Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for the opportunity to review this manuscript on the downsizing of Neutron Resonance Transmission Analysis (NRTA) system. While the idea of a compact NRTA system is indeed timely and attractive, the current manuscript does not yet meet the standards required for publication. The main shortcomings are outlined below; unless these are fully addressed, the paper will remain insufficiently substantiated.

Major Comments

1. Lack of Explicit Design Assumptions
The manuscript mentions a flight path length of 1 m but provides no quantitative description of the other essential components:

• Neutron source (type, energy spectrum, flux level).
• Collimator geometry (material, size…).
• Detector system (type, efficiency..).

Without these specifications it is impossible to assess whether the proposed configuration is realistic, to reproduce the results, or to compare its performance with existing systems. Please supply a complete set of design parameters.

2.  Absence of Benchmarking Against Prior Work
Several groups (refer to references below) have already demonstrated compact NRTA systems using D-T neutron generator or a radiation source. The present manuscript does not discuss how their design differs from or improves upon these studies. 
In particular:

•  What are the novel design elements that enable further miniaturisation?
•   How does the expected spatial resolution, detection efficiency, and measurement time compare with the cited works?
•   Are there any trade‑offs (e.g., reduced flux, increased background) that must be acknowledged?

*[Ref]
1. Klein, E. A. et al. Neutron-Resonance Transmission Analysis with a Compact Deuterium-Tritium Neutron Generator. Phys Rev Appl 15, 054026 (2021).
2. Tsuchiya, H. et al., Development of an integrated non- destructive analysis system, Active-N, Journal of Nuclear Science and Technology, 60:11, 1301-1312

3. Naqvi, F., Watts, H., Levine, P. & Danagoulian, A. Feasibility studies of doing NRTA measurements using an AmBe neutron source. in Dedicated to the safe, secure, and effective stewardship of nuclear and other radioactive materials and related technologies (ed. INMM) (INMM, 2023).

In its present form the manuscript is not suitable for publication. I encourage the authors to address all major points above, supplement the work with a rigorous Monte‑Carlo study anchored in the existing literature, and provide quantitative evidence of the claimed improvements. 

Minor comments
1.    Section 2 (Line 118)
The procedure used to obtain the simulated energy spectrum is unclear. Please provide more details on the Monte‑Carlo (MC) settings.

2.    Section 3 (Line 156)
The variable n is introduced as an areal density (nk). For clarity, explicitly state that n denotes the areal density in the text.

3.    Figure 2
When performing the χ² comparison, have the authors accounted for experimental uncertainties or simulation statistical errors? Conventional practice is to include the experimental error bars (and, if relevant, the MC statistical uncertainties) in the χ² evaluation. Please clarify how uncertainties are treated in the analysis.

4.    Section 4 (Lines 170‑174)
The assumptions made in this section imply a relatively large sample area, which in turn suggests a correspondingly large detector area. It would be helpful to comment on the dimensions of both the sample and the detector (e.g., typical footprint, active area) and to discuss any constraints these sizes impose on the proposed a compact NRTA system.

5.    Table 1
The entry for U‑235 lacks a simulated value. Please provide the missing simulated data (or indicate “N/A” if the simulation was not performed for this isotope).

Author Response

"Please see the attachment."

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article is solid, there are however a few comments I would like to make.

 

The true novelty of this paper lies in the methodology for determining the sample properties, however, the paper regrettably addresses these issues very briefly, unfortunately, many crucial details are lacking. For instance, how is the theoretical spectrum generated? Which sections of the data are fitted—only the resonances, or the full energy range? How are resonances chosen? What is the procedure used for mixed isotopic samples? How are the Monte Carlo spectra produced? Are the theoretical and simulated spectra aligned on the same time/energy grid? What method is used for bin alignment?

I really would appreciate if some of these points would be clearer elaborated.

 

I have some more serious concerns regarding the theoretical formula. Firstly, it is never mentioned whether the cross sections are Doppler broadened—I assume they are, but this should be explicitly stated. More concerning is the claim that T_theo (line 96) can be directly compared to T_exp. (line 99). The statement, found around line 105, is incorrect. As the authors themselves later acknowledge, this function must be convolved with the response function of the neutron time-of-flight spectrometer. I would appreciate it if the correct formulas were provided. This issue also applies to Figure 2, where Tconv = T_theo * G(E) is indicated; I hope the spectra are not processed this way. It should involve a convolution, an integration of the product of these two functions.

The mathematical notation in the paper should be correctly describing the applied processes!

 

While the discussion is simple,  but correct – I am having some concerns on the given expected accuracies. While I agree that with a better accounting for the neutron’s time distribution in the analysis will improve the results, experimental condition will lead to a deterioration of the results

Author Response

"Please see the attachment."

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript titled 'Study of the Industrial Feasibility of Neutron Resonance Transmission Analysis (NRTA)', submitted to the Journal of Instrumentation at MDPI, presents a brief theoretical investigation of NRTA applied to uranium samples, via a developed quantitative method in conjunction with MCNP simulations.

While the manuscript appears to be generally somehow aligned with the journal’s scope, I recommend the following improvements be addressed prior to publication.

The following general comments relate to the manuscript’s structure and analytical approach, I avoided providing line to line comment, as there need to be another version,

• Initially it is unclear whether the manuscript aimed to directly compare an actual experimental data with the developed model or with MCNP simulations. Clarifying this objective early in the manuscript would help guide the reader.
• The GELINA – JRC-Geel facility is producing a broad spectrum of neutron energies at flux levels around 10e13/cm²/s. The authors should specify the neutron flux at energy range of interest, e.g. epithermal region, which actually interact with the sample.
• While the manuscript suggests that detector resolution is considered in the quantification method, e.g. moderation and source, however the specific instruments used are not described. May be this is not considered, or will be considered in future?
• The use of a zero-time broadened neutron source in the simulation is misleading, especially given the moderated nature of the source. This assumption is physically unrealistic. Including MCNP calculated time tallies for each energy bin after moderation, will show temporal spreading effects, would provide a more accurate representation. This is quite easy to produce. You can produce similar figure to, https://doi.org/10.1038/s41598-020-77086-y , figure 6.
• The authors might consider discussing direct epithermal neutron production or using a smaller moderator to reduce temporal broadening. Techniques such as laser-driven neutron sources (LDNS) or proton-lithium (p-Li) reactions could be explored. Please see https://doi.org/10.35848/1347-4065/ad9f00, table III. These sources can be positioned close to the sample, and given their high repetition rates, the neutron flux at the sample location is likely to be comparable to that of conventional sources.

         Although some broadening is inevitable, these methods offer lower neutron temperatures and safer operational environments, potentially allowing for more compact setups.

 

• Codes like CONRAD offer more detailed resonance analysis and fitting capabilities. The authors may benefit from incorporating or referencing such tools to enhance the robustness of their analysis.
• On page 6, the manuscript mentions ensuring that all detected neutrons have passed through the sample, not sure how.
• Including schematic figures of both the simulation and theoretical setups would greatly aid in understanding the experimental design.

The manuscript currently lacks several key details and would benefit from a clearer justification of the proposed quantitative method, particularly in comparison to established techniques. Additionally, the neutron source model used not realistic. The authors mention planned experiments at the GELINA and MONNET facilities, which adds potential value and relevance to the study. While it may not be necessary for the authors to implement all of the suggestions above, adopting a more realistic approach would be greatly appreciated and would enhance the credibility of the study.

Author Response

"Please see the attachment."

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you to the authors for getting back to me. I’m now happy for the manuscript to be published with the applied changes.