Relieving Your Stress Over Leaking Reactor Vessel Bottom-Mounted Instrumentation Nozzles

Westinghouse Mechanical Nozzle Seal Assembly

The degradation of materials currently used in aging nuclear power plants is a growing concern to both utilities and regulatory bodies. One such issue is primary water stress corrosion cracking (PWSCC) of reactor vessel bottom-mounted instrumentation (BMI) nozzle welds in pressurized water reactor (PWR) plants. These cracks can be challenging to detect by nondestructive evaluation (NDE) methods, and so will often go unnoticed until a leak occurs. By that point, the repair cost and schedule can lead to significant availability losses.

To help utilities avoid costly and unreliable welded repairs resulting from PWSCC, Westinghouse now also offers a mechanical nozzle seal assembly (MNSA) that addresses stress corrosion cracking of 3” BMI nozzle welds on Westinghouse System 80 reactors. Should an inspection yield questionable results, our proactive MNSA contingency solution can be installed on a leaking BMI nozzle by replacing the original weld and performing two functions:

• Acting as the primary pressure boundary for the reactor coolant system (RCS)
• Structurally replacing the weld to prevent the nozzle from ejecting from the reactor vessel

Compared to a typical welded repair, our MNSA BMI nozzle weld solution:

• Can be installed from outside the reactor vessel without breaching the pressure boundary and requiring drain-down or core offload
• Can be installed on an actively leaking nozzle
• Reduces risk of rework for bad welds
• Significantly decreases dose and impact to outage schedule as competed to half or full nozzle repair

Westinghouse’s MNSA repair has been implemented on many Westinghouse and Westinghouse-CE designed pressurizers and RCS instrument nozzles. This experience, along with our advanced technology, helps our customers to experience less repair time and reduced dose to repair personnel.

To learn more about the new Westinghouse’s MNSA BMI nozzles, please contact Kris Paserba at (1) 412-374-4971.