Patent Number: 049922319
Section: claims

1. An emergency core cooling system for spraying cooling water onto a nuclear reactor core of a nuclear reactor comprising: at least one header disposed in the nuclear reactor and arranged at an upper and outer circumferential position with respect to the reactor core;  a plurality of spray nozzles mounted on the at least one header so as to define a circumferential row of spray nozzles about the reactor core for spraying cooling water onto the reactor core, the spray nozzles having a center axis, at least one of the plurality of spray nozzles of the row being mounted on the at least one header so that the center axis thereof extends upwardly with respect to a horizontal axis and at least one of the remaining plurality of spray nozzles of the row has the center axis thereof extending downwardly with respect to the horizontal axis; and  means for conducting cooling water to the at least one header.  at least two headers disposed in the nuclear reactor and arranged at an upper and outer circumferential position with respect to the reactor core, the two headers including an upper header and a lower header, a plurality of spray nozzles being mounted on each of the upper and lower headers for spraying cooling water onto the reactor core, a first group of the nozzles mounted on the lower header having the center axis thereof extending upwardly with respect to the horizontal axis, a second group of nozzles mounted on the lower header having the center axis thereof extending downwardly with respect to the horizontal axis, the first group of spray nozzles and the second group of spray nozzles being arranged alternately; and  means for conducting cooling water to the two headers. 2. An emergency core cooling system according to claim 1, wherein a first plurality of spray nozzles have the center axes thereof extending upwardly and a second plurality of remaining spray nozzles have the center axis thereof extending downwardly. 3. An emergency core cooling system according to claim 2, wherein the at least one header is a ring header. 4. An emergency core cooling system according to claim 3, wherein the first plurality of spray nozzles having nozzle center axes extending upwardly are mounted on the at least one header at mounting angles .theta. which fall within a range of +8.degree..ltoreq..theta..ltoreq.+25.degree. with respect to the horizontal axis where .theta.=0.degree.. 5. An emergency core cooling system according to claim 4, wherein the second plurality of spray nozzles having nozzle center axes extending downwardly are mounted on the at least one header at mounting angles .theta. which fall within a range of -6.degree..theta..ltoreq.-1.degree. with respect to the horizontal axis where .theta.=0.degree.. 6. An emergency core cooling system according to claim 3, wherein the second plurality of spray nozzles having nozzle center axes extending downwardly are mounted on the at least one header at mounting angles .theta. which fall within a range of -6.degree..ltoreq..theta..ltoreq.-1.degree. with respect to the horizontal axis where .theta.=0.degree.. 7. An emergency core cooling system according to claim 3, wherein the first and second plurality of spray nozzles of the row are alternately arranged about the header. 8. An emergency core cooling system according to claim 1, wherein two headers are provided, the two headers including an upper header and a lower header arranged at an upper and outer circumferential position with respect to the reactor core, a plurality of spray nozzles being mounted so as to define a circumferential row of spray nozzles about the reactor core on each of the upper and lower headers for spraying cooling water onto the reactor core, and at least one of the plurality of nozzles of the row mounted on the lower header having the center axis thereof extending upwardly with respect to the horizontal axis and at least one of the remaining plurality of nozzles of the row mounted on the lower header having the center axis thereof extending downwardly with respect to the horizontal axis. 9. An emergency core cooling system according to claim 8, wherein a first plurality of the spray nozzles mounted on the lower header have the center axes thereof extending upwardly and a second plurality of the remaining spray nozzles have the center axes thereof extending downwardly. 10. An emergency core cooling system according to claim 9, wherein the upper and lower headers are ring headers. 11. An emergency core cooling system according to claim 10, wherein the first plurality of spray nozzles having nozzle center axes extending upwardly are mounted on the lower header at mounting angles .theta. which fall within a range of +8.degree..ltoreq..theta..ltoreq.+25.degree. with respect to the horizontal axis where .theta.=0.degree.. 12. An emergency core cooling system according to claim 11, wherein the second plurality of spray nozzles mounted on the lower header and having nozzle center axes extending downwardly are mounted at mounting angles .theta. which fall within a range of -.ltoreq..theta..ltoreq.-1.degree. with respect to the horizontal axis where .theta.=0.degree.. 13. An emergency core cooling system according to claim 12, wherein the plurality of spray nozzles mounted on the upper header have center axes mounted at mounting angles .theta. which fall within a range of -10.degree..theta..ltoreq.+15.degree. with respect to the horizontal axis where .theta.=0.degree.. 14. An emergency core cooling system according to claim 13, wherein the first and second plurality of spray nozzles mounted on the lower header are alternately arranged about the lower header, and the plurality of spray nozzles mounted on the upper header are arranged thereon so that the center axes are downwardly directed and alternate ones of the spray nozzles have the same mounting angle which is different from the mounting angle of an adjacent spray nozzle. 15. An emergency core cooling system according to claim 19, wherein the first group of spray nozzles having nozzle center axes extending upwardly are mounted at mounting angles .theta. which fall within a range of +8.degree. .ltoreq..theta..ltoreq. +25.degree. with respect to the horizontal axis where .theta.=0.degree.. 16. An emergency core cooling system according to claim 15, wherein the second group of spray nozzles having nozzle center axes extending downwardly are mounted at mounting angles .theta. which fall within a range of -6.degree..ltoreq..theta..ltoreq. -1.degree. with respect to the horizontal axis where .theta.=0.degree.. 17. An emergency core cooling system according to claim 16, wherein the plurality of spray nozzles mounted on the upper header have center axes mounted at mounting angles .theta. which fall within a range of -10.degree..ltoreq..theta..ltoreq.+15.degree. with respect to the horizontal axis where .theta.=0.degree.. 18. An emergency core cooling system for spraying cooling water onto a nuclear core of a nuclear reactor comprising: 19. An emergency core cooling system according to claim 18, wherein the upper and lower headers are ring headers. 20. An emergency core cooling system according to claim 18, wherein the plurality of spray nozzles are mounted so as to define a circumferential row of the spray nozzles about the reactor core on each of the upper and lower headers, alternate ones of the spray nozzles of the row mounted on the lower header having the center axis thereof extending upwardly and downwardly.