Patent Application
20130025212
Not applicable
Not applicable
1. Field of the Invention
The invention relates to passive systems and structures suitable for prefabrication and installation as a variable volume unit enclosing industrial components, systems, buildings or structures such as nuclear reactor containment buildings, spent fuel pool buildings, nuclear auxiliary buildings, outlets of pressure relief valves, stacks, discs, or blowout preventer systems.
2. Description of the Prior Art and State of Technology
During normal operations, the containment building of a light water reactor nuclear power plant is air tight and confined. In other radiation controlled areas (some nuclear auxiliary buildings, some spent fuel pool buildings), the air pressure is maintained negative relative to local atmospheric pressure. The negative pressure inside those buildings prevents harmful gases and particulate matter and potential toxic release from exiting the buildings when doors are opened. For example, in some circumstances like fires, some elements of these buildings and structures are isolated to control smoke extraction, deprive the fire from oxygen and limit the fire's extension. For example, isolation of a containment building can prevent a toxic release (e.g., a radioactive gas and/or steam leak) from contaminating other areas.
For all light water nuclear spent fuel rods, the physical phenomenon of steam/air replacing water along the nuclear spent fuel rods called “spent fuel or core uncovering” in the Art, whatever the reason, increases the nuclear fuel rod cladding temperature due to residual heat in the nuclear fuel pellets and changes in convective heat transfer coefficients from liquid to gas of the coolant (water). When the residual heat is important enough, nuclear fuel rod melting/damage occurs with massive hydrogen generation and liberation of consequential radioactive release (radioactive gases, steam, and particulate matters). Once initiated, this physical phenomenon is very difficult to stop and reverse. The nuclear fuel rods and/or corium are wrapped with a strong steam/air/hydrogen layer for a very long time. It requires large amounts of cold water to be continuously injected for months up until the gas layer breaks up and the liquid (water) is once again in direct contact with the spent fuel rod cladding and/or corium. The water coolant transition back from gas/steam to liquid in contact with the nuclear fuel rods or corium—called “quenching” in the Art—also generates potentially destructive explosions.
The design certifications and the operating licenses of operating light water nuclear reactors granted by the NRC protect the public and the environment from the consequences of most accidents (called design basis accidents) at nuclear power plants. The regulators require the reactor designers and operators to implement embedded design and administrative defenses to prevent reaching this “nuclear spent fuel uncovering threshold” should a design basis accident occur. The operators manage design basis accidents and inject continuously water to cool off the reactor core and prevent steam/air from replacing water along the nuclear reactor fuel rods at any time. The residual heat (water) is transferred to a heat sink and the cooled water is recycled into the reactor core, or the residual heat (steam) is transferred directly to the atmosphere. The radioactive releases are captured either within the fuel rod cladding, within the reactor pressure vessel, or within the containment buildings and spent fuel pool buildings, or specific structures and systems in radiation controlled areas of the facility. For some specific boiling water reactors design basis accident configurations, the early voluntary release of radioactive steam through hardened venting systems to the atmosphere allows depressurization of the containment building and evacuation of the residual heat outside the containment building. For some Pressurized water reactors design basis accident configurations, the early voluntary release of radioactive steam through containment bypass systems to the atmosphere allows evacuation of the residual heat outside the containment building.
Extremely rare events such as—but not limited to—external disasters (Flooding, earthquakes, tsunamis, hurricanes, tornadoes, dust storms, fires and explosions) are beyond the design basis of current operating light water reactors. They are called Severe Accidents in the Art. These accidents lead to core damage and generate consequential voluntary and/or unexpected radioactive release (radioactive gases, steam, and particulate matters) into the atmosphere outside the reactor containment buildings, spent fuel pool buildings, and radiation controlled areas.
Prior Art in the field of the invention in the nuclear industry to mitigate the consequences of severe accidents at light water reactor power plants is oriented toward:
Attempts to limit the hydrogen produced during severe accidents with non metallic fuel rod cladding material, higher melting point of oxide metallic cladding material (U.S. Pat. No. 5,182,077). Although a lot of public and private research is involved worldwide, it is generally accepted in the Art that no new material breakthrough is expected to comply with all the competing requirements imposed upon nuclear fuel rod cladding material over the next decade.
Attempts to isolate the hydrogen produced during severe accidents from air with a passive safety system transferring hydrogen in a new additional air filled containment building without mixing of the two gases (JP 2009-206761). This improvement is not suitable for installation at current operating nuclear boiling water reactors. The improvement creates a new almost twice larger containment building enclosing the existing containment building (the design pressure of the new containment building is equal to the design pressure of the smaller current containment building and the nuclear spent fuel pool). Furthermore, JP 2009-206761 does not address the total amount of energy (residual heat and hydrogen generated) stored inside the “combined” containment building created by the airbag passive system during severe accidents and thus the consequences of the failures of the airbag fabric, of the “combined” containment building and of the penetration systems initiated by over temperature and over pressure.
Attempts to eliminate the hydrogen produced during those severe accidents with hydrogen igniters and recombiners inside the containment building (U.S. Pat. No. 4,407,774). These improvements have yet to be tested in the complex dynamic local hydrogen/air environment of containment buildings during severe accidents. They are not suitable for installation at most operating nuclear light water reactors at reasonable cost. While they may decrease the explosive nature of some of the containment building local atmosphere, they increase the amount of heat stored and accumulated in the containment building and thus do not address the potential failure of the containment building and penetration systems initiated by over pressure and over temperature.
Attempts to limit the destructive consequences of reactor fuel cladding, steam, concrete, hydrogen and air interactions (explosions) during severe accidents with core catchers (U.S. Pat. No. 7,949,084), or underground systems, buildings and structures (U.S. Pat. No. 6,658,077). The core catchers are meant to encapsulate the corium outside the reactor pressure vessel and address potential pollution of groundwater during severe accidents. Underground facilities (such as underground containment buildings and spent fuel pool buildings) are meant to avoid atmospheric contamination during severe accidents and thus improve the safety of new nuclear plants. Both improvements are not suitable for installation at operating nuclear light water reactors at reasonable cost.
It is acknowledged in the Art that none of the above inventions solves the issue of removing the energy accumulated from residual heat and hydrogen inside current operating containment buildings during severe accidents.
Accordingly as of today, the mitigation guidelines for severe accidents at operating light water reactors around the world require the operators to voluntary release heat, steam, radioactive gases and particulate matters through dedicated venting systems when installed. The purpose of those voluntary releases is to avoid more severe uncontrollable releases caused by catastrophic failure of the containment buildings and penetration systems initiated by over temperature and over pressure from residual heat and hydrogen. Voluntary release is accomplished with hardened and sealed—sometimes filtered—venting systems, structures and buildings. The voluntary releases—including Iodine 131, Cesium 137 and noble gases—are usually subsequent to mandatory evacuation and or sheltering at home of the population in the emergency preparedness zones. In the meantime, such venting systems do not apply to some spent fuel pool severe accidents where a large enough breach in the pool walls structures may rapidly generate severe and uncontrolled atmospheric releases.
Prior Art in the field of the invention relates to protection of buildings and structures against potential external explosions. U.S. Pat. No. 7,806,037 B2, adapted to blast protection, does not prevent dissemination of airborne fallout and is not suitable for large existing buildings surrounded with underground tunnels and piping. Likewise, U.S. Pat. No. 6,886,299 B2 does not protect the whole protected volume. It does not mitigate the dissemination of toxic airborne matter and gases. U.S. Pat. No 7,866,101 B2, because air inflatable to define the fire protected structure or building, is not capable of withstanding a large blast. It requires prior deployment with active systems which may not be actionable in the course of an accident. It does not mitigate the dissemination of toxic airborne matter and gases. U.S. Pat. No. 6,782,792 B1 is not designed to prevent dissemination of airborne toxic release but rather to shield the building from the blast wave. Its detection and delivery system have to be energized.
Prior Art in the field of the invention relating to bomb disposal is not relevant. U.S. Pat. No. 5,864,767 does not contain large explosions and or dissemination and cannot be applied to large structures, since its portability by one person makes it suitable for small improvised explosive devices (IED) in conjunction with blast suppression devices. Likewise, U.S. Pat. No. 7,712,405 B2 has a bottom end indispensable to the system as support and armor, not suitable for installation on large structures or explosions of large structures, since the IED has to be positioned inside the device to make it air tight and blast proof. If adapted on a large scale building, its weight would be significant on the structure, while it may deploy unexpectedly and unnecessarily with high winds. It would also prevent access to protected areas. Prior Art in the field also includes spraying of radioactive dust abatement coating on the surrounding soils such as U.S. Pat. No. 5,489,370. These measures can only be attempted as a mitigation effort after the severe accident has occurred and the dissemination of the contamination is widespread and mapped. Given the magnitude of the long term radioactive contamination consequences of a severe accident at a light water nuclear reactor, these measures are extremely expensive.
As evidenced by the four severe accidents at the Fukushima Daichi nuclear facility (Japan) in 2011, it is very well documented in the field that severe accidents still present unresolved challenges to operating light water reactors. For these operating light water reactors, none of the inventions in prior Art solves the issue of removing the energy from residual heat and hydrogen generation inside the containment buildings and spent fuel pool buildings challenged by over temperature (concrete, penetrations) and over pressure (steam explosions, hydrogen deflagration/detonation) during severe accidents while encapsulating the radioactive atmospheric fallout.
For currently operating light water reactors, no invention in prior Art solves the issue of removing the energy from residual (decay) heat and hydrogen generation inside the containment buildings and spent fuel pool buildings challenged by over temperature (concrete, steel, penetrations) and over pressure (steam, air, hydrogen) during severe accidents while encapsulating the radioactive atmospheric fallout from voluntary and/or uncontrolled releases.
The present invention overcomes the problems associated with the prior Art for those facilities, essentially insufficient design free volume, insufficient design pressure, insufficient energy storage capacity and insufficient heat exchange capacity. This invention removes the energy from residual heat and hydrogen generation inside the structures and buildings challenged by over temperature and over pressure during severe accidents, while encapsulating the radioactive atmospheric fallout, retaining vapors, gases and particulate matters.
This passive system is suitable for prefabrication and installation as a variable volume unit enclosing industrial components, systems, buildings and structures such as nuclear reactor containment buildings, spent fuel pool buildings, power plants auxiliary buildings, outlets of pressure relief valves and venting systems.
The enclosing unit comprises one or more retention covers, and one or more anchoring modules. The passive system is suitable for prefabrication, installation, test and maintenance, and operational without interference with the design basis operations and performances of the enclosed industrial components, systems, buildings and structures. Because of the simplicity, modularity, small footprint, light weight and robustness of its stand alone design withstanding major external events (ground motion, flooding, high winds, and large debris), the passive system constitutes a readily implementable cost effective solution for currently operating light water reactors facilities.
Because the passive system deploys only when the releases occur, without human intervention or active system, the unit encapsulates releases from voluntary venting and uncontrolled releases without damage to the population and the environment caused by exposure to Iodine 131 and long term contamination of the land with Cesium 137 in the emergency evacuation zones around the facilities. It overcomes the prior Art issues of human intervention issues during severe accident.
The high velocity deployment of the passive system maintains the integrity of the enclosing unit when exposed to high velocity fallout, allowing retention of releases such as vapors, gases, steam, particulate matters and debris. With a deployment velocity of the retention cover of 90 m/second, a design pressure of 4 bar and a fully deployed volume of 3 to 4 times the volume of the enclosed structure, the invention overcomes the issues of hydrogen explosion, design pressure and free volume of the enclosed structure encountered with prior Art.
The deployment of the system in the atmosphere transfers the heat from the releases enclosed in the unit to the atmosphere, cooling off encapsulated gases and particulate matters, condensing steam and vapors in the unit and retaining water and liquids. The volume of the unit depends on the energy of the releases enclosed in the unit, on the outside air temperature and humidity rate, and on gravity. Unlike prior Art, the volume of the fully deployed unit allows steam and vapors condensation, water and liquids retention with a heat exchange capacity in the range of 30 MW under average weather conditions. This capacity is sufficient to evacuate the energy from residual heat and hydrogen from operating light water reactors structures during severe accidents.
This invention also encapsulates design basis accidents releases such as the early release of radioactive steam through hardened venting systems to the atmosphere (boiling water reactors), the early release of radioactive steam through containment bypasses systems to the atmosphere (pressurized water reactors).
The system is active whatever the level of integrity of the enclosed components, systems, buildings and structures after the severe accident and loss of large areas of the plant buildings due to explosions and fires, collecting the fallout from voluntary releases or from the explosions or leaks caused by the loss of integrity of the structures and buildings. Because the passive system retains most of the radioactive fallout on the roof and around the containment buildings, spent fuel pool buildings and nuclear auxiliary buildings, the invention reduces the risks of inadvertent radiation exposure of the first responders and facilitates first emergency response operations such as power restoration, restoration of cooling of the nuclear fuel rods and/or corium, and access to the buildings and structures.
The usefulness of the present invention is not limited to nuclear containment buildings. The passive system can also encapsulate the uncontrolled releases from radioactive gas storage nuclear auxiliary buildings, the uncontrolled releases from spent fuel rods damage in the spent fuel pool buildings during manipulation. Actually, the unit can be used anywhere it is desirable to control potential consequential atmospheric releases, such as from relief valves, industrial buildings, structures and systems, nuclear reactors, spent fuel pool buildings or power plants, stacks and other blowout preventer systems.
The present invention can also be very useful in the field of planned demolition of industrial and commercial buildings in populated areas where air quality is a legitimate concern of the neighboring community, and can provide a cost effective alternative to prolonged temporary evacuation and clean-up plans.
The passive system can also be used to control potential consequential releases in the water, including to retain or to control releases from installed relief valves, and other systems. The invention can be useful to encapsulate releases from accidents at deep water oil and gas wells such as blowout preventer systems failures.
Brief Description of Figures:
The present invention provides a passive system suitable for customized design, prefabrication and installation as a unit around confined industrial buildings, systems, and structures such as nuclear reactor containment buildings, spent fuel pool buildings or power plants. In the following description, specific details are set forth in order to provide a thorough understanding of the invention. Those skilled in the Art will recognize, however, that the invention may be practiced apart from these specific details. In other instances, details of well known design and construction practices and components have been omitted, such as those related to earthquakes and flooding, so as not to unnecessarily obscure the present invention.
A general view of the unit installed on a nuclear containment building is represented on
One or more retention covers (2).
One or more anchoring modules (4).
The retention cover, shown on
The embodiment of the anchoring module, shown on
An upper internal panel (12)
An upper external panel (14)
A lower internal panel (16)
A lower external panel (18)
A support structure (20)
An anchoring casing (22)
A protective skirt (24)
The internal panels (12)(16) are light and multilayered. One layer is made of blast absorbent material such as expended perlite. One layer is heat resistant, perforation resistant and shock wave reflective such as Kevlar or fiberglass. One layer is flame resistant up to 1800-2210 Celsius degrees, such as ceramic coating. The external panels (14)(18) are light and multilayered. One layer is made of blast absorbent material such as expended perlite. One layer is heat resistant, perforation resistant and shock wave reflective such as Kevlar or fiberglass. One layer is flame resistant up to 1800-2210 Celsius degrees, such as ceramic coating. The anchoring casing (22) is light and multilayered. Two layers are made of blast absorbent material such as expended perlite. One layer is heat resistant, perforation resistant and shock wave reflective such as Kevlar or fiberglass. Two layers are flame resistant up to 1800-2210 Celsius degrees, such as ceramic coating. The support structure (20) of the anchoring module comprises one or more poles made of stainless steel, and one or more dampers and springs (26). The protective skirt (24) is flame resistant up to 1800-2210 C. degrees, flexible and heat resistant (such as made primarily from tungsten with iron metal powder immersed in a silicone polymer or Nomex). A flexible seal (28) made of material such as rubber, can be inserted at the base of the protective skirt. The flexible stop (30) can also be made out of rubber. The protective skirt may be equipped with heat resistant flexible piping (such as Nomex material) and fasteners.
In the embodiment disclosed, the anti-tornado system consists of:
One or more seals, such as a flexible seal (28) and a flexible stop (30) which can be made out of rubber at the basis of each anchoring module along the protected structure.
One or more static pressure equalizers (32). The exterior casing of the pole of the support structure (32) constitutes a heat and flames resistant piping and is made of fiberglass or Kevlar or stainless steel. It is connected to the anchoring casing (22) with one or more heat resistant flexible piping on one end made of heat 30 to 50 bar pressure resistant and flames resistant material such as Nomex and to the base of the system with explosion-proof metal or fiberglass piping, all but one equipped with fasteners (34) on the other end.
One or more pressure activated devices (36) on the upper external panel (14). In the disclosed embodiment, the dynamic pressure activated rotating device (36) is made of the same material as the panels. The blade outside the retention cover casing is at least twice as long as the one inside. The blades are at an angle of 100 to 120 degrees apart.
At a minimum, the outer layer (10) of the retention cover is anchored at one point to each anchoring module (4). The outer layer can be equipped with fabric piping allowing connection through the support structure to water systems, venting systems, and treatment systems as needed. The retention cover layers may be attached to each others or independent. The outer layer may be in one piece or multiple pieces. The mid-layers and inner layer may be of a different size and shape than the outer layer. In the preferred embodiment shown, the mid-layers and inner layer only cover the roof of the building and are independent from the outer layer. The bottom of each piece of the outer layer folded in the anchoring module is sealed to each anchoring module. The top of each piece of the outer layer folded in the anchoring module is anchored to each anchoring module with a tensioner to facilitate the folding back of the deployed outer layer in the anchoring module. The internal panels (12) (16) are overlapping each others as shown on
The anchoring casing (22) anchors the retention cover and the protective skirt. It is connected to the support structure (20) with the dampers and springs (26). It also constitutes the structure where the panels are attached. The anchoring casing allows drainage of the cavity where the retention cover is folded. It also contributes to balancing the static pressure between the covered section of the structure and the exterior. The main pole of the support structure (20) is anchored to the ground with one or more dampers and springs (26). The main pole is connected to the anchoring casing (22) with one or more dampers and springs (26). The exterior casing of the pole (32) constitutes a piping. It is connected to the anchoring casing (22) with flexible piping on one end and to the base of the system with piping, all but one equipped with fasteners (34), on the other end. The protective skirt is anchored to the anchoring casing (22).
Each retention cover and anchoring module can be assembled prior to shipping and installation. Therefore, each anchoring module can be pretested and/or pre-certified prior to installation.
The installed passive self deployable unit deploys when a release occurs from the protected structure, without human intervention or active system, using only the energy and pressure of the gases and debris to deploy both the protective cover and the protective skirt.
When the release occurs, it pushes some of the anchoring modules (4) away from the building. The gases and debris are deflected by the anchoring modules internal panels (12) (16) (22). The module absorbs some of the energy by moving away and staying away from the building as allowed by the dampers and chock absorbers (26) at a distance of 5 to 10 times the width of the anchoring casing. The gases, flames and lighter debris are mostly funneled upwards and push against the top of the internal upper panels (12) of some anchoring modules away from the building. When the mixture reaches the inner layer (6) of the retention cover, the flames are stopped. The gases and particle matter reach the middle layer (8) of the retention cover and some of the energy is absorbed by the mid-layer. The steam and moisture going through also allow the mid-layer to absorb some of the radioactive particles, the mid-layer acting as an emergency filter and or a scrubber. The hot gases and remaining particle matter then pressurize the outer layer (10) of the retention cover and deploy the retention cover. The maximum deployed volume of the retention cover depends on the volume of the protected structure and the pressure inside the structure or depends on the volume, duration and pressure of the voluntary expected release. In this embodiment, with the protective cover 2 to 4 times the volume of the nuclear containment building, the convective heat exchange capacity of the unit with the atmosphere, depending on outside temperature and humidity rate, condensing steam and vapors and retaining water and liquids in the enclosed structure, is in the 20-30 MW range. The protective skirt (24) is deployed when the blast pushes the anchoring module away from the building, thus deploying only from its own weight. The protective skirt (24) deploys downwards, thus funneling the heavier debris along the base of the building. The exterior casing of the pole (32) of the support structure (20) is now connected to the interior of the deployed retention cover on one side, and to the base of the system inside the protective skirt (24) on the other end. These spaces can now be connected through the fasteners (34) to water systems, inert gases injection systems, venting systems, hydrogen recombination systems, visualization or treatment systems as needed after the accident or voluntary release. Likewise, the flexible piping of the retention cover and the protective skirts are now deployed and allow first responders actions such as video recording, sampling, injection of inert gases, water spraying or decontaminants spraying. Moreover, the protective skirt can be easily cut after radiation mapping.
The internal panels (12) (16) absorb some of the energy of the blast, reflect the chock waves, deflect the debris from the blast of the building and shield the housing of the folded retention cover and protective skirt from the debris. The external panels (14) (18) guide the deployment of the retention cover and protective skirt, while shielding them from the debris and flames. The external panels also deflect the debris from high winds and external threats. The anchoring casing (22) holds the retention cover and the protective skirt to the support structure, and facilitates the safe deployment of the retention cover and protective skirt. It absorbs some of the energy of the blast, reflects the chock waves, deflects the debris from the blast of the building and shields the housing of the folded retention cover and protective skirt from the debris. It acts as a shield, deflecting the debris and flames from high winds and external threats. The support structure (20) of the module supports the weight of the anchoring module. It maintains the structural integrity of the anchoring module during earthquakes, high winds and flooding, fire and explosions of the buildings and structures. The dampers and springs (26) allow the anchoring module to move away and stay away from the building, thus absorbing some of the energy of the blast. The protective skirt (24) funnels the heavier debris as close as possible to the source. It shields responders from radiation, covering most significant radioactive debris and collecting water.
The tornado anti-deployment passive system prevents the unwanted deployment of the retention cover from high ascendant winds. When high ascendant winds occurs, the flexible seal (28) and flexible stop (30) at the basis of each anchoring module along the protected structure prevent high ascendant winds to enter the space between the retention cover and the building. The static pressure equalizer (32) redirects the excess static pressure in the covered section of the structure to the exterior at the base of the building. High ascendant winds also create the rotation of the external blade of the pressure activated device (36) on the upper external panel (14). The equal rotation of the internal blade closes the casing of the folded retention cover. Gravity reopens the casing as soon as the ascendant wind speed decreases.
The protective skirt may deploy during an earthquake, since the unit is independent from the protected building and the stop (30) is not. The protective skirt can be secured when activities are scheduled in the immediate proximity of the protected building.
The unit may be locally perforated by high energy debris from an explosion outside the protected building. However, due to its modular structure, this does not impair the ability of the unit to deploy fully and capture most of the fallout if the explosion occurs close to the protected building.
The description of particular embodiments of the present invention is now complete.
Many of the described features may be substituted, altered or omitted without departing from the scope of the invention. For example, the anchoring system may be substituted for the particular model of anchoring disclosed, such as a heat and flame resistant rope circling the base of the retention cover. Similarly, alternate support structures of anchoring modules may be substituted for the particular support structure disclosed, such as rails. As another example, one can build the upper external panel, upper internal panel, anchoring casing, lower internal panel and lower external panel individually and assemble them or build them as one piece. Their size and shape are adjusted to the protected structure or source of potential voluntary release. The anchoring casings can be attached to each other or independent. As another example, the anti-tornado system may also depart from the model disclosed, such as using the dynamic pressure differential to close the lid of the casing where the retention cover is folded, or using dynamic seals, or modifying the shape of the retention cover exposed to the elements to reduce its susceptibility to lifting during high ascendant winds, or using rain water drains to create a liquid seal.
Likewise, components may be omitted depending on the specific protected structure, such as some layers of the retention cover. As an example, dampers and springs may be positioned on both sides from the axle of the main pole of the support structure. Those can be of different types.
These and other deviations from the particular embodiments shown will be apparent to those skilled in the Art, particularly in view of the present disclosure. As an example, the heat resistant flexible piping can be embedded around the damper and spring.
Indeed, unless explicitly stated, no single component is considered to be an essential element of the invention.
The usefulness of the present invention is not limited to nuclear buildings, structures and systems. Actually, the unit can be used anywhere it is desirable to control potential consequential atmospheric releases, such as relief valves, industrial buildings, structures and systems, nuclear reactors, spent fuel pool buildings or power plants, stacks and other blowout preventer systems. The present invention can also be very useful in the field of planned demolition of industrial and commercial buildings in populated areas where air quality is a legitimate concern of the neighboring community, and can provide a cost effective alternative to temporary evacuation plans. The passive system can also be used to control potential consequential releases in the water, including to retain or to control releases from installed relief valves, and other systems. The invention can be useful to encapsulate releases from accidents at deep water oil and gas wells such as blowout preventer systems failures.
This application claims the benefit of priority date from provisional application No. 61/512,406 Filing or 371(c) date Jul. 28, 2011 under 35 U.S.C. 119(e), the entire content of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61512406 | Jul 2011 | US |
