Irradiation Effects on Reinforced Concrete Structures – Experimental and Analytical Study on Irradiated Concrete – Steel Bonding, Modeling and Simulation of Structural Response (NUREG/CR-7312)
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Publication Information
Manuscript Completed: November 2024
Date Published: July 2025
Prepared by:
Y. Le Pape
M. Alnaggar
E. Tajuelo Rodriguez
A. Brooks
Oak Ridge National Laboratory
One Bethel Valley Road
Oak Ridge, TN 37831
Madhumita Sircar
Technical Lead and NRC Project Manager
Prepared for:
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001
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Abstract
This report summarizes the research accomplishments of U.S. Nuclear Regulatory Commission project IAA # 31310018S0021, “Effects of Irradiation on Bond Strength in Concrete Structures”. This project includes a scoping irradiation experiment on reinforced concrete specimens and a numerical simulation study of concrete biological shields that supports the reactor pressure vessel in a pressurized water reactor.
A first-of-a-kind irradiation experiment of reinforced concrete was designed and executed by the Oak Ridge National Laboratory and the Centrum Vizkumu ReŽ in the Czech Republic. The raw materials for the two types of studied concretes are (1) coarse aggregate consisting of a quartz metachert and a terrigenous felsic sandstone and (2) fine aggregate and cement— were provided by the Japan Concrete Aging Management Program (JCAMP). Use of the same concrete constituents enables comparison with the previously published results obtained by JCAMP regarding plain concrete irradiated in the JEEP II Reactor in Norway. This approach was preferred instead of attempting to choose aggregates to represent those from a particular U.S. Nuclear Power Plant (NPP). This is because aggregates in an NPP are site dependent and vary from plant to plant, and their characterization data are not publicly available. In general, quartz-bearing rocks and sandstones are quite common in the United States.
In this experiment, specimens were irradiated for the duration of approximately 800 days (accounting for outages) in an out-of-core position in the LVR-15 test reactor to achieve ~1019 n.cm-2 (E > 0.1 MeV) of fast neutron fluence and ~1 GGy of gamma dose while keeping the irradiation temperatures of the specimens in the 37–52 °C range. A companion experiment exposing a different set of specimens to the temperature from the monitored irradiation temperature alone was conducted in parallel to distinguish the effects of prolonged curing at a moderate temperature from the combined effects of irradiation and temperature. Unirradiated specimens at room temperature were also tested to provide baseline data of reference. Preand post-irradiation examination (PIE) and testing included visual and optical microscopy, x-ray computed tomography, mass and dimensional measurements, ultrasound wave velocity measurements, splitting tests, direct compression tests, and bond tests. The PIE and testing data were interpreted using literature data, as well as analytical and numerical models including fast Fourier transform–based nonlinear simulation of aggregate polycrystalline assemblage and meso scale simulation of plain and reinforced concrete using the lattice discrete particles model (LDPM). A scaling effects study for unirradiated specimens was campaigned by using specimens at three different sets of parameters: specimen size, rebar diameter, and aggregate size. The main findings of the scoping irradiation experiment are (1) the irradiation experiment provided evidence of the importance of fast neutron flux on the radiation-induced expansion of concrete aggregates, and (2) the bond strength of steel reinforcement bars embedded in concrete is governed by the square root of residual compressive strength of the surrounding irradiated concrete. However, an additional scaling factor of approximately 0.75–0.85 was required to determine the bond strength of the specimens built with the #2 bar. Finally, the report also presents the results of the numerical simulation study using LDPM and finite element analysis with the objective of proposing methodological guidelines for the assessment of irradiation effects on in-service irradiated concrete biological shields, specifically the irradiationinduced damage depth in the concrete biological shields.
Page Last Reviewed/Updated Thursday, July 31, 2025