{"id":26750,"date":"2020-03-16T16:50:14","date_gmt":"2020-03-16T16:50:14","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=26750"},"modified":"2023-07-15T07:44:14","modified_gmt":"2023-07-15T07:44:14","slug":"self-powered-neutron-detector","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-reactor\/nuclear-instrumentation\/incore-nuclear-instrumentation\/self-powered-neutron-detector\/","title":{"rendered":"Self-Powered Neutron Detector"},"content":{"rendered":"
Self-Powered Neutron Detectors<\/strong> (SPND<\/strong>) are neutron detectors widely used in reactors to monitor neutron flux<\/a> due to their adaptability for in-core severe environments. SPNDs<\/strong> may be a part of the incore neutron flux monitoring system, which provides detailed information on neutron flux distribution and thus the margins to these peak power limits. These detectors use its neutron activation material’s basic radioactive decay<\/a> process to produce an output signal. As the name implies, \u00a0SPNDs do not require an external voltage source<\/strong> to create a voltage potential in the detector. Instead, a current is produced in the detector as the result of neutron activation<\/strong> and subsequent beta decay<\/strong><\/a> of the detector itself. Because of the emission of these beta particles (electrons), the wire becomes more and more positively charged. The positive potential of the wire causes a current to flow in the resistor, R. The electron current from beta decay can be measured directly with an ammeter.<\/p>\n There are two main advantages of the self-powered neutron detector:<\/p>\n On the other hand, there are also disadvantages, and one is associated with the fact that currents, even at full power operation, are very low. Therefore, SPNDs cannot provide information about flux distribution at low power operation (10% and less). The main disadvantage of the self-powered neutron detector is that the emitter material decays with a characteristic half-life, which determines the detector’s response time. Depending on the response time, these detectors are broadly classified as:<\/p>\n The typical SPND is a coaxial cable consisting of:<\/p>\n Self-powered neutron detectors<\/strong> are usually placed into the instrumentation tube of a fuel assembly. They can monitor the entire length of selected fuel assemblies to provide an accurate, three-dimensional map<\/strong> of the neutron flux distribution<\/strong>. Neutron flux reconstruction can also be performed in the rest of the reactor core using these data.<\/p>\n Typical materials used for the emitter are cobalt, cadmium, rhodium, and vanadium. These materials should be used because they possess relatively high melting temperatures and high cross sections to thermal neutrons and are compatible with the SPND manufacturing process.<\/p>\n Special Reference: William H. Todt, Sr. CHARACTERISTICS OF SELF-POWERED NEUTRON DETECTORS USED IN POWER REACTORS. Imaging and Sensing Technology Corporation. New York.<\/p>\n\n
\n
\n