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Title: An Enhanced In-Vessel Core Catcher for Improving In-Vessel Retention Margins

Abstract

In-vessel retention (IVR) of core melt that may relocate to the lower head of a reactor vessel is a key severe accident management strategy adopted by some operating nuclear power plants and proposed for several advanced light water reactors. A U.S.-Korean International Nuclear Energy Research Initiative project has been initiated to explore design enhancements that could increase the margin for IVR for advanced reactors with higher power levels [up to 1500 MW(electric)]. As part of this effort, an enhanced in-vessel core catcher is being designed and evaluated. To reduce cost and simplify manufacture and installation, this new core catcher design consists of several interlocking sections that are machined to fit together when inserted into the lower head. If needed, the core catcher can be manufactured with holes to accommodate lower head penetrations. Each section of the core catcher consists of two material layers with an option to add a third layer (if deemed necessary). The first is a base material that has the capability to support and contain the mass of core materials that may relocate during a severe accident; the second is an oxide coating on top of the base material, which resists interactions with high-temperature core materials; andmore » the third is an optional coating on the bottom side of the base material to protect it from oxidation during the lifetime of the reactor. This paper summarizes results from the invessel core catcher design and evaluation efforts, focusing on recently obtained results from materials interaction tests and prototypic testing activities.« less

Authors:
Publication Date:
Research Org.:
Idaho National Laboratory (INL)
Sponsoring Org.:
DOE - NE
OSTI Identifier:
912287
Report Number(s):
INEEL/JOU-04-01983
Journal ID: ISSN 0029-5450; NUTYBB; TRN: US0800348
DOE Contract Number:
DE-AC07-99ID-13727
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nuclear Technology; Journal Volume: 152; Journal Issue: 2
Country of Publication:
United States
Language:
English
Subject:
22 - GENERAL STUDIES OF NUCLEAR REACTORS; ACCIDENTS; COATINGS; CORE CATCHERS; DESIGN; FOCUSING; LIFETIME; MANAGEMENT; NUCLEAR ENERGY; NUCLEAR POWER PLANTS; OXIDATION; OXIDES; REACTOR VESSELS; RETENTION; TESTING; WATER; core catcher; in-vessel retention; severe accidents

Citation Formats

Joy L. Rempe. An Enhanced In-Vessel Core Catcher for Improving In-Vessel Retention Margins. United States: N. p., 2005. Web.
Joy L. Rempe. An Enhanced In-Vessel Core Catcher for Improving In-Vessel Retention Margins. United States.
Joy L. Rempe. Tue . "An Enhanced In-Vessel Core Catcher for Improving In-Vessel Retention Margins". United States. doi:.
@article{osti_912287,
title = {An Enhanced In-Vessel Core Catcher for Improving In-Vessel Retention Margins},
author = {Joy L. Rempe},
abstractNote = {In-vessel retention (IVR) of core melt that may relocate to the lower head of a reactor vessel is a key severe accident management strategy adopted by some operating nuclear power plants and proposed for several advanced light water reactors. A U.S.-Korean International Nuclear Energy Research Initiative project has been initiated to explore design enhancements that could increase the margin for IVR for advanced reactors with higher power levels [up to 1500 MW(electric)]. As part of this effort, an enhanced in-vessel core catcher is being designed and evaluated. To reduce cost and simplify manufacture and installation, this new core catcher design consists of several interlocking sections that are machined to fit together when inserted into the lower head. If needed, the core catcher can be manufactured with holes to accommodate lower head penetrations. Each section of the core catcher consists of two material layers with an option to add a third layer (if deemed necessary). The first is a base material that has the capability to support and contain the mass of core materials that may relocate during a severe accident; the second is an oxide coating on top of the base material, which resists interactions with high-temperature core materials; and the third is an optional coating on the bottom side of the base material to protect it from oxidation during the lifetime of the reactor. This paper summarizes results from the invessel core catcher design and evaluation efforts, focusing on recently obtained results from materials interaction tests and prototypic testing activities.},
doi = {},
journal = {Nuclear Technology},
number = 2,
volume = 152,
place = {United States},
year = {Tue Nov 01 00:00:00 EST 2005},
month = {Tue Nov 01 00:00:00 EST 2005}
}
  • In-vessel retention (IVR) of core melt that may relocate to the lower head of a reactor vessel is a key severe accident management strategy adopted by some operating nuclear power plants and proposed for several advanced light water reactors. A U.S.-Korean International Nuclear Energy Research Initiative project has been initiated to explore design enhancements that could increase the margin for IVR for advanced reactors with higher power levels [up to 1500 MW(electric)]. As part of this effort, an enhanced in-vessel core catcher is being designed and evaluated. To reduce cost and simplify manufacture and installation, this new core catcher designmore » consists of several interlocking sections that are machined to fit together when inserted into the lower head. If needed, the core catcher can be manufactured with holes to accommodate lower head penetrations. Each section of the core catcher consists of two material layers with an option to add a third layer (if deemed necessary). The first is a base material that has the capability to support and contain the mass of core materials that may relocate during a severe accident; the second is an oxide coating on top of the base material, which resists interactions with high-temperature core materials; and the third is an optional coating on the bottom side of the base material to protect it from oxidation during the lifetime of the reactor. This paper summarizes results from the in-vessel core catcher design and evaluation efforts, focusing on recently obtained results from materials interaction tests and prototypic testing activities.« less
  • If there were inadequate cooling during a reactor accident, a significant amount of core material could become molten and relocate to the lower head of the reactor vessel, as happened in the Three Mile Island Unit 2 (TMI-2) accident. If it is possible to ensure that the vessel lower head remains intact so that relocated core materials are retained within the vessel, the enhanced safety associated with these plants can reduce concerns about containment failure and associated risk. For example, the enhanced safety of the Westinghouse Advanced 600 MWe Pressurized Water Reactor (AP600), which relied upon External Reactor Vessel Coolingmore » (ERVC) for in-vessel retention (IVR), resulted in the United States Nuclear Regulatory Commission (US NRC) approving the design without requiring certain conventional features common to existing Light Water Reactors (LWRs). Accordingly, IVR of core melt is a key severe accident management strategy adopted by some operating nuclear power plants and proposed for some advanced light water reactors. However, it is not clear that currently-proposed methods to achieve ERVC will provide sufficient heat removal for higher power reactors. A US–Korean International Nuclear Energy Research Initiative (INERI) project has been initiated in which the Idaho National Engineering and Environmental Laboratory (INEEL), Seoul National University (SNU), Pennsylvania State University (PSU), and the Korea Atomic Energy Research Institute (KAERI) will determine if IVR is feasible for reactors up to 1500 MWe. This paper summarizes results from the first year of this 3-year project.« less
  • An enhanced in-vessel core catcher is being designed and evaluated as part of a joint United States (US)–Korean International Nuclear Energy Research Initiative (INERI) investigating methods to insure retention of materials that may relocate to the lower head of a reactor vessel under severe accident conditions in advanced reactors. This enhanced core catcher design consists of several interlocking sections that are machined to fit together when inserted into the lower head. Each section of the core catcher consists of two material layers with an option to add a third layer (if deemed necessary): a base material, which has the capabilitymore » to support and contain the mass of core materials that may relocate during a severe accident; an insulator coating material on top of the base material, which resists interactions with high-temperature core materials; and an optional coating on the bottom side of the base material to prevent any potential oxidation of the base material during the lifetime of the reactor. This paper summarizes results from thermal, flow, and structural analyses as well as initial scoping materials interaction tests that were completed to support the conceptual design of the core catcher.« less
  • In order to enhance the feasibility of in-vessel retention (IVR) of molten core material during a severe accident for high-power reactors, an in-vessel core catcher (IVCC) was designed and evaluated as part of a joint United States-Korean International Nuclear Energy Research Initiative (INERI). The proposed IVCC is expected to increase the thermal margin for success of IVR by providing an “engineered gap” for heat transfer from materials that relocate during a severe accident and potentially serving as a sacrificial material under a severe accident. In this study, LAVA-GAP experiments were performed to investigate the thermal and mechanical performance of themore » IVCC using the alumina melt as simulant. The LAVAGAP experiments aim to examine the feasibility and sustainability of the IVCC under the various test conditions using 1/8th scale hemispherical test sections. As a feasibility test of the proposed IVCC in this INERI project, the effects of IVCC base steel materials, internal coating materials, and gap size between the IVCC and the vessel lower head were examined. The test results indicated that the internally coated IVCC has high thermal performance compared with the uncoated IVCC. In terms of integrity of the base steel, carbon steel is superior to stainless steel and the effect of bond coat is found to be trivial for the tests performed in this study. The thermal load is mitigated via boiling heat removal in the gap between the IVCC and the vessel lower head. The current test results imply that gaps less than 10mm are not enough to guarantee effective cooling induced by water ingression and steam venting there through. Selection of endurable material and pertinent gap size is needed to implement the proposed IVCC concept into advanced reactor designs.« less
  • A core catcher is adopted in the EU-APR1400 reactor design for management and mitigation of severe accidents with reactor core melting. The core catcher concept incorporates a number of engineering solutions used in the catcher designs of European EPR and Russian WER-1000 reactors, such as thin-layer corium spreading for better cooling, retention of the melt in a water-cooled steel vessel, and use of sacrificial material (SM) to control the melt properties. SM is one of the key elements of the catcher design and its performance is critical for melt retention efficiency. This SM consists of oxide components, but the coremore » catcher also includes sacrificial steel which reacts with the metal melt of the molten corium to reduce its temperature. The paper describes the required properties of SM. The melt retention capability of the core catcher can be confirmed by modeling the heat fluxes to the catcher vessel to show that it will not fail. The fulfillment of this requirement is demonstrated on the example of LBLOCA severe accident. Thermal and physicochemical interactions between the oxide and metal melts, interactions of the melts with SM, sacrificial steel and vessel, core catcher external cooling by water and release of non-condensable gases are modeled. (authors)« less