Patent Number: 042382904
Section: claims

1. A controllable valve for the live steam line extending from the inside to the outside of the containment of a nuclear reactor plant comprising: (a) a valve body having an inlet, an outlet and a valve seat, each with a cross section corresponding to that of the live steam line;  (b) probe means in the live steam line for detecting the pressure therein in order to detect a leak in said steam line;  (c) a movable valve disk disposed within said valve body;  (d) operating means coupled to said probe means and responsive thereto for moving the valve disk to a closed position in the event of a leak in the live steam line, said operating means being further responsive to the application of the pressure on the valve disk in excess of the normal operating pressure of the live steam line to move the valve toward an open position; and  (e) limiting means for limiting the reopening of the valve in response to said excessive pressure to a maximum of one half the outlet cross section, whereby after closing, in response to a leak in the live steam line, said valve will reopen to prevent a build-up of pressure on its inlet side to prevent damage to the nuclear reactor plant. 2. The valve of claim 1 in which the disk has retard means for holding it from opening for more than about 30% of said aperture cross section under the force of said excessive pressure, at least for a short time interval. 3. The valve of claim 2 in which said retard means is adjustable. 4. The valve of claim 3 in which the valve disk has an operating stem and the said retard means comprises an adjustable mechanical stop for the stem and powered means for adjusting the stop. 5. The valve of claim 1 in which said operating means is for sequentially partially closing and thereafter fully closing the valve disk on the valve seat, under said force which is overcome by said excessive pressure. 6. The valve of claim 5 in which said partial closing leaves the valve with a residual aperture cross section of from 5% to 20% of said maximum aperture cross section. 7. The valve of claim 5 in which said partial closing is adjustable. 8. The valve of claim 1 in which said valve disk and valve seat have conical surfaces differently angled to form an annular Venturi when the valve disk is partially closed on the seat. 9. The valve of claim 1 in which the fast-acting valve is inside said containment. 10. The valve of claim 1 in which said operating means has a statically stored energy source controllably connected thereto.