Surveillance capsule holder

The surveillance capsule holder is a stainless steel container, which houses RPV surveillance specimen capsules used to monitor embrittlement due to neutron irradiation of the vessel shell. A bracket holds the surveillance capsule holder to the vessel wall. Capsule holders are removed with RPV surveillance specimens on a pre-planned basis in accordance with the plant surveillance plan. 

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Surveillance Capsule Holder Not considered to be important to safety... 

Capsule holders are typically located circumferentially around the core to provide assurance that test specimens and monitors duplicate, as closely as possible, the irradiation history of the reactor vessel, including neutron spectrum, temperature history and maximum neutron fluence. Holders must be designed to avoid interference with in-service inspections required by Section XI of the ASME Code (ASME, 2010a). Most surveillance programs have the capsules located between the thermal shield and the reactor vessel wall with the vertical center at the core mid-plane. C-E, General Electric and B W designs have the holders attached directly to... 

A typical capsule assembly, illustrated in Figure 5.3-1, consists of a series of three specimen compartments, connected by wedge couplings, and a lock assembly. Each compartment enclosure of the capsule assembly is internally supported by the surveillance specimens and is externally pressure tested to 3125 psi during final fabrication. The wedge couplings also serve as end caps for the specimen compartments and position the compartments within the capsule holders which are attached to the reactor vessel cladding. The lock assemblies fix the locations of the... 

The capsule assemblies remain within their holders until the specimens contained therein have been exposed to predetermined levels of fast neutron fluence. At that time, the capsule assembly is removed and the surveillance materials are evaluated. 

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