Conductivity probe for use in the presence of high intensity nuclear radiation

Claim 1

An electrical conductivity sensor designed to withstand high temperatures, pressures and nuclear radiation, an alumina insulator having a base region with an external attachment surface, and an integrally formed post with an external attachment surface, the post extending from the base region and having a channel extending through the post and base for conveying a conductor insulatively through the insulator; a first metallic coating intimately adhered to the external attachment surface of the post, and a second metallic coating intimately adhered to the base external attachment surface, the first and second metallic coatings being formed to accept a braze bond; a central electrode formed from a select metal exhibiting a coefficient of thermal expansion compatible with the alumina insulator and resistant to corrosion in a boiling water reactor, the central electrode having a concave interior surface with a third metallic coating intimately adhered thereto for accepting a braze bond, the central electrode being positioned over the external attachment surface and brazed thereto in a compressive seal; sleeve means formed of a first select metal exhibiting a coefficient of thermal expansion compatible with the alumina insulator and resistant to corrosion in a boiling water reactor, the sleeve means having an acceptance portion with a fourth metallic coating intimately adhered thereto for accepting a braze bond, the acceptance portion being in compressive sealed brazed connection with the base external attachment surface of the insulator and insulatively separated from the central electrode, the sleeve means having a first internal channel extending along the lengthwise extent thereof; a counter-electrode formed from a select metal resistive to corrosion in a boiling water reactor, the counter-electrode being attached with an electrically conducting bond to the sleeve means and extending over the central electrode at a fixed spaced distance, the counter-electrode containing a plurality of openings to permit a continuous exchange of fluid to fill the gap between the central electrode and the counter-electrode; a conductor connected in electrical contact with the interior surface of the central electrode and insulatively extending therefrom through the channel in the insulator and insulatively extending through the first internal channel in the sleeve means; and positioning and signal transfer means for operatively supporting the sleeve means and conveying signals to and from the conductor and the sleeve means.