Patent Description:
Several different pools and flowpaths constitute an emergency core coolant system inside containment <NUM> to provide fluid coolant to reactor <NUM> in the case of a transient involving loss of cooling capacity in the plant. For example, containment <NUM> may include a pressure suppression chamber <NUM> surrounding reactor <NUM> in an annular or other fashion and holding suppression pool <NUM>. Suppression pool <NUM> may include an emergency steam vent used to divert steam from a main steam line into suppression pool <NUM> for condensation and heat sinking, to prevent over-heating and over-pressurization of containment <NUM>. Suppression pool <NUM> may also include flow paths that allow fluid flowing into drywell <NUM> to drain, or be pumped, into suppression pool <NUM>. Suppression pool <NUM> may further include other heat-exchangers or drains configured to remove heat or pressure from containment <NUM> following a loss of coolant accident. An emergency core cooling system line and pump <NUM> may inject coolant from suppression pool <NUM> into reactor <NUM> to make up lost feedwater and/or other emergency coolant supply.

As shown in <FIG>, a gravity-driven cooling system (GDCS) pool <NUM> can further provide coolant to reactor <NUM> via piping <NUM>. A passive containment cooling system (PCCS) pool <NUM> may condense any steam inside containment <NUM>, such as steam created through reactor depressurization to lower containment pressure or a main steam line break, and feed the condensed fluid back into GDCS pool <NUM>. An isolation cooling system (ICS) pool <NUM> may take steam directly at pressure from reactor <NUM> and condense the same for recirculation back into rector <NUM>. These safety systems may be used in any combination in various reactor designs, each to the effect of preventing overheating and damage of core <NUM>, reactor <NUM> and all other structures within containment <NUM> by supplying necessary coolant, removing heat, and/or reducing pressure. Several additional systems are typically present inside containment <NUM>, and several other auxiliary systems are used in related art ESBWR. Such ESBWRs are described in "<NPL>, hereinafter referred to as "ESBWR.

Some background information can be found in <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>.

According an aspect there is provided an apparatus in accordance with the appended claims. According to another aspect there is provided a method in accordance with the appended claims.

Example embodiments include nuclear reactors with an isolation condenser system connecting to the nuclear reactor through integrally isolatable connections that have a minimal risk of leakage or failure. In this way, example nuclear reactors may be effectively completely isolated from the isolation condenser system. Example embodiment isolation condenser systems include one or more isolation condensers immersed in a segregated coolant such that the condenser can transfer heat to the immersive coolant when receiving a working coolant or moderator from the nuclear reactor. The immersive coolant can be drawn from a separate coolant reservoir that supplies one or more separate isolation condensers. Barriers may prevent flow between the various isolation condensers; for example, a check valve may permit coolant to flow only from the reservoir to the isolation condenser and separate the two if the immersive coolant level becomes too high, too hot, too radioactive, etc. about the isolation condenser. A switch can passively monitor coolant level between the isolation condenser and reservoir, selectively permitting flow based on relative elevation of floats in the reservoir and coolant surrounding the isolation condenser. Movement of the floats may actuate the check valve and/or the isolation condenser itself. Isolation condensers in example systems can be activated by opening a fluid loop through the condenser to/from the reactor. For example, fluidic controls and/or a pressure pulse transmitter may monitor reactor conditions and selectively activate individual isolation condensers, trip and/or isolate the reactor, and/or trip the rest of the plant based on detected reactor pressures, coolant levels, etc. Such passive and reliable sensors may place the plant in a safe shutdown condition with indefinite cooling capacity if operations divert from design bases. Example embodiment isolation condenser systems may be positioned outside of containment in an underground silo with the containment, which may not have any other coolant source.

Example embodiments will become more apparent by describing, in detail, the attached drawings, wherein like elements are represented by like reference numerals, which are given by way of illustration only and thus do not limit the terms which they depict.

Because this is a patent document, general, broad rules of construction should be applied when reading it. Everything described and shown in this document is an example of subject matter falling within the scope of the claims, appended below. Any specific structural and functional details disclosed herein are merely for purposes of describing how to make and use examples. Several different embodiments and methods not specifically disclosed herein may fall within the claim scope; as such, the claims may be embodied in many alternate forms and should not be construed as limited to only examples set forth herein.

It will be understood that, although the ordinal terms "first," "second," etc. may be used herein to describe various elements, these elements should not be limited to any order by these terms. These terms are used only to distinguish one element from another; where there are "second" or higher ordinals, there merely must be that many number of elements, without necessarily any difference or other relationship. 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 or methods. As used herein, the term "and/or" includes all combinations of one or more of the associated listed items. The use of "etc." is defined as "et cetera" and indicates the inclusion of all other elements belonging to the same group of the preceding items, in any "and/or" combination(s).

It will be understood that when an element is referred to as being "connected," "coupled," "mated," "attached," "fixed," etc. to another element, it can be directly connected to the other element, or intervening elements may be present. In contrast, when an element is referred to as being "directly connected," "directly coupled," etc. to another element, there are no intervening elements present. Similarly, a term such as "communicatively connected" includes all variations of information exchange and routing between two electronic devices, including intermediary devices, networks, etc., connected wirelessly or not.

As used herein, the singular forms "a," "an," and "the" are intended to include both the singular and plural forms, unless the language explicitly 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, characteristics, steps, operations, elements, and/or components, but do not themselves preclude the presence or addition of one or more other features, characteristics, steps, operations, elements, components, and/or groups thereof.

The structures and operations discussed below may occur out of the order described and/or noted in the figures. For example, two operations and/or figures shown in succession may in fact be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Similarly, individual operations within example methods described below may be executed repetitively, individually or sequentially, so as to provide looping or other series of operations aside from single operations described below. It should be presumed that any embodiment or method having features and functionality described below, in any workable combination, falls within the scope of example embodiments.

The inventors have recognized that conventional auxiliary or emergency coolant systems typically require powered, digital controls to activate and operate in nuclear reactors. Such emergency systems typically require pumps and/or active valves and monitors for proper operation. With several, diverse coolant systems, complex logic and controls may be required to achieve activation protocols and selectively activate individual safety systems. These systems are typically positioned inside containment for immediate reactor access, requiring a large and complex containment. To overcome these newly-recognized problems as well as others, the inventors have developed example embodiments and methods described below to address these and other problems recognized by the inventors with unique solutions enabled by example embodiments.

The present invention is isolation cooling systems, plants containing the same, and methods of operating such systems and plants. In contrast to the present invention, the few example embodiments and example methods discussed below illustrate just a subset of the variety of different configurations that can be used as and/or in connection with the present invention.

<FIG> is a schematic of an example embodiment reactor system <NUM> including example embodiment reactor <NUM>, example embodiment containment <NUM>, and related cooling and power generation systems. System <NUM> is similarly described in co-owned <CIT> for VERY SIMPLIFIED BOILING WATER REACTORS FOR COMMERCIAL ELECTRICITY GENERATION. Although not shown in <FIG>, example embodiment system <NUM> is useable with conventional and known power generating equipment such as high- and low-pressure turbines, electrical generators, switchyards, condensers, cooling towers or heat sinks, etc., which may connect, for example to main feedwater line <NUM> and main steam line <NUM> in a similar fashion to any power generation facility. Example embodiment containment <NUM> is composed of resilient, impermeable material for limiting migration of radioactive material and plant components in the case of a transient or accident scenario. For example, containment <NUM> may be an integrally-formed concrete structure, potentially with reinforcing internal steel or rebar skeleton, several inches or feet thick. Or, for example, as discussed below, because containment <NUM> may be relatively smaller, an all-steel body may be used without being prohibitively expensive or complexly-fabricated, to enhance strength, radiation shielding, and lifespan of containment <NUM>.

As shown in <FIG>, example embodiment containment <NUM> may be underground, potentially housed in a reactor silo <NUM>. A concrete lid <NUM> or other surface shield level with, or below, ground <NUM> may enclose silo <NUM> housing example embodiment reactor <NUM> and containment <NUM>. Silo <NUM> and lid <NUM> may be seismically isolated or hardened to minimize any shock wave encountered from the ground and thus minimize impact of seismic events on reactor <NUM> and systems in silo <NUM> such as example ICS <NUM> and/or control system <NUM>. If underground as shown in <FIG>, example embodiment system <NUM> may present an exceedingly small strike target and/or be hardened against surface impacts and explosions. Further, if underground, example embodiment system <NUM> may have additional containment against radioactive release and enable easier flooding in the case of emergency cooling. Although not shown, any electricity-generating equipment may be connected above ground without loss of these benefits, and/or such equipment may also be placed below ground.

Based on the smaller size of example embodiment reactor <NUM> discussed below, example embodiment containment <NUM> may be compact and simplified relative to existing nuclear power plants, including the ESBWR. Conventional operating and emergency equipment, including a GDCS, PCCS, suppression pools, Bimacs, backup batteries, wetwells, torii, etc. may be wholly omitted from containment <NUM>. Containment <NUM> may be accessible through fewer access points as well, such as a single top access point under shield <NUM> that permits access to reactor <NUM> for refueling and maintenance. The relatively small volume of example embodiment reactor <NUM> and core <NUM> may not require a bimac for floor arrest and cooling, because no realistic scenario exists for fuel relocation into containment <NUM>; nonetheless, example embodiment containment <NUM> may have sufficient floor thickness and spread area to accommodate and cool any relocated core in its entirety, as shown in <FIG>. Moreover, total penetrations through containment <NUM> may be minimized and or isolated to reduce or effectively eliminate risk of leakage from containment <NUM>.

Example embodiment reactor <NUM> may be a boiling-water type reactor, similar to approved ESBWR designs in reactor internals and height. Reactor <NUM> may be smaller than, such as one-fifth the volume of, ESBWRs, producing only up to <NUM> megawatts of electricity for example, with a proportionally smaller core <NUM>, for example operating at less than <NUM> megawatt-thermal. For example, example embodiment reactor <NUM> may be almost <NUM> meters in height and slightly over <NUM> meters in diameter, with internals matching ESBWR internals but scaled down proportionally in the transverse direction to operate at approximately <NUM> megawatt-thermal and <NUM> megawatt-electric ratings. Or, for example, reactor <NUM> may be a same proportion as an ESBWR, with an approximate <NUM> height-to-width ratio, scaled down to a smaller volume. Of course, other dimensions are useable with example embodiment reactor <NUM>, with smaller height-to-width ratios such as <NUM>, or <NUM>, that may enable natural circulation at smaller sizes or proper flow path configuration inside the reactor.

Keeping a relatively larger height of example embodiment reactor <NUM> may preserve natural circulation effects achieved by known ESBWRs in example embodiment reactor <NUM>. Similarly, smaller reactor <NUM> may more easily be positioned underground with associated cooling equipment and/or possess less overheating and damage risk due to smaller fuel inventory in core <NUM>. Even further, smaller example embodiment reactor <NUM> with lower power rating may more readily satisfy modular power or peaking power demands, with easier startup, shutdown, and/or reduced power operations to better match energy demand.

A coolant loop, such as main feedwater line <NUM> and main steam line <NUM>, may flow into reactor <NUM> to provide moderator, coolant, and/or heat transfer fluid for electricity generation. An emergency coolant source, such as one or more example embodiment isolation condenser systems (ICS) <NUM>, may further provide emergency cooling to reactor <NUM> in the instance of loss of feedwater from line <NUM>. Example embodiment ICS <NUM> may include steam inlet <NUM> from example embodiment reactor <NUM> and condensate return <NUM> to reactor <NUM>. Each of these connections to reactor <NUM> may use isolation valves <NUM> that are integrally connected to reactor <NUM> inside containment <NUM> and represent negligible failure risk.

Aside from valves <NUM>, example embodiment containment <NUM> may be sealed about any other valve or penetration, such as power systems, instrumentation, coolant cleanup lines, etc. The fewer penetrations, smaller size, lack of systems inside, and/or underground placement of containment <NUM> may permit a higher operating pressure, potentially up to near reactor pressures of several hundred, such as <NUM>, psig without any leakage potential.

As seen in example embodiment reactor system <NUM>, several different features permit significantly decreased loss of coolant probability, enable responsive and flexible power generation, reduce plant footprint and above-ground strike target, and/or simplify nuclear plant construction and operation. Especially by using known and approved ESBWR design elements with smaller volumes and core sizes, example embodiment reactor <NUM> may still benefit from passive safety features such as natural circulation inherent in the ESBWR design, while allowing a significantly smaller and simplified example embodiment containment <NUM> and reliance on passive isolation condensers <NUM> for emergency heat removal.

<FIG> is an illustration of an example embodiment ICS <NUM> useable in example embodiment plant <NUM>. As shown in <FIG>, example embodiment ICS <NUM> may include multiple isolation condensers <NUM>, <NUM>, etc. in fluid connection with a large reservoir or ICS pool <NUM>. Although only a first isolation condenser <NUM> and a second isolation condenser <NUM> are shown in <FIG>, it is understood that any number of isolation condenser(s) may feed from ICS pool <NUM>. Each isolation condenser <NUM> and <NUM> may include its own ICS chambers <NUM> and <NUM> with independent coolant control and levels that may be replenished by ICS pool <NUM>. Because ICS <NUM> may be outside of any containment, ICS pool <NUM>, isolation condensers <NUM> and <NUM>, and any other component of ICS <NUM> may be easily reached for maintenance, inspection, emergency refill, and/or operation, regardless of plant state.

As shown in <FIG>, each isolation condenser <NUM> and <NUM> may be fed by steam inlet <NUM> providing steam produced in the nuclear reactor. The steam may pass down through a heat exchanger in isolation condenser <NUM> transferring heat to a fluid, such as water, in chamber <NUM> that condenses the steam back to liquid water. Condensate return line <NUM> then allows this condensed water to flow back into the reactor, driven by gravity, steam inertia, and density gradient between the steam and condensed water. Isolation condensers <NUM> and <NUM> may use a double, split loop through two, multi-channel heat exchangers as shown in <FIG>, or use other known designs, such as ICS designs from approved ESBWR plants or others.

If installed in an example embodiment plant system <NUM> (<FIG>) using a lower-thermal-power reactor, such as in the lower hundreds-megawatt-thermal range, a single isolation condenser <NUM> may have cooling capacity for the entire reactor. That is, isolation condensers <NUM> and <NUM> may each be able to condense a full volume of steam produced by an example embodiment lower power reactor to maintain a steady liquid level in the same. Similarly, isolation condensers may have lower and/or varying capacities and be used in any number to provide a margin of safety, such as four total condensers each with a condensing capacity of <NUM>% total core flow for a 3x safety margin.

Although each isolation condenser <NUM> and <NUM> is shown with its own steam line <NUM> and condensate return line <NUM>, it is understood that actual supply and return may branch from a shared steam <NUM> and condensate return <NUM> line, so as to require only a single isolation valve <NUM> (<FIG>) for all of ICS <NUM> having multiple isolation condensers <NUM>, <NUM>. Control of each isolation condenser may be individualized as discussed below through valves on steam line <NUM> and/or condensate return line <NUM>. Or, first isolation condenser <NUM> and second isolation condenser <NUM> may each use an individual steam line <NUM> and condensate return line <NUM> with separate isolation valves <NUM>, such as in the example of <FIG>.

Because each isolation condenser <NUM> and <NUM> may use its own chamber <NUM> and <NUM>, respectively, coolant levels may be maintained for each, despite drawing from a common pool <NUM>. For example, check valves <NUM> between pool <NUM> and chamber <NUM> may permit only one-way flow from pool <NUM> into chamber <NUM>. In this way, evaporation or boil-off from chamber <NUM> may be replenished from pool <NUM> without necessarily lowering or affecting levels in other chamber <NUM>. Similarly, if chamber <NUM> is at a higher fill level, check valves <NUM> may not allow coolant to flow out into pool <NUM>.

Passive switch <NUM> may detect when an ICS chamber should be isolated via check valve <NUM> or other connections to pool <NUM>, without active or DCIS controls. Passive switch <NUM> may further indicate when an isolation condenser <NUM>, <NUM>, etc. should be deactivated. For example, passive switch <NUM> may use two floats, <NUM>, one in pool <NUM> and another in ICS chamber <NUM>. As floats move on the surface of the coolant, such as liquid water, they may move a position of switch <NUM> when joined on either side of a pivot. If coolant level in ICS chamber <NUM> is lower than pool <NUM>, this may be reflected in positioning of floats <NUM>, and switch <NUM> may open (shown by an arrow) check valve <NUM> between floats <NUM> and keep isolation condenser <NUM> active and ICS chamber <NUM> replenished. Or for example, as coolant level in ICS chamber <NUM> exceeds a level in pool <NUM>, this may indicate malfunction or rupture in isolation condenser <NUM> where reactor coolant may be entering ICS chamber <NUM>. Floats <NUM> in an opposite vertical relative positioning in this circumstance may close switch <NUM>, which may close check valve <NUM> (shown by an X) and potentially deactivate or isolate isolation condenser <NUM> to prevent further reactor leakage and/or coolant flow into ICS chamber <NUM> and pool <NUM>.

Although floats <NUM> are used by passive switch <NUM> in <FIG>, it is understood that other passive or low-failure-mode devices can be used to detect abnormal or undesired conditions of isolation condensers and their chambers. For example, relative pressure detectors, radiation detectors, level-based coolant contact actuators, temperature monitors, etc. may all signal that an isolation condenser should be removed from service and/or cut-off from common coolant sources such as pool <NUM>. Similarly, passive switch <NUM> or another detector may detect additional ICS cooling or condensation is necessary, such as if chamber <NUM> has approached boiling, and activate additional isolation condensers. Aside from check valves <NUM>, additional isolating structures may be actuated upon detection of undesired operating conditions in example embodiment ICS <NUM>, such as inoperable or leaking isolation condenser <NUM> requiring isolation of chamber <NUM>. Additional modes of activating and deactivating isolation condensers <NUM> and <NUM> are discussed below in connection with <FIG>.

<FIG> is an illustration of an example embodiment selective activation and isolation system <NUM>. As seen in <FIG>, example embodiment system <NUM> may connect to or be interfaced with reactor <NUM>, valves <NUM>, ICS <NUM>, and/or containment <NUM> to control operation of the same. As seen in <FIG>, activation and isolation system <NUM> may include multiple fluidic controls 166A, 166B, etc. each interfaced with an isolation condenser <NUM>, <NUM>, etc. Although only two fluidic controls and two isolation condensers are shown in <FIG>, it is understood that any number may be used. Fluidic controls 166A and 166B may connect to reactor <NUM> through a shared pressure line <NUM>. Pressure line <NUM> may extend through containment with appropriate penetration seal or fluidic controls <NUM> may be inside containment.

At a pressure setpoint in pressure line <NUM>, which reflects pressure in reactor <NUM>, fluidic control 166A may activate isolation condenser <NUM>. The pressure setpoint may be a high pressure associated with reactor overheat or isolation from feedwater or turbine loss, for example. Fluidic control 166A may be configured to directly actuate a valve, rupture an accumulator, passively use reactor pressure to open a valve, and/or otherwise reliably open a coolant loop to isolation condenser <NUM> at the setpoint. As shown in <FIG>, the actuated valve may be a valve on the condensate return line <NUM>; for example, the valve may be an isolation valve <NUM> (<FIG>) connecting condensate return line <NUM> to reactor <NUM> or another valve dividing individual isolation condensers from such a line. Fluidic control 166A may further actuate a valve on steam inlet <NUM>, or it is also possible that steam inlet <NUM> is always open to isolation condenser <NUM>, such that opening only a single valve for condensate return <NUM> causes flow through isolation condenser <NUM>, already at reactor pressure to prevent water hammer.

Another fluidic control 166B may open a valve associated with another isolation condenser <NUM> at the setpoint. Or, for example, fluidic control 166B may have a higher pressure activation setpoint, such that isolation condenser <NUM> is only activated if the setpoint for activation of fluidic control 166A for isolation condenser <NUM> has already been activated. For example, isolation condenser <NUM> may be leaking or not working, as determined by passive switch <NUM> (<FIG>), which may re-close the valve opened by fluidic control 166A, deactivate fluidic control 166A, close another valve such as a steam inlet valve for condenser <NUM>, or otherwise take isolation condenser <NUM> offline. If isolation condenser <NUM> is inadequate, inoperable, or deactivated, pressure in reactor <NUM> may rise again without any cooling or condensing system, particularly if reactor <NUM> (<FIG>) is isolated by isolation valves <NUM> in the event of a transient. Eventually the pressure will rise to the higher setpoint of fluidic control 166B, which will activate isolation condenser <NUM> and provide pressure relief and cooling. This setup may be repeated for any number or independently-operable fluidic controls <NUM> at any number of different, desired pressure setpoints, to provide a throttled and redundant amount of heat removal and condensation to reactor <NUM>.

As shown in <FIG>, pressure pulse transmitter <NUM> is interfaced with reactor <NUM> through a reactor fluid line <NUM>. Pressure pulse transmitter <NUM> may similarly activate one or all isolation condensers <NUM>, <NUM>, etc. Pressure pulse transmitter <NUM> may be a passive instrument that detects water level in reactor <NUM> and can, through hydraulic pressure, open and/or close any valve, including isolation valves <NUM>, to activate isolation condenser <NUM> and/or <NUM>, isolate reactor <NUM> from main steam line <NUM>, isolate reactor <NUM> from main feedwater line <NUM>, etc. Pressure pulse transmitter <NUM> may be of a type described in "Passive Pressure Pulse Transmitter" by Areva, or another known type of pressure pulse transmitter.

Pressure pulse transmitter <NUM> may actuate valves based on water level in reactor <NUM> instead of pressure. As such, pressure pulse transmitter <NUM> may offer an alternative and independent metric of reactor functionality and safety on which to trigger safety functions. For example, pressure pulse transmitter <NUM> may detect an abnormal water level approaching a top of the reactor core or fuel, at which point all isolation condensers <NUM>, <NUM>, etc. may be activated by opening valves associated with the same. Or, for example, pressure pulse transmitter <NUM> may be configured with several water level setpoints to selectively activate or turn off systems, such as isolation condenser <NUM> at a first low reactor coolant level, isolation condenser <NUM> at a second lower reactor coolant level, etc. Still further, pressure pulse transmitter <NUM> may deactivate isolation condensers <NUM>, <NUM>, etc. or shut ICS valves on a condensate return line <NUM> or steam inlet <NUM> at detection of a high reactor coolant level.

As shown in <FIG>, fluidic controls <NUM> and/or pressure pulse transmitter <NUM> in example embodiment selective activation and isolation system <NUM> may also interface with isolation valves <NUM> that isolate reactor <NUM> from main feedwater line <NUM> and/or main steam line <NUM>, in addition to valves associated with isolation condensers <NUM>, <NUM>. Control connections <NUM> are used to illustrate operative control over the various valves controlling flow to isolation condensers, main steam, feedwater, etc.; it is understood that control connections may be contained in a single body with fluidic controls and manipulated valve or may be an actuator line or other powered connection that opens or closes the valve, for example. Similarly, fluidic controls <NUM> and/or pressure pulse transmitter <NUM> may use control logic to selectively open or close combinations of valves to place a plant in a desired configuration. For example, along with actuation of ICS <NUM>, isolation valves <NUM> for main feedwater <NUM> and main steam outlet <NUM> may be closed to isolate reactor <NUM> by a single fluidic control 166A or transmitter <NUM>. Or, different fluidic controls <NUM> may place the plant in differing configurations including triggering a reactor scram and/or main turbine trip, based on worsening detected pressure.

Claim 1:
A nuclear reactor system (<NUM>) for commercially generating electricity, the system comprising:
a nuclear reactor (<NUM>);
at least one primary coolant loop (<NUM>, <NUM>), containing reactor coolant, connecting to the nuclear reactor (<NUM>); and
at least one isolation condenser system (<NUM>) connecting to the nuclear reactor (<NUM>), wherein the isolation condenser system (<NUM>) includes,
an isolation condenser (<NUM>, <NUM>) connected between a steam inlet (<NUM>) and a condensation return line (<NUM>) of the nuclear reactor (<NUM>) and immersed in a chamber (<NUM>, <NUM>) filled with isolation condenser coolant, wherein the isolation condenser includes a heat exchanger configured to transfer energy from the reactor coolant to the isolation condenser coolant,
characterised by
a reservoir (<NUM>) storing additional isolation condenser coolant for the chamber (<NUM>), a check valve (<NUM>) allowing coolant flow from the reservoir (<NUM>) to the chamber (<NUM>) and preventing coolant flow from the chamber (<NUM>) to the reservoir (<NUM>),
a switch (<NUM>) configured to determine relative coolant level between the chamber (<NUM>) and the reservoir (<NUM>) and operate the check valve (<NUM>) based on the relative coolant level.