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Title: Multifunctional Cement-Based Materials to Improve the Service Life of NPP Concrete Structures

Author(s): Patel

Publication: Web Session

Volume: ws_S22_Patel.pdf

Issue:

Appears on pages(s):

Keywords:

DOI:

Date: 3/28/2022

Abstract:
Nuclear power plants commonly utilize concrete biological shields to protect plant personnel from excessive radiation dose uptake. Concrete, however, degrades under long-term neutron radiation exposure in a process called radiation-induced volumetric expansion (RIVE). This results when high-energy, or fast, neutrons induce crystalline disorder in aggregate minerals, leading to aggregate swelling and subsequent cracking of the surrounding hardened concrete matrix. Neutron-induced amorphization in siliceous aggregates also increases the probability of radiation-induced ASR (R-ASR). As nuclear power plants operate beyond their initial design lives, novel strategies are needed to ensure that RIVE and R-ASR do not damage aging concrete biological shields. Boron is often added to cement systems to improve low-energy, or thermal, neutron shielding. Though, boron may mitigate R-ASR damage since boron transmutes to lithium under neutron exposure. This study investigates the use of finely dispersed boron to reduce the risk of RIVE and R-ASR in operational and new cement-based biological shields. First, boron-to-lithium transmutation under neutron irradiation was verified. Second, boron compounds were down-selected based on calorimetry and time of set experiments. Then, the neutron attenuation efficiency of thin mortars dosed with varying quantities of boron was evaluated using a 239PuBe neutron source and a 3He neutron detector. Boron was found to improve both thermal and fast neutron shielding when hydrogen content is boosted by the addition of plastic polymers, with minimal impact on setting time. Further testing will involve verifying lithium production in irradiated cement systems with boron and large-scale attenuation testing using the University of Florida Training Reactor.