WS/T 676-2020 in English
VALIDMethod for measuring radon emanation coefficient of building materials
- Issued on:2020-04-03
- Implemented on:2020-10-01
- File Format:PDF
- Delivery:Via email within 1~3 business days
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Introduction
Analysis of the core content of the standard
This standard systematically specifies for the first time the whole process method of measuring the radon emission coefficient of building materials using the circulating gas radon detector, focusing on solving key technical problems in traditional measurements such as radon leakage rate control and environmental parameter standardization.
Comparison of key technical indicators
| Parameters | Requirements of this standard | International standard (IS5098) |
|---|---|---|
| Radon leakage rate | ≤0.0007h-1 | Not clearly specified |
| Measurement time | ≥7 days | ≥5 days |
| Uncertainty | ≤35%(k=2) | ≤40% |
Key requirements for measurement systems
Clause 4.2.1 of the standard clearly states that the measurement chamber must be made of low-adsorption materials such as stainless steel or plexiglass, and its free gas volume must meet the key design criteria of Vair≥5(Vsample+Vdetector+Vpipe). A laboratory uses a 30cm diameter 316L stainless steel chamber. After verification by a helium mass spectrometer leak detector, the actual leakage rate can reach 0.0003h-1, which is better than the standard requirements.
Operation points
- Sample pretreatment: Need to be balanced in 20-22℃, 40-50%RH environment for ≥24h
- Leakage rate test: Use 500-800Bq/m3 standard radon source and perform exponential decay fitting according to formula (1)
- Constant weight determination: Dry at 105±5℃ for 6h and the mass change is ≤0.1%
Uncertainty control strategy
Appendix B points out that the main sources of uncertainty include:
1) Radon concentration measurement (Class A, 6%)
2) 226Ra activity determination (Class B, 4%)
3) Instrument calibration deviation(Class B, 10%)
It is recommended to use a high purity germanium gamma spectrometer to verify the 226Ra activity, which can reduce the uRa component to 2%
Standard implementation recommendations
- New laboratories should give priority to pulsed ionization chamber radon detectors (detection limit ≤10Bq/m3)
- It is recommended to conduct system radon leakage rate verification tests every quarter
- For porous building materials (such as aerated concrete), the measurement period needs to be extended to 10 days
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