• Journal of Radiation Protection and Research
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• 제42권3호
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• pp.158-165
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• 2017

Background: Nuclear facilities in South Korea have generally adopted pressurized ion chambers to measure ambient gamma ray exposure rates for monitoring the impact of radiation on the surrounding environment. The rates assessed with pressurized ion chambers do not distinguish between natural and man-made radiation, so a further step is needed to identify the cause of abnormal variation. In contrast, using NaI(Tl) scintillation detectors to detect gamma energy rates can allow an immediate assessment of the cause of variation through an analysis of the energy spectra. Against this backdrop, this study was conducted to propose a more effective way to monitor ambient gamma exposure rates. Materials and Methods: The following methods were used to analyze gamma energy spectra measured from January to November 2016 with NaI detectors installed at the Korea Atomic Energy Research Institute (KAERI) dormitory and Hanbat University. 1) Correlations of the variation of rates measured at the two locations were determined. 2) The dates, intervals, duration, and weather conditions were identified when rates increased by $5nSv{\cdot}h^{-1}$ or more. 3) Differences in the NaI spectra on normal days and days where rates spiked by $5nSv{\cdot}h^{-1}$ or more were studied. 4) An algorithm was derived for automatically calculating the net variation of the rates. Results and Discussion: The rates measured at KAERI and Hanbat University, located 12 kilometers apart, did not show a strong correlation (coefficient of determination = 0.577). Time gaps between spikes in the rates and rainfall were factors that affected the correlation. The weather conditions on days where rates went up by $5nSv{\cdot}h^{-1}$ or more featured rainfall, snowfall, or overcast, as well as an increase in peaks of the gamma rays emitted from the radon decay products of $^{214}Pb$ and $^{214}Bi$ in the spectrum. This study assumed that $^{214}Pb$ and $^{214}Bi$ exist at a radioactive equilibrium, since both have relatively short half-lives of under 30 minutes. Provided that this assumption is true and that the gamma peaks of the 352 keV and 1,764 keV gamma rays emitted from the radionuclides have proportional count rates, no man-made radiation should be present between the two energy levels. This study proved that this assumption was true by demonstrating a linear correlation between the count rates of these two gamma peaks. In conclusion, if the count rates of these two peaks detected in the gamma energy spectrum at a certain time maintain the ratio measured at a normal time, such variation can be confirmed to be caused by natural radiation. Conclusion: This study confirmed that both $^{214}Pb$ and $^{214}Bi$ have relatively short half-lives of under 30 minutes, thereby existing in a radioactive equilibrium in the atmosphere. If the gamma peaks of the 352 keV and 1,764 keV gamma rays emitted from these radionuclides have proportional count rates, no man-made radiation should exist between the two energy levels.

• Journal of Radiation Protection and Research
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• 제31권4호
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• pp.197-201
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• 2006

Daily and seasonal variations of the ambient gamma ray exposure rates were measured by using a pressurized ion chamber from January 2003 to December 2005 in the CheongJu Regional Radiation Monitoring Post and the patterns of the distributions were studied. The annual average of the daily variation of the exposure rate was $\sim0.17{\mu}R/h$. The exposure rate was found to be maximum during 8:00 am to 9:00 am and minimum during 8:00 pm to 10:00 pm. For the annual data, the exposure rate was the minimum during the month of February. The exposure rate increased from February to mid-October (except during the period from May to July with no change) and decreased from October to February. The seasonal variation was found to be about $1{\mu}R/h$. Most of the measured values (96%) of the exposure rates fell under the normal distribution with a deviation of less than 4.8% and the remaining 4% had large fluctuations caused mainly by the rainfalls.

• Journal of Radiation Protection and Research
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• 제19권2호
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• pp.121-132
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• 1994

본 연구는 대구지역의 지각 ${\gamma}$-선에 의한 조사선량율을 측정하고 그에 따른 성분별 공간선량율 및 지역적 분포 등의 환경방사선 특성을 조사하였다. ${\gamma}$-선 스펙트럼의 측정에는 $4^{'}{\phi}{\times}4^{'}$ NaI(T1) 계측기와 휴대용 다중파고분석장치를 이용하여 이 지역내의 28개 지점에서 in-situ spectrometry를 수행하였으며, 측정된 스펙트럼으로부터 조사선량율을 환산하여 지각 ${\gamma}$-선의 총선량율과 일반적으로 자연방사능의 주종이 되는 $^{40}K,\;^{238}U$ 계열 및 $^{232}Th$계열의 성분별 조사 선량율을 구하였다. 조사결과 대구지역의 지각 ${\gamma}$-선에 의한 평균조사선량율은 $9.4{\mu}R/h$였으며 지점별 분포는 $7.6{\sim}11.0{\mu}R/h$ 범위로 다소 차이를 보였다. 측정시에 수반되는 기후나 우주선 등에 따른 일 변화폭을 고려한다면 지점간의 차이는 주로 표토층의 자연방사성핵종인 $^{40}K,\;^{238}U$계열 및 $^{232}Th$ 계열의 핵종에 기인함을 알 수 있었으며, 성분별 선량율은 $^{40}K\;2.9{\sim}4.6{\mu}R/h,\;^{238}U$ 계열 $1.2{\sim}3,\;1{\mu}R/h,\;^{232}Th$ 계열 $2.5{\sim}5.0{\mu}R/h$의 분포를 나타냈다.

• Nuclear Engineering and Technology
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• 제13권3호
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• pp.161-167
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• 1981

자주달개비(Tradescantia) BNL clone 4430을 본 연구소 감마농장(${\gamma}$-field)에 거리별로 배치하고 ${\gamma}$-선을 3.6mR/day~182R/day의 선량율로 완조사시켜, 이 식물의 수술털에 나타나는 분홍색 체세포돌연변이를 대상으로 돌연변이의 출현율을 조사하는 한편 화기에 미치는 형태변화를 조사하였다. 분홍색 체세포돌연변이율은 22.2R/day의 선량율에서 수술털 1,000개당 85.81$\pm$6.45개로 가장 높았고, 이보다 높은 선량율에서는 오히려 변이율이 감소하여 포화선량효과를 초래하였다. 또한 3.6mR/day의 낮은 선량율체서도 이 체세포돌연변이율이 자연돌연변이율보다 증가하였음을 볼 수 있었으며 비교적 낮은 선량율 조사에서는 꽃, 수술, 수술털등의 형태적 변화가 없이 돌연 변이율만의 증가를 볼수가 있어 감마농장내에서 과수나 화목등 영년식물에 저선량의 완조사를 통해 체세포돌연변이의 유기가 가능할것으로 보이며, 한편 이 식물의 특성을 이용하여 저위 방사선에 의한 유전적변화를 탐지하는데에도 적절한 수단이 될 것 같다.

• Journal of Radiation Protection and Research
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• 제11권1호
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• pp.3-14
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• 1986

$3'{\times}3'$ 원통형 NaI(T1) 검출기와 다중파고분석기(多重波高分析器)를 사용하여 측정한 $0.05{\sim}2.0MeV$ 구간의 ${\gamma}$선 spectrum에서 실(實)spctrum을 구하기 위하여 조사선량율(照射線量率)산출에 편리한 response matrix 방법을 사용하였다. Response mateix 구성에는, 위의 에네지 구간을 0.1 MeV의 등간격으로 나눈 $20{\times}20$ matrix로 한것과 검출기의 분해능이 입사 ${\gamma}$선 에너지의 평방근(平方根)에 의존한다는 가정하에 $0.1(MeV)^{1/2}$구간으로 나누어 $14{\times}14$ matrix로 구성한, 두가지 방법을 사용하였으며 그 역(逆)matrix들은 P-E 82/32 콤퓨터로 계산하였다. 이 방법으로 얻은 조사선량율은 에너지와 flux가 알려진 ${\gamma}$선량(陽)에 대하여 흔히 사용되는 계산방법으로 구한값과 10% 이내에서 일치하고 있으며, 선량측정학적(線量測定學的) 견지에서는 $E^{1/2}$ 구간으로 형성된 matrix가 등에너지간격으로 구성된 것보다 현실적인 것으로 판단되었다.

• 대한수의학회지
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• 제12권1호
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• pp.1-5
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• 1972

In oder to investigate the effects of cobalt-60 gamma ray irradiation on the body gains of rabbits aging approximately 50-day-old rabbits were subjected to single whole-body gamma irradiation externally. The results obtained were as follows: 1. There were significant differences of the body gains between control and treated groups except the 100 rads gamma-rays exposure group. 2. There were no differences in body gains between male and female rabbits. 3. Generally, the relation between gamma irradiated doses and the growth rates of rabbits were inversly proportional. 4. The $LD_{50}$ of the rabbits was 600 rads in case of single external whole-body gamma irradiation.

• 한국산업융합학회 논문집
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• 제27권2_2호
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• pp.437-443
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• 2024

The purpose of radiological Dispersal Device(RDD) is to kill people by explosives and to cause radiation exposure by dispersing radioactive materials. And It is a form of explosive that combines radioactive materials such as Co-60 and Ir-192 with improvised explosives. In this study, we tested and evaluated whether it was possible to read the internal structure of an explosive using X-rays in a radioactive explosive situation. The improvised explosive device was manufactured using 2 lb of model TNT explosives, one practice detonator, one 9V battery, and a timer switch in a leather briefcase measuring 41×35×10 cm³. The radioactive material used was the Co-60 source used in the low-level gamma ray irradiation device operated at the Advanced Radiation Research Institute of the Korea Atomic Energy Research Institute. The radiation dose used was gamma ray energy of 1.17 MeV and 1.33 MeV from a Co-60 source of 2208 Ci. The dose rates are divided into 0.5, 1, 2, and 4 Gy/h, and the exposure time was divided into 1, 3, 5, and 10 minutes. Co-60 source was mixed with the manufactured explosive and X-ray image reading was performed. As a result of the experiment, the X-ray image appeared black in all conditions divided by dose rate and time, and it was impossible to confirm the internal structure of the explosive. This is because γ-rays emitted from radioactive explosives have higher energy and stronger penetrating power than X-rays, so it is believed that imaging using X-rays is limited By blackening the film. The results of this study are expected to be used as basic data for research and development of X-ray imaging that can read the internal structure of explosives in radioactive explosive situations.

• 방사선산업학회지
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• 제7권2_3호
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• pp.135-139
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• 2013

Recently, chronic gamma radiation exposure on biological effects in middle dose-rates have become a serious concern. We investigated the biological effects of middle dose chronic exposure to gamma ray. Fifty male 6-week-old specific free Balb/c mice were randomly divided into five groups (four groups irradiated and one non-irradiated control group). Gamma radiation exposed in Gamma phytotron on Advanced Radiation Technology Institute (Jeongeup, Korea). Irradiation was carried out for 1 or 2 weeks using gamma rays at dose rates of 45 and $50mGy\;h^{-1}$ with total doses 7.56 Gy ($45mGy\;h^{-1}$, 1 week), 8.4 Gy ($50mGy\;h^{-1}$, 1 week), 15.12 Gy ($45mGy\;h^{-1}$, 2 weeks) and 16.8 Gy ($50mGy\;h^{-1}$, 2 weeks). After irradiation, immediately we sacrificed and counted body and organ weights. Moreover we counted spleen cell numbers. Compared with control non-irradiated group, all irradiated groups of body and spleen weights showed significant decreased. However, no significant alteration was observed between same irradiated period groups. In spleen cell numbers, reduced compared to the control group. However, significant alteration was observed between same irradiated period groups ($45mGy\;h^{-1}$, $50mGy\;h^{-1}$). These results demonstrated biological effects according to the radiation dose rate and irradiated period.

• Journal of Radiation Protection and Research
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• 제10권2호
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• pp.96-108
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• 1985

감마선분광분석 및 열형광선량측정법에 의한 자연환경방사선의 선량해석에 관한 연구를 1984년 10월부터 약 1년간에 걸쳐 충남대학교 대덕캠퍼스내의 1만 $m^2$ 규모의 평면개활지에서 수행하였다. 이 연구에서 사용한 검출기는 3'${\phi}{\times}$3' NaI(T1) 섬광계수기(閃光計數器)와 plastic 에 밀봉하여 금속판에 압착 처리한 chip 과 Teflon-disk 로된 2종의 LiF TLD 였다. 실측실험으로는 3회에 걸친 24시간 cycle의 in-situ spectrometry 와 2회의 3개월 cycle 과 1회의 1개월 cycle에 걸친 TLD field dosimetry를 수행하였다. 측정한 모든 spectrum은 G(E)연산자법에 의하여 조사선량율(照射線量率)로 환산하였고 그 결과로부터 환경 방사선의 지설성분(地設成分)을 산출하였다. 결과(結果)에 의하면 spectrometry로 구한 조사선량율이 평균 $(10.54{\pm}2.96){\mu}R/hr$, TLD chip으로 측정해석한 값은 $(12.0{\pm}3.4){\mu}R/hr$, disk에서 얻은 값이 $(11.0{\pm}3.6){\mu}R/hr$로 오차범위 안에서 매우 좋은 일치를 보이고 있다. 그러나 감마선분광분석에 의한 자연방사선의 일변화(日變化)에는 가끔 심한동요가 관측되었다. 정확한 환경방사선량해석을 위하여 감마선분광분석과 TLD의 적절한 동시 배합사용이 바람직 하며, 보다 고감도의 TLD에 관한 연구와 국제비교등을 통한 선량평가의 정도향상(精度向上)을 위한 보다 깊이 있는 연구가 필요하다는 결론(結論)에 도달하였다.

• 한국산학기술학회논문지
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• 제19권9호
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• pp.124-129
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• 2018

본 연구는 Apron의 재질로 이용되고 있는 텅스텐 차폐체를 핵의학과에서 사용하는 선원의 종류와 차폐체의 두께, 선원부터 검출기 사이의 거리를 변화시켜 차폐체에 투과시킨 후 투과선량과 차폐율을 알아보고자 하였다. 실험을 위해서 선원과 차폐체와 검출기를 일직선으로 배치하고 높이 100 cm 지점에서 Inspector로 측정하였다. 그 결과 텅스텐에 차폐효과가 가장 높은 선원은 $^{201}Tl$ 선원으로 측정되었고, $^{123}I$ 선원이 $^{99m}Tc$ 선원보다 차폐효과가 높게 나타났다. 실험에 사용한 선원과 검출기 사이의 거리는 멀어질수록 투과선량은 작아졌고, 텅스텐 차폐체의 두께는 두꺼울수록 차폐율은 높게 측정되었다. 하지만 $^{131}I$와 $^{18}F$ 선원에서는 0.25 mmPb의 차폐체를 사용했을 경우 차폐체가 없을 경우 보다 차폐율이 감소하는 것을 확인하였다. 따라서 $^{13}1I$와 $^{18}F$ 선원을 사용할 경우에는 방사선 차폐효과가 높은 텅스텐일지라도 선원의 종류에 따른 특성과 차폐체의 두께를 고려하여 사용하길 권장하고, 실험 결과를 참고하여 사용한다면 피폭 저 감화방안에 도움을 줄 수 있을 것으로 생각된다.