INER is a Taiwanese research institute for nuclear development and ionizing
radiation metrology
Mr. Wen-Song Hwang
Head, Radiation Standards Laboratory, INER
1. Introduction
The Institute of Nuclear Energy Research (INER) of Atomic Energy Council
under the Executive Yuan was formally established in July 1968. Currently,
the organization of INER comprises two committees, two centers, eleven
functional divisions, and one project and four staff offices. INER is well
equipped for nuclear R&D. INER's goals are set to apply nuclear technology,
to improve civilian welfare, and to assure nuclear plus radiation safety.
The R&D work at INER can be classified to nuclear safety, nuclear engineering
technology, radiation protection and detection, radioactive waste treatment,
civilian nuclear applications, and measurement standards.
2. Measurement Standards at INER
The standards for ionizing radiation consist of photon, beta, neutron dosimetry
and radio nuclide acdvity. These tandards held by INER could be traced
to the BIPM through regional comparisons in the Asia Pacific and bilateral
comparisons with other national metrology institutes (NMIs). We also extend
the application of these standards to areas of medicine, agriculture, industry
and business via traceability system of instrument and radionuclide calibration.
2.1 X-ray and Gamma Ray Standards
A constant potential X-ray machine operable in the range between 30 kV
to 250 kV is used to generate BIPM and NIST X-ray spectra. Air kerma in
the X-ray ranging 60 kV to 250 kV and 30 kV to 60 kV are determined by
a home-made free air ionization chamber and a transfer ionization chamber
calibrated by NIST, respectively. 137Cs and 60Co teletherapy sources are used to produce gamma ray. The primary standard
is a set of self-fabricated spherical chambers with chamber volumes of
3 cm3 and 30 cm3, which were made of graphite with wall thickness of 3 to 4 mm. There are
60 chambers a year coming from hospitals and secondary standard laboratories
islandwide for calibration in terms of air kerma.
To provide calibration service in terms of absorbed dose to water in 60Co, a transfer chamber NE2561 calibrated by NPL, has been installed in
the water phantom with dlmension of 30 cm x 30 cm x 30 cm for the measurement
of absorbed dose at the depth of 5¥gem-2. The hospital can determine 60Co absorbed dose in water directly using a transfer chamber that has been
calibrated by this standard.
2.2 Radionuclide Activity Standards
Two kinds of measurement standards can be used to measure the radioactive
activity. One is 4pb-g coincidence method which uses a 4p proportional counter working at atmosphere pressure as the b detector and two 3" x 3" NaI (Tl) as the g detector. The count rate in b channel is often expressed as a function of observed detection efficiency
for those b particles. Then the activity of the source may be obtained by extrapolating
the b efficiency to 100 % and therefore no standard source is needed. The other
method is using a well-type ionization chamber which consists essentially
of two electrodes insulated from each and mounted in an envelop containing
a suitable gas, for example argon at a pressure of 20 atmosphere. Other
measurement standards, such as high purity germanium system and 2 pc-b proportional system, have been properly employed for the provision of
calibration services as well.
2.3 Proficiency Test for Personnel Dosimeters
The Chinese National Laboratory Accreditation (CNLA) Scheme was established
in 1990. The CNLA provides independent and third party accreditation by
testing laboratories in accordance with well-defined, pre-established accreditation
criteria. CNLA accreditation is conducted in ten areas including acoustics
and vibration, biological testing, calibration, chemical testing, electncal
testing, heat, ionizing radiation, mechanical testing, non-destructive
testing, optical testing, and temperature.
The effective period of accreditation is three years (since 1996) and accredited
laboratories may request accreditation renewal prior to the end of the
effective period. The renewal process remains the same as the initial process
except that the reassessment may take less time.
The Ionization Radiation Assessment Technical Committee of CNLA was founded
in 1989. Following that, in 1990, INER was entrusted by CNLA as the central
laboratory to perform the proficiency test of personnel dosimeters for
laboratory accreditation. The first proficiency test was carried out in
1991 based on the criteria of ANSI N 13.11 (1983). Until now, seven dosimeter
processors in Taiwan have participated in the proficiency tests which have
been performed in the years of 1991, 1993, 1995 and 1998.
3. INER as a Member of APMP
INER was entrusted by the Bureau of Standards, Metrology and Inspection,
Ministry of Economic Affairs, to establish a radiation stan dard laboratory
in the year of 1992. The major missions for the laboratory are to set up
and maintain metrology standards for ionizing radiation to provide the
traceability of calibrated instruments nationwide, and assist in the establishment
of CNLA. In addition to its R&D work, INER has always welcomed responsibilities
that help advance its techniques and strengthen its capabilities.
It is indeed a great pleasure of INER to be a full member of APMP. INER
has served its role as the first chairperson of the TCRI, APMP in the hope
that through the establishment and efforts of the TCRI, the member laboratories
in TCRI will enhance their interaction and cooperation.
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