A shape memory radial seal was fabricated with a ''U'' cross section. Upon heating the seal recovered its original ''V'' shape and produced a high pressure seal. The sealing pressure which can be developed is approximately 41 MPa (60,000 psi), well in excess of the pressure which can be produced in conventional elastomeric seals. The low modulus martensite can conform readily to the sealing surface, and upon recovery produce a seal capable of high pressure fluid or gas confinement. The corrosion resistance of nickel-titanium in a broad range of aggressive fluids has been well established and, as such, there is little doubt that, had time permitted, a geothermal pump of flange fluid tried would have been successful.