Title: Concrete as an Engineered Alternative to Shallow Land Disposal of Low Level Nuclear Waste: Overview

Author(s): J. Philip and J. R. Clifton

Publication: Symposium Paper

Volume: 132

Issue:

Appears on pages(s): 713-730

Keywords: alkali-aggregate reactions; chloride ions; leaching; nuclear waste; service life; sulfate attack; General

DOI: 10.14359/1323

Date: 5/1/1992

Abstract:
Engineered enchancement of or engineered alternatives to shallow land disposal of low-level radioactive (LLW) is likely to be the disposal technique adopted by a majority of states in the U.S. Such disposal techniques involve extensive use of concrete as an engineered barrier to prevent the escape of radionuclides into the environment. The LLW will be contained in concrete vaults or bunkers buried underground or covered with earth. U.S. Regulation 10 CFR 61 establishes the regulatory responsibilities for licensing LLW disposal sites. Implicit in the regulations is the need for the concrete of the LLW disposal system to have a service life of 500 years. Discusses the regulatory responsibilities governing LLW disposal. It also discusses results of a research project at the National Institute of Standards and Technology for the U.S. Nuclear Regulatory Commission to predict the service life of underground concrete for LLW applications. Assuming that disposal will be above the water table, the major degradation mechanisms affecting the concrete would be those due to sulfate attack, chloride ions, alkali-aggregate reaction, and leaching. Mathematical modeling of the degradation mechanisms and the validation of those models with accelerated laboratory tests suggests that service lives of 500 years for concrete structures can be reliably achieved.