Method and apparatus for in situ detection of defective nuclear fuel assembly

A gas sipping hood for positioning on top of a fuel assembly comprising:

• means for defining a chamber above said fuel assembly;
• means for preventing escape of fluid from said chamber;
• and
• valve means for releasing a fluid sample from said chamber.

A method for detecting a defective fuel rod in a fuel assembly, comprising the steps of:

• arranging a hood on top of said fuel assembly;
• accumulating a gas sample from fluid trapped under said sipping hood;
• and
• detecting for the presence of krypton in said gas sample.

A system for detecting a defective fuel rod in first and second fuel assemblies, comprising:

• first and second sipping hood means arranged on top of said first and second fuel assemblies respectively;
• first and second bundle selection valve means respectively coupled to said first and second sipping hood means;
• means for detecting the level of beta activity in a gas sample;
• first and second gas sample valve means respectively coupled to said beta activity level detecting means;
• first and second channels having respective inlets selectively coupled to said first and second sipping hood means by said first and second bundle selection valve means respectively, and having respective outlets selectively coupled at different times to said beta activity level detecting means by said first and second gas sample valve means respectively;
• and
• programmable logic control means coupled to said first and second bundle selection valve means and to said first and second gas sample valve means for controlling said valve means to multiplex respective gas samples from said first and second sipping hoods through said first and second channels respectively.