The existing core loading optimization packages(codes) based on several strategies, i.e., in-or-out and maximum burn-up minimum discharge at the end of the cycle for large cores runs on multiple cycles to optimize those critical strategies to reach the required economy. However those codes apply only as far as I remember for large commercial cores works like a charm.. For small cores like research reactors they may not be feasible but requires to be experimented. Since you are doing this as a research, Aldo Dall'Osso's company's (AREVA) may provide you one of their commercial packages that you can test that. It is also good for them. However, if you are going to develop a new concept and generate a new technique using several of the plenty algorithms available in the literature and come with a best one that optimize the benefits. This looked like a theses subject offer rather than a known publication offer but I recommend you check the ANS first. 

https://www.researchgate.net/publication/245134327_Core_loading_pattern_optimization_for_research_reactors

may be helpful

Article Core loading pattern optimization for research reactors

Araound twenty years ago we used for a PWR reactor in the Netherlands simulated annealing i which fuelelements were exchanged and a new neutronic calculation was made and a qualifty factor calculated. Based on this a probability for the exchange was obtained and the elements exchanged or not. Unfortunatedly we never made a write up on the subject. The annealing procedure was described in an paper in Physics today for the optimization of patterns for microchips by IBM.

A Google search with  "Verhagen" "pwr" 'ed to a number of hits. Two of which I have attached.

merry Christmas and a good beginning of the new year

The "best loading pattern" is not defined in the original question .If the core to be optimized is a high-flux-core, the treatment of the neutron leakage may be important. The geometry of a research reactor may be strongly diffeentr from the geometry of power reactors.

For these reasons I try  to show a code developed at the Hungarian NPP Paks.

The Russian type PWRs use VVER reactors with hexagonal fuel elements. (These cannot be calculated in square system. The latter ones are subject of several publications.) To increase the service life of the pressure vessel the neutron exposition has to be decreased. The "low leakage core map" means that the fuel assemblies at the outer surface of the core have to be selected accordingly.

This point of view may be of great importance. 

Note. The code ROSE referred by W. J. Oosterkamp is limited to lattices with sqare fuel elements. Furthermore, in its description there are several parameters to be optimized., but I could not find there the "leakage minimization".

Dear Dr. Szondi,

Thank you for your clarification. The original neutronic model used in the optimization for the Borsele PWR was based on age theory (c.f. Weinberg Wigner) which would be easy to modify for hexagonal latttices. this was in fact a modification of a model used for the calculation of BWR reactors, which showed some idiosyncracies. It is possible to add a weight to the target function in order to reduce the fast flux to the vessel wall. In 1983 after ten years of operation we looked at the vessel embrittlement and showed that it was not a problem for an operation period of fourty years, that has since then be surpassed.Optimization with regard to burnup reduced the fluxes to the vessl wall significantly, but that was not included into the target. 

litt. Neutorn ebrittlement of the reactor vessel in Borssele as determined from Charpy specimens" Kema scientific & technical reports (10 4 

The different objectives of core loading optimization between large NPP

cores  & small research reactor cores, as I also alluded to earlier, important. Research reactors for several irradiation projects requires same high neutron flux for a short irradiation time of samples e. g., radioisotopes production and stable flux for several other sensitive experiments. Therefore, irradiated vessel embrilittlement issue for large pool walls is not as a prime concern as in the NPPs. Most of the research reactors besides the Triga's, do not have a reactor vessel.

I agree with you Aldo. Whatever algorithms you choose,YES.

Thanks for the answers. In our case it's a research reactor under small scale studies. We are doing some neutronic calculations to evaluate the best positions for the neutron detectors and also to check the best loading pattern, try and error process at first, to achieve a good reactor control when the subcritical factor starts to reach the critical one. it's a matter of how close we can get to the critical factor as long as the fuel plates (at  fuel elements in the corners) are being added, in order to have a small multiplication factor increment, then with a good control from the instrumentation point of view. In our Critical Unit, where the experiment will be performed, we have to set the diferente detectors and  their positions as long as the neutron flux increases (using the Monte Carlo Approach). We already have all theses models working well, but the detector positions, detector types and the fine adjustment are still under discussion. 

There are two nuclear research reactors: one at MIT and one at WPI. I'm familiar withe MIT research reactor since I was a graduate student there as well as being a teaching faculty on nuclear risk assessment.

The MIT reactor is called a "Pool" type reactor and is used mostly for medical research and materials testing. The best core loading design is the one that minimuzes neutrons losses from the reactor core. Also, an optimal core loading design is the one that allows efficient heat transfer from the fuel to the cooling medium and also makes fuel shuffling easy.

You may want to search for published dissertations on optimization of core loading patterns at the MIT engineering an science libraries in Cambridge, Massachusetts.

Hope this helps answer your question.

Professor Yehia Khalil

Yale University

USA

For sure it's a usefull answer. I'll check about that online, cause i'm in south america for the time being, far from the physical libreries that you have suggested. 

Dear Thiago,

Are your working in the Institue of Atomic Energy  in Sao Paulo. they used tohave a good library there, when I was a visiting professor 1973 -1977

Willem Jan Oosterkamp

Yes, the institute's name was changed, but it's in the same place. Nice to hear you worked here. I'm on vacation until next week, for sure I'll be cheking the library there, but I guess is more reasonable starting a discussion here, cause lots of years passed and new things are going on out there in this subject.