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Once Through Steam Generators (OTSG)

Once Through Steam Generators (OTSG)

BWXT has the experience, expertise and flexibility to design and build steam generators to the demanding specifications of each individual customer.

The OTSG is a vertical shell counterflow straight-tube heat exchanger design which directly generates superheated steam as the feedwater flows through the steam generator in a single pass.

We are currently the only company in the world authorized to design and manufacture OTSGs using the proprietary BWXT technology.

  • Full pitch pattern occupied by tubes or tie-rods
  • No tube-free lane (eliminates moisture carry-up into superheat regions and localized high velocities)

We consistently meet or exceed OTSG design objectives:

  • Form fit and function design to simplify licensing
  • Retain all terminal points
  • Overall performance consistent with existing steam generators
  • Structural compatibility with Nuclear Steam Supply System (NSSS)
  • Design for maximum reliability
  • Minimize tube residual stress
  • Avoid flow-induced vibration
  • Assure high steam superheat under all operating conditions
  • Prevent loose parts
  • Facilitate inspection and maintenance

REPLACEMENT STEAM GENERATORS:

Of the 69 operating PWR nuclear power plants in the U.S., 56 had 163 individual steam generators replaced or awarded by 2005. Additional RSG replacements are anticipated as the remaining installations age.

The previously unanticipated aging issues experienced by nuclear steam generators usually involve complex interactions between the materials of construction, water chemistry operation and contaminant ingress, tube support arrangements, fabrication techniques, and local thermal-hydraulic conditions.

BWXT’s advanced series replacement steam generators are designed with the most current technology available to overcome the steam generator issues while still meeting or exceeding all of the steam generator functional requirements.

Our replacement steam generators are designed to support extension of power plant operating life. In many cases, the plants with replacement unites have received extended licenses to operate 20 years beyond the original plant life span and may eventually operate even further. To achieve these objectives, while combating the causes of component degradation, We place emphasis on upgrading component materials, introducing advanced design features and manufacturing methods, and incorporating the latest technical developments.

Hour-glassed broached plate configuration:

  • Reduces pressure drop
  • Provides flat surface contacts between tube support plates and tubes
  • Facilitates tubing
  • More accessible for water lance, chemical or water slap cleaning

Tube bundle arrangement

  • Full pitch pattern occupied by tubes or tie-rods
  • No tube-free lane (eliminates moisture carry-up into superheat regions and localized high velocities)