装饰建材辐射剂量模式及其无损检测筛选方法研究

发布时间：2018-06-13 06:59

本文选题：装饰建筑材料 + 核素　；参考：《四川大学》2003年博士论文

【摘要】： 如果使用天然放射性核素比活度增高的建筑材料，室内空气中剂量率就相应升高。但目前对于建材的辐射剂量还缺乏较精确的定量表示，从一定程度上制约了建筑材料这种持续性低剂量照射对公众健康影响的研究。本研究对几类建筑装饰材料的辐射剂量学模式及其放射性核素限量进行了研究，并找到一种可用于已建住房装饰建筑材料放射性水平检测判断的检测筛选方法。得到如下结论。 1．给出了各类装饰建筑材料的辐射剂量模式由于各种装饰材料的厚度、密度和核素活度浓度都不一样，它们的核素放射性比活度—空气吸收剂量率转换因子应有很大差别；同时，土壤作为半无限大的体源，其空气吸收剂量率转换因子较装饰材料这种有限大的体源要大得多。显然，建筑装饰材料不能近似采用室外土壤的转换因子。要较准确地反应各类装饰建材对室内空气吸收剂量率的贡献，必须考虑各类材料本身的特性。本研究用蒙特卡罗方法的应用程序EGSnrc计算出几类饰材的核素比活度—室内空气吸收剂量转换系数。得到各类饰材的Y外照射剂量学计算模式如下：花岗石 (?)=0.0648C_(Ra)+0.0750C_(th)+0.0516C_K 抛光砖 (?)=0.0273C_(Ra)+0.0376C_(th)+0.0227C_K 彩釉砖 (?)=0.0190C_(Ra)+0.0215C_(th)+0.0171C_K 式中，(?)为空气吸收剂量率，nGyh~(-1)；C_(Ra)、C_(th)、C_K分别为各类材料中~(226)Ra、四川大学博士学位论文 ”勺h和气的放射性比活度，Bqkg一，;式中的常数分别为各类材料中鞠系、脚h 系和，0K的核素放射性比活度一空气吸收剂量率转换因子(nGyh-l/Bqkg一，). 用该模式算出的空气吸收剂量率与实测值一致。而用UNSCEAR(联合国原子辐射效应科学委员会)报告给出的土壤Y外照射剂量计算模式算出的装饰材料的空气吸收剂量率与实测值相差很大。说明该模式更符合实际。 2.推导出各类装饰建材的放射核素限t 由于装饰材料不能使用土壤的剂量模式。同时，Ic即(国际放射防护委员会)和U王A(国际原子能机构)都已明确我国《放射卫生防护基本标准》 GB 4792一1984对公众的剂量限值不适用于天然放射性，而我们的国家标准仍使用土壤的剂量转换因子和公众的年剂量限值来推导建筑材料的核素限量。显然，要较合理地限制装饰材料对公众的照射，必须使用装饰材料本身的剂量模式，以及可用于天然源的年剂量限值。本论文根据三类不同装饰材料核素比活度一空气吸收剂量转换因子，对花岗石和抛光砖使用ICRP第82号报告“在持续照射情况下公众的防护一委员会辐射防护体系应用于由天然源和长寿命放射性残存物引起的可控制的辐射照射”:用于单一源的辐射防护最优化的年剂量约束不大于每年0.3msv，对彩釉砖使用“含放射性物质消费品”的年有效剂量限制O.05msv。得到各类装饰材料的天然放射性核素限制式为: 花岗石: Y外照射限制:Cth/570+C、/660+C‘/830蕊1 内照射限制:C、/200簇l 抛光砖: Y外照射限制:Cth/1140+C、/1570+Q/1890蕊1 内照射限制:CRa/200续1 彩釉砖:Y外照射限制:Ctn/332 内照射限制:釉面料中 +C、/375+ 2肠Ra的比活度 CK/417蕊1 C澎1000蕊1 虽然本论文推导Y外照射限制采用的年剂量限值较现行国家标准的小，本论文给出的花岗石和抛光砖的外照射限制都较现行国家标准要宽，这是因为本四川大学博士学位论文论文算出的这些饰材天然放射性核素比活度一空气吸收剂t转换因子要比现行国家标准采用的土坡剂t转换因子小得多。彩釉砖由于采用“含放射性物质消费品”的附加年剂t限值，加上表层釉面的放射性水平较高，它的外照射限制较现行国家标准要严格一些;内照射限制也与现行国家标准完全不同。 3.建立起装饰建材的无损检测筛选方法并给出了结果判断筛选值根据核素衰变纲图，对天然放射性核素均匀分布的材料来说，，幻勺h、226Ra、气的Y比活度就与单位质t材料中的。、p辐射水平有固定的关系，这时，由于单位质盘材料中的Q、p辐射水平与其表面的。、p水平有确定的关系，而表面。、p辐射水平可以在其表面无损侧出。因此，只要通过上述关系，找到比活度超限值时对应的表面Q、p放射性水平，以后就可以通过测得的。、p 水平来判断样品的丫放射性是否超限值。这样就将丫射线强度的测量问题转化为表面Q、B射线的强度测量问题，从而实现建材较准确的无损检测筛选。由于天然放射系中最大能t的p射线在建筑装饰材料中的最大射程大于单块饰材的厚度，在对已装饰室内测盆时，测得的p辐射水平还包括饰材下面主体建材的贡献，此时用测得的p辐射水平来判断就会产生错误。然而a粒子在材料中的射程只有几微米，因此可用材料的表面Q水平与国家标准内、外照射指数分类临界值对应的值，来进行无损检测筛选结果的判断。由于用于表面Q辐射水平侧量的仪器(进口仅万元人民币左右)相对高纯锗Y谱仪(进口需要近六十万人民币)来说便宜许多，而且携带方便，可用于现场检测;表面a水平也不用像Y谱分析那样
[Abstract]:If natural radionuclides are used for building materials with higher specific activity, the rate of indoor air dose increases correspondingly. However, there is a lack of precise quantitative expression for the radiation dose of building materials, which restricts the study of the health impact of building materials on public health to a certain extent.
In this study, the radiation dosimetry model and the radionuclide limit of several kinds of building decoration materials are studied, and a screening method which can be used to determine the radioactivity level of the built housing materials is found. The following conclusions are obtained.
1. the radiation dose pattern of all kinds of decorative building materials is given.
Because of the thickness, density and nuclide activity concentration of all kinds of decorative materials, their radionuclide radioactivity - air absorption dose rate conversion factor should be greatly different. At the same time, the soil as a semi infinite body source, its air absorption dose rate conversion factor is much larger than that of the limited bulk material such as ornamental material. In order to accurately reflect the contribution of all kinds of decorative materials to indoor air absorption rate, the characteristics of all kinds of materials must be considered more accurately. This study uses the Monte Carlo method EGSnrc to calculate the nuclide activity of several kinds of ornamental materials - indoor air absorbent. The Y external radiation dosimetric calculation models for all kinds of decorative materials are as follows:
Granite (?) =0.0648C_ (Ra) +0.0750C_ (th) +0.0516C_K
Polished brick (?) =0.0273C_ (Ra) +0.0376C_ (th) +0.0227C_K
Colored glazed tiles (?) =0.0190C_ (Ra) +0.0215C_ (th) +0.0171C_K
In the formula, the absorbed dose rate for air is nGyh~ (-1); C_ (Ra), C_ (th), C_K are ~ (226) Ra in all kinds of materials, respectively.
Doctoral Dissertation of Sichuan University
"Spoon h and the specific radioactivity of the gas, Bqkg 1, the constants in the formula are the bow and foot h of all kinds of materials, respectively.
The radionuclide specific activity of the system and 0K is an air absorbed dose rate conversion factor (nGyh-l/Bqkg 1).
The air absorbed dose rate calculated by this model is consistent with the measured value, while UNSCEAR (United Nations origin) is used.
The scientific report of the sub radiation effect Committee) the decorative material calculated from the Y external radiation dose calculation model of the report.
The air absorbed dose rate of the material is quite different from the measured value, which shows that the model is more practical.
2. deduce the radionuclide limit t of all kinds of decorative building materials
Because decorative materials can not use the dose pattern of soil. At the same time, Ic is the International Radiation Protection Committee.
The U and A of the International Atomic Energy Agency (IAEA) have clearly defined the basic standards for radiological protection in China.
GB 4792 1984 to the public dose limit does not apply to natural radioactivity, and our national standard still makes
The nuclide limit of building materials is derived from the dose conversion factor of the soil and the annual dose limit of the public.
However, to reasonably restrict the exposure of decorative materials to the public, we must use the dose pattern of decorative materials themselves.
And the annual dose limits for natural sources. According to three types of decorative materials, nuclide specific activity
Degree 1 air absorption dose conversion factor for granite and polished tiles using ICRP eighty-second report "hold"
Public protection under continuous exposure. A committee's radiation protection system is applied to natural sources and long-life releases.
Controlled radiation exposure caused by ejection residues: an annual optimization for single source radiation protection
The quantity constraint is not greater than 0.3msv per year, which is effective for the use of "radioactive consumer goods" in coloured glazed tiles.
The natural radionuclide restrictive formula for various decorative materials is O.05msv..
Granite:
Y external exposure limit: Cth/570+C, /660+C '/830 pistil 1
Internal radiation restriction: C, /200 cluster L
Polishing brick:
Y external exposure limit: Cth/1140+C, /1570+Q/1890 pistil 1
Internal radiation restriction: CRa/200 continued 1
Colored glaze brick: Y external irradiation limit: Ctn/332
Internal radiation restriction: Glazed fabric
+C, /375+
Specific activity of 2 intestinal Ra
CK/417 pistil 1
C 1000 stamens 1
Although this paper deduces the annual dose limit of Y external exposure limitation, it is smaller than the current national standard.
The limits of external exposure of granite and polished tiles are wider than those of existing national standards.
Doctoral Dissertation of Sichuan University
The specific activity of these natural radionuclides calculated by the paper is more than that of the air absorbent t conversion factor.
The conversion factor of soil slope agent t used in the national standard is much smaller.
The limit of T added to the product is higher than that of the surface glaze, and its external exposure limits.
It is more stringent than the current national standards, and the internal exposure limits are totally different from the existing national standards.
3. establish a nondestructive testing and screening method for decorative building materials and give the results to determine the screening value.
According to the diagram of radionuclide decay, the magic h, 226Ra, for natural materials with uniform radionuclide distribution,
The Y specific activity of the gas has a fixed relationship with the radiation level of T in the unit P material.
The level of Q and P radiation in the unit material is determined by its surface and P levels.
On the surface, the radiation level of P can be lossless on its surface. Therefore, as long as the above relations are found,
When the specific activity exceeds the limit, the corresponding surface Q and P radioactivity levels will be measured later, P.
In order to judge whether the sample's sub radioactivity is out of limit, the problem of measuring the intensity of the gamma ray is transformed.
For the surface Q, B ray intensity measurement problems, so as to achieve accurate NDT screening of building materials.
In natural radiation, the maximum range of T P ray in building decoration materials is larger than that of single piece.
The thickness of the material is measured in the decorated room, and the measured P radiation level also includes the main building below the decorating material.
The contribution of the material will be erroneous at this time by using the measured P radiation level. However, a particles are in the material.
The range is only a few microns, so the surface Q level of the material can be applied to the national standard and the external exposure index.
The values corresponding to the classification of critical values are used for non-destructive testing of the screening results. As for surface Q radiation
The horizontal lateral volume instrument (imported only around 10000 yuan) is relative to the high purity germanium Y spectrometer (import needs nearly six).
One hundred thousand yuan) is much cheaper, and is easy to carry and can be used for on-site testing. The surface a level is also very low.
Not like Y spectrum analysis
【学位授予单位】：四川大学
【学位级别】：博士
【学位授予年份】：2003
【分类号】：X837

【参考文献】