Measurements of impact loads and expansion of flashing water jets

Abstract

Tests were carried out at Westinghouse Canada Inc., Hamilton, Ontario, to measure impact forces and axial depressurization of initially subcooled water jets discharging into the atmosphere. The purpose of the tests was to provide data for model studies investigating the consequences of a hypothetical nuclear reactor primary coolant circuit rupture. Break openings of 25 mm, 76 mm and 102 mm were tested using simple convergent nozzles. Two targets were used: a 1 m diameter flat circular plate and a section of 57 mm diameter pipe with axis on the jet centreline and perpendicular to it. Further tests were conducted with a slender instrumented probe supported on the jet centreline to measure the depressurization of the “free” jet. Test conditions included initial reservoir pressures up to 7 MPa and liquid subcooling to 60 K. The impingement plate test results with the 25 mm nozzle indicate that a thrust coefficient of from 1.3 to 1.4 is appropriate, except where surrounding structures restrict free expansion. For the latter case, thrust coefficients up to 4 were measured. Also there are indications that a subcooled core exists within the jet extending to an L/D of at least 1.