Point Lepreau Primary Heat Transport Pump Wear Ring Cracking
9th International Conference on CANDU® Maintenance - 2011 December 04-06

Presented at:
9th International Conference on CANDU® Maintenance
2011 December 04-06
Toronto, Canada
Session Title:
Getting it Right Session B2

George Licina (Structural Integrity Associates, Inc.)
Bill Rankin (New Brunswick Power Nuclear)


The #3 Primary Heat Transport (PHT) pump from Point Lepreau Nuclear Generating Station (Point Lepreau) was disassembled after more than 30 years of service for inspection during station refurbishment.  The disassembly and inspection were performed to provide assurance of continued satisfactory operation during life extension.  The inspection revealed cracks in the wear ring, at and near the tack welds (Type 309 stainless steel weld metal) at the cap screws that attach the Type 420 stainless steel wear ring to the body of the pump.  Investigative work consisted of on-site PT and replication of the microstructure at the surface of the wear ring, subsequent impressions of two crack faces, and hardness determinations.

This paper describes the investigative work and conclusions associated with resolution of the following questions:

  1. What is the most likely cause of the cracking?
  2. Will the cracks propagate within the base metal of the wear ring?
  3. If propagation is possible, what is the risk of cracks intersecting, such that a piece of metal could become dislodged?

Results will be applied to wear rings in other PHT pumps at Point Lepreau and are likely to be applicable to similar components in other CANDU® PHT pumps.

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