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GBZ/T 201.1-2007 PDF in English


GBZ/T 201.1-2007 (GBZ/T201.1-2007, GBZT 201.1-2007, GBZT201.1-2007)
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GBZ/T 201.1-2007: PDF in English (GBZT 201.1-2007)

GBZ/T 201.1-2007
GBZ
NATIONAL OCCUPUATIONAL HEALTH STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
ICS 13.100
C 57
Radiation shielding requirements in room of
radiotherapy installations - Part 1. General principle
ISSUED ON. SEPTEMBER 25, 2007
IMPLEMENTED ON. MARCH 1, 2008
Issued by. Ministry of Health of the People 's Republic of China
3. No action is required - Full-copy of this standard will be automatically &
immediately delivered to your EMAIL address in 0~60 minutes.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Terms and definitions ... 4 
3 Dose reference control level of therapy room radiation shielding ... 6 
4 General shielding requirements for therapy room ... 8 
5 Verification rules for therapy room radiation shielding ... 14 
Annex A (Informative) Occupancy factor at different place... 16 
Annex B (Normative) Examples for week workload W and week illumination
time t ... 17 
Annex C (Informative) Illustration of therapy room with labyrinth and dose
focus point ... 19 
Foreword
This Standard was drafted based on Law of the People 's Republic of China
on Prevention and Control of Occupational Diseases.
GBZ/T 201 Radiation shielding requirements for radiotherapy room was
issued in parts. It consists of the following five parts.
- Part 1. General principle;
- Part 2. Radiotherapy room of electron linear accelerators;
- Part 3. Radiotherapy room γ-ray sources;
- Part 4. Radiotherapy room of 252Cf neutron after loading;
- Part 5. Radiotherapy room of proton accelerators.
This Part is the first part of GBZ/T 201.
Annex A, Annex B and Annex C of this Part are informative.
This Part was proposed by Ministry of Health Radiation Health Protection
Standards Professional Committee.
This Part was approved by Ministry of Health of the People 's Republic of
China.
The drafting organization of this Part. Beijing Center for Disease Control and
Prevention.
Main drafters of this Part. Wei Yun, Wang Shijin, Meng Qinghua, Zhang Zhuo.
Radiation shielding requirements in room of
radiotherapy installations - Part 1. General principle
1 Scope
This Part specifies the dose reference control level, general shielding
requirements and radiation shielding evaluation requirements for radiation
shielding of room of radiotherapy installation (hereinafter referred to as
therapy room).
This Part is applicable to the room of external irradiation source treatment
device.
This Part is not applicable to the radiotherapy room of human body
implantation of radionuclide particle source and the room of radionuclide
source applicator therapy.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1 controlled areas out of radiotherapy room
radiation staff working area directly connected with the radiotherapy room and
related to the treatment device in the room, such as treatment device control
room, treatment device auxiliary room, etc.
2.2 uncontrolled areas out of radiotherapy room
outside the radiotherapy room, other area except the controlled area out of
radiotherapy room, including radiation oncologist clinic, waiting room, etc.
2.3 T occupancy factor
within the start time of radiation source, the share of the average time spent
on the maximum exposure of the radiated person occupying the start time
within the area
2.4 U use factor
the share of the time at which the primary radiation beam (useful beam) is
irradiated in a direction of beam shielding occupying the total exposure time
≤ 2.5 µSv/h (staff total occupancy place, T>1/2)
≤ 10 µSv/h (staff partial and occasional occupancy place, T≤1/2)
3.2 Radiation dose rate reference control level of therapy room roof
shield
3.2.1 At the built, to-be-built two-storey building above therapy room or
when the height of neighboring building near therapy room exceeds the area
from radiation source point to the solid angle area of surface edge inside the
room roof, at the place 30 cm from therapy room roof external surface or at
the staff stay location in the high-rise building within this solid angle area, the
radiation dose rate reference control level shall be the same with 3.1.
3.2.2 In addition to 3.2.1 conditions, it shall consider the radiations of
skyshine radiation and side-scattered radiation to the public near the ground
and in the building outside the therapy room, as well as the illumination of the
radiation getting through the therapy room roof to the staff who occasionally
reach the top. Use equation (1) and take Hc=5 µSv/week, T=1/40. Use the
ambient dose equivalent rate determined at the place 30 cm from the therapy
room external surface as the radiation dose rate reference control level of
therapy room roof shielding.
3.3 Procedures for determination of ambient dose equivalent rate
reference control level
3.3.1 Ambient dose equivalent rate reference control level of therapy room
wall and at the place 30 cm from entrance door external surface
(1) select the assessment points and identify the partitions where the
assessment points are located (controlled areas out of radiotherapy
room and uncontrolled areas out of radiotherapy room);
(2) according to the radiotherapy workload given by the radiotherapy
organization, determine the week workload (W) of radiotherapy device
used, and refer to the method in Annex B to estimate the maximum
illumination time (h) of therapy device;
(3) estimate ; compare it with the dose rates in 3.1 and 3.1.2 and take
the smaller one as the ambient dose equivalent rate reference control
level.
3.3.2 Ambient dose equivalent rate reference control level of lager
occupancy factor (T>1/4) of neighboring therapy room
4.3.6 Secondary shielding radiation might contain the compound effect of
leakage radiation and scattered radiation. Usually, it shall respectively
estimate the leakage radiation and each scattered radiation. When the
difference between their shielding thicknesses is one layer (TVL) or more, it
shall use a thicker shielding. When the difference is less than one TVL, it shall
add half a layer (HVL) of thickness on the thicker shielding.
4.4 Considerations of therapy room shielding
4.4.1 In a choice of therapy conditions for radiotherapy device, it shall take
radiant matter of which the penetrating ability is relatively strong and
commonly used highest therapeutic output as radiation source parameters. It
shall also consider all the primary and secondary radiation factors of each
shielding locations.
4.4.2 Radiation dose rate reference control level of therapy room shielding
4.4.3 Week maximum workload and week therapy illumination time of
therapy device application
4.4.4 Use factor (U) of possible useful beam illumination direction during the
use of wide beam therapy device
4.4.5 See Annex A for personal area occupancy factor (T) in different places
at the peripherals of therapy room. The staff at the peripherals of therapy
room and at the neighboring places of therapy device are major consideration
objects. When some place that is directly connected with therapy room is
used for the place of smaller occupancy factor (T< 1/8), it shall also consider
the public members at the far place of larger occupancy factor.
4.5 Considerations of therapy room shielding with labyrinth
4.5.1 At the mouth of labyrinth, it shall prevent direct illumination of wide
beam useful beams on labyrinth external wall (see position k in Annex C).
And try to avoid the direct illumination of 4π useful beam and leakage
radiation on labyrinth external wall.
4.5.2 When 4.5.1 is met, position k in Annex C shall consider the possible
scattered radiation illumination of useful beam and (or) leakage radiation.
When 4.5.1 is not met, position k in Annex C shall consider oblique
illumination of 4π useful beam and (or) leakage radiation.
4.5.3 It shall consider the illumination from the radiation source in the
therapy room to corresponding wall of labyrinth mouth (see position k in
Annex C) and the scattered radiation dose from it to labyrinth mouth (see path
o-i-g in Annex C).
compensation to the place where partial shielding is weakened due to inlay
installation.
4.6.5 The pipeline holes (including ventilation, electrical appliances, water
pipes, etc.) that get through therapy room wall shall avoid the console and
other areas where staff often stay. And it shall use multi-fold road to efficiently
control the radiation leakage of pipeline hole.
4.7 Considerations of neutron shielding
4.7.1 While neutron shielding, it shall consider the shielding to neutron
capture γ ray.
4.7.2 When accelerator therapy X ray is greater than 10 MV, because (γ, n)
react to produce “spurious” neutron, it shall consider the neutron shielding in
the therapy room according to the indicators that are given by the therapy
device manufacturer and not exceed national standard.
4.7.3 For X ray therapy room greater than 10 MV, when it uses single
concrete shielding, the wall, roof shielding shall only consider the shielding to
X ray and neglect the shielding t...
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.