中低放射性废物活度无源γ测量实验及模拟计算研究
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摘要
在核材料的生产、加工、运输、贮存和使用过程中不可避免地会产生一定量的中低放射性废物,按照国家相关规定和要求,在对这些废物进行最终处置之前必须对其中所含核素及其核素的量进行准确的鉴别和测量,以检验是否满足中低放废物的入库条件要求并制定相应措施对其进行处置。目前对废物桶活度的测量主要有化学破坏法和无损检测法(Non-Destructive Assay-NDA)。由于废物桶内固体废物空间密度变化大,核素分布不均匀,对样品进行整体测量的无损检测方法比需要对样品取样分析的化学破坏法更为优越。无源和有源的γ射线测量分析法是各种无损测量法中较为先进和常用的一类,如以无源γ射线测量分析法为原理的ISOCS(In-Situ Object Count System)测量系统和以有源γ射线测量分析法为原理的分段γ测量技术、层析γ扫描技术等。
而在实际测量中,桶内放射性物质的分布随机,故只有在假设桶内放射性物质分布已知的基础上才能得出最终的测量结果,如分段γ测量方法假设废物桶分层内分布均匀、无源γ测量方法假设放射性物质废物桶整桶内分布均匀。这样必然使测量结果存在一定的不确定度。本文主要研究无源γ测量方法、分段γ测量方法由于桶内放射性物质实际分布与假设分布不同而导致的测量结果不确定度,以提高测量精度。国内对此开展的研究很少,有必要对其进行研究。
本文对无源γ测量方法在对标准200L钢桶放射性物质的活度测量进行了实验和模拟计算分析,首先通过实验验证MCNP模型准确可信,再通过此模型模拟计算出钢桶在4种不同密度和10种核素条件下,系统测量结果的不确定度,并对其进行了修正,修正后测量结果精度得到明显改善。另外,还通过实验对不同特征能量放射源,在层内分布不均匀时,分段γ测量结果的不确定度进行了研究,并提出通过拟合重建的方法确定层内放射源位置,从而获得精确活度测量值的方法。研究结果表明,当分层内为高能区放射源分布不均匀时,测量结果与真实值偏差不大,而当放射源特征能量较低时,偏差则较大,需要修正。由拟合重建而得测量结果精度得到明显提高。
Amount of low intermediate-level waste must be produced when the nuclear material is produced, processed, transported, storage and used. Conditioned radioactive waste has to meet the specification and acceptance criteria defined by national regulatory and management authorities. The nuclide and the radioactivity should be identified and measurement before the final disposal. At present, the measurements of waste drums activity mainly have the analysis of chemical destruction and Non Destructive Assay-NDA. As the density of solid waste in waste bins changes, and the radionuclide distribution is non uniform, the NDA method is better than the analysis of the chemical destruction during the overall measurement of samples. The passive and active gamma measurement are common used in various NDA, such as the measurement principle of ISOCS (In-Situ Object Count System) is the passive gamma measurement while the segment gamma scanning technology and the tomography gamma scanning take the active gamma measurement as the measurement principle.
In actual measurement, the radioactive material in the drums distributed random, it can be measured only on the assumption that the distribution of drums of radioactive materials based on the known, such as segment gamma scanning technology with the assumption that waste drums layered distribute uniform, passive gamma measurement assumptions the radioactive material distributed uniform throughout the drums. So there is uncertainty in the measurement results. This paper mainly studies the uncertainty of measurement results of passive gamma measurement and segment gamma scanning technology, which caused by the radioactive material actual distribution different from the assumption distribution. There are few people studies on this subject internal, so there is a need to research.
In this paper, we analysis the uncertainty of radioactivity measurement results of 200L steel drum by passive gamma measurement. The credible of MCNP model is verified by experiments, then simulate the uncertainty of system by this model, when steel drums in four kinds of different densities and 10 kinds of nuclide conditions. Then amend the results, the accuracy of the measurement results to be significantly improved after amended. In addition, this paper study on the uncertainty of measurement results of segment gamma scanning by experiments, when different energy sources distribution non uniform. The sources in the layer are located by the fitting method, and obtain accurate measurement results of activity. The result shows, when high-energy sources distribution non uniform in the layer, the measurement results just little deviation of the true activity, and when the sources’energy is low, the deviation is greater, need to be amended. By the fitting reconstruction, the accuracy of the measurement results has a marked improvement.
而在实际测量中,桶内放射性物质的分布随机,故只有在假设桶内放射性物质分布已知的基础上才能得出最终的测量结果,如分段γ测量方法假设废物桶分层内分布均匀、无源γ测量方法假设放射性物质废物桶整桶内分布均匀。这样必然使测量结果存在一定的不确定度。本文主要研究无源γ测量方法、分段γ测量方法由于桶内放射性物质实际分布与假设分布不同而导致的测量结果不确定度,以提高测量精度。国内对此开展的研究很少,有必要对其进行研究。
本文对无源γ测量方法在对标准200L钢桶放射性物质的活度测量进行了实验和模拟计算分析,首先通过实验验证MCNP模型准确可信,再通过此模型模拟计算出钢桶在4种不同密度和10种核素条件下,系统测量结果的不确定度,并对其进行了修正,修正后测量结果精度得到明显改善。另外,还通过实验对不同特征能量放射源,在层内分布不均匀时,分段γ测量结果的不确定度进行了研究,并提出通过拟合重建的方法确定层内放射源位置,从而获得精确活度测量值的方法。研究结果表明,当分层内为高能区放射源分布不均匀时,测量结果与真实值偏差不大,而当放射源特征能量较低时,偏差则较大,需要修正。由拟合重建而得测量结果精度得到明显提高。
Amount of low intermediate-level waste must be produced when the nuclear material is produced, processed, transported, storage and used. Conditioned radioactive waste has to meet the specification and acceptance criteria defined by national regulatory and management authorities. The nuclide and the radioactivity should be identified and measurement before the final disposal. At present, the measurements of waste drums activity mainly have the analysis of chemical destruction and Non Destructive Assay-NDA. As the density of solid waste in waste bins changes, and the radionuclide distribution is non uniform, the NDA method is better than the analysis of the chemical destruction during the overall measurement of samples. The passive and active gamma measurement are common used in various NDA, such as the measurement principle of ISOCS (In-Situ Object Count System) is the passive gamma measurement while the segment gamma scanning technology and the tomography gamma scanning take the active gamma measurement as the measurement principle.
In actual measurement, the radioactive material in the drums distributed random, it can be measured only on the assumption that the distribution of drums of radioactive materials based on the known, such as segment gamma scanning technology with the assumption that waste drums layered distribute uniform, passive gamma measurement assumptions the radioactive material distributed uniform throughout the drums. So there is uncertainty in the measurement results. This paper mainly studies the uncertainty of measurement results of passive gamma measurement and segment gamma scanning technology, which caused by the radioactive material actual distribution different from the assumption distribution. There are few people studies on this subject internal, so there is a need to research.
In this paper, we analysis the uncertainty of radioactivity measurement results of 200L steel drum by passive gamma measurement. The credible of MCNP model is verified by experiments, then simulate the uncertainty of system by this model, when steel drums in four kinds of different densities and 10 kinds of nuclide conditions. Then amend the results, the accuracy of the measurement results to be significantly improved after amended. In addition, this paper study on the uncertainty of measurement results of segment gamma scanning by experiments, when different energy sources distribution non uniform. The sources in the layer are located by the fitting method, and obtain accurate measurement results of activity. The result shows, when high-energy sources distribution non uniform in the layer, the measurement results just little deviation of the true activity, and when the sources’energy is low, the deviation is greater, need to be amended. By the fitting reconstruction, the accuracy of the measurement results has a marked improvement.
引文
[1]杨明太,张连平,桶装核废物的非破坏性分析,核电子学与探测技术,2003,Vol.23,No.6,PP600~603;
[2]杨明太,核材料的非破坏性分析,核电子学与探测技术,2001,Vol.21,No.6,PP501-504;
[3]吴伦强,韦孟伏,辐射探测技术在核保障中运用简述,和电子学与探测技术,2005,Vol.25,No.4,PP442～449;
[4] Menlove HO,el al, High-performance neutron time correction counter, Nuclear Tech,1985,71;
[5] Menlove HO,el al, A 132Cf-based nondestructive assay system for fissile material, Nucl Instrum Methods, 1978,152:549;
[6] Crane TW, Liquid sample shuffler for gamma active solution, LANL Report, LA-10925-MS, 1987;
[7]付杰,徐翠华等.无源效率刻度技术研究进展及应用概况.核电子学与探测技术,2007,Vol.4:48;
[8] Sprinkle JK, Hsue ST, Recent Advances in SGS Analysis. In: Proc. 3rd Int. Conf. Facility Operation-Safeguards Iterface, Saniego.1987. American Nuclear Society;
[9] A.G. Espartero et al , Development and Application of a Radioactivity Characterization System for Low-level Radioactive Waste,Nuclear Instruments and Methods in Physics Research,1999 ,Vol .A 422,PP790-794;
[10] T.Q. Dung,Calculation of The Systematic Error and Correction Factors in Gamma Waste Assay System,Annals of Nuclear Energy,1997,Vol.24,No.1,PP33-47;
[11] R.J. Estep,Tomographic Gamma Scanning to Assay Heterogeneous Radioactive Waste,Nuclear science and engineering,1994,Vol.118;
[12] Tran Ha Anh,Nguyen Duc Thanh,Tran Quoc Dung,Evaluation of Performance of a New Gamma Technique for Assay of Radioactive Waste,Annals of NuclearEnergy,2005,Vol.32,PP1516-1523;
[13]肖雪夫,就地HPGe谱仪校正系数的蒙特卡罗计算,辐射防护,1999,Vol.19,No.1,PP43;
[14]徐翠华,张庆等,HPGe探测效率和符合相加修正系数的蒙特卡罗计算,中国辐射卫生,2004,Vol.13,No.2,PP92;
[15]朱荣保,谭亚军,袁晓鑫等,大型高分辨分段γ扫描装置的研制,原子能科学技术,1994,Vol.28, No.1,PP16-24;
[16]谭亚军,朱荣保,吴昕等,分段γ扫描装置数据获取与处理软件系统的研制,原子能科学技术,1994,Vol.28, No.1,PP26-30;
[17]吕峰,曹斌,辛标等,分段γ扫描自吸收校正法分析残渣和废物中的铀、钚含量,原子能科学技术,1998,Vol.32, No.5,PP445-449;
[18]吕峰,曹斌,辛标等,可移动式高分辨率分段γ扫描现场测量装置的研制,原子能科学技术,1998,Vol.32,No.3,PP239-243;
[19]张怀礼,吴继宗,石有卿等,铀冶金炉渣的破坏性分析及对NDA分析仪器SGS和AWCC的校验,原子能科学技术,1998,Vol.32,No.3,PP269-273;
[20]成宇.层析γ扫描技术效率矩阵刻度模型研究[硕士论文].上海:上海交通大学. 2007.2.
[21]翁文庆.层析γ扫描透射图像重建算法研究[硕士论文].上海:上海交通大学. 2008.1.
[22]王汝瞻,卓韵裳,核辐射测量与防护,原子能出版社,1990;
[23]龚建、郝樊华、熊宗华,相对效率法同位素丰度分析的研究,核电子学与探测技术,2001,Vol.21,No.4,PP287-289;
[24] R.Venkataraman et al, Validation of In Situ Object Counting System(ISOCS) Mathematical Efficiency Calibration Software, NuclearInstruments and Methods in Physics Research, 1999 , PP450-454;
[25] Frazier L. Bronson et al. Mathematical Efficiency Calibration of Ge Detectors for Laboratory Sample Gamma Spectroscopy, 46th Annual Conference on Bioassay, Analytical and Environmental Radiochemistry, USA, 2000;
[26]复旦大学等.原子核物理实验方法[M].原子能出版社,1997,212;
[27] Canberra. User’s Manual of Model S573 ISOCS Calibration Software. USA,2002;
[28] Tran Quac Dung, Some theoretical results of gamma techniques for measuring large samples, Nuclear Instruments and Methods in Physics Research, A 416 1998:505-515;
[29] Tran Ha Anh, Tran Quoc Dung, Evaluating of performance of gamma tomographic technique for correcting lump effect in radioactive waste assay, Annals of Nuclear Energy, 2001:265-273;
[30]裴鹿成等,蒙特卡罗方法及其在粒子输运问题中的应用,科学出版社,1980;
[31]许淑艳,蒙特卡罗方法在实验核物理中的应用,原子能出版社,2006;
[32]许淑艳,刘保杰等,核技术应用中的蒙特卡罗计算问题,核技术,2007,Vol.30,No.7,PP597～599;
[33] MCNP3B Monte Carlo Neutron and Photo Transport Code System, ccc-2000, 1989;
[34]傅玉川,冉蜀阳,罗正明,蒙特卡罗技术在辐射剂量学中的应用,中国医学物理杂志,2003,Vol.20,No.4,PP210-211;
[35]肖雪夫,张积运,王仲奇,环境电离辐射体源表面剂量率的MC模拟计算及实验比较,中华放射医学与防护杂志,2004,Vol.24,No1,PP61-65;
[36]张锋,孙建孟,孙燕,脉冲中子伽马能谱测井中探测器响应得数值模拟研究,测井技术,2005,Vol.29,No.4,PP316-320;
[37]邓力,蒙特卡罗方法及其在核探测和反应堆临界计算中的应用研究,[学位论文],西安交通大学,2001;
[38] Parker JL, The Use of Calibration Standards and the Correction for Sample Self Attenuation in Gamma-Ray Nondestructive Assay. LA-10045, Rev, 1986;
[39] D Reilly, N Ensslin et al. Passive Nondestructive Assay of Nuclear Materials:NUREG/CR-5550-90-732. LA-UR-90-732;
[40]周志波,桶装核废物快速检测方法研究,[学位论文],中国原子能科学研究院,2007;
[41]李德平,潘自强等.辐射防护手册第一分册,原子能出版社,1987:278-286;
[42]郑阿奇,曹弋等. Matlab实用教程,电子工业出版社,2005;
[43]李人厚,张平安等.精通Matlab5,西安交通大学出版社,2001;
[44]李庆扬,王能超等.数值分析,华中科技大学出版社,2001;
[45]卢希庭,陈志才等.核数据手册,原子能出版社,1981:419~423;
[46]朱文凯,陈军等.ISOCS系统无源效率刻度测量方法的准确性检验[J].核电子学与探测技术,2005,Vol.25,No.3,PP285～287;
[47]潘京全,γ射线的线性吸收系数拟合,中华放射医学与防护,1998,362~364;
[2]杨明太,核材料的非破坏性分析,核电子学与探测技术,2001,Vol.21,No.6,PP501-504;
[3]吴伦强,韦孟伏,辐射探测技术在核保障中运用简述,和电子学与探测技术,2005,Vol.25,No.4,PP442～449;
[4] Menlove HO,el al, High-performance neutron time correction counter, Nuclear Tech,1985,71;
[5] Menlove HO,el al, A 132Cf-based nondestructive assay system for fissile material, Nucl Instrum Methods, 1978,152:549;
[6] Crane TW, Liquid sample shuffler for gamma active solution, LANL Report, LA-10925-MS, 1987;
[7]付杰,徐翠华等.无源效率刻度技术研究进展及应用概况.核电子学与探测技术,2007,Vol.4:48;
[8] Sprinkle JK, Hsue ST, Recent Advances in SGS Analysis. In: Proc. 3rd Int. Conf. Facility Operation-Safeguards Iterface, Saniego.1987. American Nuclear Society;
[9] A.G. Espartero et al , Development and Application of a Radioactivity Characterization System for Low-level Radioactive Waste,Nuclear Instruments and Methods in Physics Research,1999 ,Vol .A 422,PP790-794;
[10] T.Q. Dung,Calculation of The Systematic Error and Correction Factors in Gamma Waste Assay System,Annals of Nuclear Energy,1997,Vol.24,No.1,PP33-47;
[11] R.J. Estep,Tomographic Gamma Scanning to Assay Heterogeneous Radioactive Waste,Nuclear science and engineering,1994,Vol.118;
[12] Tran Ha Anh,Nguyen Duc Thanh,Tran Quoc Dung,Evaluation of Performance of a New Gamma Technique for Assay of Radioactive Waste,Annals of NuclearEnergy,2005,Vol.32,PP1516-1523;
[13]肖雪夫,就地HPGe谱仪校正系数的蒙特卡罗计算,辐射防护,1999,Vol.19,No.1,PP43;
[14]徐翠华,张庆等,HPGe探测效率和符合相加修正系数的蒙特卡罗计算,中国辐射卫生,2004,Vol.13,No.2,PP92;
[15]朱荣保,谭亚军,袁晓鑫等,大型高分辨分段γ扫描装置的研制,原子能科学技术,1994,Vol.28, No.1,PP16-24;
[16]谭亚军,朱荣保,吴昕等,分段γ扫描装置数据获取与处理软件系统的研制,原子能科学技术,1994,Vol.28, No.1,PP26-30;
[17]吕峰,曹斌,辛标等,分段γ扫描自吸收校正法分析残渣和废物中的铀、钚含量,原子能科学技术,1998,Vol.32, No.5,PP445-449;
[18]吕峰,曹斌,辛标等,可移动式高分辨率分段γ扫描现场测量装置的研制,原子能科学技术,1998,Vol.32,No.3,PP239-243;
[19]张怀礼,吴继宗,石有卿等,铀冶金炉渣的破坏性分析及对NDA分析仪器SGS和AWCC的校验,原子能科学技术,1998,Vol.32,No.3,PP269-273;
[20]成宇.层析γ扫描技术效率矩阵刻度模型研究[硕士论文].上海:上海交通大学. 2007.2.
[21]翁文庆.层析γ扫描透射图像重建算法研究[硕士论文].上海:上海交通大学. 2008.1.
[22]王汝瞻,卓韵裳,核辐射测量与防护,原子能出版社,1990;
[23]龚建、郝樊华、熊宗华,相对效率法同位素丰度分析的研究,核电子学与探测技术,2001,Vol.21,No.4,PP287-289;
[24] R.Venkataraman et al, Validation of In Situ Object Counting System(ISOCS) Mathematical Efficiency Calibration Software, NuclearInstruments and Methods in Physics Research, 1999 , PP450-454;
[25] Frazier L. Bronson et al. Mathematical Efficiency Calibration of Ge Detectors for Laboratory Sample Gamma Spectroscopy, 46th Annual Conference on Bioassay, Analytical and Environmental Radiochemistry, USA, 2000;
[26]复旦大学等.原子核物理实验方法[M].原子能出版社,1997,212;
[27] Canberra. User’s Manual of Model S573 ISOCS Calibration Software. USA,2002;
[28] Tran Quac Dung, Some theoretical results of gamma techniques for measuring large samples, Nuclear Instruments and Methods in Physics Research, A 416 1998:505-515;
[29] Tran Ha Anh, Tran Quoc Dung, Evaluating of performance of gamma tomographic technique for correcting lump effect in radioactive waste assay, Annals of Nuclear Energy, 2001:265-273;
[30]裴鹿成等,蒙特卡罗方法及其在粒子输运问题中的应用,科学出版社,1980;
[31]许淑艳,蒙特卡罗方法在实验核物理中的应用,原子能出版社,2006;
[32]许淑艳,刘保杰等,核技术应用中的蒙特卡罗计算问题,核技术,2007,Vol.30,No.7,PP597～599;
[33] MCNP3B Monte Carlo Neutron and Photo Transport Code System, ccc-2000, 1989;
[34]傅玉川,冉蜀阳,罗正明,蒙特卡罗技术在辐射剂量学中的应用,中国医学物理杂志,2003,Vol.20,No.4,PP210-211;
[35]肖雪夫,张积运,王仲奇,环境电离辐射体源表面剂量率的MC模拟计算及实验比较,中华放射医学与防护杂志,2004,Vol.24,No1,PP61-65;
[36]张锋,孙建孟,孙燕,脉冲中子伽马能谱测井中探测器响应得数值模拟研究,测井技术,2005,Vol.29,No.4,PP316-320;
[37]邓力,蒙特卡罗方法及其在核探测和反应堆临界计算中的应用研究,[学位论文],西安交通大学,2001;
[38] Parker JL, The Use of Calibration Standards and the Correction for Sample Self Attenuation in Gamma-Ray Nondestructive Assay. LA-10045, Rev, 1986;
[39] D Reilly, N Ensslin et al. Passive Nondestructive Assay of Nuclear Materials:NUREG/CR-5550-90-732. LA-UR-90-732;
[40]周志波,桶装核废物快速检测方法研究,[学位论文],中国原子能科学研究院,2007;
[41]李德平,潘自强等.辐射防护手册第一分册,原子能出版社,1987:278-286;
[42]郑阿奇,曹弋等. Matlab实用教程,电子工业出版社,2005;
[43]李人厚,张平安等.精通Matlab5,西安交通大学出版社,2001;
[44]李庆扬,王能超等.数值分析,华中科技大学出版社,2001;
[45]卢希庭,陈志才等.核数据手册,原子能出版社,1981:419~423;
[46]朱文凯,陈军等.ISOCS系统无源效率刻度测量方法的准确性检验[J].核电子学与探测技术,2005,Vol.25,No.3,PP285～287;
[47]潘京全,γ射线的线性吸收系数拟合,中华放射医学与防护,1998,362~364;