野外γ能譜儀效率刻度方法研究及軟件設(shè)計(jì)
發(fā)布時(shí)間：2018-09-13 10:16
【摘要】：野外γ能譜測量是指通過γ譜儀直接測量地表巖石、土壤等,從得到的γ譜特征中分析出地層中核素的活度濃度、含量及相關(guān)信息。該方法是地質(zhì)勘查和放射性測量中經(jīng)濟(jì)、準(zhǔn)確、高效的核地球物理方法,廣泛應(yīng)用于環(huán)境監(jiān)測、鈾資源勘探、核應(yīng)急處理等方面,而準(zhǔn)確的效率刻度是伽馬能譜儀應(yīng)用的重要環(huán)節(jié)之一。尤其是處理核應(yīng)急事件,需要工作人員根據(jù)測量環(huán)境,選擇適合的效率刻度方法,快速準(zhǔn)確的完成現(xiàn)場檢測。分別從γ能譜儀絕對測量和相對測量兩個(gè)方面進(jìn)行研究,包括數(shù)值計(jì)算法、無源效率刻度法、有效刻度法等三種主要的效率刻度方法,對比三種方法各自的原理、特點(diǎn),并分析影響效率刻度的因素以及提出合適的修正方法,方便使用者因地制宜選擇適合的刻度方法,是γ能譜儀能準(zhǔn)確完成環(huán)境放射性核素定量分析的重要前提�，F(xiàn)場γ能譜測量往往受地表土壤密度、濕度、地形、核素分布不均勻、表層覆蓋物、介質(zhì)自吸收、土壤或巖石孔隙度、鈾鐳不平衡等因素的影響,尤其是地表濕度和地形的影響,導(dǎo)致測量結(jié)果存在較大的誤差,這些問題都需要測量人員依據(jù)測量環(huán)境對結(jié)果進(jìn)行適當(dāng)?shù)男拚�。以國家�?jì)量站的標(biāo)準(zhǔn)模型為研究對象,為準(zhǔn)確的完成對Na I(Tl)數(shù)字化γ譜儀的效率刻度,通過理論公式及蒙特卡羅方法,確定γ譜儀的有效探測范圍、計(jì)算上述因素對測量結(jié)果的影響,并研究其變化規(guī)律,為修正定量分析的測量結(jié)果提供理論依據(jù)。此外,為方便用戶對野外γ能譜儀進(jìn)行效率刻度、選擇合適的測量位置以及修正測量結(jié)果,尤其是在核應(yīng)急事件中,用戶需要根據(jù)現(xiàn)場測量環(huán)境的變化,及時(shí)準(zhǔn)確完成對γ能譜儀的效率刻度或校正效率刻度的結(jié)果以及γ譜儀的穩(wěn)定性檢測等,采用無源效率刻度方法,基于Lab Windows/CVI開發(fā)環(huán)境下,編寫高效的效率刻度分析軟件,并通過實(shí)驗(yàn)進(jìn)行驗(yàn)證(此外,用戶若采用數(shù)值計(jì)算法、有源效率刻度法對γ譜儀進(jìn)行效率刻度,也可采用該軟件實(shí)現(xiàn)部分理論相關(guān)參數(shù)的計(jì)算)。通過對現(xiàn)場γ能譜測量影響因素的研究,得出如下結(jié)論:(1)在半無限測量條件下,通過蒙特卡羅方法可較準(zhǔn)確的計(jì)算出特定型號的Na I(Tl)γ譜儀貼地測量時(shí)的有效可探測范圍為?180×60cm,且隨著γ能譜儀距離地面高度的增加,其探測效率降低。(2)當(dāng)現(xiàn)場測量的地表起伏,如γ能譜儀貼地測量時(shí),可能發(fā)生傾斜,實(shí)驗(yàn)表明,探測器傾斜角度在±10°范圍內(nèi)對測量結(jié)果的影響較小,可忽略不計(jì)。(3)γ能譜儀對不同入射方向的γ射線探測效率不同,隨入射角度(偏離晶體正前方的角度)的越大,探測效率越高,表明圓柱形探測器側(cè)面的探測效率相對越高。(4)不同能量γ射線的探測效率與地表土壤的濕度呈線性負(fù)相關(guān)關(guān)系,且線性變化的趨勢不同。其中,低能γ射線受介質(zhì)濕度的影響最大。(5)土壤對不同能量γ射線自吸收效應(yīng)隨介質(zhì)密度的增大而逐漸減弱。土壤的密度從1.3g?cm-3增加到2.2 g?cm-3,0.609 Me V、1.46 Me V、1.76 Me V、2.62Me V特征γ射線的探測效率分別減小了41.17%、38.78%、42.98%、40.56%,且不同能量特征γ射線間探測效率差異也逐漸減小。(6)當(dāng)基巖表層覆蓋物土壤厚度增加時(shí),高能γ射線的衰減量明顯小于低能γ射線,且總的探測效率符合多項(xiàng)式衰減規(guī)律。(7)土壤顆粒半徑由0.005cm至0.2cm變化時(shí),隨著粒徑的增加,γ射線的探測效率逐漸降低,且對測量低能γ射線的影響最大,其最大偏大可達(dá)70%;當(dāng)粒徑大于0.1cm時(shí),其γ射線的探測效率基本不變。(8)針對野外測量環(huán)境,分析了臺階地形、山坡地形、沖溝地形等三種地形對測量結(jié)果的影響,并提出了模型簡化的理論計(jì)算方法。
[Abstract]:Field gamma-ray spectrometry is an economical, accurate and efficient nuclear geophysical method for geological exploration and radioactivity measurement, which is widely used in environmental monitoring and uranium resource exploration. Accurate efficiency calibration is one of the important links in the application of gamma spectrometer in nuclear emergency treatment. Especially in dealing with nuclear emergency, it is necessary for staff to select appropriate efficiency calibration methods according to the measurement environment and complete the field detection quickly and accurately. Three main efficiency calibration methods, including numerical calculation method, passive efficiency calibration method and effective calibration method, are studied. The principle and characteristics of the three methods are compared. The factors affecting the efficiency calibration are analyzed and the appropriate correction methods are put forward. It is convenient for users to choose the appropriate calibration method according to local conditions. The gamma spectrometer can complete the ring accurately. Field gamma-ray spectrometry is often affected by factors such as surface soil density, humidity, topography, uneven distribution of nuclides, surface cover, self-absorption of media, porosity of soil or rock, imbalance of uranium and radium, especially surface humidity and topography, resulting in errors in measurement results. In order to calibrate the efficiency of Na I (Tl) digital gamma spectrometer accurately, the effective detection range of the gamma spectrometer is determined by theoretical formula and Monte Carlo method, and the above factors are calculated. In addition, in order to facilitate users to calibrate the efficiency of field gamma spectrometer, select the appropriate measurement position and correct the measurement results, especially in nuclear emergency, users need to be timely and accurate according to the changes of the field measurement environment. Accurately complete the efficiency calibration or calibration efficiency calibration results of the gamma spectrometer and stability testing of the gamma spectrometer, using passive efficiency calibration method, based on Lab Windows/CVI development environment, write efficient efficiency calibration analysis software, and verify by experiments (in addition, if users use numerical calculation method, active efficiency calibration method) The efficiency calibration of gamma spectrometer can also be carried out by this software. Through the study of the influence factors of gamma spectrometer measurement, the following conclusions can be drawn: (1) Under the semi-infinite measurement conditions, the Monte Carlo method can accurately calculate the validity of a specific type of NAI (Tl) gamma spectrometer when it is applied to the ground. The detection range is 180 The detection efficiency of the cylindrical detector is higher with the increase of the incidence angle (the angle away from the front of the crystal), which indicates that the detection efficiency of the cylindrical detector is higher. (4) The detection efficiency of the different energy gamma rays has a linear negative correlation with the surface soil moisture, and the trend of the linear change is different. Among them, low-energy gamma rays are most affected by medium humidity. (5) Soil self-absorption effect of different energy gamma rays gradually weakens with the increase of medium density. Soil density increases from 1.3 g? Cm-3 to 2.2 g? Cm-3, 0.609 Me V, 1.46 Me V, 1.76 Me V, 2.62 Me V. The detection efficiency of characteristic gamma rays decreases by 41.17%, 38.78%, 42.98%, 40.56%, respectively. (6) The attenuation of high-energy gamma rays is obviously less than that of low-energy gamma rays when the soil thickness of bedrock surface mulch increases, and the total detection efficiency conforms to the polynomial attenuation law. (7) When the radius of soil particles varies from 0.005 cm to 0.2 cm, with the increase of particle size, the attenuation of gamma rays is obviously smaller than that of low-energy gamma rays. The detection efficiency decreases gradually, and the influence on the measurement of low-energy gamma rays is the greatest, and the maximum is 70%. When the particle size is larger than 0.1 cm, the detection efficiency of gamma rays is basically unchanged. (8) Aiming at the field measurement environment, the influence of terrain, such as step terrain, hillside terrain and gully terrain on the measurement results is analyzed, and the simplified model is proposed. Theoretical calculation method.
【學(xué)位授予單位】：成都理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TH842
本文編號：2240886
[Abstract]:Field gamma-ray spectrometry is an economical, accurate and efficient nuclear geophysical method for geological exploration and radioactivity measurement, which is widely used in environmental monitoring and uranium resource exploration. Accurate efficiency calibration is one of the important links in the application of gamma spectrometer in nuclear emergency treatment. Especially in dealing with nuclear emergency, it is necessary for staff to select appropriate efficiency calibration methods according to the measurement environment and complete the field detection quickly and accurately. Three main efficiency calibration methods, including numerical calculation method, passive efficiency calibration method and effective calibration method, are studied. The principle and characteristics of the three methods are compared. The factors affecting the efficiency calibration are analyzed and the appropriate correction methods are put forward. It is convenient for users to choose the appropriate calibration method according to local conditions. The gamma spectrometer can complete the ring accurately. Field gamma-ray spectrometry is often affected by factors such as surface soil density, humidity, topography, uneven distribution of nuclides, surface cover, self-absorption of media, porosity of soil or rock, imbalance of uranium and radium, especially surface humidity and topography, resulting in errors in measurement results. In order to calibrate the efficiency of Na I (Tl) digital gamma spectrometer accurately, the effective detection range of the gamma spectrometer is determined by theoretical formula and Monte Carlo method, and the above factors are calculated. In addition, in order to facilitate users to calibrate the efficiency of field gamma spectrometer, select the appropriate measurement position and correct the measurement results, especially in nuclear emergency, users need to be timely and accurate according to the changes of the field measurement environment. Accurately complete the efficiency calibration or calibration efficiency calibration results of the gamma spectrometer and stability testing of the gamma spectrometer, using passive efficiency calibration method, based on Lab Windows/CVI development environment, write efficient efficiency calibration analysis software, and verify by experiments (in addition, if users use numerical calculation method, active efficiency calibration method) The efficiency calibration of gamma spectrometer can also be carried out by this software. Through the study of the influence factors of gamma spectrometer measurement, the following conclusions can be drawn: (1) Under the semi-infinite measurement conditions, the Monte Carlo method can accurately calculate the validity of a specific type of NAI (Tl) gamma spectrometer when it is applied to the ground. The detection range is 180 The detection efficiency of the cylindrical detector is higher with the increase of the incidence angle (the angle away from the front of the crystal), which indicates that the detection efficiency of the cylindrical detector is higher. (4) The detection efficiency of the different energy gamma rays has a linear negative correlation with the surface soil moisture, and the trend of the linear change is different. Among them, low-energy gamma rays are most affected by medium humidity. (5) Soil self-absorption effect of different energy gamma rays gradually weakens with the increase of medium density. Soil density increases from 1.3 g? Cm-3 to 2.2 g? Cm-3, 0.609 Me V, 1.46 Me V, 1.76 Me V, 2.62 Me V. The detection efficiency of characteristic gamma rays decreases by 41.17%, 38.78%, 42.98%, 40.56%, respectively. (6) The attenuation of high-energy gamma rays is obviously less than that of low-energy gamma rays when the soil thickness of bedrock surface mulch increases, and the total detection efficiency conforms to the polynomial attenuation law. (7) When the radius of soil particles varies from 0.005 cm to 0.2 cm, with the increase of particle size, the attenuation of gamma rays is obviously smaller than that of low-energy gamma rays. The detection efficiency decreases gradually, and the influence on the measurement of low-energy gamma rays is the greatest, and the maximum is 70%. When the particle size is larger than 0.1 cm, the detection efficiency of gamma rays is basically unchanged. (8) Aiming at the field measurement environment, the influence of terrain, such as step terrain, hillside terrain and gully terrain on the measurement results is analyzed, and the simplified model is proposed. Theoretical calculation method.
【學(xué)位授予單位】：成都理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TH842
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