The dissemination of the secondary standard is performed via calibration of gamma-ray measuring i...

Start Date

2010

End Date

2012

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General Information:

Address: No.18,Bei San Huan
Dong Lu,Chaoyang
Dist,Beijing,P.R.China, 100013

ws@nim.ac.cn
Tel:+86-10-64525678

Establishment Of The Air Kerma And Ambient Dose Equivalent National Standards For The NIM 137Cs Beam And Protection-Level 60Co Beam

 

Description:

It is very important to disseminate ambient dose equivalent and personal dose equivalent to user to control the occupational exposure.The dissemination of the secondary standard is performed via calibration of gamma-ray measuring instruments using gamma-ray irradiator sources.  The main gamma-ray exposure unit contains three 137Cs and two 60Co sources of different activity. These calibration facilities provide a range of air-kerma rates that help to serve a large number of users: three 137Cs sources provide air-kerma rates from 50μGy/h to 170 mGy/h; two 60Co sources provide air-kerma rates from 60μGy/h to 4 mGy/h, respectively. In addition, an 241Am source with optional collimator is housed on the outer face of the exposure unit, producing an air kerma rate of about 0.4 mGy h-1.

    Measurement conditions of protection-level field at the NIM

 

Humidity range / %

50±20

Temperature/℃

20±1

Pressure/kPa

99 to 102

Position of the centre of the standard chamber

From  80cm to 600cm

Measurement of charge

Keithley electrometer or standard dosimeter

 

The motivation of this project is to establish facilities and national rules to resolve the traceability. This project was supported by fund from government and finished in 2012.