Minimizing the Standard Deviation of the Thermal Load in the Spent Nuclear Fuel Cask Loading Problem
Round 1
Reviewer 1 Report
consider changing the title to have main focus.
Introduction should be improved, include detailed analysis of methods for optimization and compare with MILP, in view of the target model and objective function.
change style of writing, many places have bullets, should be text, with tables
add nomenclature to describe variables used
add list of abbreviations
include graphs to show trending and analysis between tables and results
data should be included in tables, like in line 445...
conclusion should be revised to include achieved results , impacts
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Minimizing the standard deviation of the thermal load in the Spent nuclear fuel encapsulation problem
Terminology:
It is usual to call installation for interim dry storage of Spent Nuclear Fuel (SNF) simply dry storage installation instead of warehouse. In part of the paper you used common terminology ISFSI and that is good approach.
It s usual to call the container where SNF is stored cask. I would not recommend to call that capsule or process encapsulation (including in the title). The encapsulation is somehow reserved for HLW and SNF final long term storage and includes methodology different than one used for temporary dry storage.
References:
General nuclear references on safety culture were mentioned like IAEA-TECDOC-1329. It would be more appropriate to mention IAEA_TECDOC-1523 Optimization Strategies for Cask
Design and Container Loading in Long Term Spent Fuel Storage, IAEA 2006.
In addition there is no reference covering similar problem, optimization of dry cask loading. I will mention couple of them:
Kristina Yencey, Optimization of dry cask loadings for used nuclear fuel management, strategies, Progress in Nuclear Energy, 2018,
Kristina Yencey, A greedymemetic algorithm for a multiobjective dynamic bin packing problem for storing cooling objects, Journal of Heuristics, 2018,
Petersen, Determining Optimal Used Fuel Allocation Strategies, Nuclear Technology, 2017,
Gomes, A Methodology for Optimizing the Management of Spent Fuel of
Nuclear Power Plants Using Dry Storage Casks, STNI 2019,
Page 2 of 35
At the end of its service, each Spent Fuel Assembly (SFA) has produced around 50GWd/t of heat.
It is better to say Up to the end of….. They are talking about integral property called burnup, and it is specific energy released up to the point in fuel cycle.
The statement: Radiation emitted in the spent fuel generate the so-called “decay heat”, is not completely correct. e.g. SNF is source of neutrons and gammas (as well as other particles) and part of emitted particles and gamma rays are not captured by fuel. Usual definition of decay heat is “heat released during radioactive decay of fission products and other radioactive materials present in SNF (e.g. actinides, activated materials)”.
Page 3
Acronym MPC in HI terminology means Multi-Purpose Canister.
I think that HI storage system shown on Fig. 1 has official name HI-STORM system not HI-STAR system, but in any case should be called the same way through the paper.
Regarding Fig 2. Why you are calling outer cask region severe region and SFA there have smaller heat load and inner region permissive region where SFA power is higher? Compromise in selecting limiting heat loads for two regions is based on cooling capability for inner region and cask surface dose for outer region (there is no self shielding).
Page 5 line 145 it is more usual to say that SFA is unloaded from the pool than evacuated.
Line 151 I think that word optimization is missing after NF encapsulation problem. Again, I think that word encapsulation is not proper word for what is going on during SNF dry storage.
Sentence starting on line 155 could be improved from English point of view.
Line 159 probably be is missing like “be such value”.
What means “cost thermal” in line 194. You can minimize cost (basically number of required casks, for practical reasons all of them are of the same type) or you can remove more or less heat load from the pool. Cask loading is operation that last some time (e.g. about one week).
Line 200 I assume empty at once
Top of page 7. Probablly c i,k(T) and not c i,j(T)
Change Sujeto a t o Subject to
Line 207 Equality instead of Equalities
Line 209 Constraint instead of Constraints
Line 233 Statement 5 instead of Sentence 5 the same in Line 235 and further . We have algorithm then it is better to use statement than sentence.
Line 240 should be some kind of title, like Algorithm 1 for A1 pseudo code that follows.
GRASP algorithms are rather known but because you provided meaning for MILP acronym please do the same here.
Regarding minimization of heat load standard deviation Eq 10 it is like you did at cask level. Did you think about doing that on region level in each cask (meaning to have similar average region heat loads in different casks)?
Use 315 as title of algorithm that follows (A2). Use similar format of labeling the steps/statement of algorithm A1 and A2. Some words in A2 are in Spanish.
Line 341 denote instead of notice
Line 353. Numbering of steps in algorithms A1, A2 and MS.
Hypothesis H4, to have only one type of container is more realistic than more container types present in the development of algorithms.
Line 390 it is enough to say no capacity limit in ITW. The structure of ITW is not shown in the paper and there is no need to talk about casks position within storage.
Regarding assumption H6 it is not possible to unload all SFA present in the pool even if we neglect emergency unload of current core. The minimum cooling time is 3 to 5 years and assumed cycle duration is 18 months.
Regarding H7, as already said cask loading is not instantaneous process. E.g. to unload 1024 SFA with MPC-32 you will typically need 8 months.
Line 401, please use decay heat consistently, not heat of decay.
Regarding H8 in addition to have balance of total thermal load of cask it is usually good to have balance between regions of the casks (what implicitly means balancing of total load).
Regarding R6 limits on maximum SFA region heat load is not subjected to this type of optimization and it is prescribed by cask design and contact dose.
Line 438. In real situation you have not uniform cooling time in the pool. You can specify only minimum cooling time. Other things are determined with plant operational history. In this case you got variation in decay heat only due to different SFA burnups.
What actually means to have 3 container types in Section 4.3 if we have just one type of MPC-32.
Section 4.4 If commercial code CPLEX was used to solve MILP what was used to solve/implement algorithms A1 and A2?
Line 619 ENRESA instead of ENDESA.
It is recommended to show some of the results found in tables graphically too.
The tables in App I and II are not necessary except for repeating algorithm results and testing. Table A1 uses unrealistic assumption of uniform cooling time, tables A2 to A4 show identifiers assignment in the optimization problem.
Appendix II gives distribution of SFA “names” within casks and corresponding decay heat values. Uniformity of the values is much better shown by standard deviation in body text of the paper.
English language could be improved in some parts of the paper.
I had no time to study proposed algorithms in more details, but approach is proper one from optimization point of view. It can be simplified (be less theoretical) if real limits are taken into account. That is type of optimization (more practical one) is usually used by vendors like HI.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The first part can be improved in terms of english and clearness of exposure.
The second part discussing the implementation and the application of the method seems better written.
Please use numbers with a meaningful number of digits!
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
The Authors report a computational study aimed to optimize the storage of nuclear wastes in terms of number of capsules needed for the determined amount of radioactive waste.
The topic is interesting, nevertheless, the manuscript is not properly presented and written. The main issues encountered are reported as follows.
- The English level is too low and the understanding of many periods is too difficult. Some examples:
- Line 36: “In all the stages of the electricity system…”
- Line 37: “and for that of…”
- Line 38: “there are studies..”
- Line 44: “The balance between……is resolved in nuclear power plants…”
- Line 49: “nuclear fuel is uranium slightly enriched..:” maybe “is constituted by uranium…”
In general, the description of the topic, of the bibliography, and of the results is poor.
- Line 59: “In the fission process, uranium atoms are transformed into fission products” No doubt on this, maybe a short explanation on the specific products which are formed during the fission process would help the Reader.
- Line 62: “The hazard of spent fuel is due to the potentially harmful effects of ionizing radiation.” harmful for whom? and “potentially”? The radioactive spent fuel is highly dangerous for human been as well as for animals and plants. A minimal exposition produces severe consequences including death.
- UO2, not UO2.
- Line 98: “The organization of the paper is as follows.” This sentence doesn’t provide any information.
- Line 106: “In Spain, Enresa has proposed and adopted different solutions in those Spanish NPP that have…” If we remove “has proposed and” and “Spanish” the sentence gain in clarity and it is more correct: “In Spain, Enresa adopted different solutions in those NPP that have….”
Many more issues of this type are present along the manuscript.
Other issues:
- In the Abstract section a very short description of the context should be provided, followed by the main results achieved. The provided Abstract is not organized in this way.
- An experimental part chapter is missing, in general the organization of the chapter is not in according with the usual structure of the scientific papers of the journal. E.g., “Conclusions and future research “. This seem more suitable for a thesis. Also, no future research is commented in the section.
- In general, the discussion about the bibliography is not homogeneous and in the results sections the data herein presented are not compared with the ones of previous studies.
- In the first part of the introduction seems that the presented study it is referred to the Spanish nuclear plants, but after that, suddenly, the Authors start to refer to Ascò, without any introduction (line 52). Only later it is possible to understand that Ascò is a location of nuclear plants, or is a nuclear plant? I thought it was a plant but at line 108 it is written “Ascò plants are using….”.
- The format employed for the bibliography is not correct.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
accept
Author Response
We sincerely thank the Reviewer for accepting our work for the journal Energies.
JBV · LBM · MMD / 2020-09-12
Author Response File: 
Author Response.docx
Reviewer 4 Report
Dear Authors
Many improvements have been done with respect to the first version of the manuscript.
Now the paper would be suittable for pubblication.
Nevertheless, I have a big concern: the paper "Modelado y resolución del problema del encapsulamiento de combustible nuclear gastado", Dirección y Organización 71 (2020) 46-70, by the same Authors, it seems to me the same paper of the herein presented one but in Spanish language.
So, please, provide explanation about the differences between the two papers, in order to clarify that your manuscript it is not a simple English translation of something already published.
Author Response
The reviewer is right. Thanks for the feedback.
We have rewritten part of sections "4.5 Results" and "5. Conclusions" in order to highlight the differences between: (i) the deterministic procedure DP [·] presented in reference [29] and the MS[·] multi-start metaheuristic that we have prepared for Energies.
JBV · LBM · MMD / 2020-09-12
Author Response File: Author Response.docx
Round 3
Reviewer 4 Report
All the issues have been addressed.
