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AECL Scope

AECL’s scope of work is defined in two contracts, one that covers the retubing of the reactor (retube), and the second that covers a series of other activities that are required for the long term operation of Point Lepreau Generating Station (non-retube). Some of the non-retube activities involve design modifications, while others are support activities such as analyses or inspections. A brief description of the main AECL activities is given below

Retube Activities

The major activity to be performed during the outage is the replacement of all 380 fuel channel assemblies, calandria tubes, and the entire length of connecting inlet and outlet feeder piping from the end fittings back to the headers. This activity is referred to as retube. Directly related to retube are a number of support activities such as the transfer of radioactive reactor component waste to the on-site Solid Radioactive Waste Management Facility (SRWMF). Together with the shutdown and restart activities, the retube-related activities are the longest chain of critical path activities in the outage. They will run the complete duration of the 18-month outage and as such, work will be performed on an around-the-clock basis.

The scope of retube work covers design, procurement engineering, supply, erection, commissioning and operation of the structures that would be used to store the radioactive reactor components following their removal during the retube process. Sorting, segregation, measurement, transfer and storage of radioactive waste arising during the retube campaign and decontamination of the facilities or components before, during or after the work is undertaken is also included in the scope of work.

The addition of five retube canisters and two vault structures is part of the AECL scope of work, and these are included in the latest Waste Facility Operating Licence.

Non Retube Activities

Replace Turbine Controls with More Modern Controllers

The Turbine Electro-Hydraulic Governor System, Turbine Supervisory System, and the Turbine Mechanical Over-Speed Protection will be replaced with current technology. This change will ensure continued high reliability throughout the extended life of the station.

Shutdown System #1 Trip Coverage Improvements

To improve coverage for moderator related events involving leak, loss of circulation and loss of cooling, a moderator high/low level trip would be added to Shutdown System #1 to replace the existing moderator temperature trip.

Shutdown System #2 Trip Coverage Improvements

To improve coverage for moderator related events involving leak, loss of circulation and loss of cooling, a moderator high/low level trip would also be added to Shutdown System #2. To provide improved coverage for loss of flow events in the Heat Transport System, a high-pressure trip on reactor outlet headers would also be added.

Moderator Sub-cooling Margin Improvement

Upgrades to the Moderator Heat Exchanger to achieve 100% of the Re-circulated Cooling Water (RCW) flow will be performed to improve the moderator sub-cooling margin. Additional sealing strips and rods would be incorporated into the upgrades.

Shield Cooling System Improvement

This change would improve the capability of the Shield Cooling System by adding a rupture disk on top of the existing inspection port and a locally operated isolation valve for the head tank.

Heat Transport System (HTS) Pump Trip on High Thrust Bearing Temperature

A software design change will be implemented to the Heat Transport Temperature Control Program to ensure that the Heat Transport System Pumps are tripped if two of the four temperature detectors indicate overheating due to loss of service water.

Main Control Room Filter System

A filtering system will be added to the main control room ventilation system to protect its air supply in the event of an accidental release of radioactive material following a severe accident.

Modify Assembly to Allow Independent Movement of In-core Start-Up Detectors

This design change would improve functionality of start-up instrumentation, allowing two detectors to continue to function while one is being moved.

Replace Certain Resistance Temperature Detector (RTD) Cables

Safety related detector circuits located within the Reactor Building would have the existing poly-vinyl chloride insulated cables replaced using single and multi-triad cables complete with dedicated junction boxes. This would prevent a potential drift of signals under accident conditions of high temperature and humidity.

Replace Underground Fuel Storage Tank with New Design

The underground fuel storage tank for the Emergency Power System diesels will be replaced to ensure the integrity for the tank for extended life. In addition to the original requirements, the new tank will be designed to meet the current New Brunswick environmental standards for underground fuel storage tanks.

Replace Valves in the Moderator Systems

A number of gate valves in the Main Moderator System will be replaced to eliminate leakage and allow these important isolation valves to carry out their function for the extended life of the station.

Replacement of Inverters and Rectifiers in the Uninterruptible Power Supply System (UPS)

The Station Inverter and the Rectifier equipment associated with the Uninterruptible Power Supply System will be replaced as the present equipment has been assessed as being impractical to maintain over an extended station life.

Raw Service Water (RSW) System Refurbishment

In order to ensure long term continued reliable operation of the Raw Service Water (RSW) System, the following refurbishment work will be performed to address age related degradation of system piping, valves and expansion joints:

  • Inspect and refurbish various valves
  • Replace various expansion joints
  • Replace certain sections of piping
  • Inspect / recoat certain sections of piping

Re-Circulated Cooling Water (RCW) System Refurbishment

In order to ensure long term continued operation of the Re-circulated Cooling Water System, various valves in the system will be inspected and refurbished as necessary and the six expansion joints will be replaced. To enable this work to be performed, a temporary cooling system for the Spent Fuel Bay will be provided.

Dousing Tank and D2O Storage Tank Liner Refurbishment

The dousing tank liner will be replaced to repair blisters that have formed during past reactor building pressure tests. In addition, the D2O Storage Tank liner will be replaced.

Modifications to the Solid Radioactive Waste Management Facilities

In order to provide required space for the radioactive waste generated during extended life normal operations and from refurbishment outage work, modifications are required to expand the capacity of the existing waste management facilities. This work is in addition to the structures to be added for storage of reactor components under the retube agreement.

Inspections during Refurbishment Outage

In addition to changes and repairs discussed above, certain specific inspections are planned for the refurbishment outage, as this is the only time such inspections would be able to be performed. These include inspections of the calandria vessel internals as well as parts of the Raw Service Water and Re-circulating Cooling Water System.

Deterministic Safety Analysis

Perform deterministic safety analysis for those safety cases which require inclusion of new requirements from codes and standards or design modification in order to demonstrate compliance with current regulatory requirements.

Probabilistic Safety Assessment

Develop and document a probabilistic safety assessment for internal and external events (seismic, fires, flooding) and for shutdown state for internal events.