The problem was solved for the reaction at safety valve exhuast pipes, see B31.1 or otehr codes regardign releif valve exhaust piping . Safety valves flow is almost always choked flow( inlet pressure > 2*exhaust pressure), original tech paper that the code calcs is based on the Bechtel/Liao paper of 1971.
"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick