Patent Number: 
Section: claims

1. A sensor for measuring electrochemical corrosion potential in a nuclear reactor comprising: a tubular ceramic probe having a closed tip at one end packed with a metal and metal oxide powder;  a metal support tube having one end receiving an opposite end of said probe, and joined thereto by a braze joint therewith;  an electrical conductor extending through said support tube and probe, and having an end buried in said powder for electrical contact therewith; and  a plasma sprayed ceramic band disposed on an outer surface of said tubular ceramic probe and said metal support tube, said plasma sprayed ceramic band bridging said tubular ceramic probe and said metal support tube at said joint for sealing thereof, said plasma sprayed ceramic band having a coefficient of expansion that is compatible with that of said tubular ceramic probe. 2. A sensor according to  claim 1  wherein said band locally coats said probe and tube at said braze joint, and is spaced from said probe tip. claim 1 3. A sensor according to  claim 2  wherein both said probe and band comprise zirconia. claim 2 4. A sensor according to  claim 3  wherein said powder comprises iron and iron oxide. claim 3 5. A sensor according to  claim 3  wherein said powder comprises copper and copper oxide. claim 3 6. A sensor according to  claim 3  wherein said powder comprises nickel and nickel oxide. claim 3 7. A sensor according to  claim 3  wherein said band comprises yttria-stabilized-zirconia or magnesia-stabilized-zirconia. claim 3 8. A sensor according to  claim 3  wherein said band is directly bonded to said probe and tube at said braze joint. claim 3 9. A sensor according to  claim 3  further comprising a bond coating underlaying said band and bonded to said probe and tube at said braze joint. claim 3 10. A sensor according to  claim 3  wherein said probe comprises magnesia-stabilized-zirconia. claim 3 11. The sensor according to  claim 1 , further comprising a bond layer, said bond layer underlaying said band and being bonded to said probe and tube at said braze joint. claim 1