the present invention relates to a system , teaches a technique , and provides apparatus eminently useful for the installation / removal , from a remote and protected location , of nozzle dams onto and from nozzle holddown rings within the channel heads of certain steam generators , including the types typically used in conjunction with the operation of pressurized hot - water nuclear power plants . the technique or method of the instant invention involves methodology for remotely introducing usually with the aid of tackle insertion tool means , through an open channel head manway requisite tubesheet tackle means , or tackle means , as well as strapping means and the securing of same therein ; inserting through said open manway , usually with the aid of lifting means , folded nozzle dam means ; opening said dam means and properly orientating same relative to said nozzle holddown ring ; inserting , orientating , and securing the center portion of said nozzle dam means , torquing bolting means to predetermined limits ; and removing from said channel head all said attendant tubesheet means . the effecting of the instant technique requires only a minimal amount of relatively inexpensive , but specifically designed equipment and is simply , quickly , and easily placed into practice by , for example , manipulation of same by one or more human operators who are physically located outside said channel head and adjacent said open manway thereby substantially reducing the effective radiation dose heretofore normally associated with such nozzle dam installation and removal .