Current status of core degradation and melt progression in severe LWR accidents

Journal Article · Sat Mar 01 04:00:00 EST 1997 · Advances in Nuclear Science and Technology

OSTI ID:447508

Wright, R W

This paper is a summary of the current state of technical understanding and the principal remaining technical uncertainties regarding the processes of core degradation and core melt progression in severe Light Water Reactor (LWR) accidents. It is to be emphasized initially that technical resolution of all these uncertainties is not required for making safety assessments of different issues in the regulatory process, nor is such resolution probably feasible. Different regulatory issues require knowledge of different aspects of melt-progression technology and at different levels of accuracy. Regulatory considerations will not be further addressed in this paper, which treats the technology of core degradation and core melt progression. In-vessel core degradation and core melt progression describe the state of the reactor core in severe LWR accidents from core uncovery to reactor vessel failure, or to temperature and geometry stabilization in accidents which are recovered by core reflooding. Melt progression provides the characteristics of the melt released from the damaged core and possibly later from the reactor vessel. These characteristics are the melt mass, the melt composition (in particular the metal fraction), the melt temperature, and the rate of melt release. They provide the initial conditions for assessing the loads on the reactor vessel and possibly later on the containment in severe LWR accidents. The uncertainties in these initial conditions often provide the largest of the uncertainties in assessing the integrity of the vessel lower head and the integrity of the containment. Melt progression also provides the in-vessel hydrogen generation, the core conditions that determine the in-vessel fission-product release, transport, deposition, and revaporization, and also the core conditions for assessing the consequences of accident-recovery actions, core reflooding and vessel depressurization in particular.

• OSTI ID: 447508
• Journal Information: Advances in Nuclear Science and Technology, Journal Name: Advances in Nuclear Science and Technology Vol. 24; ISSN 0065-2989; ISSN ANUTAC
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
22 GENERAL STUDIES OF NUCLEAR REACTORS
MELTDOWN
REACTOR CORES
SIMULATION
WATER COOLED REACTORS