Determining the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow/><mml:mn>239</mml:mn></mml:msup></mml:math>Np<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mo>(</mml:mo><mml:mi>n</mml:mi><mml:mo>,</mml:mo><mml:mi>f</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math>cross section using the surrogate ratio method
Bibliographic record
Abstract
Background: Neutron-induced fission cross-section data are needed in various fields of applied and basic nuclear science. However, cross sections of short-lived nuclei are difficult to measure directly due to experimental constraints.Purpose: The first experimental determination of the neutron-induced fission cross section of ${}^{239}$Np at nonthermal energies was performed. This minor actinide is the waiting point to ${}^{240}$Pu production in a nuclear reactor.Method: The surrogate ratio method was employed to indirectly deduce the ${}^{239}\text{Np}(n,f)$ cross section. The surrogate reactions used were ${}^{236}\text{U}{(}^{3}\text{He},p)$ and ${}^{238}\text{U}{(}^{3}\text{He},p)$ with the reference cross section given by the well-known ${}^{237}\text{Np}(n,f)$ cross section. The ratio of observed fission reactions resulting from the two formed compound nuclei, ${}^{238}$Np and ${}^{240}$Np, was multiplied by the directly measured ${}^{237}\text{Np}(n,f)$ cross section to determine the ${}^{239}\text{Np}(n,f)$ cross section.Results: The ${}^{239}\text{Np}(n,f)$ cross section was determined with an uncertainty ranging between 4$%$ and 30$%$ over the energy range of 0.5--20 MeV. The resulting cross section agrees closest with the JENDL-4.0 evaluation.Conclusions: The measured cross section falls in between the existing evaluations, but it does not match any evaluation exactly (with JENDL-4.0 being the closest match); hence reactor codes relying on existing evaluations may under- or overestimate the amount of ${}^{240}$Pu produced during fuel burnup. The measurement helps constrain nuclear structure parameters used in the evaluations.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 0.004 |
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 source (direct Gemma or distilled Codex), 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".