• Nuclear Engineering and Technology
• /
• 제56권1호
• /
• pp.56-63
• /
• 2024

In high radiation fields, gamma cameras suffer from pulse pile-up, resulting in poor energy resolution, count losses, and image distortion. To overcome this problem, various methods have been introduced to reduce the size of the aperture or pixel, reject the pile-up events, and correct the pile-up events, but these technologies have limitations in terms of mechanical design and real-time processing. The purpose of this study is to develop a real-time gamma camera to evaluate the radioactive contamination in high radiation fields. The gamma camera is composed of a pinhole collimator, NaI(Tl) scintillator, position sensitive photomultiplier (PSPMT), signal processing board, and data acquisition (DAQ). The pulse pile-up is corrected in real-time with a field programmable gate array (FPGA) using the start time correction (STC) method. The STC method corrects the amplitude of the pile-up event by correcting the time at the start point of the pile-up event. The performance of the gamma camera was evaluated using a high dose rate ¹³⁷Cs source. For pulse pile-up ratios (PPRs) of 0.45 and 0.30, the energy resolution improved by 61.5 and 20.3%, respectively. In addition, the image artifacts in the ¹³⁷Cs radioisotope image due to pile-up were reduced.

• 방사선산업학회지
• /
• 제7권1호
• /
• pp.51-54
• /
• 2013

Chitosan is a useful natural polymer material in many application fields such as biomaterials, water-treatment, agriculture, medication, and food science. However, the poor solubility limits its application. In this study, the effects of radiation on chitosan were investigated using gamma ray and electron beam irradiation. The chemical structure and molecular weight analysis show similar degradation effects of chitosan powder in both gamma ray and electron beam irradiation. However, the radiation irradiated chitosan in $H_2O$ has a lower molecular weight, since the hydroxyl radicals attack the glycosidic bonds. This effect is more clearly shown in the electron beam irradiation results.

• 대한방사선치료학회지
• /
• 제3권1호
• /
• pp.27-36
• /
• 1989

In order to calculate the dose on each interest point in five types of irregularly shaped fields used commonly in radiotherapy, the tissue-air ratios (TAR) in these fields for Go-60 gamma radiation were calculated using the newly devised SAR-chart. The TARs calculated from newly method of using the SAR-chart, computer method and approximation method at the interest point were compared to the TARs obtained from measurement. The result are as follows; In case of the interest points on central axis the calculated TARs in irregularly shaped fields by the above mentioned methods were well agreed within the error of $1\%$, whereas for the interest points on off-axis the calculated TARs were resulted in the maximum errors of $2.4\%,\;2.3\%$ and $8.8\%$ respectively. From these results, the accuracy of calculation method of using the SAR-chart was comfirmed.

• Journal of Radiation Protection and Research
• /
• 제23권4호
• /
• pp.229-236
• /
• 1998

개인 피폭선량 평가의 검증체계를 확립함에 있어서 기본적으로 갖추어야할 방사선장은 감마선, X-선, 베타선 및 중성자이다 금년에 한국원자력안전기술원에서는 중성자를 제외한 방사선장을 위한 기준조사장치(빔)를 확보하였다. 이 기준조사빔이 국제적으로 소급할 수 있는 방사선장의 역할을 수행할 수 있도록 하기 위하여 국제 표준기구규정 및 선진국의 표준규격 등의 기준과 요구조건에 충족되도록 하였다. 본 논문은 감마선장에 대한 기준조사장치에 관한 것으로서의 기여도 및 방사선장의 균질도를 평가하였고, 이를 국제 기준과 비교한 결과 국내 및 국제 기준을 잘 만족하고 있는 것으로 평가되었다. 또한, 측정된 공기커마율은 $^{137}Cs$ 선원에 대하여 $0.1891{\sim}23.4967{\mu}Gy/s$, $^{60}Co$ 선원에 대해서는 $0.588{\sim}15.9954{\mu}$Gy/s의 값으로 결정하였으며, 공기커마율이 가지는 불확도는 95% 신뢰도 범위에서 2.5% 이내로 결정되었다. 측정된 공기커마율의 신뢰성을 검증하기 위하여 전리함의 교정정수를 독일 PTB의 교정정수에 대하여 재평가한 결과 교정정수가 가지는 불착도(1.2%) 범위 내에서 일치하고 있었으며, 미국의 측정값과 비교한 결과 0.03% 범위 내에서 일치하고 있음이 판명되었다. 그러므로 한국원자력안전기술원에 설치된 감마선장은 국내의 표준 소급체계를 유지하고 있을 뿐만 아니라 미국 및 독일의 소급체계를 확보하게 되었고, 국내 및 국제 기준 방사선장으로 활용 가능하게 되었다.

• 전기학회논문지
• /
• 제58권7호
• /
• pp.1450-1455
• /
• 2009

Assumed that an IPTV camera system is to be used as an ad-hoc sensor for the surveillance and diagnostics of safety-critical equipments installed in the in-containment building of the nuclear power plant, an major problem is the presence of high dose-rate gamma irradiation fields inside the one. In order to uses an IPTV camera in such intense gamma radiation environment of the in-containment building, the radiation-weakened devices including a CCD imaging sensor, FPGA, ASIC and microprocessors are to be properly shielded from high dose-rate gamma radiation using the high-density material, lead or tungsten. But the passive elements such as mirror, lens and window, which are placed in the optical path of the CCD imaging sensor, are exposed to a high dose-rate gamma ray source directly. So, the gamma-ray irradiation characteristics of the passive elements, is needed to test. A CCD camera lens, made of glass material, have been gamma irradiated at the dose rate of 4.2 kGy/h during an hour up to a total dose of 4 kGy. The radiation induced color-center in the glass lens is observed. The degradation performance of the gamma irradiated lens is explained using an color component analysis.

• Nuclear Engineering and Technology
• /
• 제56권1호
• /
• pp.160-166
• /
• 2024

The inversion of radiation field distribution is of great significance in the decommissioning sites of nuclear facilities. However, the radiation fields often contain multiple mixtures of radionuclides, making the inversion extremely difficult and posing a huge challenge. Many radiation field reconstruction methods, such as Kriging algorithm and neural network, can not solve this problem perfectly. To address this issue, this paper proposes an optimized inverse distance weighted (IDW) interpolation algorithm for reconstructing the gamma radiation field. The algorithm corrects the difference between the experimental and simulated scenarios, and the data is preprocessed with normalization to improve accuracy. The experiment involves setting up gamma radiation fields of three Co-60 radioactive sources and verifying them by using the optimized IDW algorithm. The results show that the mean absolute percentage error (MAPE) of the reconstruction result obtained by using the optimized IDW algorithm is 16.0%, which is significantly better than the results obtained by using the Kriging method. Importantly, the optimized IDW algorithm is suitable for radiation scenarios with multiple radioactive sources, providing an effective method for obtaining radiation field distribution in nuclear facility decommissioning engineering.

• Nuclear Engineering and Technology
• /
• 제21권2호
• /
• pp.63-72
• /
• 1989

연구용 원자로 MAPLE-X10 시설의 안전성을 평가하기 위하여 원자로 pool 및 보조 pool로부터 물의 상실이 가정되었을 때 시설에 대한 감마 방사선장을 해석하였다. 차폐 해석에 고려된 4개의 photon 선원항은 ORIGEN-S코드를 이용하여 계산하였다. 또한, pool물 상실 사고 조건하에서 원자로 pool 및 보조 pool에서의 감마 선량율은 QAD-CG코드를, 그리고 pool외부의 방사선장은 입체각 외부에서의 산란 photon 선량율 계산에도 적합한 MCNP 코드를 이용하여 평가하였다.

• Nuclear Engineering and Technology
• /
• 제54권12호
• /
• pp.4679-4683
• /
• 2022

Environmental radiation monitoring is required to protect from the effects of radiation in industrial fields such as nuclear power plant (NPP) monitoring, and various gamma camera systems are being developed. The purpose of this study is to optimize parameters of a diverging collimator composed of pure tungsten for compactness and lightness through Monte Carlo simulation. We conducted the performance evaluation based on spatial resolution and signal-to-noise ratio for point source and obtained gamma images and profiles. As a result, optimization was determined at a collimator height of 60.0 mm, a hole size of 1.5 mm, and a septal thickness of 1.0 mm. Also, the full-width-at-half-maximum was 3.5 mm and the signal-to-noise ratio was 53.5. This study proposes a compact 45° diverging collimator structure that can quickly and accurately identify the location of the source for radiation monitoring.

• 전기전자학회논문지
• /
• 제15권2호
• /
• pp.143-148
• /
• 2011

MOS (Metal-Oxide Semconductor) devices among the most sensistive of all semiconductors to radiation, in particular ionizing radiation, showing much change even after a relatively low dose. The necessity of a radiation dosimeter robust enough for the working environment has increased in the fields of aerospace, radio-therapy, atomic power plant facilities, and other places where radiation exists. The power MOSFET (Metal-Oxide Semiconductor Field-Effect Transistor) has been tested for use as a gamma radiation dosimeter by measuring the variation of threshold voltage based on the quantity of dose, and a maximum total dose of 30 krad exposed to a $^{60}Co$ ${\gamma}$-radiation source, which is sensitive to environment parameters such as temperature. The gate oxide structures give the main influence on the changes in the electrical characteristics affected by irradiation. The variation of threshold voltage on the operating temperature has caused errors, and needs calibration. These effects can be overcome by adjusting gate oxide thickness and implanting impurity at the surface of well region in MOSFET.

• 방사선산업학회지
• /
• 제6권3호
• /
• pp.251-255
• /
• 2012

Pulp is typically used for paper industry to manufacturing various types of papers. However simply chemical modification makes enable the pulp to a wide range of application in various industrial fields. To bring the polymerization the gamma ray irradiated on the mixture of kenaf and PEGMA in various dose ranges from 20 to 60 kGy. As a results, the graft degree of 20.0% was obtained from 475 g of gamma ray irradiated pulp and PEGMA. After the polymerization, the chemical structure and morphology of the surfaces were examined by Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscope. Chemical structure of grafted pulp has significantly growth in carbonyl content with increasing the radiation dose. Also surface morphology was distinctly changed with decreased the degree of roughness and increasing the diameter. These results were explained gamma ray irradiation improve performance of graft polymerization efficiency.