Impact of Approximations in Operating History Data on Spent Fuel Properties with Serpent 2

In this work, the effect of averaging operating history parameters such as power history, boron concentration and coolant density and temperature on spent nuclear fuel properties was investigated. The examined properties were assembly activity, decay heat, photon emission rate, spontaneous fission rate and the concentration of some mobile nuclides and fissile nuclides. Calculations were performed on two similar VVER-440 fuel assemblies irradiated in different positions of the core using Serpent 2. Averaging power history over the entire irradiation history had a significant effect on assembly activity, decay heat and photon emission rate overestimating these properties approximately 70 % right after irradiation. However, the effect quickly died out and after 10 years of cooling the effect was less than 1 %. If the last cycle (3rd cycle) was modelled accurately and the power density of only the first two cycles were averaged, the differences remained always below 1 %. The effect of operating history approximations on spontaneous fission rate and the nuclide concentrations was much smaller reamaining mostly below 1.5 %. The sensitivity of nuclide concentrations to approximations in individual operating history parameters was dependent on the nuclide in question and no trend applying to all studied nuclides could be observed.

An Application of ASP in Nuclear Engineering: Explaining the Three Mile Island Nuclear Accident Scenario

The paper describes an ongoing effort in developing a declarative system for supporting operators in the Nuclear Power Plant (NPP) control room. The focus is on two modules: diagnosis and explanation of events that happened in NPPs. We describe an Answer Set Programming (ASP) representation of an NPP, which consists of declarations of state variables, components, their connections, and rules encoding the plant behavior. We then show how the ASP program can be used to explain the series of events that occurred in the Three Mile Island, Unit 2 (TMI-2) NPP accident, the most severe accident in the USA nuclear power plant operating history. We also describe an explanation module aimed at addressing answers to questions such as “why an event occurs?” or “what should be done?” given the collected data.

Clinical and neurophysiological peculiarities of health disorders in workers in dependence on the vinyl chloride exposure load

Results of the clinical and neurophysiological examinations of 42 workers with operating history at the chemical plant exposed to vinyl chloride (VC) are presented. The purpose of research was the identification ofpeculiarities of clinical manifestations and disorders of the functional activity of the brain in workers at the vinyl chloride production, with taking into account the exposure toxic load (ETL). There were made clinical and electroencephalographic examinations with the detection of cognitive evoked potentials (CEP) and statistical analysis of results with the use of the Mann-Whitney U-test, Fisher’s F-test, calculation of Spearman’s correlation coefficient. The features in clinical picture of the pathology of the nervous system were detected in the form of asthenic disorders with cognitive impairment and autonomic dysfunction syndrome. There was established the increase in the cognitive impairment rate (p = 0.03), the decline in a-EEG activity (p = 0.01) and the worsening of indices of the amplitude (p = 0.011) and latency (p = 0,05) of CEP in extremely high level of ETL in comparison with same indices in the group with moderately high ETL. In the first group there was revealed a statistically significant exceedance of the frequency of hypertension - by 1.6 times, skin diseases - by 9 times, chronic subatrophic rhino-pharyngitis by 1.4 times in comparison with cases from the second group. In the group with moderately high level of ETL there was established the statistically significant inverse correlationship between the ETL and the index of P300 amplitude from the left side (r = -0.38, p = 0.019) and in the group with extremely high level ETL - between ETL and index of the β2 - rhythm (r = - 0.73, p = 0.0008).

Modelling of fine fragmentation and fission gas release of UO2 fuel in accident conditions

In reactor accidents that involve rapid overheating of oxide fuel, overpressurization of gas-filled bubbles and pores may lead to rupture of these cavities, fine fragmentation of the fuel material, and burst-type release of the cavity gas. Analytical rupture criteria for various types of cavities exist, but application of these criteria requires that microstructural characteristics of the fuel, such as cavity size, shape and number density, are known together with the gas content of the cavities. In this paper, we integrate rupture criteria for two kinds of cavities with models that calculate the aforementioned parameters in UO2 LWR fuel for a given operating history. The models are intended for implementation in engineering type computer programs for thermal-mechanical analyses of LWR fuel rods. Here, they have been implemented in the FRAPCON and FRAPTRAN programs and validated against experiments that simulate LOCA and RIA conditions. The capabilities and shortcomings of the proposed models are discussed in light of selected results from this validation. Calculated results suggest that the extent of fuel fragmentation and transient fission gas release depends strongly on the pre-accident fuel microstructure and fission gas distribution, but also on rapid changes in the external pressure exerted on the fuel pellets during the accident.

ФОРМИРОВАНИЕ ТИПОВЫХ ПРОФИЛЕЙ ПОЛЕТОВ САМОЛЕТА ТРАНСПОРТНОЙ КАТЕГОРИИ С УЧЕТОМ ИСТОРИИ ЭКСПЛУАТАЦИИ ПАРКА

The design resource of the airframe structure is assigned in the number of generalized typical flights or flight hours for all aircraft of the park. Both in the design and in the operational phases, the parameters of typical flight profiles serve as initial data for substantiating the design, accumulated or residual resources of the structural elements. An analysis of the load conditions of the transport category airplanes shows that even airplanes of the same type can have a completely different operating history. The projected typical flight profiles do not always correspond to the actual tasks performed by a particular aircraft. In addition, the operator does not have an explicit definition of the concept of a generalized type of flight. The question of the actual loads on the aircraft becomes particularly relevant at the stage of making a decision on the possible extension of the resource or the cancellation of the aircraft. The creation of modifications also requires the specification of the resource characteristics of the structure at the design stage. Definitely, such tasks are solved by the systems for monitoring the loads on the aircraft and onboard resource counters. The modern airplanes are equipped with this equipment. This study gives an estimation to the outmode park of transport category aircraft operating in Ukraine this year. It is proposed for the first time the method of determining the parameters of typical flight profiles according to the aircraft log-books and engines, as well considering the requirements of the flight manual of the considered type of transport aircraft. The algorithm for calculating the operation characteristics of the aircraft park was developed. The statistical analysis of the data of the Il-76T (TD) aircraft log-books was carried out in order to identify correlative dependencies on the duration of performed flights and relative operating time between some aircraft of the park. Recommendations are given for estimation the operating history of a specific aircraft and aircraft park. The obtained results in the future will serve as initial data for calculating the loads' influence on the aircraft during its operation, as well as for evaluating the accumulated and residual life of the transport category aircraft structure

THE GOOD EGG

“Now what?” Ken pondered as he stared out the window on his flight back from Phoenix having just closed on the acquisition of a 20-unit restaurant company: The Good Egg. Ken Pendery, the CEO of the First Watch restaurant chain for the last 30 years, had just recently grown the company by 20% in one fell swoop. But what was he to do with these Arizona restaurants located more than 1,000 miles from the nearest company-owned First Watch…convert them to First Watch, leave them be, institute the First Watch menu but leave The Good Egg flag…? Ken understood that the decision regarding what to do with The Good Egg brand would have far-reaching consequences. The purchase and conversion to First Watch of two J. Christopher’s restaurants in Atlanta 18 months earlier had not gone as planned. Part of the predecessor’s loyal customer base defected, sales fell by nearly 20%, and the company struggled for the next year to restore sales and profits to pre-conversion levels. If The Good Egg were to have the same fate upon conversion, the results would be devastating for the company and the management team. Recognizing that The Good Egg was the most highly-penetrated breakfast, brunch, and lunch brand with 15 locations in Phoenix and 5 in Tucson as well as a 30-year operating history made the decision even more precarious. The reasons for conversion were clear in Ken’s mind. First Watch had 10% higher average unit sales volumes than The Good Egg. Additionally, having 20 newly-converted First Watch restaurants would provide a foothold in the West, further expanding the brand’s presence. Finally, upon the inevitable sale of First Watch by its private equity group, the valuation of First Watch would be enhanced if those 20 restaurants were converted to First Watch as opposed to selling two disparate brands. Allowing The Good Egg to simply continue to operate independently would provide a predictable, stable revenue and profit stream, and remove the possibility of conversion loss as was realized in Atlanta. Straying from this strategy posed the possibility of considerable upside potential, but also significant downside risk. This would be one of the most pivotal decisions Ken would have to make as CEO and the decision consumed him for the remainder of his 5-hour flight back to Sarasota.