Methods and systems for detecting an individual leaking fuel channel included in a reactor. One system includes a plurality of inlet lines and a plurality of outlet lines. Each of the plurality of inlet lines feeding annulus fluid in parallel to an annulus space of each of a first plurality of fuel channels included in the reactor, and each of the plurality of outlet lines collecting in parallel annulus fluid exiting an annulus space of each of a second plurality of fuel channels included in the reactor. In some embodiments, the system also includes a detector positioned at an outlet of each of the plurality of outlet lines configured to detect moisture in annulus fluid and identify a first position of an individual leaking fuel channel, and an isolation valve positioned at an inlet of each of the plurality of inlet lines operable to stop annulus fluid from circulating through one of the plurality of inlet lines and to identify a second position of the individual leaking fuel channel.

Methods and systems for detecting an individual leaking fuel channel included in a reactor. One system includes a plurality of inlet lines and a plurality of outlet lines. Each of the plurality of inlet lines feeding annulus fluid in parallel to an annulus space of each of a first plurality of fuel channels included in the reactor, and each of the plurality of outlet lines collecting in parallel annulus fluid exiting an annulus space of each of a second plurality of fuel channels included in the reactor. In some embodiments, the system also includes a detector positioned at an outlet of each of the plurality of outlet lines configured to detect moisture in annulus fluid and identify a first position of an individual leaking fuel channel, and an isolation valve positioned at an inlet of each of the plurality of inlet lines operable to stop annulus fluid from circulating through one of the plurality of inlet lines and to identify a second position of the individual leaking fuel channel.

An detector-assembly for measuring flux in a nuclear reactor core includes self-powered in-core detector arrangements each for measuring flux at a different one of a plurality of axial locations in the core, and an assembly connector configured to be connected to a power plant connector. The assembly connector includes a plurality flux signal terminals each connected to one of self-powered in-core detector arrangements. At least one of the self-powered in-core detector arrangements comprises a set of at least two self-powered in-core detectors for measuring flux at a same one of the axial locations in the nuclear reactor core. Each of the at least two self-powered in-core detectors includes a sheath, a detector material section inside the sheath, an insulator between the sheath and the detector material, and a flux signal output line. The flux signal output lines of the at least two self-powered in-core detectors are joined together.

A method for detecting a leak in a cladding tube in a nuclear reactor is described. The method is well-suited for use in a reactor having a plurality of cladding tubes housed in a plurality of linearly arranged channels for flowing coolant past the cladding tubes. The method includes monitoring the channels for the occurrence of an increase in radiation above a selected base line indicative of the presence of at least one fission product in the coolant in at least one of the plurality of channels, and monitoring the channels for the occurrence of time dependent changes in the strength of radiation in the coolant above the base line along the length of the at least one of the plurality of channels. The leak location is calculated by triangulating the radiation readings from a fixed linear array of detectors positioned adjacent to the channels to determine the location of the strongest radiation reading and the location along the length of the channel where the increase in radiation occurred.

A defective fuel bundle location system for use with a heavy water moderated nuclear fission reactor having a fueling machine, including a test tool defining an internal volume, the test tool being configured to be received within both the fueling machine and a corresponding fuel channel of the reactor, and a test container defining an internal volume, wherein the test container is configured to be received within the internal volume of the test tool and the internal volume of the test container is configured to receive primary fluid from the reactor when the test tool is disposed within the corresponding fuel channel of the reactor.

A defective fuel bundle location system for use with a heavy water moderated nuclear fission reactor having a fueling machine, including a test tool defining an internal volume, the test tool being configured to be received within both the fueling machine and a corresponding fuel channel of the reactor, and a test container defining an internal volume, wherein the test container is configured to be received within the internal volume of the test tool and the internal volume of the test container is configured to receive primary fluid from the reactor when the test tool is disposed within the corresponding fuel channel of the reactor.

A defective fuel bundle location system for use with a heavy water moderated nuclear fission reactor having a fueling machine, including a test tool defining an internal volume, the test tool being configured to be received within both the fueling machine and a corresponding fuel channel of the reactor, and a test container defining an internal volume, wherein the test container is configured to be received within the internal volume of the test tool and the internal volume of the test container is configured to receive primary fluid from the reactor when the test tool is disposed within the corresponding fuel channel of the reactor.

A defective fuel bundle location system for use with a heavy water moderated nuclear fission reactor having a fueling machine, including a test tool defining an internal volume, the test tool being configured to be received within both the fueling machine and a corresponding fuel channel of the reactor, and a test container defining an internal volume, wherein the test container is configured to be received within the internal volume of the test tool and the internal volume of the test container is configured to receive primary fluid from the reactor when the test tool is disposed within the corresponding fuel channel of the reactor.

A defective fuel bundle location system for use with a heavy water moderated nuclear fission reactor having a fueling machine, including a test tool defining an internal volume, the test tool being configured to be received within both the fueling machine and a corresponding fuel channel of the reactor, and a test container defining an internal volume, wherein the test container is configured to be received within the internal volume of the test tool and the internal volume of the test container is configured to receive primary fluid from the reactor when the test tool is disposed within the corresponding fuel channel of the reactor.

A radiation detecting attachment comprising four radiation detectors configured to detect radiation from an object of detection W, attached removably to a working machine, wherein the radiation detecting attachment is supported by the working machine movably when the radiation detecting attachment is attached to the working machine, and is supported by an arm body of the working machine swingably, and a distance between the radiation detectors and the other radiation detectors is changeable. This makes it possible to use the radiation detectors efficiently and in a versatile manner.