GBZ/T 250-2014 PDF in English
GBZ/T 250-2014 (GBZ/T250-2014, GBZT 250-2014, GBZT250-2014)
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[Including 2017XG] Radiation shielding specifications for room of industrial X-ray radiography
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Standards related to (historical): GBZ/T 250-2014
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GBZ/T 250-2014: PDF in English (GBZT 250-2014) GBZ/T 250-2014
GBZ
NATIONAL OCCUPATIONAL HEALTH STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
ICS 13.100
C 57
Radiation shielding specification for room of
industrial X-ray radiography
ISSUED ON. MAY 14, 2014
IMPLEMENTED ON. OCTOBER 01, 2014
Issued by. National Health and Family Planning Commission of the
People's Republic of China
Table of contents
Foreword ... 3
1 Scope ... 4
2 Terms and definitions ... 4
3 Shielding requirements of detection room ... 5
4 Estimation method of detection room radiation shielding ... 8
5 Detection room shielding thickness table under typical conditions ... 13
APPENDIX A (Informative) Residence factor ... 17
APPENDIX B (Informative) Typical parameters for radiation shielding
estimation ... 18
Appendix C (Informative) Example of X-ray detection room shielding estimation
... 21
References ... 26
Foreword
This standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This standard was formulated in accordance with Law of PRC on Prevention
and Control of Occupational Diseases.
The main drafting organizations of this standard. Beijing Disease Control and
Prevention Center, Beijing Beta-Lab Technology Testing Co., Ltd., Tsinghua
University.
The main drafters of this standard. Wan Ling, Feng Zechen, Lou Yun, Ma
Yongzhong, Peng Jianliang, Zhai Shuguang, Kong Yuxia, Wang Shijin, Li Junli.
Radiation shielding specification for room of
industrial X-ray radiography
1 Scope
This standard specifies the radiation shielding requirements for industrial X-ray
radiography room.
This standard applies to the industrial X-ray radiographic device room below
500 kV.
2 Terms and definitions
The following terms and definitions apply to this document.
2.1
Room of X-ray detection
It refers to the dedicated X-ray detection device room which is used for X-
ray detection work with a shield structure to protect the outdoor radiation
safety.
2.2
Reference point
It refers to the location outside the detection room which has decisive effect
onto the detection room shielding structure AND needs to be determined
during the detection room shielding design and dose estimation. It is
generally the location 30 cm away from the external surface of the detection
room where personnel may be exposed to the maximum dose. At a certain
distance to the detection room, the locations where the public member
residence factor is high AND the exposure dosage is high shall also be
focused.
2.3
Shielding transmission factor
penetrating through the detection room wall, it shall be controlled based
on the dose rate reference control level of 3.1.1 c).
2) As for the inaccessible detection room roof, the dose rate reference
control level at the location 30 cm away from the detection room roof
external surface is generally taken as 100 μSv/h.
3.2 Radiation needed Shielding
3.2.1 The entire wall surface of the corresponding primary radiation shall adopt
the primary radiation shielding, AND it is not needed to consider the scattered
radiation entering into the primary radiation region.
3.2.2 As for the scattered radiation, CONSIDER the 90° scattered radiation
which is incident into the detected work piece at 0°.
3.2.3 When there is a possibility of a combined effect of leakage radiation and
scattered radiation, generally respectively ESTIMATE the leakage radiation and
each scattered radiation; when the difference between their shielding
thicknesses is equal to or more than one tenth value layer (TVL) thickness,
SELECT the thicker shielding; when the difference is less than one tenth value
layer (TVL), then at the thicker shielding, ADD a half value layer (HVL).
3.3 Other requirements
3.3.1 The detection room shall generally be provided with personnel doors and
separate work-piece doors. As for the small work piece detection room wherein
detection can be through manual handling, it can only provide the personnel
door. AND the personnel door for the detection room shall adopt the labyrinth
type.
3.3.2 The control room of the detection device shall be placed outside the
detection room, AND the control room and personnel door shall avoid the
direction of irradiation from primary radiation.
3.3.3 In the shielding design, it shall consider the shielding for the gap, pipe
hole and other weak links.
3.3.4 When the detection room uses multiple X-ray radiography devices,
DESIGN the shielding based on the maximum tube voltage and the normally
used maximum tube current under such tube voltage.
3.3.5 It shall consider the detection room structure, building cost, and space
covered; AND the commonly used material is concrete, lead, and steel plate,
etc.
Ro - The distance from the radiation source point (target) to the work
piece under detection, in meters (m);
I - The commonly used maximum tube current of X-ray radiography
device at the maximum tube voltage, in milliamps (mA);
Ho - The output at the location 1 m away from the radiation source point
(target), μSv • m2/(mA • h), USE the value in the unit of mSv • m2/(mA
• min) to multiple by 6 x 104; SEE Table B.1 of Appendix B.
F - The radiation field area at Ro, in square meters (m2);
α - Scattering factor, which is the ratio of the scattered radiation dose
rate of the incident radiation onto the location 1 m away from it by the
scatterer of 1m2 unit area to the incident radiation dose rate on this unit
area. α is related to the scattering material; if the α value of the
corresponding material does not obtained, USE the α value of water
scatterer for conservative estimation; SEE B.4 of Appendix B;
c) When the shielding material thickness X is given, as for the corresponding
shielding transmission factor B, in accordance with Table 2 and the
corresponding values in Table B.1 of Appendix B, DETERMINE the TVL
of 90° scattered radiation, then USE the equation (5) for calculation. The
scattering dose rate for the reference point is calculated in
accordance with the equation (10).
Where.
I - The commonly used maximum tube current of X-ray radiography
device at the maximum tube voltage, in milliamps (mA);
Ho - The output at the location 1 m away from the radiation source point
(target), μSv • m2/(mA • h), USE the value in the unit of mSv • m2/(mA
• min) to multiple by 6 x 104; SEE Table B.1 of Appendix B.
B - Shielding transmission factor;
F - The radiation field area at Ro, in square meters (m2);
α - Scattering factor, which is the ratio of the scattered radiation dose
rate of the incident radiation onto the location 1 m away from it by the
scatterer of 1m2 unit area to the incident radiation dose rate on this unit
that is, the required shielding wall thickness of the detection room is more
than that of the sidewalk; in accordance with the dose rate requirements f
the office building, ESTIMATE the final shielding thickness.
C.1.2.2 Examples of north wall (primary radiation) shielding estimation
a) CONDUCT estimation in accordance with the methods of 4.1. from Table
B.1, the primary radiation output of the 300 kV tube voltage under 3 mm
copper filtering conditions is 11.3 mGy•m2/(mA•min).
CALCULATE in accordance with the equation (3).
From the lead transmission curve of Figure B.1, the required lead
thickness is 22.4 mm. It can also calculate the required concrete thickness
is 560 mm.
b) ESTIMATE using the typical data sheet method. from Table 4, it is found
that lead required at 2m and 3m is 23 mm and 21 mm respectively.
Through the interpolation, the lead shielding thickness at 2.3 m is 22.4
mm. It can also calculate the required concrete thickness which is 560 mm.
C.1.2.3 Example of west wall (leakage radiation and scattered radiation
combination) shielding estimation.
a) ESTIMATE in accordance with the methods in 4.2.
1) Leakage radiation.
From Table 1, the leakage dose rate of 300 kV X-ray at 1 m from the
target is 5 × 103 μSv/h. From Table C.1, is 1.2 μSv/h. CALCULATE
In accordance with the equation (7).
From the Table B.2 of Appendix B, the tenth value layer of 300 kV X-
ray in lead is 5.7 mm, and then USE the equation (6) to calculate the
required lead thickness.
2) Scattered radiation.
References
[1] International Commission on Radiological Protection. Protection against
ionising radiation from external sources used in medicine. ICRP Report 33.
Oxford. Pergamon Press, 1982.
[2] National Council on Radiation Protection and Measurements. Structural
Shielding and Evaluation for Medical Use of X-Rays and Gamma-Rays of
Energies Up To 10 MeV, NCRP Report 49, NCRP, Bethesda, MD, 1976.
[3] National Council on Radiation Protection and Measurements. Structural
Shielding Design for Medical X-Ray Imaging Facilities, NCRP Report 147,
NCRP, Bethesda, MD, 2004.
[4] American National Standards Institute, Inc. For General Radiation Safety-
Installations Using Non-Medical X-Ray and Sealed Gamma-Ray Sources,
Energies Up to 10 MeV, ANSI/HPS N43.3, ANSI, 2008.
[5] HMSO. Handbook of radiological protection, part 1. data. London. HMSO,
1971.
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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