Disclosed herein is a nuclear power plant main steam system, which reduces the atmospheric discharge of radioactive materials generated in an accident, the system including: a decontamination water tank containing decontamination water; and a connection pipe for connecting the decontamination water tank from a main steam pipe which connects a steam generator and a turbine, wherein the connection pipe is connected to the decontamination water tank through a main steam safety valve or a connection valve, wherein the main steam safety valve or the connection valve is configured by a three-way valve and is configured to discharge the generated steam to the air when an accident occurs within a design basis and to transfer the generated steam to the decontamination water tank when a severe accident occurs. A main steam system according to the present invention has an effect of reducing discharge of radioactive materials to the air when a containment bypass accident including a steam generator tube rupture caused by high-temperature steam occurs.

A failed fuel pin emits cesium into the primary sodium coolant and xenon into the cover gas in a reactor vessel. A pipe containing radioactive liquid sodium accepts flowing primary sodium from the reactor vessel. A radiation detector is positioned adjacent the pipe such that gamma radiation emitted from the pipe can be measured. The pipe may be isolated to increase detection limits by allowing short-lived isotopes to decay. The isotopic ratio of .sup.137Cs/.sup.134Cs can be measured, which can be used to determine the burnup of a fuel assembly from within the core, and therefore, the failed fuel assembly can be identified based at least in part on the burnup. Further, mass spectrometry may be used to measure the ratio of a stable and unstable xenon isotope. The identification techniques may be used in conjunction to quickly identify a failed fuel assembly in-situ and during reactor operation.

The invention relates particularly to a device (3) for controlling and measuring welding defects on a cylindrical wall (140) such as a vessel bottom penetration (14) wall) (140) of a nuclear reactor, said device comprising a control head (4) forming a probe which has a proximal end (EP) and a distal end (ED), along the longitudinal axis (X-X) thereof, and includes a first side (42), a so-called inner side, provided with at least one ultrasonic wave translator, characterized in that: said control head (4) comprises a second side (43), a so-called outer side, opposing the first side (42), which has a curved surface in the form of a cylinder fraction, with a longitudinal axis parallel to the longitudinal axis (X-X) of the head (4) and an outwardly facing convexity; said wave translator consists of a series (5) of adjacent elements (50), each element (50) being both an emitter and a receiver, said series (5) having a curved surface in the form of a cylinder fraction in the same direction as said longitudinal axis (X-X) and an outwardly facing concavity; and the plane (P1) containing the two end generatrices of the cylinder fraction of the second side (43) forms a non-null acute angle with the plane (P2) containing the two end generatrices of said cylinder fraction of the wave translator (5).

An emission monitoring system for a venting system of a nuclear power plant is configured for low consumption of energy and high reliability. The emission monitoring system has a pressure relief line connected to a containment and contains a high-pressure section, a low-pressure section, and a sampling line. The sampling line opens into the low-pressure section of the pressure relief line and is guided from there to a functional path and through the sampling line steam flows. A jet pump containing a pump fluid connector, a suction connector and an outlet connector is provided. A pump fluid feed line has an inlet side opening into the high-pressure section of the pressure relief line and is guided from there to the jet pump and connected to the pump fluid connector. A sample return line is guided from the functional path to the jet pump and connected to the suction connector.

A nuclear instrumentation system and method for locating the same are disclosed. The nuclear instrumentation system includes a source range channel, an intermediate range channel and a power range channel, wherein each channel includes one detector installed around the pressure vessel, the detectors of the power range channel and the intermediate range channel both include several fission chambers, the detectors of the intermediate range channel and power range channel share several fission chambers. Some detectors employ fission chambers, so the Gamma radiation resistance property, anti-noise property and anti-electromagnetic interference property are improved. Sharing fission chambers reduces the number of detectors to be installed, thus relieving the workload of the installation and positioning of the follow-up detector. Further, the present application increases the number of some channels, which increases the redundancy, improves system reliability.

A gravity-based, non-invasive method of measuring a level of fluid in a container comprises use of at least one gravity meter located as proximate a center of mass of the fluid as possible. In a nuclear reactor system a method for monitoring the level of fluid in a nuclear reactor module, a report of a loss or gain of fluid within a cylindrical module may be generated from capturing a time series of gravity data from a first gravity meter mounted as an upper gravity meter and a second gravity meter mounted as a lower gravity meter, for example, proximate a cylindrical nuclear reactor module so as not to require any invasive conduit through, for example, a containment pressure vessel (CPV) or a reactor pressure vessel (RPV). In one embodiment, the upper and lower gravity meters are mounted on stable mounts as close to the fluid in the module as possible within a coolant pool or a structure containing cooled air. If a coolant pool of water surrounds a nuclear reactor module, the meters may be housed within a dry housing in the coolant pool such that the meters may be accessed from above the coolant pool and are located as close as possible to the reactor module and its contained mass of fluid.

An apparatus including an integrated system, which can include a nuclear reactor; and a containment isolation system configured to prevent release of radioactive material from the nuclear reactor. The containment isolation system can include a containment vessel and a containment isolation test valve. The containment isolation test valve can include a body having a first test port and a first test port plug. The containment isolation test valve can include a cover configured to couple with the body, the cover having, a first seal, a second seal, an area between the first seal and the second seal, a second test port, and a second test port plug. The containment isolation system can include a containment isolation valve.

A leak detection system includes a leak detection apparatus. The leak detection apparatus includes an electrode mesh and an insulative layer associated with the electrode mesh. The insulative layer is engageable with a conducting fluid containing component. The electrode mesh is configured to output an electric signal responsive to a conducting fluid reaching the electrode mesh through the insulative layer. The leak detection apparatus further includes a computing device configured to receive said electrical signal and associate said electrical signal with a leak event by correlating said electrical signal with a baseline electrical output of the electrode mesh.

The present disclosure relates to an apparatus for detecting nuclear reactor coolant leaks that is capable of maintaining radiation detection reliability and the integrity of a radiation detector from high-dose background radiation inside a nuclear reactor when a coolant leaks from the primary coolant system of the nuclear reactor. The apparatus of the present disclosure includes a shield having an internal space into which sample air containing a coolant leaking from a primary coolant system pipe of a nuclear reactor is introduced. The shield is configured to close the exposed internal space or expand the internal space through detachable coupling. The apparatus of the present disclosure further includes a first sensor disposed in the internal space to obtain a radiation measurement signal from the sample air. The apparatus of the present disclosure further includes a discriminator for determining whether a coolant is leaking based on the radiation measurement signal.

Leakage detection systems and methods of monitoring leakage using probes of fiber optic and/or Time Domain Reflectometry (TDR) cables that provide at least one of an electric and electromagnetic signal upon coming in contact with a liquid from the pool. An interrogator may be multiplexed with several of the cables and generate interrogation signals whose reflection determines an exact position along the cable of leakage contact. The cables may be run under a floor and/or wall of a spent fuel pool or other liquid volume in a nuclear power plant. Leakage even of deionized water near room temperature may be detectable. The cables may be a single serpentine cable or several straight cables wrapping around the volume. The cables may be small, such as 10 millimeters or less in diameter. Cables may be run behind liners at any pitch or interval, potentially between supporting structures and the liner.