Radiation laboratory

The Radiation Dosimetry Laboratory at KEBS is the custodian of the national standards in the field of Ionizing Radiation. It is a Secondary Standard Dosimetry Laboratory (SSDL), which was established in 2007 as a result the collaboration of International Atomic Energy Agency (IAEA) and the Government of the Republic of Kenya through the project KEN/6/016. It is located in the radiation complex at the KEBS Centre premises within the radiation complex. The SSDL has developed and maintains the national standards of Gy and Sv (for γ, and X radiation). Since August 2007, the SSDL at KEBS provides calibrations in terms of Air Kerma, Personnel Equivalent Dose Hp(10) and Hp(0.07), Ambient Dose Equivalent H*(10) radiology and radiation protection.The main tasks of the Radiation Dosimetry Laboratory are:-

1. The establishment and maintenance of the national standards of dosimetric quantities and units (Gy and Sv) for gamma and X-ray radiation
2. The determination of the necessary techniques and methods for performing measurements  
3. To develop and transfer of scientific knowledge and know-how in the field of metrology of ionizing radiation and so to bridge the gap between the Primary Standard Dosimetry Laboratory (PSDL) and the users of the ionizing Radiation
4. To provide calibrations to end users of equipment used for ionizing radiation measurements
5. To improve dosimetric accuracy and reliability of ionizing radiation measurements and to promote the compatibility of dosimetric methods in order to achieve homogenization and uniformity of dosimetry in all ionizing radiation laboratories
6. To advice, inform and guide the users of ionizing radiation on dosimetry issues as well as to exchange the experience and knowledge between users
7. To represent the country in regional and in international organizations on issues related to metrology of ionizing radiation, as well as the collaboration with  other organizations for the mutual recognition of measurement results
8. To contribute to the education in metrology of ionizing radiation
Diagnostic Air Kerma
KEBS's diagnostic calibration service is for ionization chambers to be used intentionally as secondary standards or instruments required for measurement of the greatest accuracy. Calibration of either an ionization chamber alone or of a complete instrument is available.

X-ray calibration system at the SSDL

KEBS’s accurate measurements of delivered patient radiation dose are traceable to international standards. These measurements, used in diagnostic examinations, ensure:

• Effective, low doses are used, and
• Potential hazards in relation to regulation and Codes of Practice are identified.

Features

• Calibrated directly against the national air kerma standards.
• X-ray qualities in accordance with IEC 1267: Medical Diagnostic X-ray Equipment – radiation conditions for use in the determination of characteristics.
• Air kerma rates in the range 5 mGy/hr to 50 mGy/hr.

Calibration Service Specification and AvailabilityCalibrations are normally carried out between throughout the year, and are undertaken with X-ray qualities in accordance with IEC 1267.Environmental Dose Rate Monitor Calibration Service

Regulatory agencies, monitoring laboratories and industry all require accurate, well calibrated instruments in order to monitor environmental dose rates at successively lower levels.KEBS’s calibration service is specifically tailored for environmental dose rate monitors used for air kerma measurements at very sensitive levels.Features

• Calibrations are traceable to international standards (IAEA for secondary standards and PTB for primary standards).
• Calibrations are available all the year round.
• Gamma radiation from 137Cs source is used at a range of air kerma rates from 3 µGy/hr to 58 mGy/hr.

Calibration Service for Protection-Level Dosemeters

The SSDL’s protection-level calibration service is tailored for ionization chambers used as secondary standards or instruments required for measurement of the greatest accuracy. Calibration of either an ionization chamber alone or as a complete system is available.Features

• Calibrated directly against the national air kerma standards or via specially constructed transfer chambers.
• X-ray qualities in accordance with ISO 4037 narrow spectrum series
• 137Cs source and X –ray source
• Air kerma rates in the range 3 μGy/hr to 48 mGy/hr

Availability

• 137Cs calibrations and calibrations in X-ray qualities are available throughout the year.

Instrument Calibration and Characterization 
If you have an instrument requiring calibration or characterization we may be able to assist you. Please contact us for further details.Calibration of environmental dose rate monitors (Survey meters and personal dosemeters) using Cs-137 sources is at air kerma rates between 3 μGy/hr to 48 mGy/hr  

1. in terms of H*(10) : 3 μSv/hr to 58 mSv/hr
2. in terms to Hp(10) : 3 μSv/hr to 58 mSv/hr)

An example of a Electronic Personal dosemeter (EPD) National Dosimetry StandardsRadiation Dosimetry Laboratory has established the following dosimetry standards:-

1. Air Kerma (Gy) and Air Kerma rate (Gy s-1) for Ɣ and X radiation
2. Ambient Equivalent Dose H*(10) (Sv) and rate (Sv hr-1) for Ɣ and X radiation
3. Personnel Equivalent Dose Hp(10) (Sv) and Hp(0,07) (Sv)

TraceabilityAll reference standard equipment have been calibrated against primary standards, i.e BIPM through IAEA.Radiation Protection and Personnel DosimetryCalibration of dosimeters, survey meters, detectors used in radiation protection. 
Calibration is performed at three points in each equipment scale. Calibration factors (eg NH* (10), Nk), calibration curves and calibration formulas (eg H*(10) = f(cpm) are provided.Calibration is also done in terms of NHP (10) and / or irradiation at prescribed doses of personnel dosemeters (TLD, electronic and pencil type personnel dosimeters, etc). Calibrations are performed in accordance with ISO 4037. 
Radiation Sources:

1. Cs137 irradiator: G10-1-12/20 Gamma beam Irradiator, HOPEWELL DESIGNS Inc, with a Cs137 source 647 GBq (17.5 Ci) in 24-05-2006 (Container model SC10-1-12 s/n 806-791 USA DOT-7A Type A UN3332). The source moving device is made by HOPEWELL DESIGNS Inc Model G10-1-12/20 s/n 806-792. Two ISO collimators, three beam intensity attenuators (with thickness 18, 40 and 62 mm made of Pb) and one secondary diaphragm are available.

2. GULMAY Ltd X-ray system 225 kVp – 30 mA, high frequency running in fluoroscopy mode. The system is comprised by a COMET X80-225 kV (sn 406-724) X-ray tube with a tungsten tube anode, a HV generator GULMAY CP 225/17 s/n 682-0506, a cooling system XRC-3000 WA, a control desk HOPEWELL DESIGNS Inc MP1. An AUTOMATIC VOLTAGE REGULATOR JACOBS JBS-15 kW had been installed and connected to the power supply of the X-ray generator.

Transfer Standard ionizing chambers and electrometers:X-radiation

1. A radiation protection level ionization chamber PTW TW32002 LS01, 1 litre, with s/n 0243
2. An electrometer PTW UNIDOS T10002 with s/n 20706
3. A Monitor chamber PTW T786 (s/n 0161)  connected to a PTW UNIDOS E 10008 (s/n 80434) electrometer
4. Other working standard ionization chambers electrometers

X-radiation

1. A radiation protection level ionization chamber PTW TW32002 LS01, 1 litre, with s/n 0247
2. An electrometer PTW UNIDOS T10002 with s/n 20707
3. A Sr90 check source Type T48010 (20 MBq – in 2006) with s/n 0198 for the LS01 ionization chamber.  
   

Traceability:BIPM through IAEA

• ISO4037 S-Cs,
• ISO4037 S-Co
• ISO4037 Narrow spectra

N-40: 40 kV/HVL: 0.2 Cu + 0,2 Al

N-60: 60 kV/HVL: 2.0 Cu

N-80: 80 kV/HVL: 0, 58 mm Cu

N-100: 100 kV/HVL: 1, 11 mm Cu

N-120: 120kV/HVL: 1.0 Sn + 5.0 Cu + 1 Al

N-150: 150 kV/HVL: 2.5 Sn

N-200: 200 kV/HVL: 1.0Pb +3.0Sn +2.0Cu

Calibrations or Measurements Service:

Kair and H*(10) 

• 137Cs Approximate Range: 3 μGy/hr – 48 mGy/hr and H*(10) rate 3 μSv/hr – 58 mSv/hr.
Expanded uncertainty u = 2, 7% for Kair & 4, 8% for H*(10) with k = 2

• ISO 4037 Narrow Appr. Range: 1,0 10-5 to 1,0 10-1 Gy h-1 or Sv h-1

Expanded uncertainty u = 3% for Kair & 5, 5% for H*(10) with k =2

Future outlook

1. Establishment of RQR, RQT and RQM beam qualities so as to be able to calibrate diagnostic dosimeters
2. Establishment of capacity for calibration kVp Meters (diagnostic and mammographic)
3. Acquisition and installation of 60Co source for medical therapy calibrations
4. Participation in bilateral and IAEA organized inter-comparison tests. These will generate data for publication in the Key Comparison Data Base (KCDB) at BIPM