• Title, Summary, Keyword: Neutron Noise

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High accurate three-dimensional neutron noise simulator based on GFEM with unstructured hexahedral elements

  • Hosseini, Seyed Abolfazl
    • Nuclear Engineering and Technology
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    • v.51 no.6
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    • pp.1479-1486
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    • 2019
  • The purpose of the present study is to develop the 3D static and noise simulator based on Galerkin Finite Element Method (GFEM) using the unstructured hexahedral elements. The 3D, 2G neutron diffusion and noise equations are discretized using the unstructured hexahedral by considering the linear approximation of the shape function in each element. The validation of the static calculation is performed via comparison between calculated results and reported data for the VVER-1000 benchmark problem. A sensitivity analysis of the calculation to the element type (unstructured hexahedral or tetrahedron elements) is done. Finally, the neutron noise calculation is performed for the neutron noise source of type of variable strength using the Green function technique. It is shown that the error reduction in the static calculation is considerable when the unstructured tetrahedron elements are replaced with the hexahedral ones. Since the neutron flux distribution and neutron multiplication factor are appeared in the neutron noise equation, the more accurate calculation of these parameters leads to obtaining the neutron noise distribution with high accuracy. The investigation of the changes of the neutron noise distribution in axial direction of the reactor core shows that the 3D neutron noise analysis is required instead of 2D.

Adaptive group of ink drop spread: a computer code to unfold neutron noise sources in reactor cores

  • Hosseini, Seyed Abolfazl;Afrakoti, Iman Esmaili Paeen
    • Nuclear Engineering and Technology
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    • v.49 no.7
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    • pp.1369-1378
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    • 2017
  • The present paper reports the development of a computational code based on the Adaptive Group of Ink Drop Spread (AGIDS) for reconstruction of the neutron noise sources in reactor cores. AGIDS algorithm was developed as a fuzzy inference system based on the active learning method. The main idea of the active learning method is to break a multiple input-single output system into a single input-single output system. This leads to the ability to simulate a large system with high accuracy. In the present study, vibrating absorber-type neutron noise source in an International Atomic Energy Agency-two dimensional reactor core is considered in neutron noise calculation. The neutron noise distribution in the detectors was calculated using the Galerkin finite element method. Linear approximation of the shape function in each triangle element was used in the Galerkin finite element method. Both the real and imaginary parts of the calculated neutron distribution of the detectors were considered input data in the developed computational code based on AGIDS. The output of the computational code is the strength, frequency, and position (X and Y coordinates) of the neutron noise sources. The calculated fraction of variance unexplained error for output parameters including strength, frequency, and X and Y coordinates of the considered neutron noise sources were $0.002682{\sharp}/cm^3s$, 0.002682 Hz, and 0.004254 cm and 0.006140 cm, respectively.

A new approach for calculation of the neutron noise of power reactor based on Telegrapher's theory: Theoretical and comparison study between Telegrapher's and diffusion noise

  • Bahrami, Mona;Vosoughi, Naser
    • Nuclear Engineering and Technology
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    • v.52 no.4
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    • pp.681-688
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    • 2020
  • The telegrapher's theory was used to develop a new formulation for the neutron noise equation. Telegrapher's equation is supposed to demonstrate a more realistic approximation for neutron transport phenomena, especially in comparison to the diffusion theory. The physics behind such equation implies that the signal propagation speed is finite, instead of the infinite as in the case of ordinary diffusion. This paper presents the theory and results of the development of a new method for calculation of the neutron noise using the telegrapher's equation as its basis. In order to investigate the differences and strengths of the new method against the diffusion based neutron noise, a comparison was done between the behaviors of two methods. The neutron noise based on SN transport considered as a precision measuring point. The Green's function technique was used to calculate the neutron noise based on telegrapher's and diffusion methods as well as the transport. The amplitude and phase of Green's function associated with the properties of the medium and frequency of the noise source were obtained and their behavior was compared to the results of the transport. It was observed, the differences in some cases might be considerable. The effective speed of propagation for the noise perturbations were evaluated accordingly, resulting in considerable deviations in some cases.

Spectrum analysis of acoustic Barkhausen noise on neutron irradiated material

  • Sim Cheul-Muu;Park Seung-Sik;Park Duck-Gum;Lee Chang-Hee
    • Proceedings of the Acoustical Society of Korea Conference
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    • pp.231-234
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    • 2000
  • In relation to a non-destructive evaluation of irradiation damage of micro-structure of interstitial, void and dislocation, the changes in the hysteresis loop and Barkhausen noise amplitude and the harmonics frequency due to neutron irradiation were measured and evaluated. The Mn-Mo-Ni low alloy steel of reactor pressure vessel was irradiated to a neutron fluence of $2.3\times10^{19}n/cm^2$ $(E\ge1MeV)$ at $288^{\circ}C.$The saturation magnetization of neutron irradiated metal did not change. Neutron irradiation caused the coercivity to increase, whereas susceptibility to decrease. The amplitude of Barkhausen noise parameters associated with the domain wall motion were decreased by neutron irradiation. The spectrum of Barkhausen noise was analyzed with an applied frequency of 4Hz and 8Hz, and a sampling time of 50 $\mu$ sec and 20 $\mu$ sec. The harmonic frequency of Joule effect shows 4Hz, 8Hz, 12Hz and 16Hz reflected from an unirradiated specimen. On the contrary, the harmonic frequency disappeared for the irradiated specimen. Harmonic frequency of induced voltage of sinusoidal magnetic field And Spectrum of Barkhausen noise on material is determined.

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Harmonic frequency analysts of acoustic Barkhausen noise on neutron irradiated material (중성자조사재료의 acoustic Barkhausen noise의 harmonic frequency 분석)

  • Sim Cheul-Muu;Park Seung-Sik;Koo Kil-Moo;Sohn Jae-Min;Lee Chang-Hee
    • Proceedings of the Acoustical Society of Korea Conference
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    • pp.401-406
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    • 1999
  • In relation to a non-destructive evaluation of irradiation damages of micro-structure interstitial, void and dislocation, the changes in the hysteresis loop, Barkhausen noise amplitude and the harmonics frequency due to a neutron irradiation were measured and evaluated. The Mn-Mo-Ni low alloy steel of RPV was irradiated to a neutron fluence of $2.3\times10^{19}\;n/cm^2\;(E\geq1\;MeV)\;at\;288^{\circ}C$. The saturation magnetization of neutron irradiated metal did not change. The neutron irradiation caused the coercivity to increase, whereas susceptibility to decrease. The amplitude of Barkhausen noise parameters associated with the domain wall motion were decreased by a neutron irradiation. The spectrum of Barkhausen noise is analysed with an applied frequency of 4 Hz and 8 Hz, sampling time of $50\;{\mu}sec\;and\;20\;{\mu}sec$. The harmonic frequency shows 4 Hz, 8 Hz, 12 Hz; and 16 Hz reflected from an unirradiated specimen. On the contrary, the harmonic frequency disappeared on the irradiated specimen.

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The Analysis of Spectrum on the Barkhausen Noise of Hysteresis Loops on Neutron Irradiated Material

  • Sim, Cheul-Muu;Chang, Kee-Ok;Park, Kook-Nam;Cho, Man-Soon;Park, Chang-Oong
    • The Journal of the Acoustical Society of Korea
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    • v.18 no.1E
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    • pp.7-12
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    • 1999
  • In relation to a non-destructive evaluation of irradiation damages, the changes in the hysteresis loop and Barkhausen noise amplitude and the harmonics frequency due to a neutron irradiation were measured and evaluated. The Mn-Mo-Ni low alloy steel of RPV was irradiated to a neutron fluence of 2.3 ×10/sup 19/ n/㎠ (E ≥1 MeV) at 288℃. The saturation magnetization of neutron irradiated metal did not change. The neutron irradiation caused the coercivity to increase, whereas susceptibility to decrease. The amplitude of Barkhausen noise parameters associated with the domain wall motion were decreased by a neutron irradiation. The spectrum of Barkhausen noise is analysed with an applied frequency of 4 Hz and 8 Hz, sampling time of 50 μ sec and 20 μ sec. The harmonic frequency shows 4 Hz, 8 Hz, 12 Hz and 16 Hz reflected from an unirradiated specimen. On the contrary, the harmonic frequency disappeared on the irradiated specimen. In addition to the amplitude, the harmonic frequency of Barkhausen noise is taken into accounts as a promising tool for monitoring the irradiation induced degradation of the reactor materials such as a SA508 of PWR-RPV steel and a Zr₄ of HANARO-CNH.

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Design of Diagnostic System for Reactor Internal Structures Using Neutron Noise (중성자 신호이용 원자로 내부 구조물 감시시스템 설계)

  • Park, Jong-Beom;Park, Jin-Ho;Hwang, Choong-Hwan;Kim, In-Kook
    • Proceedings of the KIEE Conference
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    • pp.638-640
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    • 2000
  • Reactor Noise is defined as the fluctuations of measured instrumentation signals during full-power operation of reactor which have informations on reactor system dynamics such as neutron kinetics, thermal-hydraulics, and structural dynamics. Reactor noise analyses of ex-core neutron detector internals such as fuel assembly and Core Support Barrel in Nuclear Power Plant. A real time mode separation technique have been developed and applied for the analyses. The analyses data base have been constructed for the continuous monitoring and diagnose of the reactor internals. Detailed design of diagnostic system reactor internal structures using neutron noise(RIDS).

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Assessment of the Implementation of a Neutron Measurement System During the Commissioning of the Jordan Research and Training Reactor

  • Bae, Sanghoon;Suh, Sangmun;Cha, Hanju
    • Nuclear Engineering and Technology
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    • v.49 no.3
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    • pp.504-516
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    • 2017
  • The Jordan Research and Training Reactor (JRTR) is the first research reactor in Jordan, the commissioning of which is ongoing. The reactor is a 5-MWth, open-pool type, light-water-moderated, and cooled reactor with a heavy water reflector system. The neutron measurement system (NMS) applied to the JRTR employs a wide-range fission chamber that can cover from source range to power range. A high-sensitivity boron trifluoride counter was added to obtain more accurate measurements of the neutron signals and to calibrate the log power signals; the NMS has a major role in the entire commissioning stage. However, few case studies exist concerning the application of the NMS to a research reactor. This study introduces the features of the NMS and the boron trifluoride counter in the JRTR and shares valuable experiences from lessons learned from the system installation to its early commissioning. In particular, the background noise relative to the signal-to-noise ratio and the NMS signal interlock are elaborated. The results of the count rates with the neutron source and the effects of the discriminator threshold are summarized.

Design of Hardward Diagnostic System for Reactor Internal Structures Using Neutron Noise (중성자 신호이용 원자로 내부 구조물 감시시스템 하드웨어 설계)

  • Park, Jong-Beom;Park, Jin-Ho;Hwang, Choong-Hwan;Kim, Soo-Hong
    • Proceedings of the KIEE Conference
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    • pp.2166-2168
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    • 2001
  • Reactor Noise is defined as the fluctuations of measured instrumentation signals during full-power operation of reactor which have informations on reactor system dynamics such as neutron kinetics. The Reactor internal structures which consist of many complex components are subjected to flow-induced vibration due to high temperature and pressure in reactor coolant system. The above flow-induced vibration causes degradation of structural integrity of the reactor and may result in loosing mechanical binding component which might impact other equipment and component or cause flow blockage. It is important to analyze reactor noise signal for the early detection of potential problem or failure in order to diagnosis reactor integrity in the point of view of safety and plant economics. Detailed design of hardware diagnostic system reactor internal structures using neutron noise(RIDS).

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Neutron Noise Analysis in Ulchin Nuclear Unit 1 & 2 (울진 1, 2호기의 중성자 잡음신호 분석)

  • 김태룡;박진호;고병무;배용채
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.582-589
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    • 1998
  • This paper presents the analysis results of ex-core and in-core neutron noise, acceleration signals and pressure fluctuation measured at Ulchin Nuclear Unit 1 & 2 to identify and monitor the reactor internals vibration including fuel motion. A phase separation algorithm developed by authors was applied to the neutron noises to clearly identify the reactor internals vibratory motion. The beam mode frequency of the core support barrel was identified to be 8Hz and the shell mode to be 20Hz. The first frequency of the fuel assembly was also found to be 3Hz, while first two acoustic frequencies of the primary coolant system were 6 and 17.5Hz. By monitoring and analyzing these frequencies periodically, it is possible to diagnose the operating condition of reactor internals and to provide an early detection of faults for the predictive maintenance.

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