(247a) Mobile Boration System

After the event at Fukushima in March 2011, the global nuclear industry developed strategies and regulatory requirements with the goal to enhance plant safety and defense-in-depth coping strategies. The specific regulations varied between countries and included a range of response strategies, from mobile equipment being stored in diverse, protected buildings to separate permanently-installed response systems. With this new ideology of being able to cope with extreme and unknown hazards beyond those already evaluated as part of the design basis of the respective sites, the design of ancillary nuclear response equipment and subsequently, portable response equipment, emerged.

Critical aspects of post-accident response would be to ensure core sub-criticality and continuous core cooling. In pressurized water reactors, sub-criticality relies partially on the use of borated water within the reactor coolant system. Certain postulated scenarios may require borated water sources to be protected from external hazard events as well as require the ability to generate borated coolant indefinitely. A desirable feature of a system that is able to produce borated coolant would be for the system to be able to be easily transported, easy to commission and use, and have the ability to generate a borated discharge stream continuously.

Westinghouse has designed, manufactured, and tested a mobile unit that is able to continuously generate borated coolant using an automated platform, minimal site interfaces, and efficient design characteristics. The design takes advantage of a multiple, high-concentration batch to dilution style system in order to produce a continuous discharge. Because, energy efficiency and timing is crucial to system functionality, there are custom designed and tested heating sources as well as a programmable logic controller that monitors and controls all of the instrumentation, feedback signals, and automated actions. The system reduces the days required by other mobile systems using existing technology to hours, and can be used outside of controlled areas. The current system design uses boric acid as the neutron poison but the system can be designed to accept other powder, such as sodium pentaborate, as required by a reactor design and accident scenario.

The purpose of this presentation and paper is to outline and describe novel aspects of the Westinghouse system, describe the system’s ability for enhancement of plant safety and risk mitigation, and identify potential future areas of use that would enhance plant operational efficiency. The system has been delivered to a site in the United States with plans for defense-in-depth implementation as well as outage enhancements.