Nuclear and thermal hydraulic calculation of a representative I2S-LWR first core

The Integral Inherently Safe Light Water Reactor (I2S-LWR) concept developed by Georgia Tech is a novel PWR reactor delivering electric power of 1000 MWe while implementing inherent safety features typical for Generation III+ small modular reactors. The main safety feature is based on integral primary circuit configuration, bringing together compact design of the reactor core (121 fuel assembly), control rod drive mechanism (CRDM), 8 primary heat exchangers (PHE), 4 passive decay heat removal systems (DHRS), 8 pumps, and other integral components. A high power density core based on silicide fuel and APMT (FeCrAl) stainless steel cladding is selected to achieve a high thermal power. Initial representative first core nuclear design is proposed by Westinghouse. Full core 3D depletion calculation was performed using PARCS code. The cross section library is prepared using FA2D code and verified using Polaris sequence from SCALE 6.2 beta5. The axial and radial reflectors are assumed to be homogeneous water-APMT mixtures. The axial reflectors are both assumed to be 12 inch (30.48 cm) sections composed of 30% APMT steel by volume. The radial reflector is assumed to be 90% APMT steel by volume. The reflector constants were calculated using SCALE TRITON sequence. The thermal hydraulic part of the model is based on COBRA subchannel code coupled to PARCS code. Initial depletion calculation is based on one thermal hydraulics channel per fuel assembly approach. The hot fuel assembly is determined using separate pin-by-pin COBRA subchannel model and pin power reconstruction data from PARCS. The objective of the paper is demonstration of LWR design methodology applicability to silicide fuel and identification of possible improvements in the first core design

O modeliranju standardnih problema poslovne matematike pomoću rekurzija

U radu se opisuje matematičko modeliranje nekih standardnih problema poslovne matematike (konačna vrijednost glavnice pri jednostavnom i složenom obračunu kamata, te određivanje početne, odnosno konačne vrijednosti prenumerando i postnumerando uplata/isplata) pomoću rekurzija. Komentiraju se i neke prednosti takvoga načina modeliranja navedenih problema

Utjecaj enzimski hidrolizirane laktoze na fermentaciju i rast probiotičkih bakterija u sirutki

Taking in consideration the long time for whey fermentation using probiotic bacteria, the aim of this research was to determine if prior enzymatic hydrolysis of lactose influences microbial activities of Lactobacillus acidophilus La-5 or Bifidobacterium animalis subsp. lactis BB-12 in reconstituted sweet whey. During fermentation (at 37 °C), pH-value and viable cell counts were monitored. The fermented samples were sensory profiled. Lactose hydrolysis shortened the fermentation time of Lactobacillus acidophilus La-5 by 2 h, and viable cell count at the end of fermentation time was greater in hydrolyzed whey sample (~9.45 log10 CFU/mL) when compared with the control sample (~8.91 log10 CFU/mL). In contrast, lactose hydrolysis in whey did not enhance the activity of Bifidobacterium animalis subsp. lactis BB-12. Lactose hydrolysis had slightly influence on sensory score of fermented samples, probably due to sweetness that masked the acidic taste of the product.Uzimajući u obzir dužinu fermentacije sirutke probiotičkim bakterijama, cilj ovog rada bio je ispitati utječe li prethodna enzimska hidroliza laktoze na aktivnost bakterije Lactobacillus acidophilus La-5 ili Bifidobacterium animalis subsp. lactis BB-12 u rekonstituiranoj slatkoj sirutki. Tijekom fermentacije (pri 37 °C) praćena je promjena pH-vrijednosti i broj živih bakterijskih stanica. Fermentirani uzorci su senzorski analizirani. Hidroliza laktoze skratila je fermentaciju sirutke s Lactobacillus acidophilus La-5 za oko 2 sata, a broj živih bakterija na kraju fermentacije bio je nešto veći u hidroliziranoj sirutki (~9,45 log10 CFU/mL), u odnosu na kontrolni uzorak (~8,91 log10 CFU/mL). Međutim, hidroliza laktoze nije utjecala na aktivnost bakterije Bifidobacterium animalis subsp. lactis BB-12. Hidroliza laktoze neznatno je utjecala na senzorska svojstva fermentirane sirutke, jer vjerojatno stvorenu kiselinu prikriva osjet slatkoće

Nuclear and thermal hydraulic calculation of a representative I2S-LWR first core

The Integral Inherently Safe Light Water Reactor (I2S-LWR) concept developed by Georgia Tech is a novel PWR reactor delivering electric power of 1000 MWe while implementing inherent safety features typical for Generation III+ small modular reactors. The main safety feature is based on integral primary circuit configuration, bringing together compact design of the reactor core (121 fuel assembly), control rod drive mechanism (CRDM), 8 primary heat exchangers (PHE), 4 passive decay heat removal systems (DHRS), 8 pumps, and other integral components. A high power density core based on silicide fuel and APMT (FeCrAl) stainless steel cladding is selected to achieve a high thermal power. Initial representative first core nuclear design is proposed by Westinghouse. Full core 3D depletion calculation was performed using PARCS code. The cross section library is prepared using FA2D code and verified using Polaris sequence from SCALE 6.2 beta5. The axial and radial reflectors are assumed to be homogeneous water-APMT mixtures. The axial reflectors are both assumed to be 12 inch (30.48 cm) sections composed of 30% APMT steel by volume. The radial reflector is assumed to be 90% APMT steel by volume. The reflector constants were calculated using SCALE TRITON sequence. The thermal hydraulic part of the model is based on COBRA subchannel code coupled to PARCS code. Initial depletion calculation is based on one thermal hydraulics channel per fuel assembly approach. The hot fuel assembly is determined using separate pin-by-pin COBRA subchannel model and pin power reconstruction data from PARCS. The objective of the paper is demonstration of LWR design methodology applicability to silicide fuel and identification of possible improvements in the first core design

PCA Benchmark Analysis with ADVANTG3.0.1. and MCNP6.1.1b Codes

The Pool Critical Assembly Pressure Vessel (PCA) benchmark is a well known benchmark in the reactor shielding community which is described in the Shielding Integral Benchmark Archive and Database (SINBAD). It is based on the experiments performed at the PCA facility in the Oak Ridge National Laboratory (ORNL) and it can be used for the qualification of the pressure vessel fluence calculational methodology. The measured quantities to be compared against the calculated values are the equivalent fission fluxes at several experimental access tubes (A1 to A8) in front, behind, and inside the pressure-vessel wall simulator. This benchmark is particularly suitable to test the capabilities of the shielding calculational methodology and cross-section libraries to predict invessel flux gradients because only a few approximations are necessary in the overall analysis. This benchmark was analyzed using a modern hybrid stochastic-deterministic shielding methodology with ADVANTG3.0.1 and MCNP6.1.1b codes. ADVANTG3.0.1 is an automated tool for generating variance reduction (VR) parameters for Monte Carlo (MC) calculations with MCNP5v1.60 code (and higher versions). It is based on the multigroup, discrete ordinates solver Denovo, used for approximating the forward-adjoint transport fluxes to construct VR parameters for the final MC simulation. The VR parameters in form of the weight windows and the source biasing cards can be directly used with unmodified MCNP input. The underlining CADIS methodology in Denovo code was initially developed for biasing local MC results, such as point detector or a limited region detector. The FW-CADIS extension was developed for biasing MC results globally over a mesh tallies or multiple point/region detectors. Both CADIS and FW-CADIS are based on the concept of the neutron importance function, which is a solution of the adjoint Boltzmann transport equation. The equivalent fission fluxes calculated with MCNP are based on several highenergy threshold reactions from international dosimetry libraries IRDF-2002 and IRDFF-2014, distributed by the IAEA Nuclear Data Section. The obtained results show a good agreement with referenced PCA measurements. Visualization of the deterministic solution in 3D was done using the VisIt code from the Lawrence Livermore National Laboratory (LLNL)

PCA Benchmark Analysis with ADVANTG3.0.1. and MCNP6.1.1b Codes

The Pool Critical Assembly Pressure Vessel (PCA) benchmark is a well known benchmark in the reactor shielding community which is described in the Shielding Integral Benchmark Archive and Database (SINBAD). It is based on the experiments performed at the PCA facility in the Oak Ridge National Laboratory (ORNL) and it can be used for the qualification of the pressure vessel fluence calculational methodology. The measured quantities to be compared against the calculated values are the equivalent fission fluxes at several experimental access tubes (A1 to A8) in front, behind, and inside the pressure-vessel wall simulator. This benchmark is particularly suitable to test the capabilities of the shielding calculational methodology and cross-section libraries to predict invessel flux gradients because only a few approximations are necessary in the overall analysis. This benchmark was analyzed using a modern hybrid stochastic-deterministic shielding methodology with ADVANTG3.0.1 and MCNP6.1.1b codes. ADVANTG3.0.1 is an automated tool for generating variance reduction (VR) parameters for Monte Carlo (MC) calculations with MCNP5v1.60 code (and higher versions). It is based on the multigroup, discrete ordinates solver Denovo, used for approximating the forward-adjoint transport fluxes to construct VR parameters for the final MC simulation. The VR parameters in form of the weight windows and the source biasing cards can be directly used with unmodified MCNP input. The underlining CADIS methodology in Denovo code was initially developed for biasing local MC results, such as point detector or a limited region detector. The FW-CADIS extension was developed for biasing MC results globally over a mesh tallies or multiple point/region detectors. Both CADIS and FW-CADIS are based on the concept of the neutron importance function, which is a solution of the adjoint Boltzmann transport equation. The equivalent fission fluxes calculated with MCNP are based on several highenergy threshold reactions from international dosimetry libraries IRDF-2002 and IRDFF-2014, distributed by the IAEA Nuclear Data Section. The obtained results show a good agreement with referenced PCA measurements. Visualization of the deterministic solution in 3D was done using the VisIt code from the Lawrence Livermore National Laboratory (LLNL)

The use of spectroscopic techniques and chemometric methods in milk technology

Upotreba i primjena spektroskopskih tehnika u prehrambenoj industriji sve više raste, a odgovori koje daju olakšavaju rješavanje problema u proizvodnji i distribuciji hrane. Primjena spektroskopskih tehnika u mljekarstvu omogućava brzu i jeftinu kvalitativnu i kvantitativnu analizu, ali ima i važnu ulogu u opisivanju strukture i teksture mliječnih proizvoda. Kvalitativna i kvantitativna analiza pojedinih sastojaka u složenim sustavima može biti problematična zbog preklapanja spektralnih odgovora, a kao idealan put za rješenje tog problema je kemometrija, disciplina koja koristi matematičke i statističke metode kako bi oblikovala ili odabrala optimalan mjeriteljski postupak ili eksperiment i omogućila dobivanje, maksimalnog broja informacija analizom dobivenih podataka. Najčešća primjena kemometrije je u analizi skupa podataka i prepoznavanju matematičkih modela. Spektroskopske tehnike u kombinaciji s kemometrijskim metodama omogućavaju praćenje procesa i upravljanje kontrolom kvalitete.The use of spectroscopic techniques is on the rise in food industry, and the answers they provide facilitate problem solving in food production and distribution. The application of spectroscopic techniques in dairy technology allows quick and cheap qualitative and quantitative analyses, and is essential in describing the structure and texture properties of dairy products. The qualitative and quantitative analyses of individual components in composite systems may be problematic due to overlaps in spectral responses. An ideal tool to solve this problem is chemometry, a discipline using mathematical and statistical methods to design or choose an optimum measuring procedure or experiment, and to facilitate obtaining the maximum number of information by analysing the data provided. Chemometry is most frequently used in the analysis of data groups and recognition of mathematic models. Spectroscopic techniques combined with chemometric methods make a valuable tool for process monitoring and quality control management

The causes of milk deposit formation on the walls of the heat exchangers during the heat treatment of milk

Ovim radom opisani su rezultati istraživanja u otkrivanju uzroka i sprječavanju nastajanja mliječnog taloga. Toplinskom obradom mlijeka dolazi do nepoželjne pojave, nastajanja mliječnog taloga na ogrjevnoj površini izmjenjivača topline. Ova pojava uzrokuje smanjenje koeficijenta prijenosa topline i pad tlaka, blokira put mlijeku, stvara dodatne troškove u proizvodnji i povećava proizvodne gubitke. Nastajanje mliječnog taloga rezultat je složenih procesa uzrokovanih zagrijavanjem proteina i mineralnih tvari mlijeka. Nastajanje mliječnog taloga uzrokuje: pH-vrijednost, količina proteina i mineralnih tvari mlijeka, plinovi otopljeni u mlijeku, karakteristika ogrjevne površine, razlika temperature mlijeko - ogrjevna površina i režim strujanja mlijeka. Na kemijski sastav mlijeka ne možemo utjecati u većoj mjeri, ali zato možemo utjecati na parametre procesa toplinske obrade kako bi minimalizirali ovu pojavu, a to i je predmet novijih istraživanja.The results of research on finding the causes and preventing the formation of milk deposit are described in this paper. During the heat treatment of milk, an unwanted phenomenon occurs; the formation of milk deposit on heating surfaces of heat exchangers. This phenomenon causes the decrease of heat transfer coefficient as well as the pressure drop, it restricts the flow of milk, and causes additional production costs and increases production loss. The formation of milk deposit is a result of complex processes caused by thermal treatment of proteins and mineral substances in milk. Factors which cause milk deposit are: pH-value, the amount of proteins and mineral substances in milk, dissolved gases in milk, characteristics of heating surface, the difference in temperatures of milk and heating surfaces, and the regime of milk circulation. The chemical composition of milk can not be influenced, but the standards of heat treatment in order to minimise this phenomenon can, and that is precisely the topic of the latest researches

Nash equilibrium

Jedan od najvažnijih i najpopularnijih pojmova teorije igara je Nashova ravnoteža. U ovom radu želja nam je objasniti pojam Nashove ravnoteže u slučaju igranja čistih i mješovitih strategija na jednostavan i razumljiv način. Brojnim primjerima uvest ćemo i objasniti temeljne pojmove teorije igara. Demonstrirat ćemo razliku između racionalnosti igrača i zajedničke spoznaje svih igrača o tome jesu li svi ostali igrači racionalni, te kako iskoristiti takvo znanje pri odabiru pobjedničke strategije. U tu svrhu smo odigrali jednu od popularnih igara "Pogodi 2/3 od prosjeka" u nekoliko različitih osječkih srednjih škola.One of the most important and probably the most popular concepts of game theory is Nash equilibrium. In this paper we wish to explain the notion of Nash equilibrium in presence of pure and mixed strategies in simple and understandable way. With numerous examples we will motivate and introduce some basic game theory notions. We will illustrate the difference between perfect rationality of a player and the common knowledge of rationality of all players, and how to use that knowledge in order to win the game. In order to demonstrate that we have performed the popular "Guess 2/3 of the average" game in several high-schools in the city of Osijek