 University of Auckland. I started my accounting work life in the summer of 2012 and I am currently completing my Chartered Accountancy qualification.
At Walker Wayland I work on Nick's team with a role involving both audit and business advisory services.
In my spare time I enjoy playing basketball and soccer. Based on the season I also enjoy snowboarding or getting down to the beach.
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I joined Walker Wayland in September 2014 as a senior
accountant in the Business Advisory Services team. I have a BCom in Accounting
with 8 ½ years' experience as an auditor and 3 years' experience in Business
Advisory services. I look forward to meeting new clients and helping them grow
by understanding their business and financial needs.
I enjoy spending quality time with family and friends,
reading, playing board games and solving mechanical puzzles in my spare time.
I have recently joined the business advisory services team at Walker Wayland, having previously worked as a tax consultant at a Big 4 firm. I am looking forward to getting more exposure to accounting work, further developing my tax skills, and studying towards becoming a Chartered Accountant.
I have a BCom in Accounting and Commercial Law, and a BCom(Hons) in Commercial Law. Prior to that I also completed a BA in Social Anthropology.
In my spare time I enjoy watching movies, catching up with friends and family, and spending time with my partner.
I joined Walker Wayland in 2013 after many years working for various accounting firms in Auckland mainly in the secretarial/HR administration areas.
My interests are cooking, sewing, running and spending time with my family.The invention relates to the field of materials research radiation methods, for example by means of neutron irradiation for the detection and creation of local defects and can be used in the nuclear industry to predict the safe operation of nuclear reactors.
Currently, in our country are operated by 8 blocks reactors operating under pressure with a water coolant: VVER-1000. One of the factors that determine the resource reactor (KR)is the impact of elevated temperatures on materials irradiated and neobluchennykh parts of CU, i.e. thermal aging.
The results of studies of thermal ageing of materials used for the manufacture of the WWER-1000, presented in the technical literature [1-10]. It was shown that the base metal exposed parts of the CU VVER-1000 (steel NF) according to [4-7] are subject to thermal aging, and the weld metal CU VVER-1000 according to [4] are not susceptible to thermal aging. As has been shown in studies [4-7], the mechanism of thermal ageing in steel HF caused by the deposition process and subsequent coagulation of the carbides. The absence of thermal aging is usually associated with low carbon content in the weld metal (CC≤0,07%, where CC- carbon content in wt.%), and as a consequence, there is no the of carbide precipitation during operation. At the same time, in [8-10], it is shown that for weld metal steel ANF there is a dependence of the shift of the critical temperature of brittleness from time ΔTk(t)non-zero: if t>105hours ∆ Tk≈20°C, a max ΔTk(t)≈30°C. This result is obtained on the basis of processing results of the tests of thermal sets of specimens CU VVER-1000 and says, apparently, on the allocation of a process of operation of any other phases, except carbides, and/or about the absence of their full coagulation. Perhaps this result is associated with segregation processes of phosphorus.
It should be noted that when the operating temperature Tperfo=(300÷320°C "carbide" and "phosphorus" embrittlement are not cumulative, as these processes are shifted in time. Thus, the maximum ∆ Tkwhen carbide embrittlement corresponds to the time when the phosphorus embrittlement little. With increasing time t ∆ Tkdue to the "carbide" aging, decreases, while the phosphorus embrittlement continues to grow.
At the same time, the materials neobluchennykh parts (the nozzle) CU VVER-1000 can have a high phosphorus content compared to the exposed parts of the CU (shell active zone and the supporting shell). The materials most loaded parts of the reactor (area of pipe) the phosphorus content can be achieved (according to the SPECS) to C P=0,020% (CPthe phosphorus content in wt.%).
Given that today the task of extending the service life of VVER-1000 not less than 60 years (~5·105hours), and the new CR designed for a period of more than 60 years, the question arises about the reliability of the prediction of thermal ageing of CU metal.
Made estimates based on the kinetics of segregation of phosphorus at grain boundaries, and the relationship of these segregation with a critical temperature of brittleness show that for steel reactor containing phosphorus 0.020 wt.% and for weld metal with a Nickel content of 1.90 wt.% and with phosphorus 0.010 wt.% at a temperature of 320°C and holding time of 5·105hours of shift of the critical temperature of brittleness of steel may exceed 40°C.
One of the most important moments used in the estimation of the shift of the ductile-brittle transition temperature of the materials CU, requiring justification, is the value of the equilibrium segregation of phosphorus at grain boundaries or phase boundaries at the operating temperature of the reactor vessel. It is clear that this dependence is almost impossible to verify experimentally, since the temperatures corresponding to the operating temperature of the reactor, the time to reach equilibrium segregation of phosphorus more than 106hours.
In this regard, the urgent task is to develop a CSP is both embrittlement evaluation of the critical temperature of the material of the reactor at the operating temperature of 300-320°C for 5·10 5and more hours.
Known closest analogue to the technical nature and adopted for the prototype "Method of determining the shift of the ductile-brittle transition temperature due to thermal aging"set forth in the "calculation Standards on the strength of the equipment and pipelines of nuclear power installations PNAE G-7-002-86" of the USSR State Committee for supervision of safe working practices in the nuclear industry (Gosatomenergonadzor the USSR), Moscow, Energoatomizdat, 1989 str-201.
where TCT- the critical temperature of brittleness of the material subjected to thermal aging; Tk0- a critical temperature of brittleness of the material in the initial state (before aging).
While calculated values of ∆ Ttfor the duration of use not more than 105hours determined by empirical dependence in which the time of operation δ t t=f(t).
The disadvantage of this method is inadequate assessment of the degree of embrittlement of the steel of the reactor vessel due to thermal aging, as the method does not include the effect of segregation processes of phosphorus at a temperature during operation of the reactor VVER-1000 for 5·105and more hours.
The technical result of the invention is to improve the accuracy of the assessment of the degree of embrittlement of the steel reactor due to thermal aging in operation for 5·105and more hours.
whereDeffF - the effective diffusion coefficient during irradiation,DeffF=DFγ2⋅d2 DFis the diffusion coefficient of phosphorus in irradiated material, DFis a function of the flux of neutrons;ΔTklim - residual shift of the ductile-brittle transition temperature ofΔTklim=Tklim-Tk0 whereTklim - the value of the critical ones is the temperature brittleness, the resulting test material, annealed after irradiation.
The main idea of the new method is to create an artificial acceleration of segregation processes by neutron irradiation directly at the operating temperature of Tperfo. In contrast to accelerate segregation processes by increasing temperature, neutron irradiation practically does not change the value of the equilibrium segregation of phosphorus. At the same time, neutron irradiation accelerates the formation of segregation of phosphorus due to radiation-stimulated diffusion.
The mechanisms of irradiation embrittlement is caused by hardening of the material due to the formation of dislocation loops and precipitates, which leads to the relief of the origin and development of microcracks due to the increase of the effective stress, create additional microcracks in the body of the grain and increase the likelihood of the formation of dislocation clusters of barriers, which nucleate microcracks. The mechanism leading to the hardening associated with segregation, mainly phosphorus at phase boundaries carbide-matrix and at grain boundaries. This mechanism facilitates the nucleation of microcracks at phase boundaries, and facilitates their development at the grain boundaries.
It was established experimentally that the General mechanism of development is pivonia metal during thermal aging and neutron irradiation is the segregation mechanism, which accelerates the diffusion of phosphorus. This acceleration is due to the fact that the diffusion of phosphorus, mainly occurs by vacancy method. When the diffusion coefficient is greatly increased due to the generation of point defects under neutron irradiation.
Comparing the values of the diffusion coefficient in the initial state and after neutron irradiation, it was found that neutron irradiation leads to an increase of the diffusion coefficient of more than 103time flux ~1,0·1011n/cm2·sec and more than 10stime flux ~1,0·1013n/cm2·sec.
Therefore, subjecting the material to the neutron irradiation at a temperature aging (the operating temperature of the reactor vessel 320°C) very limited time, for example, 103hours a flux of 1011-1013n/cm2·sec (which corresponds to the