The Reactor Vessel Under-Head Shield is designed to reduce radiation exposure from the underside of the reactor vessel head while on the head stand. It is positioned before the head is placed on the stand and extends up into the cavity of the head. The shield consists of nine support frame sections which will support up to three layers of Lead Wool Blankets. The shield support structure includes an extending shield plate the top of the support frame that is retracted and latched until the head is on the stand. It is then moved outward into close proximity of the head. The extending shield has a series of bumper pads to protect the head. This reduces exposure during work evolutions close to the head such as O-ring maintenance. The height of the shield allows for inspection of the dryer hold down lugs. A lockable shielded door is provided for under-head access. A vertical adjustable security barrier is located at the bottom of each shield support section. The barrier is lowered to reach the floor to complete the security barrier and meet the requirements of a “Locked High Radiation Area”. The under-head shield has a series of height adjustable O-ring supports to aid in O-ring maintenance/replacement.
The under-head shield can be lifted and moved from one head stand location to another. Once it is located in the appropriate position, the vertical adjustable security barrier is lowered to the floor and the appropriate layers of blankets installed. The head is then placed on the head stand. The extending shield plates are positioned close to the head.
The Reactor Vessel Head Stand Shield Ring offers simplified erection and is used outside the Reactor Head Flange. Featuring epoxy coated steel plate construction, it can be sized to suit specific reactor vessel head diameter. The standard unit is constructed of 4” plate, with other thicknesses available. The ring provides for the use of interchangeable components as well as providing access for robots and personnel through three shielded doors. Ventilation ports are also provided for engineering controls. A lockable latch at the access point door creates a locked high rad area. A base plate is provided to distribute the load, and lifting provisions are provided for the overhead crane.