US 4,062,725 A · Part length control rod

Abstract

A new part length rod is provided which may be used to not only control xenon induced power oscillations but also to contribute to shutdown reactivity when a rapid shutdown of the reactor is required. The part length rod consists of a control rod with three regions. The lower control region is a longer weaker active portion separated from an upper stronger shorter poison section by an intermediate section which is a relative non-absorber of neutrons. The combination of the longer weaker control section with the upper high worth poison section permits the part length rod of this invention to be scrammed into the core, when a reactor shutdown is required but also permits the control rod to be used as a tool to control power distribution in both the axial and radial directions during normal operation.

Claims17

Dependent claims

A moveable control rod having first and second ends for the control of power oscillations in a nuclear reactor having a core with an active length L, said control rod comprising:

a. a first portion of said control rod's first end comprising a first neutron poison with a length no longer than 20 percent of the length L;
b. a second portion at said control rod's second end comprising a second neutron poison, said second neutron poison having a smaller macroscopic absorption cross-section than said first neutron poison and having a high number density but having a low microscopic neutron absorption cross-section;
and
c. a third portion between said first and second portions, said third portion comprising a material which is substantially non-neutron absorbing relative to said first and second portions, and the sum of the lengths of said first, second, and third portions being substantially equal to the length of the core's active length L.

1 more element

Dependencies are inferred from the claim text.

Part length control rod

Life of this patent

Part length control rod

Life of this patent

Abstract

Claims17