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Shut-down Cooling Nozzle (SDCN) Dam

Nuvision has the capability to design, test, and implement specialized nozzle dams for a variety of applications.

NuVision designed a shut-down cooling nozzle (SDCN) dam that can be used to keep water isolated in one section of piping, allowing the utility to maximize the amount of work it performs during the outage.

  • Keeps water isolated in one section of piping, which allows multiple tasks to be performed during an outage
  • Able to hold back approx. 2500 lbs. of force
  • Reduces contamination and personnel dose exposure
  • Factory acceptance tested
  • Qualification tested

APS Palo Verde outage managers wanted to find a way to flood the Unit 2 reactor cavity, but keep the water out of downstream piping. NuVision was asked to provide input about the feasibility of installing a plug or dam inside the reactor coolant system. The dam would keep water isolated in one section of the piping, where it would be needed to make reactor cavity inspections possible, and simultaneously keep water from flowing through to downstream sections of the piping, where pipe sections and a large valve had to be cut out, relocated, and re-welded back in to the system.

NuVision provided the solution with the use of the SDCN dam eliminated nine days from the outage schedule, according to the APS outage manager. The dam held back water inside the RCS piping for 20 days.

Highlights of the NuVision team’s work include:

  • Completion of design, procurement and factory acceptance testing in fewer than 30 days
  • Deflation and removal of the dam in 3 minutes with a team dose of approx. 166 mR. Measurements of the dose rate inside the hot leg included areas as high as 6K mR/hour, emphasizing the need for a well-coordinated installation and removal effort

Mock-up training to work inside the reactor coolant system piping

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