Emergency mitigating equipments – post Fukushima actions at Canadian nuclear power plants portable AC power sources

An abstract of the technical presentation presented at:
CSNI International Workshop on Robustness of Electrical Systems of NPPs in Light of the Fukushima Dai-Ichi Accident
Paris, France
April 1–3, 2014

Prepared by:
Jasmina Vucetic, Ram Kameswaran and Krishnan Ramaswamy
Canadian Nuclear Safety Commission (CNSC)
Ottawa, Ontario, Canada

Abstract

In response to the Fukushima Daiichi NPP accident in 2011, the Canadian Nuclear Safety Commission set up a Task Force to evaluate operational, technical and regulatory implications on Canadian NPPs. While accepting that the risk from beyond-design-basis accidents (BDBA) at Canadian NPPs is very low, the Task Force identified a number of areas where additional improvements or confirmatory assessments would further enhance safety.

As a result, a set of 36 Fukushima Action Items (FAls) were assigned to the licensees.

This presentation focuses on the FAI related to electrical power system enhancements to address a total loss of all AC Power leading to a possibility of loss of heat sinks (i.e. Station Blackout). This required the licensees to implement the following:

• additional back up power supplied by portable diesel generator(s) to allow key instrumentation and control equipment and key electrical loads to remain operable;
• provisions for a storage and timely transportation and connection of the portable generator(s) to the applicable units;
• provisions for testing of the portable generator;
• provisions for fuelling of portable generators;
• provisions such as panels, receptacles, and connectors to quickly deploy the portable generators to plant system, and separate feeder cables route to avoid a common mode failure;
• load shedding strategy to extend the existing station’s battery life to ensure that the connection of portable generators can be completed before the batteries are depleted;
• provisions to supply water to steam generators and Irradiated Fuel Bay using portable pumps;

The presentation will also provide a brief description of Electrical power systems of the Canadian NPPs designed to satisfy the high safety and reliability requirements for nuclear systems, which are based on the following:

• 2 group design philosophy ( Group 1 and Group 2 Electrical Power Systems )
• 2 separate groups of onsite emergency generators (Class III Standby generators and Emergency Power generators )
• 4-7 days’ supply of fuel for standby and emergency generators,
• the capability to transfer power between units in a multi-unit plant

Finally the presentation will describe the implementation experience at Canadian plants and the related regulatory oversight activities.

To obtain a copy of the abstract's document, contact the CNSC. When contacting the CNSC, please provide the title and date of the abstract.