Dose-rate effects in water radiolysis from 25 to 700 °C: A Monte Carlo multi-track chemistry simulation study with applications in supercritical water-cooled nuclear reactors and FLASH radiotherapy.
Bibliographic record
Abstract
Abstract: Nuclear energy is one of the most demanded low-carbon energy sources in this era of climate change. The “Generation IV International Forum” has selected the concept of supercritical water-cooled reactors as one of the six innovative reactor concepts to be the subject of international collaborations in terms of research and development. It is difficult to make direct experimental measurements of the primary radiolytic products of supercritical water (SCW) (e_aq^-, OH–, H+, H•, •OH, H2, H2O2, HO_2^•/O_2^(• -),…), which are corrosive for materials under extreme conditions of temperature (~350 to 650°C), pressure (25 MPa) and mixed radiation field inside the reactor core. In this study, we have developed Monte Carlo simulation programs of the chemistry involved in the trajectories in order to explore the effect of temperature and pressure (density) in the radiolysis of SCW, to calculate the yields of radiolytic species (oxidizing and reducing ) and to reveal the reaction mechanisms involved. To our knowledge, we are the first to have studied the effects of radiation dose rate in Generation IV reactors or small modular reactors cooled with supercritical water, under conditions normal operation or in an emergency or accidental situation (where the dose rate may exceed 10^10 Gy/s). For this, we irradiated the water with single pulses of N incident protons of 300 MeV kinetic energy (which mimic the ⁁ rays of cobalt-60) and varies N to study the dose rate effect. In addition, we have developed a model of water radiolysis in a cell-like environment to examine the mechanism of radiolytic oxygen depletion by e_aq^- and H• produced by radiolysis, which has been proposed to explain the protection of healthy tissue in FLASH radiotherapy (which uses instantaneous dose rates of ~10^6-10^7 Gy/s). We have shown that this radiolytic depletion of O2 is considerably attenuated in the presence of cellular components having the property of being excellent sensors of e_aq^- and •OH. We finally studied the effect of dose rate on the peaks of transient acidity produced at short times by radiolysis of pure SCW deaerated at 400°C and aerated water at 25°C. In all the environments considered, the pH of the solution remains very acidic (between ~2.8 and 3.5) for a long period of time and this acidity increases with the increase in the dose rate. This acidity can contribute to corrosion in nuclear reactors and play an important role in the mechanisms of the FLASH effect.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".