Gamma-Rays Filling Level Inspection


Introduction

ft70 gamma rays med hr

The early fill level inspections were using a small plate of a fast decaying radioisotope, like the Americium, to generate highly penetrating photons named gamma-rays (γ-rays).  Only later, during past twenty-five years, technology progressed to lower energies low-burocracy X-rays. 

Americium-241 is a metal obtained irradiating Plutonium.  We’ll see in the following it is surely the best technology to detect the fill level of non-foaming beverages and that it is today nearly no more used only as a consequence of negative factors only burocratic, not technical.  The spreading of terrorism after 1990 implied side-effects also with respect to fill level technologies. Gamma-rays filling level inspections terminated between its casualties!

Gamma-ray fill level inspection out of a Filler Machine filling carbonated soft-drinks, in an Coca-Cola® Hindustan (Mumbai, India) Packaging Line


Advantages 

Americium-241 emissions. Americium-241, see figure on right side, decays in the element Neptunium-239 via continous and random emission of:

alpha-particles, consisting of two protons and two neutrons bound together into a particle identical to a Helium nucleus;
gamma-rays. 
The Electronic Inspectors for bottles or cans’ fill level inspection, take advantage of the Gamma-Rays emission along four main pathways:  









  1 mm under filling level rejected with hit ratio >99.99 %, extremely high;
  false rejection (false positives FP) ratio <0.01 %, extremely low;
  constant gamma-rays emission along >10 years, say much longer than X-ray generators  limited to (5 - 7) years;
  lowest existing Total Cost of Operation (TCO), when compared to the other kinds of fill level inspection.   Effective Working Life

Americium-241 decays in the element Neptunium-239 via continous random emission of alpha-particles and γ-rays whose energy is 59.6 keV
 Americium-241 decays in the element Neptunium-239 via continous random emission of alpha-particles and gamma-rays whose energy is 59.6 keV.  The half-life of the decay is 432.2 years and it  fully decays along over 2 million years 





“The effective working life of γ-rays sources is 60 years”



The Effective Working Life (EWL) of gamma-rays sources is > 200 years and the period recommended by their Vendors is actually 60 years.  A gamma-rays based equipment must be serviced by licensed gamma-rays' source service providers, i.e., by the Vendors’ staff but it’s a fact that we are speaking of maintenances and services reduced to the same minimum terms of Infra-Red and LASER fill level inspectors.  Along its entire life time a gamma-rays’ fill level inspector sees the Service Technician each several years and always because of common reasons totally unrelated with the radioisotope.  A few examples of these causes: rejectors’ pneumatics and mechanics maintenance and repair, fine-adjustment of the Shifting-Register dependant parameters, replacement of electronic cards, etc. 

When comparing these with the common High Frequency fill level inspection intervals, it is immediately discovered that the γ-rays (gamma-rays) inspectors rank highest: they have the lowest Total Cost of Operation, jointly with IR and LASER. Finally, when comparing γ-rays (gamma-rays), IR and LASER in terms of inspection performances (size of the defect and associated false rejects), it is discovered that γ-rays are the best fill level inspection at all.  Americium-241 based inspection devices use low energy radiation for inspection. The radiation level outside of the machines is less than 0.05 mrem/hour. The regulatory limit for exposure of the public is 40 times greater at 2 mrem in an hour, or 100 mrem in a year above natural background.   Thus, no special precautions are needed when working with gamma-rays inspection machines.  

To have an idea: 

a person in the US is commonly exposed to 620 mrem a year from natural background; 
a single tomographic scan exposes a patient to 200 to 2000 mrem of radiation.

Americium-241 (see figure on right side) decays in the element Neptunium-239 via continous, random emission of:

  • alpha-particles, consisting of two protons and two neutrons bound together into a particle identical to a Helium nucleus;
  • gamma-rays. 

The Electronic Inspectors for bottles or cans’ fill level inspection, take advantage of the Gamma-Rays emission along four main pathways:  

 Americium-241 emission is a mix of material particles and high-energy photons, like the Gamma-Rays

  1.   1.0 mm under filling level rejected with hit ratio >99.99 %, extremely high;
  2.   false rejection (false positives FP) ratio < 0.01 %, extremely low;
  3.   constant gamma-rays' emission along > 10 years, say much longer than X-ray generators limited to (5 - 7) years;
  4.   lowest existing Total Cost of Operation (TCO), when compared to the other kinds of fill level inspection


Effective Working Life

Americium-241 decay. Americium-241 decays in the element Neptunium-239 via continous random emission of alpha-particles and gamma-rays whose energy is 59.6 keV.  The half-life of the decay is 432.2 years and it  fully decays along over 2 million years

 Americium-241 decays in the element Neptunium-239 via continous random emission of alpha-particles and gamma-rays whose energy is 59.6 keV.  The half-life of the decay is 432.2 years and it  fully decays along over 2 million years 


“The effective working life of γ-rays sources is 60 years”

The Effective Working Life (EWL) of gamma-rays sources is > 200 years but the period recommended by their Vendors is ~ 60 years.  A gamma-rays based equipment must be serviced by licensed gamma-rays' source service providers, i.e., by the Vendors’ staff but it’s a fact that we are speaking of maintenances and services reduced to the same minimum terms of Infra-Red and LASER fill level inspectors. Along its entire life time a gamma-rays’ fill level inspector sees the Service Technician each several years and always because of common reasons totally unrelated with the radioisotope. A few examples of these causes: rejectors’ pneumatics and mechanics maintenance and repair, fine-adjustment of the Shifting-Register dependant parameters, replacement of electronic cards, etc. Comparing these with the common High Frequency fill level inspection intervals, it is immediately discovered that the gamma-rays inspectors rank highest: they have the lowest Total Cost of Operation, jointly with IR and LASER.   

Finally, when comparing gamma-rays, IR and LASER in terms of inspection performances (size of the defect and associated false rejects), it is discovered that gamma-rays are the best fill level inspection at all. Americium-241 based inspection devices use low energy radiation for inspection. The radiation level outside of the machines is less than 0.05 mrem/hour. The regulatory limit for exposure of the public is 40 times greater at 2 mrem in an hour, or 100 mrem in a year above natural background. Thus, no special precautions are needed when working with gamma-rays inspection machines.  To have an idea: 

  • a person in the US is commonly exposed to 620 mrem a year from natural background; 
  • a single tomographic scan exposes a patient to 200 to 2000 mrem of radiation.
gamma-ray-inspector-tag med


More, during normal operation, gamma-rays based systems do not pose a safety risk. Americium-241 used in gamma sources is fused into a solid ceramic and sealed in a stainless steel housing, designed to withstand the temperatures associated to any industrial fire.  The stainless steel housing is designed to withstand pressures ~7000 psi. The helium release builds pressure to only 30 psi over a 60 year recommended working life.   This is less than 0.04% of the pressure that the housing that holds the source.  The housing itself is designed to withstand, implying that the helium gas that the Americium-241 source emits could not cause a breach othe stainless steel.  

Americium is a byproduct of the operation of nuclear power reactors and is recycled from nuclear waste.  This byproduct is primarily encountered present in the home smoke detectors and a much smaller amount is used in our industrial inspection applications. When in normal use in the electronic inspector, there is no danger to employees' health and safety.  The radiation source cannot be turned off: if there is a need, it is however very simple to eliminate the radiation  closing the manual shutter. 




Why Gamma-Rays Outperforms all other Technologies?


“If the γ-rays fill level inspection is applied to the inspection of cans, PET or glass bottles, the resolution is 1 mm and associated to a false reject ratio < 99.99 %”



The answer to the question in the title of this section is implicit in the special extremal position of the Gamma-Rays with respect to the other technologies:

  • X-rays;
  • Optic, with camera;
  • LASER;
  • Infrared (IR);
  • High Frequency (HF).

Applying Plack’s law we discover that each individual gamma-photon is approximately ten times more energetic than a X-photon.   A huge packet of energy: one capable to cross a block of solid steel whose thickness is several centimetres.   A packet of energy so big to result intrinsically independent on environmental conditions.  

x-ray-ir-and-hf-energy med

 Benchmark of four different fill level technologies. Gamma-rays, X-rays, Infra Red (IR) and High Frequency (HF) in the electromagnetic spectrum, based on the energies involved by mean of the  E  =  hν fundamental formula, where  v  =  c / λ,  c speed of propagation of em waves in the vacuum,   λ wave length,  ν frequency,  h  Planck's constant,  E energy of the photon.     In the case of the Bottling Controls the energy of a single gamma-ray photon results eleven order of magnitudes greater than that associated to an High Frequency (HF) at 21 MHz, minimising the false rejects rates related to ambient conditions’ fluctuations (image adapted under Creative Commons 3.0)


























If we compare it with the High Frequency (HF), we see immediately that the energy of gamma photons result eleven orders of magnitudes greater than that associated to an High Frequency (~21 MHz) photons.  Thus zeroing the false rejects rates related to ambient and beverage conditions’ fluctuations. What above is just an intuitive explanation, making use of laymen language. The deeper explanation starts by the standpoint that a measurement, whatever measurement, happens always and only after a single correlated state of two physical systems is established.   In our present case, to definetely perceive a correlated Liquid-Gamma Rays Inspection State, they are necessary:

  1. Timeto transform the previous state, in which all possible kinds of correlation of the Gamma-Rays’ Inspection solid state detector coexist, in a following state in which the Inspection is “aware” to be correlated to a Liquid, because having recorded eigenvalues for the eigenfunction ΦiS1 describing a certain level of a Liquid.   The correlation between the two systems, Inspection and Liquid, is progressively established during interaction and proportional to the natural logarithm (ln t) of the interaction time t.   An ideal correlation, one corresponding to a maximised information of the Inspection about the level of the Liquid, can only be reached allowing an infinite time.   The fact we cannot wait for an infinite time causes the measurements’ fluctuations, a synonimous of the spectrum of the eigenvalues, resulting in the Electronic Inspector's false positives (false rejects).    Time, for what ?    To transform the previous state, in which all possible kinds of correlation (superpositions) of the Inspection coexist, in a following state in which a subset of all the pixels defining the level in the solid state detector of the Inspection are aware to be correlated to a Liquid, because having recorded eigenvalues for the eigenfunction ΦiS1 describing the macromolecular Hydrogen-bond we name “Liquid”.   
  2. Interaction between the systems such that the Information in the marginal distribution of the object inspected is never decreased.   In a probability distribution deriving by two random variables, we remember that marginal distribution is where we are only interested in one of them.   Otherwise, we’d have forced a reduction in the sample space of one of the random variables and then, we could not have any more repeatability of the measurements.    As an example, this should be the case if we’d erroneously try to use a beam of high energy neutrons rather than Gamma-Rays, to interact with the beverage.   The neutrons should modify the molecular structure of the liquid, modifying its eigenstates and then the eigenvalues we expected to derive by the measurement.


Kegs' Gamma-Rays Inspection



Today, kegs' fill level inspection is probably the application where γ-ray fill level inspection shows its best in the Beverage Packaging.  Its constant radiation assures virtually no necessity for periodic readjustments of sensitivity, also in presence of thick stainless steel containers and masses of liquid to cross. 

  Today kegs' fill level inspection is probably the application where gamma-rays fill level inspection is allowed to continue to show its many advantages. Its constant radiation assures virtually no necessity for periodic readjustments of sensitivity, also in presence of thick stainless steel containers and masses of liquid to cross like those visible in this image (courtesy Straub Brewery, 2014)




The use of gamma-rays is necessary in order to have enough energy to penetrate the thick steel of beer kegs, leaving an amount of them outfeeding. An amount which, in conditions of keg's underfilling, has to be still high enough to evidentiate the change (a dip) when, on the opposite, the keg is correctly filled until that level. This technology allows a resolution of the measurement which, because of the kegs’ dimensions, results limited to ~5 mm. 

Ask yourself:

Front of so many evident advantages, why the Gamma-Rays Inspection technology would disappear?   

  Nuclear pit, in a tamper hemisphere (picture Federation of American Scientists/2014 )










After September 11, 2001 and other events the optimal technology to inspect the filling level of whatever non-foaming beverage has been condemned to oblivion. Along past twenty years the Companies adopting gamma-rays devices had been compelled to live trapped in a web of legal requirements, in terms of:

  • maintenance of a safe operating and emergency procedures policy,
  • designation of a responsible person for maintaining machine documentation and having knowledge of safety procedures related to use of the equipment,
  • registration of the devices and periodic testing of safety features,
  • many legislations have requirements to move a gamma-ray device,
  • decommissioning requirements: when a device is no longer needed or in use, the manufacturer should be notified.

A web of regulations and limits translating themselves in extracosts to be paid by a Bottling Company after deciding to use it in a Food and Beverage Bottling Line. 


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