Radiolysis of Sub- and Supercritical Water Induced by <sup>10</sup>B(<i>n</i>,α)<sup>7</sup>Li Recoil Nuclei at 300–500 °C and 25 MPa
(1) Background: Generation IV supercritical water-cooled reactors (SCWRs), including small modular reactor (SCW-SMR) variants, are pivotal in nuclear technology. Operating at 300–500 °C and 25 MPa, these reactors require detailed understanding of radiation chemistry and transient species to optimize...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-06-01
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| Series: | Journal of Nuclear Engineering |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2673-4362/6/2/17 |
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| Summary: | (1) Background: Generation IV supercritical water-cooled reactors (SCWRs), including small modular reactor (SCW-SMR) variants, are pivotal in nuclear technology. Operating at 300–500 °C and 25 MPa, these reactors require detailed understanding of radiation chemistry and transient species to optimize water chemistry, reduce corrosion, and enhance safety. Boron, widely used as a neutron absorber, plays a significant role in reactor performance and safety. This study focuses on the yields of radiolytic species in subcritical and supercritical water exposed to <sup>4</sup>He and <sup>7</sup>Li recoil ions from the <sup>10</sup>B(<i>n</i>,α)<sup>7</sup>Li fission reaction in SCWR/SCW-SMR environments. (2) Methods: We use Monte Carlo track chemistry simulations to calculate yields (<i>G</i> values) of primary radicals (e<sup>−</sup><sub>aq</sub>, H<sup>•</sup>, and <sup>•</sup>OH) and molecular species (H<sub>2</sub> and H<sub>2</sub>O<sub>2</sub>) from water radiolysis by α-particles and Li<sup>3</sup>⁺ recoils across 1 picosecond to 0.1 millisecond timescales. (3) Results: Simulations show substantially lower radical yields, notably e<sup>−</sup><sub>aq</sub> and <sup>•</sup>OH, alongside higher molecular product yields compared to low linear energy transfer (LET) radiation, underscoring the high-LET nature of <sup>10</sup>B(<i>n</i>,α)<sup>7</sup>Li recoil nuclei. Key changes include elevated <i>G</i>(<sup>•</sup>OH) and <i>G</i>(H<sub>2</sub>), and a decrease in <i>G</i>(H<sup>•</sup>), primarily driven during the homogeneous chemical stage of radiolysis by the reaction H<sup>•</sup> + H<sub>2</sub>O → <sup>•</sup>OH + H<sub>2</sub>. This reaction significantly contributes to H<sub>2</sub> production, potentially reducing the need for added hydrogen in coolant water to mitigate oxidizing species. In supercritical conditions, low <i>G</i>(H₂O₂) suggests that H<sub>2</sub>O<sub>2</sub> is unlikely to be a major contributor to material oxidation. (4) Conclusions: The <sup>10</sup>B(<i>n</i>,α)<sup>7</sup>Li reaction’s yield estimates could significantly impact coolant chemistry strategies in SCWRs and SCW-SMRs. Understanding radiolytic behavior in these conditions aids in refining reactor models and coolant chemistry to minimize corrosion and radiolytic damage. Future experiments are needed to validate these predictions. |
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| ISSN: | 2673-4362 |