The following relates to the nuclear reactor arts, nuclear power generation arts, nuclear reactor control arts, nuclear reactor electrical power distribution arts, and related arts.
In nuclear reactor designs of the integral pressurized water reactor (integral PWR) type, a nuclear reactor core is immersed in primary coolant water at or near the bottom of a pressure vessel. In a typical design, the primary coolant is maintained in a subcooled liquid phase in a cylindrical pressure vessel that is mounted generally upright (that is, with its cylinder axis oriented vertically). A hollow cylindrical central riser is disposed concentrically inside the pressure vessel. Primary coolant flows upward through the reactor core where it is heated, rises through the central riser, discharges from the top of the central riser, and reverses direction to flow downward back toward the reactor core through a downcomer annulus.
The nuclear reactor core is built up from multiple fuel assemblies. Each fuel assembly includes a number of fuel rods. Control rods comprising neutron absorbing material are inserted into and lifted out of the reactor core to control core reactivity. The control rods are supported and guided through control rod guide tubes which are in turn supported by guide tube frames. In the integral PWR design, at least one steam generator is located inside the pressure vessel, typically in the downcomer annulus, and the pressurizer is located at the top of the pressure vessel, with a steam space at the top most point of the pressure vessel. Alternatively an external pressurizer can be used to control reactor pressure.
A set of control rods is arranged as a control rod assembly that includes the control rods connected at their upper ends with a spider, and a connecting rod extending upward from the spider. The control rod assembly is raised or lowered to move the control rods out of or into the reactor core using a control rod drive mechanism (CRDM). In a typical CRDM configuration, an electrically driven motor selectively rotates a roller nut assembly or other threaded element that engages a lead screw that in turn connects with the connecting rod of the control rod assembly. In some assemblies, such as those described in U.S. Pat. No. 4,597,934, a magnetic jack may be used to control movement of one or more control rods. Control rods are typically also configured to “SCRAM”, by which it is meant that the control rods can be quickly released in an emergency so as to fall into the reactor core under force of gravity and quickly terminate the power-generating nuclear chain reaction. Toward this end the roller nut assembly may be configured to be separable so as to release the control rod assembly and lead screw which then fall toward the core as a translating unit. In another configuration, the connection of the lead screw with the connecting rod is latched and SCRAM is performed by releasing the latch so that the control rod assembly falls toward the core while the lead screw remains engaged with the roller nut. See Stambaugh et al., “Control Rod Drive Mechanism for Nuclear Reactor”, U.S. Pub. No. 2010/0316177 A1 published Dec. 16, 2010 which is incorporated herein by reference in its entirety; and Stambaugh et al., “Control Rod Drive Mechanism for Nuclear Reactor”, Intl Pub. WO 2010/144563 A1 published Dec. 16, 2010 which is incorporated herein by reference in its entirety.
The CRDMs are complex precision devices which require electrical power to drive the motor, and may also require hydraulic, pneumatic, or another source of power to overcome the passive SCRAM release mechanism (e.g., to hold the separable roller nut in the engaged position, or to maintain latching of the connecting rod latch) unless this is also electrically driven. In existing commercial nuclear power reactors, the CRDMs are located externally, i.e. outside of the pressure vessel, typically above the vessel in PWR designs, or below the reactor in boiling water reactor (BWR) designs. An external CRDM has the advantage of accessibility for maintenance and can be powered through external electrical and hydraulic connectors. However, the requisite mechanical penetrations into the pressure vessel present safety concerns. Additionally, in compact integral PWR designs, especially those employing an internal pressurizer, it may be difficult to configure the reactor design to allow for overhead external placement of the CRDMs. Accordingly, internal CRDM designs have been developed. See U.S. Pub. No. 2010/0316177 A1 and Intl Pub. WO 2010/144563 A1 which are both incorporated herein by reference in their entireties. However, placing the CRDMs internally to the reactor vessel requires structural support and complicates delivery of electrical and hydraulic power. Electrical conductors that are usable inside the pressure vessel are generally not flexible and are not readily engaged or disengaged, making installation and servicing of internal CRDM units challenging.
Disclosed herein are improvements that provide various benefits that will become apparent to the skilled artisan upon reading the following.
In one illustrative embodiment, an apparatus is disclosed comprising a plurality of control rod drive mechanisms (CRDMs) each configured to raise or lower a control rod assembly and a distribution plate configured to be mounted in a nuclear reactor pressure vessel and including a plurality of connection sites at which the CRDMS are mounted, the distribution plate including electrical power distribution lines disposed on or in the distribution plate for distributing electrical power to the CRDMs mounted on the distribution plate.
A method is also disclosed comprising installing a CRDM in a nuclear reactor by operations which include attaching the CRDM to a top plate of a standoff and connecting a mineral insulated cable between the CRDM and an electrical connector disposed in or on a bottom plate of the standoff to form a CRDM/standoff assembly and mounting the bottom plate of the CRDM/standoff assembly to a distribution plate wherein the mounting connects an electrical power line disposed on or in the distribution plate with the electrical connector disposed in or on the bottom plate of the standoff.
In another illustrative embodiment, an apparatus is disclosed comprising a nuclear reactor including a core comprising a fissile material disposed in a pressure vessel, a mechanical reactor component disposed inside the pressure vessel and having a mounting flange with a power connector, and a power distribution plate disposed inside the pressure vessel and having a connection site configured to mate with the flange of the mechanical reactor component, the connection site including a power connector configured to mate with the power connector of the flange of the mechanical reactor component when the flange of the mechanical reactor component is mated with the connection site, power lines on or in the power distribution plate being arranged to deliver power to the power connector of the connection site, wherein the flange of the mechanical reactor component is mated with the connection site of the power distribution plate.
The invention may take form in various components and arrangements of components, and in various process operations and arrangements of process operations. The drawings are only for purposes of illustrating preferred embodiments and are not to be construed as limiting the invention.
In the illustrative PWR, above the core 1 are the reactor upper internals 12 of integral PWR 10, shown in inset. The upper internals 12 are supported by a mid flange 14, which in the illustrative embodiment also supports internal canned reactor coolant pumps (RCPs) 16. More generally, the RCPs may be external pumps or have other configurations, and the upper internals may be supported otherwise than by the illustrative mid flange 14. The upper internals include control rod guide frames 18 to house and guide the control rod assemblies for controlling the reactor. Control Rod Drive Mechanisms (CRDMs) 20 raise and lower the control rods to control the reactor. In accordance with one embodiment, a CRDM distribution plate 22 supports the CRDMs and provides power and hydraulics to the CRDMs. A riser transition 24 directs coolant flow upward.
Control rods are withdrawn from the core by CRDMs to provide enough positive reactivity to achieve criticality. The control rod guide tubes provide space for the rods and interconnecting spider to be raised upward away from the reactor core. The CRDMs 20 require electric power for the motors which move the rods, as well as for auxiliary electrical components such as rod position indicators and rod bottom sensors. In some designs, the force to latch the connecting rod to the lead screw, or to maintain engagement of the separable roller nut, is hydraulic, necessitating a hydraulic connection to the CRDM. To ensure passive safety, a positive force is usually required to prevent SCRAM, such that removal of the positive force initiates a SCRAM. The illustrative CRDM 20 is an internal CRDM, that is, is located inside the reactor vessel, and so the connection between the CRDM 20 and the distribution plate 22 is difficult to access. Servicing of a CRDM during a plant shutdown should preferably be rapid in order to minimize the length of the shutdown. To facilitate replacing a CRDM in the field, a standoff assembly connected to the distribution plate 22 to provide precise vertical placement of the CRDM 20 is also configured to provide electrical power and hydraulics to the CRDM 20 via connectors that require no action to effectuate the connection other than placement of the standoff assembly onto the distribution plate 22. After placement, the standoff is secured to the distribution plate by bolts or other fasteners. Additionally or alternatively, it is contemplated to rely upon the weight of the standoff assembly and CRDM to hold the assembly in place, or to use welds to secure the assembly.
The illustrative distribution plate 22 is a single plate that contains the electrical and hydraulic lines and also is strong enough to provide support to the CRDMs and upper internals without reinforcement. In another embodiment, the distribution plate 22 may comprise a stack of two or more plates, for example a mid-hanger plate which provides structural strength and rigidity and an upper plate that contains electrical and/or hydraulic lines to the CRDMs via the standoff assembly.
The motor/roller nut assembly of the CRDM is generally located in the middle of the lead screw's travel path. When the control rod is fully inserted into the core, the roller nut is holding the top of the lead screw, and, when the rod is at the top of the core, the roller nut is holding the bottom of the lead screw and most of the length of the lead screw extends upward above the motor/roller nut assembly. Hence the distribution plate 22 that supports the CRDM is positioned “below” the CRDM units and a relatively short distance above the reactor core.
One possible arrangement for the hydraulic and/or electrical power lines is shown in
In one embodiment, the electrical cables 80 are mineral insulated cables (MI cables) which generally include one, two, three, or more copper conductors wrapped in a mineral insulation such as Magnesium Oxide which is in turn sheathed in a metal. The mineral insulation could also be aluminum oxide, ceramic, or another electrically insulating material that is robust in the nuclear reactor environment. MI cables are often sheathed in alloys containing copper, but copper would corrode and have a negative effect on reactor chemistry. Some contemplated sheathing metals include various steel alloys containing nickel and/or chromium, or a copper sheath with a protective nickel cladding.
The electrical lines 30 in the distribution plate 22 (see
A continuous flow of primary coolant is used as hydraulic fluid to maintain the CRDM latched during operation, so some leakage from the hydraulic connector into the pressure vessel is acceptable. In view of this, in some embodiments the mating of the hydraulic power connector of the CRDM 20 with the corresponding hydraulic power connector of the connection site of the distribution plate 22 forms a leaky hydraulic connection. Accordingly, a sufficient sealing force for the hydraulic connection is provided by the weight of the CRDM/standoff assembly and/or the force imparted by the hold-down bolts that pass through the bolt lead-ins 50 of the standoff assembly and bolt holes 40 of the distribution plate.
The disclosed approaches advantageously improve the installation and servicing of powered internal mechanical reactor components (e.g., the illustrative CRDM/standoff assembly) by replacing conventional in-field installation procedures including on-site routing and installation of power lines (e.g. MI cables or hydraulic lines) and connection of each power line with the powered internal mechanical reactor component with a simple “plug-and-play” installation in which the power lines are integrated with the support plate and power connections are automatically made when the powered internal mechanical reactor component is mounted onto its support plate. The disclosed approaches leverage the fact that most powered internal mechanical reactor components are conventionally mounted on a support plate in order to provide sufficient structural support and to enable efficient removal for servicing (e.g., a welded mount complicates removal for servicing). By modifying the support plate to also serve as a power distribution plate with built-in connectors that mate with mating connectors of the powered internal mechanical reactor component during mounting of the latter, most of the installation complexity is shifted away from the power plant and to the reactor manufacturing site(s).
The example of
With reference to
As yet another contemplated modification, it will be appreciated that the female connector can be located in the supporting power distribution plate while the male connector can be located in the flange, standoff or other mounting feature of the internal mechanical reactor component.
The preferred embodiments have been illustrated and described. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Number | Name | Date | Kind |
---|---|---|---|
3162579 | Thomas et al. | Dec 1964 | A |
3559674 | Ostwald et al. | Feb 1971 | A |
3843471 | Bevilacqua et al. | Oct 1974 | A |
3844882 | Bevilacqua et al. | Oct 1974 | A |
3940311 | Frisch et al. | Feb 1976 | A |
3977939 | Frisch et al. | Aug 1976 | A |
4029897 | Mayer et al. | Jun 1977 | A |
4045283 | Noyes et al. | Aug 1977 | A |
4054186 | Banks et al. | Oct 1977 | A |
4216670 | Zintel et al. | Aug 1980 | A |
4302034 | Weirich et al. | Nov 1981 | A |
4666657 | Altman | May 1987 | A |
4857264 | Veronesi et al. | Aug 1989 | A |
4863678 | Shockling et al. | Sep 1989 | A |
4876061 | Ekeroth et al. | Oct 1989 | A |
4885127 | Yokoyama | Dec 1989 | A |
4888151 | Gjertsen et al. | Dec 1989 | A |
4895698 | DeMario | Jan 1990 | A |
4923669 | DeMario | May 1990 | A |
4957697 | Wada | Sep 1990 | A |
4966745 | Widener et al. | Oct 1990 | A |
4990304 | Rylatt | Feb 1991 | A |
4993864 | Gjertsen et al. | Feb 1991 | A |
4994233 | Freeman | Feb 1991 | A |
4996018 | Bhatt et al. | Feb 1991 | A |
5009837 | Nguyen et al. | Apr 1991 | A |
5022100 | Belanger | Jun 1991 | A |
5024806 | Cioffi et al. | Jun 1991 | A |
5025834 | Stoll | Jun 1991 | A |
5030413 | Knierriem et al. | Jul 1991 | A |
5043134 | Widener et al. | Aug 1991 | A |
5051103 | Neuroth | Sep 1991 | A |
5064607 | Miller et al. | Nov 1991 | A |
5068083 | John, Jr. et al. | Nov 1991 | A |
5094268 | Morel et al. | Mar 1992 | A |
5141711 | Gjertsen et al. | Aug 1992 | A |
5158740 | Boatwright | Oct 1992 | A |
5194216 | McDaniels, Jr. | Mar 1993 | A |
5200138 | Ferrari | Apr 1993 | A |
5207980 | Gilmore et al. | May 1993 | A |
5217596 | Indig et al. | Jun 1993 | A |
5225150 | Malandra et al. | Jul 1993 | A |
5227125 | Beneck et al. | Jul 1993 | A |
5265137 | Busch | Nov 1993 | A |
5268948 | Church et al. | Dec 1993 | A |
5282231 | Adams et al. | Jan 1994 | A |
5282233 | Bryan | Jan 1994 | A |
5299246 | Bryan | Mar 1994 | A |
5301213 | Linden et al. | Apr 1994 | A |
5361279 | Kobsa et al. | Nov 1994 | A |
5367549 | Hatfield | Nov 1994 | A |
5436945 | Weisel et al. | Jul 1995 | A |
5513234 | Rottenberg | Apr 1996 | A |
5586155 | Erbes et al. | Dec 1996 | A |
5606582 | Bergamaschi | Feb 1997 | A |
5625657 | Gallacher | Apr 1997 | A |
5640434 | Rottenberg | Jun 1997 | A |
5841824 | Graham | Nov 1998 | A |
6055288 | Schwirian | Apr 2000 | A |
6088420 | Yokoyama et al. | Jul 2000 | A |
6091790 | Ridolfo | Jul 2000 | A |
6236699 | Ridolfo | May 2001 | B1 |
6421405 | Ridolfo | Jul 2002 | B1 |
6484806 | Childers et al. | Nov 2002 | B2 |
6810099 | Nakamaru et al. | Oct 2004 | B2 |
6895067 | Borum et al. | May 2005 | B2 |
7280946 | Russell, II et al. | Oct 2007 | B2 |
7412021 | Fetterman et al. | Aug 2008 | B2 |
7424412 | Kropaczek et al. | Sep 2008 | B2 |
7428479 | Boer et al. | Sep 2008 | B2 |
7453972 | Hellandbrand, Jr. et al. | Nov 2008 | B2 |
7526058 | Fawcett et al. | Apr 2009 | B2 |
7548602 | Smith, III et al. | Jun 2009 | B2 |
7574337 | Kropaczek et al. | Aug 2009 | B2 |
20030123600 | Hesketh et al. | Jul 2003 | A1 |
20030157823 | Morris | Aug 2003 | A1 |
20030169839 | Matteson | Sep 2003 | A1 |
20050069080 | Goldenfield et al. | Mar 2005 | A1 |
20060153327 | Jiang | Jul 2006 | A1 |
20060222140 | Aleshin et al. | Oct 2006 | A1 |
20060251205 | Balog | Nov 2006 | A1 |
20070133732 | Nakayama et al. | Jun 2007 | A1 |
20070140877 | Sanville et al. | Jun 2007 | A1 |
20070206717 | Conner et al. | Sep 2007 | A1 |
20080084957 | Aleshin et al. | Apr 2008 | A1 |
20080253496 | McCarty et al. | Oct 2008 | A1 |
20090032178 | Feinroth | Feb 2009 | A1 |
20090122946 | Fawcett et al. | May 2009 | A1 |
20100316177 | Stambaugh et al. | Dec 2010 | A1 |
20110222640 | Desantis | Sep 2011 | A1 |
Number | Date | Country |
---|---|---|
1040699 | Mar 1990 | CN |
1080766 | Jan 1994 | CN |
1256497 | Jun 2000 | CN |
101154472 | Apr 2008 | CN |
103295653 | Sep 2013 | CN |
3631020 | Mar 1988 | DE |
2013162661 | Oct 2013 | WO |
2013188003 | Dec 2013 | WO |
Entry |
---|
Con-O-Clad Mineral Insulated Metal Sheathed Thermocouple Cable, Catalog [online], Conax Technologies, Jun. 2009. |
International Search Report and Written Opinion for PCT/US2013/023535, dated Sep. 27, 2013. |
Extended European Search Report dated Sep. 28, 2015 for European Patent Application No. 13782394.4. |
office Action dated Mar. 4, 2016 for Chinese Application No. 201380022377.0. |
Office Action dated May 5, 2016 for Chinese Application No. 201210472772.6. |
European Search Report dated Mar. 17, 2016, for EP Application No. 13803559.7. |
Office Action dated Feb. 29, 2016, for U.S. Appl. No. 13/863,611. |
Response to Office Action dated Feb. 29, 2016 for U.S. Appl. No. 13/863,611. |
Office Action dated Aug. 3, 2016 for U.S. Appl. No. 13/860,058. |
Office Action dated Oct. 3, 2016 for U.S. Appl. No. 13/863,611. |
Response to Office Action dated Aug. 3, 2016 for U.S. Appl. No. 13/860,058. |
Number | Date | Country | |
---|---|---|---|
20130223580 A1 | Aug 2013 | US |