppression pool. Additionally, radiation dosage rates in areas of the RHR system could be excessively high during an accident, making it difficult for plant personnel to access and control the system.
Example embodiments provide a method and/or system for an alternative Boiling Water Reactor (BWR) nuclear reactor containment heat removal. The cooling system may include cooling coils in an isolation condenser that may be located at an elevation above the suppression pool. Inlet and outlet pipes may be used connect the suppression pool and isolation condenser to establish a natural convection flow to passively cool suppression pool water.
The above and other features and advantages of example embodiments will become more apparent by describing in detail, example embodiments with reference to the attached drawings. The accompanying drawings are intended to depict example embodiments and should not be interpreted to limit the intended scope of the claims. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted.
Detailed example embodiments are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. Example embodiments may, however, be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein.
Accordingly, while example embodiments are capable of various modifications and alternative forms, embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments to the particular forms disclosed, but to the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of example embodiments. Like numbers refer to like elements throughout the description of the figures.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it may be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.).
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
The cooling coils 40 may be connected to the suppression pool 2 via outlet and inlet pipes 22/24. The outlet pipe 22 may include a manually operated outlet isolation valve 26 that opens and closes the outlet 22 between the isolation condenser 20 and the suppression pool 2. The inlet pipe 24 may also include a manually operated inlet isolation valve 28 that opens and closes the inlet 24 between the isolation condenser 20 and the suppression pool 2. The inlet/outlet isolation valves 26/28 may be manually operated to ensure that external power need not be required to operate the ABCHR system 30.
An outlet pipe discharge point 22a (at the suppression pool 2) of the outlet 22 may be positioned at a location that is at or near a top elevation of the suppression pool 2. Preferably, the outlet discharge point 22a may be located above the normal water level 2a of the suppression pool 2. This ensures that only hot steam and/or water exits the suppression pool 2 via a natural convection flow to be condensed by the cooling coils 40. Likewise, an outlet pipe entry point 22b of the outlet 22 may be located at or near a top elevation of the isolation condenser 20. The outlet 22 may also be connected at or near a top elevation of the cooling coils 40. This ensures that the hot steam/water entering coils 40 may be condensed and drain (via gravity) out of the coils 40 and back into the suppression pool 2. By locating the outlet pipe entry point 22b near a top elevation of the isolation condenser 20, the outlet pipe 22 will also not heat water near a bottom floor of the isolation condenser 20 (to ensure that the inlet pipe 24 near the inlet discharge point 24a is not inadvertently heated.
The inlet pipe discharge point 24a (at the isolation condenser 20) of the inlet 24 may be positioned at a location that is at or near a bottom elevation of the isolation condenser 20. This ensures that only cooler water exits coils 40 and drains back into the suppression pool 2. An inlet pipe entry point 24b of the inlet 24 may be located at or near a bottom elevation of the suppression pool 2 (preferably, below the normal water level 2a of the suppression pool 2), to ensure that the cool water entering entry point 24b is separated from the hot steam/water near top elevations of the suppression pool 2.
Example embodiments having thus been described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the intended spirit and scope of example embodiments, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
