Hafizal Yazid

Automated thresholding in radiographic image for welded joints

Automated detection of welding defects in radiographic images becomes non-trivial when uneven illumination, contrast and noise are present. In this paper, a new surface thresholding method is introduced to detect defects in radiographic images of welding joints. In the first stage, several image processing techniques namely fuzzy c means clustering, region filling, mean filtering, edge detection, Otsus thresholding and morphological operations method are utilised to locate the area in which defects might exist. This is followed by the implementation of inverse surface thresholding with partial differential equation to locate isolated areas that represent the defects in the second stage. The proposed method obtained a promising result with high precision.

The Root Caused Analysis of Leakaged Heat Exchanger Tube

Abstract AISI type 316L stainless steel was used as a heat exchanger tube material in an inter-cooler column. After less than a year of operation, severe corrosion failures occurred and a transverse opening leakage was observed on one of the heat exchanger tubes. The failed tube was carefully analyzed using various metallurgical laboratory equipments. The root cause of the tube leakage was believed due to the presence of horizontal micro and macro pores as a hydrogen gas entrapment during casting of the parent ingot. The overlapped and gaping pores formed notch on the shell side of the tube surface, and it increasingly evident when the use of a high-energy water-jet and metal brush as cleaning procedure results in an establishment of pitting type local-action corrosion cells penetrated the tube wall. As a result, corrosive fluid in the tube side dissolved into the cooling water, accelerating the corrosion process.

Study of pipe thickness loss using a neutron radiography method

The purpose of this preliminary work is to study for thickness changes in objects using neutron radiography. In doing the project, the technique for the radiography was studied. The experiment was done at NUR-2 facility at TRIGA research reactor in Malaysian Nuclear Agency, Malaysia. Test samples of varying materials were used in this project. The samples were radiographed using direct technique. Radiographic images were recorded using Nitrocellulose film. The films obtained were digitized to processed and analyzed. Digital processing is done on the images using software Isee!. The images were processed to produce better image for analysis. The thickness changes in the image were measured to be compared with real thickness of the objects. From the data collected, percentages difference between measured and real thickness are below than 2%. This is considerably very low variation from original values. Therefore, verifying the neutron radiography technique used in this project.

Preliminary study of neutron absorption by concrete with boron carbide addition

Concrete has become a conventional material in construction of nuclear reactor due to its properties like safety and low cost. Boron carbide was added as additives in the concrete construction as it has a good neutron absorption property. The sample preparation for concrete was produced with different weight percent of boron carbide powder content. The neutron absorption rate of these samples was determined by using a fast neutron source of Americium-241/Be (Am-Be 241) and detection with a portable backscattering neutron detector. Concrete with 20 wt % of boron carbide shows the lowest count of neutron transmitted and this indicates the most neutrons have been absorbed by the concrete. Higher boron carbide content may affect the concrete strength and other properties.

Failure investigation on rusty mesh strainer of petrochemical plant

The wire material of filter mesh is made of 304 grade stainless steel. The failure to run properly was due to the impact of burst and torn. The client also expects that the failure was due to corrosion problems. A visual inspection on the strainer mesh was found covered by brownish rust layers and some scratches at the damaged area. The rusty wire mesh that was washed with pickling acid showed a clean and smooth surface. Energy dispersive spectroscopy (EDS) examination of the rusty wire mesh surface indicated that it was only normal oxide precipitates. Thus, its proven that there were no signs of severe corrosion attack on the failed sample. SEM micrographs showed the unidirectional scratch effects exist in the damaged area. The fractography study was found there was a typical ductile structure on the fracture surface of the wire. It is proven that the wire mesh was actually still in good condition and has not experienced any embrittlement problems as if it exposed to any corrosive environment. The root cause of the failure is shown by the effect of scratches in which it is usually caused by a mechanical forceful push by a hard object or in other words, it is caused by human error factor.

Effect of Boron Carbide Content on Properties of Thermoplastic Natural Rubber Composite as Thermal Neutron Shielding

In this work, thermoplastic natural rubber (TPNR) composites were produced through melt blending method. Boron carbide (B4C) as filler was added into the polymer blend (TPNR) with different weight percent from 0% to 30% and the effect of different B4C contents on mechanical and thermal neutron attenuation properties of TPNR composites has been studied. The phase formation in composites was analyzed using XRD technique. From the results, it showed that the incorporation of B4C fillers into TPNR matrix has enhanced the macroscopic cross section of the composites, however it lessens the tensile strength. Macroscopic cross section of the composites were increased from 3.34 cm-1 to 14.8 cm-1, while the tensile strength of the composites decreased from 3.79 MPa to 1.06 MPa with increasing B4C from 0 wt% to 30 wt%. B4C diffraction peaks were also increased in intensity with increasing B4C content.

Cryostat system for investigation on new neutron moderator materials at reactor TRIGA PUSPATI

A simple continuous flow (SCF) cryostat was designed to investigate the neutron moderation of alumina in high temperature co-ceramic (HTCC) and polymeric materials such as Teflon under TRIGA neutron environment using a reflected neutron beam from a monochromator. Cooling of the cryostat will be carried out using liquid nitrogen. The cryostat will be built with an aluminum holder for moderator within stainless steel cylinder pipe. A copper thermocouple will be used as the temperature sensor to monitor the moderator temperature inside the cryostat holder. Initial measurements of neutron spectrum after neutron passing through the moderating materials have been carried out using a neutron spectrometer.

Weld Detect Identification Using Texture Features and Dynamic Time Warping

In this paper, a simple yet robust algorithm for texture identification using 1 Dimensional Discrete Fourier Transform (1-D DFT) and Dynamic Time Warping (DTW) is presented with illumination variations. In the first stage, several image processing techniques namely Fuzzy C means (FCM) clustering, edge detection, Otsu thresholding and inverse surface thresholding method are utilized to locate the region of interest (ROI) where defects might exist. Next, the image undergoes the feature extraction process using 1-D DFT and finally, the features are classified using DTW. Several defect images consist of 2 types of defect namely the porosity and crack are experimented and classified using the DTW.

Proposal for grid computing for nuclear applications

The use of computer clusters for computational sciences including computational physics is vital as it provides computing power to crunch big numbers at a faster rate. In compute intensive applications that requires high resolution such as Monte Carlo simulation, the use of computer clusters in a grid form that supplies computational power to any nodes within the grid that needs computing power, has now become a necessity. In this paper, we described how the clusters running on a specific application could use resources within the grid, to run the applications to speed up the computing process.

Design of sample carrier for neutron irradiation facility at TRIGA MARK II nuclear reactor

The objective of this work is to design a sample carrier for neutron irradiation experiment at beam ports of research nuclear reactor, the Reaktor TRIGA PUSPATI (RTP). The sample carrier was designed so that irradiation experiment can be performed safely by researchers. This development will resolve the transferring of sample issues faced by the researchers at the facility when performing neutron irradiation studies. The function of sample carrier is to ensure the sample for the irradiation process can be transferred into and out from the beam port of the reactor safely and effectively. The design model used was House of Quality Method (HOQ) which is usually used for developing specifications for product and develop numerical target to work towards and determining how well we can meet up to the needs. The chosen sample carrier (product) consists of cylindrical casing shape with hydraulic cylinders transportation method. The sample placing can be done manually, locomotion was by wheel while shielding used was made of boron materials. The sample carrier design can shield thermal neutron during irradiation of sample so that only low fluencies fast neutron irradiates the sample.