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In-Core Facilities

The MITR core can accommodate three in-core irradiation facilities. The thermal and fast (>0.1 MeV) fluxes in the core region are up to 3.6 x 10 13 and 1.2 x 1014 n/cm2-s, respectively. These flux levels are comparable to a commercial Light Water Reactor (LWR). The approximate dimensions for each in-core facility are ~ 2” ID x 24” long. The in-core irradiation facilities are suitable for advanced materials and fuel research. (See In-Core Position Characteristics and Constraints.)

A license amendment is approved by the NRC to perform in-core fuel irradiations as long as the fissile material mass in limited to 100 gm or less, provided that the fuel irradiation does not contain a forced circulation loop. The MITR is the first research reactor in the U.S. that is licensed to perform in-core fissile materials irradiation.

Members of NRL's In-Core Experiments (ICE) Group have more than 15 years of experience in design and operating in-core experiment facilities. The experiments they can conduct at the MITR include, but are not limited to, the following areas:

Corrosion Testing/Environmental Degradation Testing

Nuclear Materials Irradiations / Low Dose Scoping Studies

High Temperature Irradiations of Cladding and Structural Materials

Small Aggregates Fuel Irradiations

Advanced Materials and Instrumentation Development.

A variety of in-core and support instrumentation and measurement can be provided to support in-core loop irradiation. Thermocouple temperature measurement is the most common in-core measurement. Other in-core instrumentation that has been used includes electrochemical corrosion potential and other electrode measurements and DC potential drop strain and crack growth measurement. A variety of data acquisition equipment is available if experimenters desire to use or test their own in-core instrumentation. A wide variety of parameters are routinely monitored and recorded at out-of-core locations for the in-core facilities. For water loops these include temperature, pressure, flow, dissolved hydrogen and oxygen, and conductivity. Real-time residual gas analysis (mass spectrometry) is also available for the ICSA and high temperature facilities. Radiochemical and chemical assays can be performed on site on batch-sampled radioactive coolant samples. For chemical assays, ICP-OES, INAA and prompt gamma NAA are available. MITR staff will support use of specialized instrumentation required for a particular experiment, subject to funding and manpower constraints. If interested in pursuing research utilizing the MITR-II in-core capabilities, contact Gordon Kohse.

Irradiation programs have been funded to utilize the ICSA for testing advanced high-temperature materials (MAX phases) and advanced in-core thermocouples and fiber optic sensors.