Condition Assessment of Concrete Nuclear Structures Considered for Entombment.
Condition Assessment of Concrete Nuclear Structures
Considered for Entombment.
Snyder, K. A.
NISTIR 7026; 43 p. July 2003.
Sponsor:Nuclear Regulatory Commission, Washington, DC
Available from:: National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.
1-800-553-6847 or 703-605-6000;
Fax: 703-605-6900; Rush
Service (Telephone Orders Only) 800-553-6847;
Order number: PB2003-15808
concretes; condition assessment; degradation; service
This report summarizes work to date on a project for the
U.S. Nuclear Regulatory Commission to develop guidelines
for the chemical and material assessment of an existing
structure considered for entombment. In addition, a
rational means for performing a probabilistic
calculation are addressed. This report does not include
a summary of nondestructive evaluation (NDE) techniques
applicable to existing cracks. That report will be
written separately by Dr. N.J. Carino. The assessment is
composed of a preliminary material assessment, followed
by a probabilistic calculation of the service life. The
material assessment will rely heavily on both the
permeability of the intact concrete and the
characterization of any existing cracks. The
contribution of cracks to transport is considered
independently from the intact concrete, and the bulk
properties (intact concrete plus cracks) are estimtated
by combining the two effects using a composite model.
Another aspect of the condition assessment of the
concrete barrier is the evaluation of nondestructive
techniques (NDT) as candidates for characterizing
existing cracks, and other transport pathways, in the
entombment structure. This aspect will be addressed in a
companion report. An important component of the effort
to estimate the concrete material properties is the
probability density function used to characterize the
distribution in their expected values. The "tail" of the
distribution has the greatest influence on the overall
performance, and, therefore, it should receive attention
in the analysis. A number of suitable distributions are
considered for their use in characterizing various
concrete material properties.