Investigation of the use of nanofluids to enhance the In-Vessel Retention capabilities of Advanced Light Water Reactors

Abstract

Nanofluids at very low concentrations experimentally exhibit a substantial increase in Critical Heat Flux (CHF) compared to water. The use of a nanofluid in the In-Vessel Retention (IVR) severe accident management strategy, employed in Advanced Light Water Reactors, was investigated. A model simulating the two-phase flow and heat transfer on the reactor vessel outer surface quantified the increase in decay power that can be removed using a nanofluid, predicting that the use of a nanofluid will allow a stable operating power ~40% greater than the power allowable using water to be achieved, while holding the Minimum Departure from Nucleate Boiling Ratio (MDNBR) constant. A nanofluid injection system that would take advantage of the enhanced CHF properties of the nanofluid in order to provide a higher safety margin than the current IVR strategy or, for given margin, enable IVR at higher core power, is proposed. A risk-informed analysis has revealed that this injection system has a reasonably high success probability of 0.99, comparable to the success probability without the injection system. Potential regulatory, environmental, and health risk issues were analyzed, and it was concluded that the current regulatory regimes are adequate for ensuring that the implementation of nanofluids in IVR will not endanger public health and safety. However, experimental verification of nanofluid CHF enhancement at prototypical IVR conditions and periodic nanofluid property testing as a surveillance requirement are needed to reduce the key uncertainties related to nanofluid performance. Finally, a periodic review of the health and environmental risks of nanofluids and, if necessary,follow-up research are ecommended to ensure the health of the public and environment.