Radioactive Contamination (RaC) issue is a new phenomenon for the recycled steel and foundry industry including automotive and engineering component industry. These RaC issues are important to all exporters to Europe, USA, UK & Japan. Low level contamination cases have been found to be more in the recent past. Nucleonix systems with vast design experience in the field of nuclear instrumentation have developed a package of products for the detection and measurement of RaC for this industry. Based on the questions encountered from the industry, we thought it may be appropriate to put these queries in the form of FAQ's and make an article so that majority of the industry personnel are benefitted.
1Q) What is Radioactive Contamination in Steel / Iron / Alloy / Casting Products?
A) Scrap metal, engine block scrap and other miscellaneous scrap (incoming) when purchased, may get mixed up with any of the Radionuclide substances (Sources), such as co-60, Am-241, Cs-137 etc.(medical& industrial sources) can enter the factory accidentally leading to Radioactive contamination, when processed further in a steel industry. Also semi-finished inputs such as flats, bars, rounds, castings, other parts, received from vendors as inputs to automotive or Engineering component industry may have radioactive contamination already.
2Q) How it can happen?
A) There are lot of industrial & medical radioisotope products used in cancer hospitals & industries. When they are disposed, illegally,(not following AERB guidelines) it is likely that they come into steel plants & large foundries through input scrap metal or through semi-processed inputs purchased from other industrial unit, & can lead to radioactive contamination of the end product.
3Q) What is the remedy & how to detect & segregate contaminated parts?
A) There are sensitive low level radioactive contamination inspection systems, Truck/container monitoring systems (large) and smaller Portable instruments offered by companies' world over. In India, Nucleonix Systems a reputed company with its vast design, development & manufacturing experience into Nuclear Instrumentation has developed a package of products to meet requirements of steel industry in different situations to detect radioactive contamination.
4Q) Which are these products?
A) The following are the products, offered by Nucleonix Systems
1. Rad check meter (With Internal detector) RC 705I
2. Rad check meter (With external detector probe) RC 705E
3. Radioactive Contamination Analyzer (Bq / gm system) RA 1006
4. Package monitoring system PMS 1009
5. Truck / Container Monitoring System For Radioactive Contamination TR 1021
5Q) Apart from products being offered by Nucleonix Systems to measure RaC, whether Nucleonix also offers RaC measurement & analysis services? If yes what kind?
A) Yes. Nucleonix offers (a) Radioactive Contamination Analyzer inspection services for all exporters at site & issues certification and (b) we accept samples (Approx 1Kg) by courier for RaC analysis to give certification in Bq/gm which is required in some cases. (Few customers are availing our services.)
6Q) What is Rad Check Meter, in what situations we can use this product?
A) It is a sensitive, economy model which checks for radioactive contamination (Photons / Gamma Radiation) in steel/Alloys/ Iron samples / scrap metal, Automotive and Engineering components, when the meter front face is kept close to sample (almost touching). It is a hand held instrument suitable for scanning manually. There are more than Five Hundred meters supplied by us throughout the country, which are widely in use. Recently we exported these meters to few countries.
7Q) What is a G.M detector based Radiation monitor? Whether one can use it for checking of Radioactive Contamination in steel / iron/ alloy / castings products?
A) Low cost G.M. detector based meters are offered by some companies & they cannot detect low level radioactive contaminations. Higher contamination levels, only they can detect & hence are not recommended for this application.
Only sensitive meters which can measure Dose rates from 1µR//hr or 10 nSv/hr onwards are to be used. At Nucleonix System we have a product called Rad Check Meter in our range. This is a portable meter to be used either with internal or external probe.
8Q) When Truck/Container Monitoring System is to be used for Radioactive Contamination? How does this help?
A) This system comprises of two large volume plastic scintillator detector pillars, electronic measuring & alarms unit and software with PC. Highly recommended at the entry/exit gates to check for radioactive contamination in. In-coming trucks / containers carrying scrap metal, input raw material, iron, steel, alloy products etc. Also it can be used for checking outgoing finished goods in trucks / containers.
Inspection at the 1st entry level saves the industry from buying contaminated scrap metal & saves on electricity bills & other processing costs by melting the scrap metal in smelting furnaces
9Q) When Radioactive Contamination Analyzer (Bq/gm system) for Nuclide Identification & its quantification is to be used?
A) This is a powerful tool used for exact quantification of nuclide, present in a contaminated sample. This system identifies & quantifies the contamination in Bq/Kg or Bq/gm of the sample. This is an ideal choice in quality assurance departments of all steel. / iron / alloy/Foundry casting industries (medium & large). This facilitates loading of sample up to 1 to 2 kg on to the detector area, for measurement.
10Q) What is the 'unit' of measurement that is normally used in these above systems?
A) Normally the units used in these meters globally are Sv (sivert). In India we have been using R (Roentgen). But Nucleonix Systems has been providing both these units Sv & R. Additionally meters may have CPS , CPM , modes. All Nucleonix meters have FOUR modes of operation nSv/hr, mR/hr, CPS, CPM.
In the Rad Check Meters you may find m R/hr (micro roentgen / hour) & nSv/hr (nano sivert / hour)
m = micro = 10-6
n = nano = 10-9
m = milli = 10-3
11Q) Can we have some idea on measuring units used? How do you define Sv & R ?
The SI unit of dose equivalent
1 Sv = 1 J /kg (one 'Joule' of energy deposited 1 kg of air)
Roentgen (R) : Is defined as the exposure that results in the generation of 1 electro static unit of charge (2.0 g X 109 ion pairs) per 1 cm3 of air STP (0.001293 gms)
1= 2.58 X 10-4 C/Kg.
Gray: Absorbed dose is a measure of energy deposition in any medium by all types of ionizing radiation and 1GY = 1J/Kg
Since an exposure of 1 R results in an energy deposition of 869 X 10-5 J/Kg in air it follows that
1 R = 869 X 10-5 Gy
1 R = 8.69 m Gy milli (m) = 10-3
1 R = 10 m Gy micro (?) = 10-3
1 R = 10 m Sv nano (n) = 10-9
1 Sv = 1R/10m
1 Sv = 100 R
12Q) Can we have some conversions between Sv & R ?
1 Sv/hr = 100 R/hr
1 mSv = 100 mR/hr
1 mSv = 100 mR/hr
10 nSv = 1 ?R/hr
10 mSv/hr = 1000 mR/hr
= 100 mR/hr
0.1 mSv/hr = 10 mR/hr
13Q) What is Becquerel (Bq)?
SI unit of activity. It is define as no. of radioactive transformations or isomeric transitions per second = 1 Bq. It defines the source 'activity' or 'strength'
14Q) What are the clearance levels radioactive contamination in European countries, UK & USA?
Allowable Limits for Radioactive Contamination Analyzer in steel in different countries are given below.USA it is nil.
European Union = 1.0 Bq/gm
Germany = 0.1 Bq/gm
U.K = 0.4 Bq/gm
Japan = 1.0 Bq/gm
IAEA (BSS) = 1.0 Bq/gm
For Material upto one tones IAEA = 0.1 Bq/g
For bulk material without limit ICRP= 0.1 Bq/ gm
However it may be good practice to observe the limit as <0.1 Bq / gm
15Q) What is Natural background radiation?
A) In the nature exists background radiation, due to geo-structure, terrain, rocks, cosmic radiation flooring, tiles, walls etc. also contribute to background radiation levels. Natural background varies from place to place and could be in the range of (3-4) µR/h to (30-40) µR/h. (0.03µSv/h to 0.4µSv/h). At a single location also, natural background varies and this is called statistical variation. For practical purposes, we take the highest observed reading in a location as natural background.
Rad check meter is an instrument which measures radiation dose rates from natural background radiation levels onwards. Its sensitivity is typically 1 µR/hr or 0.01 µSv /hr.
16Q) Is natural background level different at different places?
A) Yes, it is different in different cities & places, for e.g. in Hyderabad, India it is more, it is approx 30 µR /hr. In Mumbai, India it is approx (6 to 8) µR/hr. (About FIVE times less than that in Hyderabad).
17Q) Whether contamination reading as shown in the display will be same in different places for the same sample under same measurement condition?
A) No, unless the background level is same at two different places where you would have made measurement, meter reading will be different for the same contamination levels. This is because the background at these two places may be different.
Please note that natural background levels get added up to the meter reading along with reading due to sample contamination, i.e.,
Meter reading = Sample contamination + Natural Background
However if you account for reading due to background, then reading due to sample will be same, in the different places.
18Q) What is check source & why is it required?
A) Check source is a small (low level) Radioactive Gamma Source (Cs137). This is basically required to check whether your Rad Check Meter RC705 is responding to radiation.
To check your Rad Check Meter, place the radioactive source close to the front face of the meter & observe the meter reading to go up. When you take the source away, the reading drops.
This check source also could be used for carrying out QA of the product by verifying the stability of the reading with source over the one year period when calibration is valid. Incase there is a drift of more than 10% with respect to the initial reading when procured from factory, contact factory as there could be some problem with the instrument.
19Q) Does this “Rad Check Meter” indicate nuclide type and absolute level of contamination?
A) No, this meter primarily indicates (gross) or total contamination in relative terms. The reading also varies with distance from the sample.
If your interest is to know absolute nuclide which has contaminated (such as Co-60, Cs-137, Am-241 etc.) and its contamination level in terms of Bq/gm, then you need to go in for our Radioactive Contamination Analyzer (Bq / gm system) RA 1006. This is a foolproof test and recommended for steel industry having smelting/ induction furnaces.
20Q) Is there any Equipment offered by Nucleonix Systems to know the exact nuclide which has contaminated? Whether the equipment can quantify the contamination level in Bq/gm or Bq/Kg?
A) Yes, we have a system already in our manufacturing range, which is being used now by many customers in steel industry who have induction furnaces & manufacture products like billets, bars, flats, rods etc.
This system is called Radioactive Contamination Analyzer (Bq / gm system) RA 1006.
This system records gamma ray spectra of different isotopes present in the sample
under test & spectra can be analyzed to know the type of nuclide & also its
contamination level in terms of Bq/gm or Bq/kg.
21Q) Which unit of measurement is recommended for measurement in Rad Check Meter?
A) Since 'Seivert' is used in EU & UK it is better to measure in nSv/hr using Rad Check meter. Of course one can also measure in ?R/hr, but has to use conversion factor for interpretation in ?Sv/hr or nSv/hr if required.
22Q) Can we have conversion from µR/hr' or µSv/hr' or nSv/hr to Bq, as Rad Check Meter does not measure in Bq?
A) Conversion from µR/hr' or µSv/hr' or nSv/hr to Bq for a contaminated steel sample is difficult. Conversion factor cannot be given right away for the following reasons.
One is size, shape, mass of sample & sample orientation distance from the detector probe face etc influence while making measurement & hence one cannot give exactly any conversion. Also detector efficiency, Background, also are to be accounted. Further since contaminated source is embedded into steel, there will be self absorption.
It is possible to give conversion for a point source (standard source) if we know the type of nuclide.
Also in respect of contaminated steel samples, we are not sure that contamination spread, is uniform (homogeneous) throughout the mass. Precisely what we measure is what is emanating from the contaminated sample which is measured & quantified. What is embedded deep inside, which may not be emanating because of energy loss when the gamma photons reaches the surface of the sample will not be detected. Since it is not emanating it is of no consequence.
However, it is possible to make a fair judgment & arrive at a conclusion to declare a component as
ii. CONTAMINATED Or
iii.SUSPECTED ONTAMINATION/LOW LEVEL CONTAMINATION CASE
Please go through our website www.nucleonix.com & read the content under "case studies report". This will clearly give an idea on declaring a product into three categories as said above.
By going through our case studies report-1 & by making proper measurements & analysis one can perhaps say that contamination is less than 0.1Bq/g. But for exact quantification one has to go through analysis by Radioactive Contamination Analyzer only. Using Rad Check Meter you can definitely classify the product and say whether it is
ii. CONTAMINATED Or
iii.SUSPECTED CONTAMINATION CASE
Also if your industry is a steel mill / Foundry having induction / smelting furnaces, it is absolutely necessary to go in for Radioactive Contamination Analyzer to obtain contamination in Bq/g & also to identify type of nuclide that has contaminated.
23Q) Is Rad check meter a Radiation calibrated meter? What calibration standard Nucleonix Systems has at their works / factory? Up to what accuracy it reads.
A) Nucleonix Systems has two calibration labs.
i. Low Level Calibration Lab :
ii. High Dose Rate Calibration Lab
Rad Check meters are calibrated at low level calibration lab using a Gamma survey instrument calibrator make Amersham , UK/USA. It has NIST (National Institute of standards & technology, USA ) traceability.
Rad check meter is calibrated upto 15% accuracy for readings above 100 µR/hr.
24Q) Whether this Rad Check meter measure natural background radiation accurately at any Place?
A) No, this gives a background reading slightly lower than the actual natural BG. This reading we can call it as the base value. Rad check meter is designed to be more sensitive on the front face of the detector so that it can detect Radioactive Contamination (RaC) from a longer distance compared to an ordinary Micro-R-Survey meter. It is for this reason the meter will show less reading of natural BG.
25Q) When do we say that the product under inspection is contaminated?
A) If you are making measurement with Rad Check Meter & if the reading (when you touch the component closely with meter) goes even slightly higher than the background then one can declare that component as contaminated.
Even, if the reading remains equal to BG or goes marginally lower than BG when you touch front face of the meter to the sample under test then also it is a case of suspected contamination. Under this condition checkup more thoroughly & it could be a case of low level contamination.
Best way is to take more mass or material & touch the meter close to the mass & if the reading increases than the previous one then it is a contamination case.
26Q) If it is suspected contamination case (SCC.) what to do? How to analyze further to ascertain on the status of contamination?
A) In a suspected contamination case it is essential to make a through check. Take large amount / mass of sample and if the meter reading goes up with increased mass, then, it is definitely a contamination case. Also you can send the samples (1kg) to Nucleonix systems for further analysis using Rad Check Analyzer which is a 100% foolproof method of identifying RaC.
27Q) When do we say & can declare a product to be clean from RaC? (using Rad Check Meter)
A) First record the background (BG) & then go to acquire mode & record BG. Now touch the meter to the surface of the component under inspection if the reading shown goes 10 to 20% lower than the BG reading, then the sample can be declared as clean.
(If the reading is very close to BG & marginally less or equal to BG it is a suspected contamination case).
28Q) Is fixing preset alarm level advised or not for RaC inspection? Or one should look at the readings carefully & interpret?
A) Please do not fix any preset alarm level for RaC inspection. Best way is to touch the meter to the component & observe the reading (doserate) to check how closely it is to BG or away from BG or lower than BG. Based on this reading only one should interpret.
Fixing preset alarm level above BG & checking or interpreting for RaC can be misleading & one can miss definitely low level contamination cases. Hence never do this for RaC inspection.
29Q) What is the difference between suspected contamination case (SCC) & sure contamination case?
A) Suspected contamination case is a situation, when the Rad Check Meter reading is very marginally lower or same as the BG. This happens if the contamination levels are very low of the order of 0.1 to 0.4 Bq/g.
Under this condition take larger mass of 3/4 kg or much more & touch the meter if the reading goes higher then it a sure contaminated case. Also initially it when you touch the component / part if the reading goes higher than BG, even slightly more, then it is a sure contamination case. Reading need not be 2 times or 1.5 time BG. It can be slightly higher than BG. If you are not sure & think that the sample needs thorough investigation, then send it to Nucleonix for detailed analysis.
30Q) What should be the minimum mass & size of the sample to check for RaC using Rad Check Meter?
A) It is advised for one to take a sample of mass at least of three Kg (approx) or more but not less. Also the size & shape of the component should be large enough to cover the complete front face of the detector probe / meter, so that detector face is covered by the sample when touched. Higher the mass, results of inspection will be more authentic.
If your product is small in size & less in wt, then put multiples of these components together such that mass & front face of the meter covering criteria, is met. This is important.
31Q) What should be technical qualifications of the person operating the instrument?
A) The person should be a basic science graduate or a diploma engineer with an understanding of radiation. He/she should be very responsible and meticulous in taking the measurements.
32Q) What is Calibration Factor:
A) This is set at factory by Nucleonix when the equipment is calibrated in Radiation calibration lab. It may be from (0.75 to 1.5) depending upon the sensitivity of the detector. It is not same for all meters. It can be different for different meters of same type. Customer should not change this calibration factor, which is password protected. If changed will give wrong results and data.
33Q) How many background readings are to be noted and averaged to take as authentic background reading.
A) Typically 3 to 5 Background readings, averaging should be alright.
34Q) Whether Non-Ferrous Metals, such as copper, aluminum, zinc, brass & non-metals such as plastics, wood etc also can get Radioactive Contamination?
A) Normally not. Not heard of.
35Q) Can only packaging materials such as packing nail, metal strap (MS) etc. get contaminated and not the actual product under export?
A) Yes, there are such cases which have happened and hence, even these packing nails / metal straps are also to be checked for radioactive contamination.
36Q) We manufacture SS, billets rounds, square bars which are longer. Our question is at how many locations we should make measurements with Rad check meter? If it is contaminated, will it be uniform throughout the length?
A) Measurement at 2/3 locations in full length may be enough approximately one reading per meter may be enough. If it is contaminated, largely it will be distributed homogenously. Of course a non-uniform distribution of RaC is not ruled out. Your measurement readings at two/three locations will give you can idea on this.
37Q) Our Industry manufacturers small sized components such as fasteners, SS rings, door hinges, latches etc., Question is if the components are small in size do we have to check each component ?If we check each component separately whether results are meaningful?
A) If the components are small in size, then you can group them to make about 3 kg, put them in a plastic pouch & cover complete front face of the detector. This will satisfy the mass & size criteria. Measurements are to be carried out in this fashion only. If you check each component separately results will not be meaningful as mass & size criteria are not met.
38Q) Can Garments such as Jackets having iron rings, and fancy buttons of iron / SS get contaminated
A) Yes, It is possible and hence exporter of these goods with iron rings and fancy buttons of ferrous and SS materials have to check for radioactive contamination.
39Q) Can one avoid making measurements at product processing level or check only final packed wooden crate containing finished products in packed condition?
A) It is quite risky & since you will not be touching the components very closely, as wooden crate will prevent you meter touching the components, there is a possibility of low level contamination being not detected. This can be damaging to you. Hence we recommend inspection at different stages of production cycle. Also by detection at early stage of production cycle, you will save on processing costs by not processing the contaminated input material.
40Q) If you suspect radioactive contamination in your products, (final or raw materials) what is to be done by you?
A) After, ascertaining that there is a strong case of Radioactive Contamination by measuring with any of the suggested products, you can approach, Atomic Energy Regulatory Board (AERB) in India or appropriate regulatory authority in your country for further help & guidance, who will advice, actually after they inspect, your premises, on what do & how to dispose contaminated material. Please contact Head, Radiological Safety Division, AERB, (Address given below is for Indian customers)
Radiological Safety Division,
Atomic Energy Regulatory Board,
Niyamak Bhavan, Anushaktinagar,
Mumbai 400 094.
Fax : 022-25990650
Mobile : 9820864880
41Q) You have mentioned that for clean sample BG reduces by 15% in your user manual. How did you get this figure? How one should really make meaningful measurements to declare a sample a) Clean, b) Contaminated & c) Suspected contamination case ?
A) Please understand, all our observations made are based on case studies go through website done by us, for identification of Radioactive Contamination (RaC) for three situations a) Clean (b) Contaminated or c) Suspected contamination case. We have clearly mentioned in our case studies, for a clean sample when you touch the sample, background (BG) reduces from its initial value depending of the thickness/mass of the material. If the sample is clean as it is preventing natural background entering the probe the reading will fall, that is the theory.
These case studies were done in Hyderabad, India in Hyderabad BG is 30 µR/hr. we observed this phenomena of BG reducing by more than 15% for all clean samples. In some other locations/cities, BG could be low and reduction BG could be 10% to 15%, even in such cases also the material could be clean. For e.g., in case studies table for sp4 which we have classified as low level contamination, we find that by Radioactive Contamination Analyzer (Bq/gm System) method Bq/g was found to be 0.076 Bq/g which is a permissible level(<0.1 Bq/g). Hence this is a relative comparison and a guide for you to make measurements and arrive at meaningful conclusion. (These are the relative figures). You must understand the logic of making measurements.
Another situation, if it is contaminated to higher levels then reading will go higher than the BG. In which case you can say that the sample is contaminated. In case of low level contamination, reading may remain same as BG or it may fall by upto to 7% than BG, then it is a suspected contamination case. So in this kind of situation it is difficult to identify by Rad check meter some times. May be you can send one kg sample from that heat to our Radio-analytical lab for detailed analysis by our Radioactive Contamination Analyzer (Bq/gm System) which will indicate nuclide type that has contaminated & also quantify in Bq/g (This is a fool proof method)
Please go through our case study reports closely as given in the website, from that you will observe in case of suspected low level contamination the BG fall is relatively less (By 1% to 7.5%). All these case studies were undertaken by Nucleonix Systems with the interest to help the Steel Industry in identifying & tackling the radioactive contamination in their products. It is up to you to use this data for your benefit & advantage. We are not aware whether anybody else has done this kind of case study. You please check up with AERB/BARC on this subject if you wish to know further. Our studies are to help our customers in using our products to identify a contaminated sample.
One can notice from the case studies that as % BG fall, reduces contamination levels in Bq/g increase.
Fair conclusions : We can say that if BG falls by more than 8 to 10% by meeting the mass / size criteria to cover the detector face, then one can conclude that sample is having contamination levels < 0.1 Bq/g which are in acceptable limits. If the BG falls more than 12 to 15% or above then the sample can be declared as clean.
If BG falls 1% to 8% or remains same as BG then it is a suspected contamination case & if the levels are above 0.1 Bq/g then it is a contamination case.
42Q) Allowable limits of contamination being less than 0.1 Bq/gm, where as Rad Check meter measures in µR/hr or nSv/hr mode only?. How one can one correlate or come to conclusion that the contamination is less than 0.1Bq/g? (of course in other European countries acceptable level is less than 0.5Bq/g).
A) This is partly answered in the previous QA 40. We would request you to go through our website, Information about case studies, thoroughly.
Quality Control person has to know how to identify a component as
a) Clean (BG falls more than 12% on contact with sample)
b) Contaminated or (increases more than BG)
c) Suspected contamination case (BG falls marginally up to 8% or remains same on touching the Sample
In (a) & (b) cases, it is easily identifiable by Rad check meter. of course the sample size, thickness, mass criteria etc should be ensured, it should cover the front face of the detector completely when you touch the detector to the component (If the components are small in size, then you can group them to make about 2/3 kg, put them in a plastic pouch & cover complete front face of the detector).
To identify suspected contamination we have also given criteria. In such a situation, by going through our case studies reports & by making proper measurements & analysis one can perhaps say intuitively that contamination is less than 0.1Bq/g. But for exact quantification one has to go through analysis by Radioactive Contamination Analyzer (Bq/gm System) method only. Analysis by Radioactive Contamination Analyzer (Bq/gm System) Bq/g method for exact quantification is 100% authentic & foolproof. In case you encounter suspected contamination case, then you can send such type of suspected samples of about 1 kg from each 'heat” for analysis to our Radio-analytical lab.
Another important thing is all the Steel mills and also the foundries who have furnaces at their factory can purchase Radioactive Contamination Analyzer (Bq/gm System) install it at their QC department, which becomes an important analytical tool. And it will help in identifying & quantifying in Bq/g. Simply what they need to do is from each heat they have to take about one kg sample & put it for analysis to identify and quantify the contamination in bq/g .They can do self certification. As part of their QC. Already more than companies have purchased our systems for this purpose. This they can issue certificate to all their customers when they supply their products (Billets, Bars, flats, Castings etc).