Components / Samples from a few Steel industries / steel component manufacturers / exporters were analysed at Rad io-analytical lab of Nucleonix Systems for Radioactive Contamination (RaC). Also it is important to note that these measurements were made in the presence of Natural Background (BG) of --190nSv/hr & 20 mR/hr(approx). Applicability of these results/ summary is to be verified where the natural BG’s are of the order of 5/6 µR/hr or 50 to 60 nSv/hr. Our next case study with all these samples will be carried out at a location where the natural BG will be of this order.
Analysis was carried out by using three following types of equipments manufactured & offered by Nucleonix Systems.
- Rad Check Meter (with Internal detector )
- Rad Check Meter (with External Detector probe)
- Gamma Ray Spectroscopy System with MCA
Measurement summery has been tabulated. As part of the study three clean samples (SP1, SP2 & SP3), low level contaminated samples (SP4 to SP8) & high level contaminated samples (SP9 & SP10) were studied. Data was recorded with Rad Check Meters in both nSv/hr & mR/hr with sample in contact including Background (BG) as well. In respect of MCA data was recorded in Bq/g after acquiring the spectrum.
For analysis sample dimension / size & weight criteria as desired was observed. The following are the important conclusions one can make.
Clean sample : Both with Rad Check meters (Internal / external probe) when the samples were touched in contact, BG reduced from its initial value by almost above 18%. Hence when BG reduces by 15%, one can perhaps say that the sample is clean. Of course it is very important that sample weight is at least 3 to 4 kg or more but not less & it covered full face of the detector / probe when measurement are made. If the components are small then add up them to make it to meet the above mass/dimensional criteria, for better measurement data.
Effect of Weight factor : One more conclusion is if the sample is less in weight then, reduction of BG Percentage is found to be less.
Low Level Contaminated Samples : It is important to notice here in respect of samples (SP4 TO SP8) that BG has marginally reduced up to maximum of -7.5% when the meter is touched to component. Samples with level Low level contamination, when checked with MCA were found to have activity in the range of 0.076 bq/g to 0.264 bq/g. Percentage fall in BG is more if the contamination is less. Perhaps one can vaguely conclude if the percentage fall in BG is less than 10% then contamination could be less than 0.1Bq/g.
However measurement by MCA analysis is most authentic. It is tricky & difficult to identify low level contamination , & quantity actual level in terms of Bq/g by Rad Check Meter. However one can say that it is a suspected contaminated case & needs to more study & thorough investigation. Now by increasing the mass, under measurement & recording observations if one finds that that % BG has come ( thas when the mass was less) close to BG, then, certainly it is a contamination case. However whether it is less than 0.1 Bq/g can not be quantified by this measurement.
High Level Contamination Samples: Samples (SP9 & SP10) were analysed & BG was found to increase from 40% to 80%. Hence when BG increases even by a small margin or remains same, one should suspect of contamination.
Rad Check Meter with Internal Verses External Probe : From the tabulated data one can notice that external probe behaved to be more sensitive – percentage reduction in BG was less compared with internal probe for low level contamination cases & for high level contamination, % increase was more compared with internal detector probe version. Hence we advise all steel industry people to prefer external detector probe version, though it is slightly costly.
In What unit, one should measure ?Is it nSv/hr or mR/hr: % BG increase for higher contamination case is found to be high in nSv/hr mode relatively compared to mR/hr mode of dose rate measurement. Hence nSv/hr mode of measurement one should prefer. Also ‘Sv’ is an ‘SI unit’ & universally accepted (including in EU, UK & Germany and USA). Hence make measurements in nSv/hr preferably.
Hope this summary of conclusions will help you better in your day to day analysis & measurements. You may email us (email@example.com , firstname.lastname@example.org ) for more information or send your sample for (Bq/g) analysis by MCA method in case of suspected contamination cases.