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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

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.