标准编号:	GBZ/T 250-2014/XG1-2017
中文名称:	工业X射线探伤室辐射屏蔽规范（含第1号修改单）
英文名称:	Radiation shielding specifications for room of industrial X-ray radiography, includes Amendment 1
行业分类:	GB    国家标准
发布机构:	国家卫生和计划生育委员会
发布日期:	2014-05-14
实施日期:	2017-10-27
标准状态:	现行
替代旧标准:	GBZ/T 250-2014 工业X射线探伤室辐射屏蔽规范
翻译语言:	英文
文件格式:	PDF
中文字符数:	19000 字
翻译价格(元):	1140.00 元
交付时间:	付款后 1 个工作日

Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.



This standard is developed in accordance with the rules given in GB/T 1.1-2009.



This standard is formulated in accordance with Law of the People's Republic of China on Prevention and Control of Occupational Diseases.



Radiation shielding specifications for room of industrial X-ray radiography



1 Scope



This standard specifies the radiation shielding specifications for rooms of industrial X-ray radiography.



This standard applies to detection rooms for industrial X-ray radiography devices of 500 kV and below.



2 Terms and definitions



For the purposes of this document, the following terms and definitions apply.



2.1

room of X-ray detection

irradiation room for special X-ray radiography devices, used for X-ray radiography and having a shielding structure to ensure radiation safety in outdoor place



2.2

reference point

determined position beyond the detection room, which plays a decisive role in shielding structure of detection room, designed for detection room radiation shielding and dose estimation. It is usually away from the surface of detection room 30 cm where people may be exposed to the greatest dose. A position having some distance away from the detection room and that with high occupancy factors for members of the public and may be exposed to large doses shall also be considered as reference point



2.3

shielding transmission factor

ratio of radiation doses of a reference point with and without shielding between this reference point and a radiation source



3 Shielding requirements of detection room



3.1 Dose reference control level of radiation shielding for detection room



3.1.1 The ambient dose equivalent rate of the detection room wall and entrance door (hereinafter referred to as “dose rate”) and the weekly ambient dose equivalent rate (hereinafter referred to as “weekly dose”) shall meet the following requirements:



a) Weekly dose reference control level (HC) and derived dose rate reference control level (H ̇c,d):



1) Weekly dose reference control level of personnel at the reference point HC is as follows:



Vocational staff: H ̇c ≤ 100 μ Sv/week;



Public: Hc ≤ 5 μSv/week.



2) The derived dose rate reference control level H ̇c,d (μSv/h) of corresponding Hc is calculated according to Equation (1):



H ̇c,d = Hc/(t·U·T) (1)



where,



Hc——the weekly dose reference control level, μSv/week;



U——the use factor of the radiography device irradiating to the direction of reference point;



T——the occupancy factor for the personnel lingering at the corresponding reference point.



t——the weekly therapy irradiation time of the radiography device, in h/week;



t is calculated according to Equation (2):



t=W/(60∙Ι) (2)



where,



W——the weekly working load of X-ray radiography (average weekly X-ray radiographic exposure "mA·min" value), mA·min/week;



60——the conversion factor between hours and minutes;



I——the maximum common tube current of the X-ray radiography device at the highest tube voltage, mA.



b) Maximum dose rate reference control level H ̇c,max of reference point:



H ̇c,max = 2.5 μSv/h



c) Reference control level H ̇c for dose rate of reference point



H ̇c is the smaller value between the above H ̇c,d in a) and H ̇c,max in b) .



3.1.2 The dose rate reference control level at the top of the detection room shall meet the following requirements:



a) If the existing or proposed building above the detection room or the adjacent building beside it is in the solid angle area from the radiation source point to the edge of the inside surface of the detection room roof, for 30 cm away from the outer surface of the top of the flaw detection chamber as well as a personnel residence in a high-rise building within the solid angle area, the dose reference control level for radiation shielding is the same as 3.1.1.



b) In addition to the conditions in 3.1.2 a), the following circumstances shall be considered:



1) The radiation passing through the top of the detection room and the exposure to the public near the ground outside the detection room by scattered radiation generated by the action of air above the roof. The sum of the dose rate of the radiation and the transmitted radiation passing through the wall of the detection room at the corresponding reference point shall be controlled according to the dose rate reference control level H ̇c(μSv/h) in 3.1.1 c).



2) For the top of the detection room that is unnecessary for staff to reach, the dose rate reference control level at the location of 30 cm from the outer surface of the top of the detection room is taken as 100 μSv/h.



3.2 Radiation to be shielded



3.2.1 The whole end face of the corresponding useful beam is shielded by the useful beam without considering the scattered radiation entering the useful beam area.



3.2.2 Taking 90° scattered radiation which incidents the workpiece with 0° incident angle.



3.2.3 If the combined effect of leakage radiation and scattered radiation may exist, the leakage radiation and each scattered radiation are usually estimated separately; if their shielding thickness is different by tenth-value layer (TVL) or larger, the thicker shield is adopted; if the difference is less than one TVL, a half-value layer (HVL) of thickness is added to the thicker shield.



3.3 Other requirements



3.3.1 Generally, the detection room shall be equipped with a staff door and a separate workpiece door. For a small-scale workpiece detection room where the radiography device is manually transferred, only the staff door may be provided, and this staff door shall be set as a maze entrance.



3.3.2 The control room for the radiography device shall be placed outside the detection room, and the staff door shall avoid the direction irradiated by useful beam.



3.3.3 For shielding design, the shielding of gaps, pipe holes and weak links shall be considered.



3.3.4 If the detection room uses multiple X-ray radiography devices, X-ray shielding shall be designed according to the highest tube voltage and the maximum common tube current at this corresponding tube voltage.



3.3.5 The structure, construction cost and occupied space of the detection room shall be considered. Commonly used materials are concrete, lead and steel plate.



4 Estimation method of radiation shielding for detection room



4.1 Restriction of useful beam



The shielding estimation method of useful beam is as follows:



a) If the reference point reaches the dose rate reference control level H ̇c, the shielding transmission factor B required for shielding design is calculated by Equation (3), and then the corresponding thickness X of shielding materials is found out by the curve of Annex B.1.



B=(H ̇_c∙R^2)/(Ι∙H_0 ) (3)



where,



H ̇c——according to the determined dose rate reference control level in 3.1, μSv/h;



R——the distance from the radiation source point (target point) to the reference point, m;



I——the maximum common tube current of X-ray radiography device at the highest tube voltage, mA;



H0——the output 1 m away from the radiation source (target point), μSv·m2/(mA·h), the value in mSvvm2/(mA·min) multiples by 6×104. See Table B.1 in the Annex B.



b) At a given thickness X of shielding materials, the corresponding shielding transmission factor B is found out by the curve in Annex B.1. The dose rate of reference point H ̇(μSv/h) is calculated according to Equation (4):



H ̇=(I∙H_0∙B)/(Ι∙H_0 ) (4)



where,



I——the maximum common tube current of X-ray radiography device at the highest tube voltage, mA;



H0——the output 1 m away from the radiation source (target point), μSv·m2/(mA·h), the value in mSv·m2/(mA·min) multiples by 6×104. See Table B.1 in Annex B.



B——the shielding transmission factor;



R——the distance from the radiation source point (target point) to the reference point, m;



4.2 Leakage radiation and scattered radiation shielding



4.2.1 The corresponding relationship between the thickness X of shielding materials and the shielding transmission factor B.



The mutual calculation for the thickness X of shielding materials and the shielding transmission factor B is as follows:



a) For a given thickness X of shielding materials, the corresponding radiation shielding transmission factor B is calculated according to Equation (5):



B=10-X/TVL (5)



where,



X——the thickness of shielding materials, take the same unit with TVL;



TVL——see Table B.2 in Annex B.



b) For the estimated shielding transmission factor B, the required thickness X of shielding materials is calculated according to Equation (6):



X =-TVL∙lgB (6)

where,



TVL——see Table B.2 in Annex B.



B——the required shielding transmission factor if reaching the dose rate reference control level H ̇c.



4.2.2 Leakage radiation shielding



Leakage radiation shielding shall be calculated by the following method:



a) If the reference point reaches the dose rate reference control level H ̇c, the shielding transmission factor B required for shielding design is calculated by Equation (7), and then the required thickness X of shielding materials is found out by the curve of Annex B.1.

Foreword iii
1 Scope
2 Terms and definitions
3 Shielding requirements of detection room
3.1 Dose reference control level of radiation shielding for detection room
3.2 Radiation to be shielded
3.3 Other requirements
4 Estimation method of radiation shielding for detection room
4.1 Restriction of useful beam
4.2 Leakage radiation and scattered radiation shielding
5 Shielding thickness tables of detection room under typical conditions
5.1 Typical conditions
5.2 Tables of typical shielding thickness for detection room
5.3 Applications of typical shielding thickness tables
Annex A (Informative) Occupancy factor
Annex B (Informative) Typical parameters for radiation shielding estimation
Annex C (Informative) Example for shielding estimation of room of X-ray detection
Bibliography

ICS 13.100
C 57
中华人民共和国国家职业卫生标准
GBZ/T 250—2014
工业X射线探伤室辐射屏蔽规范
Radiation shielding specifications for room of industrial X-ray radiography
2014-05-14发布 2014-10-01实施
中华人民共和国国家卫生和计划生育委员会 发布
前言
本标准按照GB/T 1.1—2009规则起草。
根据《中华人民共和国职业病防治法》制定本标准。
工业X射线探伤室辐射屏蔽规范
1 范围
本标准规定了工业X射线探伤室辐射屏蔽要求。
本标准适用于500 kV以下工业X射线探伤装置的探伤室。
2术语和定义
下列术语和定义适用于本文件。
2.1
X射线探伤室 room of X-ray detection
用于X射线探伤工作具有屏蔽结构以保障室外场所辐射安全的专用X射线探伤装置照射室。
2.2
关注点 reference point
探伤室辐射屏蔽设计和剂量估算中需确定的探伤室外对探伤室屏蔽结构起决定性作用的位置，通常为距探伤室外表面30 cm处人员可能受照剂量最大的位置。在距探伤室一定距离处，公众成员居留因子大并可能受照剂量大的位置也应作为关注点。
2.3
屏蔽透射因子shielding transmission factor
在关注点与辐射源之间有屏蔽和无屏蔽时，该关注点辐射剂量的比值。
3探伤室屏蔽要求
3.1 探伤室辐射屏蔽的剂量参考控制水平
3.1.1 探伤室墙和入口门外周围剂量当量率(以下简称剂量率)和每周周围剂量当量(以下简称周剂量)应满足下列要求：
a)周剂量参考控制水平(Hc)和导出剂量率参考控制水平(H ̇c,d)：
1)人员在关注点的周剂量参考控制水平Hc如下：
职业工作人员：H ̇c≤100 μSv/周；
公众：Hc≤5 μSv/周。
2)相应Hc的导出剂量率参考控制水平H ̇c,d(μSv/h)按式(1)计算：
H ̇c,d=Hc/(t·U·T) (1)
式中：
Hc——周剂量参考控制水平，单位为微希每周(μSv/周)；
U——探伤装置向关注点方向照射的使用因子；
T——人员在相应关注点驻留的居留因子；
t——探伤装置周照射时间，单位为小时每周(h/周)。
t按式(2)计算：
(2)
式中：
W——X射线探伤的周工作负荷(平均每周X射线探伤照射的累积“mA·min”值)，mA·min/周；
60——小时与分钟的换算系数；
I——X射线探伤装置在最高管电压下的常用最大管电流，单位为毫安(mA)。
b)关注点最高剂量率参考控制水平H ̇c,max：
H ̇c,max=2.5μSv/h
c)关注点剂量率参考控制水平H ̇c：
H ̇c为上述a)中的H ̇c,d和b)中的H ̇c,max二者的较小值。
3.1.2探伤室顶的剂量率参考控制水平应满足下列要求：
a)探伤室上方已建、拟建建筑物或探伤室旁邻近建筑物在自辐射源点到探伤室顶内表面边缘所张立体角区域内时，距探伤室顶外表面30 cm处和(或)在该立体角区域内的高层建筑物中人员驻留处，辐射屏蔽的剂量参考控制水平同3.1.1。
b)除3.1.2 a)的条件外，应考虑下列情况：
1)穿过探伤室顶的辐射与室顶上方空气作用产生的散射辐射对探伤室外地面附近公众的照射。该项辐射和穿出探伤室墙的透射辐射在相应关注点的剂量率总和，应按3.1.1 c)的剂量率参考控制水平H ̇c(μSv/h)加以控制。
2)对不需要人员到达的探伤室顶，探伤室顶外表面30 cm处的剂量率参考控制水平通常可取为100 μSv/h。
3.2需要屏蔽的辐射
3.2.1 相应有用线束的整个端面均考虑有用线束屏蔽，不需考虑进入有用线束区的散射辐射。
3.2.2散射辐射考虑以0°入射探伤工件的90°散射辐射。
3.2.3 当可能存在泄漏辐射和散射辐射的复合作用时，通常分别估算泄漏辐射和各项散射辐射，当它们的屏蔽厚度相差一个什值层厚度(TVL)或更大时，采用其中较厚的屏蔽，当相差不足一个TVL时，则在较厚的屏蔽上增加一个半值层厚度(HVL)。
3.3 其他要求
3.3.1 探伤室一般应设有人员门和单独的工件门。对于探伤可人工搬运的小型工件探伤室，可以仅设人员门。探伤室人员门宜采用迷路形式。
3.3.2探伤装置的控制室应置于探伤室外，控制室和人员门应避开有用线束照射的方向。
3.3.3屏蔽设计中，应考虑缝隙、管孔和薄弱环节的屏蔽。
3.3.4 当探伤室使用多台X射线探伤装置时，按最高管电压和相应该管电压下的常用最大管电流设计屏蔽。
3.3.5 应考虑探伤室结构、建筑费用及所占空间，常用的材料为混凝土、铅和钢板等。
4探伤室辐射屏蔽估算方法
4.1 有用线束
有用线束的屏蔽估算方法如下：
a)关注点达到剂量率参考控制水平H ̇c时，屏蔽设计所需的屏蔽透射因子B按式(3)计算，然后由附录B.1的曲线查出相应的屏蔽物质厚度X。
(3)
式中：
H ̇c——按3.1确定的剂量率参考控制水平，单位为微希每小时(μSv/h)；
R——辐射源点(靶点)至关注点的距离，单位为米(m)；
I——X射线探伤装置在最高管电压下的常用最大管电流，单位为毫安(mA)；
H0——距辐射源点(靶点)1 m处输出量，μSv·m2/(mA·h)，以mSv·m2/(mA·min)为单位的值乘以6×104，见附录表B.1。
b)在给定屏蔽物质厚度X时，由附录B.1曲线查出相应的屏蔽透射因子B。关注点的剂量率H ̇(μSv/h)按式(4)计算：
(4)
式中：
I——X射线探伤装置在最高管电压下的常用最大管电流，单位为毫安(mA)；
H0——距辐射源点(靶点)1 m处输出量，μSv·m2/(mA·h)，以mSv·m2/(mA·min)为单位的值乘以6×104，见附录表B.1；
B——屏蔽透射因子；
R——辐射源点(靶点)至关注点的距离，单位为米(m)。
4.2泄漏辐射和散射辐射屏蔽
4.2.1 屏蔽物质厚度X与屏蔽透射因子B的相应关系
屏蔽厚度X与屏蔽透射因子B的相互计算如下：
a)对于给定的屏蔽物质厚度X，相应的辐射屏蔽透射因子B按式(5)计算：
B=10-X/TVL (5)
式中：
X——屏蔽物质厚度，与TVL取相同的单位；
TVL——见附录B表B.2。
b)对于估算出的屏蔽透射因子B，所需的屏蔽物质厚度X按式(6)计算：
X=-TVL·lgB (6)
式中：
TVL——见附录B表B.2；
B——达到剂量率参考控制水平H ̇c时所需的屏蔽透射因子。
4.2.2泄漏辐射屏蔽
泄漏辐射屏蔽的估算方法如下：
a)关注点达到剂量率参考控制水平H ̇c时所需的屏蔽透射因子B按式(7)计算，然后按式(6)计算出所需的屏蔽物质厚度X。
(7)
式中：
H ̇c——按3.1确定的剂量率参考控制水平，单位为微希每小时(μSv/h)；
R——辐射源点(靶点)至关注点的距离，单位为米(m)；
H ̇L——距靶点1 m处X射线管组装体的泄漏辐射剂量率，单位为微希每小时(μSv/h)，其典型值见表1。
表1 X射线探伤机的泄漏辐射剂量率
X射线管电压
kV 距靶点1 m处的泄漏辐射剂量率H ̇L
μSv/h
<150 1×103
150≤kV≤200 2.5×103
>200 5×103

b)在给定屏蔽物质厚度X时，相应的屏蔽透射因子B按式(5)计算，然后按式(8)计算泄漏辐射在关注点的剂量率H ̇单位为微希每小时(μSv/h)：
(8)
式中：
B——屏蔽透射因子；
R——辐射源点(靶点)至关注点的距离，单位为米(m)；
H ̇L——距靶点1 m处X射线管组装体的泄漏辐射剂量率，单位为微希每小时(μSv/h)，见表1。
4.2.3散射辐射屏蔽
散射辐射屏蔽估算方法如下：
a)90°散射辐射的TVL X射线90°散射辐射的最高能量低于入射X射线的最高能量，使用该散射X射线最高能量相应的X射线(见表2)的什值层(见附录B表B.2)计算其在屏蔽物质中的辐射衰减。
表2 X射线90°散射辐射最高能量相应的kV值
原始X射线
kV 散射辐射
kV
150≤kV≤200 150
200