The photon interaction is the transfer of energy to a bound electron, the electron is freed and moves rapidly through the crystal. The electron loses energy through multiple interactions. This total energy is collected as a single pulse that is proportional to the energy deposited. The information is not lost because the transfer to the conduction band is not one transfer, but many. 

The same is true for an NaI crystal except it is the total light produced by the electron passing through the crystal.

I agree with all of the above, but would like to add that it is also about the size of the detection crystal you are using.  The larger the mass, and higher the mean atomic number of the crystal, the greater the probability of actually capturing all of the incident gamma->Compton energy.  A good crystal size depends on the energies of the gammas you are measuring.  Sometimes they are small and can fit in your hand.  These are for detection only, not for spectroscopy really.  The small crystals cannot be used to say much about the emitter, but only that an emitter exists above MDA (minimum detectable activity).  Much larger (several to tens of Kg) are needed to fully contain the energy of a gamma or x-ray.  Ultimately, all of the various photon/electron/atomic excitations become light which is detected by your PMT coupled to the crystal.  The more light the PMT sees, the more energy that was deposited.  This is what becomes the "photoelectrons" signal that goes into the ADC and MCA.  At the end of the day, you don't really worry about the "fudge" factor to normalize MCA channel to energy.  You need to look for standard peaks from given sources to work out your calibration.  This calibration will change over time and temperature, crystal "health" and the thresholds on your electronics, etc.  So a calibration should be done prior to taking any measurement for a given day.

In spectroscopy, there are "false" peaks that also correspond to photons NOT leaving all of the energy in the crystal.  So, yes, some information is lost.  I hope this helps.  My best reference are the following industry-standard texts:  Please read more about this in Glen Knoll's book (chapters 4 &10 of the 3rd ed.), which I refer to below.  He is pretty much the god of radiation detection.

Numero Uno! "Radiation Detection and Measurement", Glen Knoll.  I think he has a later edition than the one I have (3rd).  If you ever go to a IEEE Nuclear Science Symposium meeting, he is likely one of the instructors to teach a unit on radiation detection.  This book is VERY readable and really starts at the beginning.  It assumes you know some calculus and that is about it.

The next reference which is also good, but I am less familiar is: "Measurement and Detection of Radiation" Tsoulfanidis and Landsberger.  It is also on my shelf and has some very good material as well.

I agree with the above. Low energy gamma rays can lose all of their energy in an event where the gamma ray creates a single photoelectron. The probability that a higher energy gamma rays will lose all of its energy as a single photoelectron is very small. Higher energy gamma rays typically undergo many Compton scattering events before they lose enough energy to create a single photoelectron.  Compton scattering occurs when a photon and an electron collide. In Compton scattering, a gamma ray never loses all of its energy. The angular trajectory of a gamma ray changes when scattered, and the amount of energy lost depends on the scattering angle. The larger the scattering angle, the more energy that is lost. A gamma ray that is backscattered by 180 degrees loses the most energy. A gamma ray that's in the detector can be scattered out of the detector, Then only faction of its energy is deposited in the detector and this gamma ray obviously won’t ‘add to the gamma peak. When you view a gamma spectrum, you can see features call Compton edges. The Compton edge corresponds to one 180 degree scattering event where the gamma ray exits the detector before it scatters again. I don’t know if you recall the cold fusion travesty of 1989. Some of Pons and Fleishmann’s gamma spectra contained no Compton edges, a sure sign that what they were observing were not gamma rays from fusion. It was an amateurish mistake.

The simple way of looking at it is that in the ideal world the amount of light generated in a NaI(Tl) crystal or the number of charge carriers formed in a HPGe detector is proportional to the amount of energy delivered to the detector crystal. However due to Compton and other effects not all the energy of the gamma ray is delivered to the crystal, also othe electronics attached are not perfect. A multistage PMT is not always perfectly linear, it can be considered to be a long cascade of class C amplifiers. A danger exists that in such a cascade that the energy of the output pulses will be the same no matter the energy of the pulses which enter the PMT chain.

The great problem with radiometric equipment is that no one detector is perfect for all measurements,

For example

The smaller a Ge crystal the larger the Compton effect will be

The larger a crystal the larger the background due to things like cosmic rays will be

Be careful while Maurizio commnets about the pulse height being proportional to the detected energy, it is important to consider the energy of what. If energy escapes from the detector as a result of X-ray emission, the Compton effect, pair production or the emission of a 512 keV photon which escapes from the crystal then a gamma spectrum will not be a simple single line for a gamma emitter nuclide which emits only photons with one energy.

Also the shortcomings of the electronics can cause funny effects such as summing of two photons, I know someone who put way too much Pu in a LSC vial and ended up with a summing peak from two alpha decays which occured at the same time. I am sure you can get the same effect in gamma spectrometers 

For good energy discrimination preferably every [[ > 99%] photon and resulting products should all be absorbed within the detector volume.

All interactions, be it electrons or resulting photons inn case of a scintillator take place on such a small timescale, that a single pulse results.

A charge amplifier is used to obtain a suitable voltage signal that buffer amplifier can be used to drive an asynchronous sample-and-hold-circuit and subsequently an asynchronous analogue-to-digital convertor circuit. 

The asynchronous sample-and-hold circuit is triggered by any signal exceeeding a [very low] treshold. The a/d convertor is triggered a fixed short time later than the sample and hold, so that the bufferamplifier between sample-and-hold  has had sufficient time to settle.

All Anger-type gamma-camera's use similar circuitries many times over, as part of  the total circuitry  to obtain not only the energy of the absorbed photon but also the location in the crystal [we use crystals up to 50 cm wide with a thickness of 3/8 or 5/8 inch].

Mark Foreman raises a serious point: the phenomenum of simultaneous detection of the effects of multiple photons, which is called pile-up and can be a serious problem in nuclear medicine especially with so-called first-pass studies.

Modern gammacamera's use an advanced trick to deal with pile-up.

One uses active pile-up detection and correction. Instead of some technique to just sample the collected charge in a fixed  time window after triggering, multiple samples in very rapid succession are taken. The results are digitally processed and when the shape of the pulse is strongly suggestive of pile-up, it is rejected entirely. This requires the use of a digital signal processor [DSP].

Some contemporary gammacamera's use 1 DSP per PMT, others one per cluster of [typical] 7 PMT's predominantl;y for this purpose.

Durations of such pulses depend on the time constant of the scintillatormaterial and vary widely. The time constants may vary between 0.6 ns [not clinically used] and > 1 microsecond.

As a result of this phenomenon, such detectors can be paralyzed when exposed to extremily high countrates.

There is no reason why LSC counters would not be equipped with similar anti-pile up circuitry. Such circuits are not perfect, but do allow for a 2 to 5 fold increase in maximum countrate. And as during each pile-up event, the detector cannot detect anything, it is reasonably straightforward to correct for this.

This problem has been soved for gamma-camera systems with over 200 PMT's per head all attached to the same scintillator crystal so I cannot image that pile-up is really that much of a problem for LSC.

We can in NM routinely detect up to 100.000 events per second per camera head, with better than 1 cm positional accuracy and better than 8% [FWHM] energy resolution using NaI and obtain data in list-mode [that is per individual photon: arrival time, location and energy]. It is not practical, but it is perfectly feasable.

If instead a pixelized Ge[Li]  detector system would be used [very, very costly], but otherwise perfectly feasable]  positional accuracies better than 5 mm and countrates per pixel [instead of per large detector in case of NaI] > 50.000 / s would be possible.

Any competent  electronic engineer graduated at university level should be able to design and build practical equipment using the description of the pile-up and sampling circuit described above.  This is certainly not rocket science!!

What should be noted is that in these days most applications for fast ADC's are used in a synchronous mode and this application explicitly calls for asynchronous sample and hold and ADC's.

Thank you all of you for your detailed answer. But my question was, suppose 10keV, 100keV, 1Mev, 1.5Mev gamma ray falls on the HPGe crystal, what they shall do is, deposite its energy (assuming infinitely large crystal) fully on the crystal. Now e-h pair only is in the picture. Hope e-h pair does not carry any info about E of the incident gamma ray.Then E info is lost. Then on what basic at latter stages MCA plots intensity vs gamma ray energy???

The information is not lost because the transfer to the conduction band is not one transfer, but many.

The initial bound electron need not be in the conduction band. This initial electron has all the energy from the photon (photoelectric or Compton). The electron will make many e-h pairs before it is stopped. The total e-h pairs comprises the pulse.

@Joseph L Alvarez

Thank you sir, for the clarification...but it is not fully clear...can you pl give me some reference regarding your answer, so that it will be easy to understand for me.

Most descriptions of the solid-state pulse process rely on an analogy to gas-filled detectors. The process of slowing down the energetic electron produced by the photon interaction produces many electron-ion pairs in the gas or electron-hole pairs in the solid. I have included two references. Here is a quote from one:

"Semiconductor detectors have a P-I-N diode structure in which the intrinsic (I) region is formed by depletion of charge carriers with application of reverse bias across the diode. Gamma rays produce energetic electrons within the depletion region by one of the three processes described earlier [photo, Compton, pair]. As these energetic electrons impart energy to the depletion region, charge carriers (holes and electrons) are freed. The high voltage bias causes the holes and electrons to be swept to the respective collecting electrodes. Figures 1.5 and 1.6 show the production in a semiconductor of electron-hole pairs. This is somewhat analogous to the production of electron-ion pairs in a gas-filled detector. Cooling is necessary to reduce the thermal charge carrier generation (noise) to an acceptable level."

Number of e-h pairs generated depends on the energy of incoming photon and this number is more or less proportional to the signal height.

There is a problem with the pile up detection method which Judocus Borm mentioned, it would work OK for two photons from different atoms / nuclei hitting the detector in a short space of time. But depending on the geometry you can get another form of summing due to two photons being emitted by the same nuclei at the same time. For example Co-60 does a beta decay to an excited state of Ni-60 which emits two photons, if both photons were to hit the Ge crystal and deliver their energy into the crystal then the detected peak would be at the sum of the two (circa 2.5 MeV). The closer the geometry is to a perfect sphere around the sample the more likely this effect is to occur.

As the emission of the photons from an meta stable state can occur very quickly when compared with the speed of the electornics this can cause a problem in well type detectors. One method of checking for it is to change the counting geometry and then see how the ratio of the peaks changes. If the effect is absent then the ratio of the gamma peaks should stay the same assuming that no absorption of photons occurs as they travel from the source to the detector.

@Mark Foreman 

You are quite right.

The pile-up detection circuit I described works fine in gamma-camera's.

Beta's very rarely make it to the actual scintillator and are hence unlikely to be detected.

In Nuclear Medicine, cobalt 60 is certainly  not routinely used at all.

The workhorse for calibration in nuclear medicine is 57Co.

In case of 'floodsources; [plate shaped uniformely coated sources, typically around 50 x 40 cm], shortly after production, high energy photons from shorter-lived contaminants from the cobalt range cause some trouble, so we often have to shelve them for 3 to 6 months, but 60Co is not encountered among them.

The fact that I mentioned Co-60 should not used in your field should not be used as an excuse to discount True Coincidence Summing. TCS is something which is function of detector geometry and the gamma spectrum of the nuclide.

While with Co-57 you are not very likely to see this effect, if you counted for plenty of time there is the potential to get this effect due to the fact that some gamma photons will come in a cascade.

http://atom.kaeri.kr/cgi-bin/decay?Co-57 EC

The worst place I see for potential with TCS is when a person is dealing with an unknown type sample or something which is very out of the ordinary. For example the water samples from the basement of the Fukushima reactor buildings were likely to be samples which were very different to what the radioanayltical person normally deals with.

I know during that event some errors were made, such as false positives for nuclides which were not present. See the paper by

Performance of the True Coincidence Correction Method in GammaVision

Keyser, Ronald M., Haywood, Susan E., and Upp, Daniel L.

ORTEC, PerkinElmer Instruments, Inc.

801 South Illinois Avenue, Oak Ridge, TN 37831

For more details

The trick is that the current produced by the bias voltage loads a condenser but before it, there is a diode connected. This means that the condenser cannot discharge back because the diode allows the current to flow only one way - to the condenser. This simple configuration is called "peak detector". It is not perfect but keeps the stored charge long enough. In the past, the so called Wilkinson-type ADC was used. A source of constant current was "sucking" the charge from the loaded condenser until it was empty. During that time, a gate was open allowing a frequency generator to stream pulses that were counted by a digital counter. A very simple, precise but slow method. Nowadays, the voltage on the peak detector is recorded digitally and analyzed using digital filters of your choice, depending upon your application. Usually there are two extremes: Very fast vs. very precise spectrometry. Read the books of Horowitz or Knoll about nuclear electronics. These are classics of my youth enabling you to understand what is behind instead of buying a black box from a chip manufacturer or NE retailer.

@Mark Foreman  I described one type of pile-up detection circuitry, as is actually used in nuclear medicine, in modern gamma-camera's. I have definitely not suggested that  True Coincidence Summing should be discounted in general.

In imaging equipment in nuclear medicine it plays no role. That is an observation.

We do not need it in imaging equipment, given all other uncertainties we have to deal with. That is my opinion.

Regarding generic acute radiation incidents, in medicine, I always advice against nuclear medicine physicians or technicians to even attempt to determine the isotope / assess the dose.

Whenever people are dealing with radiation and radioactivity and are confronted with a situation that is [potentionally] out of the ordinary, one should be very very carefull if not outright paranoid.

For them [the people in my hospital]  I advise a simple and safe approach:

[Applicable in an in-hospital, not in the field]

To protect themselves : adhere to the 'MRSA'- (clothing) regime, to protect yourselve against internal and external contamination and use a dose-rate meter with adequate energy range to assess the risk of irradiation.

For screening purposes with large numbers of people to screen:

a dose rate meter can be used to detect those that are contaminated to such an extent that they require priority during decontamination

For all else:

use a suitable surface contamination meter, preferable one capable of detecting alpha's

For rapid decontamination: strip the victims first, measure afterwards

For screening large numbers of wipetests etc. in emergencies: use an intrinsic gamma-camera covered with an extremily thin plastic foil, but do not forget to screen for alpha's with the surface meter.

For hospital staff I advice against attemping to use a multichannel analyzer under such circumstances.

These recommendations have been evaluated by a panel of external specialists and have been disseminated among hospitals in The Netherlands.

These recommendations are generic ones, to be overruled by advice from a clinical physicist, preferably after the identity of the isotopes involved has been established. This is sufficient to cover the first hours after any incident.

Most people working with radiation / radioactivty on a day to day basis are not capable of applying their knowledge and equipment in an acute setting to reliable assess dose and isotope involved. All sorts of 'beginners' mistakes will be made.

You raised the issue of the Fukushima incident.

One comment must be given.  Most training given to first responders and workers assumes 'point-contaminations', whereas the more likely pattern is that larger area's and entire objects become contaminated.

In The Netherlands, on my instigation, the training in the army has adopted a more realistic approach: multiple sources and patchy large surface contaminations instead of the more common 'find the single source' type of exercise.

For the acute phase of a large scale radiation incident the ability to detect [not measure, only assess the order of magnitude] is really important and is sufficient to guide self-protection measures. Further refinement [i.e. isotope determination] is beyond the skills of most and should not be relied upon in the acute phase.

In the example situation you referred to, I think only some-one with the skill-level of a clinical physicist should interpret any results from water samples etcetera.

For acute radiation protection measures in the first few hours, such refinements have absolutely no practical value for large scale incidents.

Not because your science is incorrect, but simply because for safety reasons, no assumptions can be made on the reliability.

In my carreer I have seen wel skilled technicians make very serious errors when dealing with samples from external sources in an acute setting on multiple occasions.

That is also why we reduced our demands on staff during acute incidents: the plan now only only includes equipment and procedures that are already embedded in their daily routine and no assumptions are made on their ability to apply their theoretical knowledge outside their daily working field. That has been proven to be unsafe.

We even added another requirement: one should be able to perform basic quality control tests for all such equipment. And I drill them to actually look at details, such as the voltage reading at start-up of battery operated equipment.

In Fukushima, outside the reactor buildings and pools, the concentration of 131I was fairly low, when compared to what we have to deal with in a hospital setting on a daily basis.

A patient with thyroid cancer may void urine, shortly after 131I-treatment, with a concentration of 3 GBq/l.

All our safety training / guidance is based on dealing with such levels. True measurements are not important for this purpose. A good estimate of the order of magnitude suffices. And I can add quite a few anecdotes on where we have found contaminations in this category of patients.

Imagine an 11 month old baby, treated with 7.4 GBq 131I-MIBG and the resulting contaminations.....

I have followed the Fukuchima incident quite closely.

Already in April 2011 I was asked to write about large scale radiation accidents and comment on the Fukushima situation for a dutch journal on radiation protection.

In 2012 the WHO reported on the potential exposure levels if people had not been evacuated, showing that for by far the most of them evacuation would not have been necessary.

In 2013 I have visited the area. I have spoken about it with quite a few Japanese people.

There I found out about the political 'why' behind the evacuation. I have a Japanese document + English translation in my possession, explaining that for internal political reasons, the treshold for evacuation was temporarily lowered to one tenth of the treshold for the expected dose during the first year, here in The Netherlands, or one fifth the treshold dose for Japan at that time.

No life was lost due to radiation. Over 60 people died because of unnecessary and badly-organized evacuations. All of this was not in dutch newspapers, but it was in the Lancet. No journalist noticed any of this. We even had a small conference December 13 2013 in Rotterdam, but it drew very very little attention from journalists.

I have read the english translation of the Japanese parlementary investigation.

Half the truth about Fukushima is left untold. Most of the other half is about politics. The fine details of the art of acurately measuring and modeling the spread of a radioactive contaminations was no more than a footnote hidden amongs reams of paper.

Fukushima is grossly abused for mass-psychological reasons by a number of political groups.

I have hard evidence that a major german magazine was involved in disseminating desinformation about the spread and about the severity of the incident.

I missed several important technical findings about the incident from public litterature or found unnecessary alarming statements about the severity of the damage to the reactors.

In this context, knowing what people actually do with, what we consider facts based in science, I wonder if we sometimes overdo our research.

This discussion has gone far afield from the original concern of the process within the detector to how the circuits handle the pulse. We could discuss all the aspects of gamma spectrometry and go totally off the subject. Why not discuss training of laboratory technicians and first responders and how errors were made regarding Fukushima? Did I miss something?

Joducus raised important points about Fukushima including proper instrumentation. These points deserve a separate discussion so they can get proper notice.

I will add a little off-topic. I performed QA for several laboratories in Japan. I received real-time downloads from their detector systems. I could not keep up with the information and attempted to correct problems that were occurring. Unfortunately, the laboratories were receiving advice from the equipment vendors (sales?). I-131 was still being identified a year after the incident. There were cases of identified Cs-137 and no Cs-134 or the inverse. Samples from the same location had vastly different Cs-134/137 ratios, etc. The results were immediately posted and have not been corrected. I was able to get the laboratories to use libraries and corrections that prevented most of the problems. Imagine the panic every time a new radionuclide was found.

What question should be asked, Joducus?

Dear Joseph,

I´m horrified by your story.

@Joseph L Alvarez

The first weeks hundreds of near real time measurements were reported. Because of complaints, mainly from China and Indonesia, language students were asked on a volunteer basis, to translate tables of measurements and many many documents. What was however not appreciated at that time is that a reported measurement is just a number, if you do not als report the equipement / sampling method / Quality assurance protocolls.

So what the world has seen is translations in up to 18 languages of interpretations by academic laymen [and women] of unstructured data, collected with great effort and the best intention, but interspersed with some seriously erratic data.

In the first 6 weeks after the seaquake I collected hundreds of snapshots from the various websites [I still have them] but could not add them up to a complete picture, because of the poorly coordinated reporting, varying definitions, missing details and conflicting data.

The fist 6 weeks I tried to collect these data in a systematic manner for as far as my routine work [patient care] allowed me to do.

My Japanese is far, far, far from sufficient to read primary documents so I had to do with them by [often] keeping both the Japanese original and a seemingly suitable translation. I have seen a few public corrections, but far too few for these amounts of data obtained under these circumstances and translated by volunteer students.

From the sociological viewpoint, it was quite a special experience. Japan tried to be very open about it all. so much different from the Russians back in 1986.

I will continue my answer later.

This is going to become a very long story.

So I will deliver it in pieces as my spare time allows.

Before continuing on the details of the measurement program, i better start with some material on nuclear reactor integrity.

All of this is in the public domain.

The IAEA has published a lot about the requirements for nuclear reactors in sysmic active area's. The Japanese have done very extensive research, often in cooperation with the americans.

The Japanese had severe troubles because of an earthquake damaging a reactor on their westcost ni -I believe- 2006 or 2007.

Since then a number of reports have been published. The best series is that of Sandia National Laboratories. Just Google on the report number and the word Sandia and you can easily find them:

Report CR6906 gives an overview, but reports 6809 and 6810 expand on them. They contain several impressive illustrations that could [and I believe should] have been used to inform the public better on whatr really happended.

So Google:  CR6906 Sandia    is all reference you need ......... to find a report

In this part I will only refer to the CR6909 report and will only use the pagenumbers on the pages and NOT the pagenumbering of Acrobat.

Please follow me through that document:

Page 15 [acrobat 40/206] Depicts a Mark I Boiling Water reactor very very similar to the ones in Fukushima.

The top picture has been used in lay press articles many times over.

Note here the very light superstructure above the concrete containment, covering the portal crane.

Now skip to page 20 [45/206]

This page depicts a Mark III containment.

Note the "Hydrogen igniters" in the dome of the containment.

Page 24 [49/206]

Tabulates the design pressures of the concrete containments. SI-units seem to be too difficult for the US-citizens.

Anyway: modest pressures can be catastrohic for a concrete containment.

Page 25 refers to several severe accidents on containments, including the Peach Bottom Mark I BWR

Page 35 gives background information on the use of scale models for containment integrity testing.

Page 37 the section with red background gives further explanation of the word 'validating' or 'benchmarking'of codes for containment design.

Pages 47 - 49 give nice pictures of tests on the steel inner vessel destructive testing

Page 54 depicts a typical Japanese steel inner vessel as used for Mark II designs.

Page 55 depicts the Japanese Ohi powerplants. A 1:4 scale model of th enumber 3 reactor was built, as shown on page 77 and tested destructively as shown on page 85.

Why this grand tour of impressive pictures:

This is what has NOT happened in Fukushima !!!!

This is what the designers and constructors of these reactors have not been thanked for. Their design an d construction performed far, far better than what actually was paid for by society.

But no one is gratefull for that!!!  That is a bloody shame. And a bloody shame too that the journalists seem to not have noticed that simple fact.

A dozen nuclear reactors 'survived' an event that far, far exceeded their design specifications. The cores were not scattered or spread over half the globe.

It is like driving a car with a speed of 150 km/h into a concrete block and walking out with a mild concussion......

Most people do not appreciate that the Richter scale used for earthquakes is a logarithmic scale !

A nuclear reactor is like a russion doll: several concentric containments.

The purpose of all these is to ensure that the worst nightmare does not occur. That the contents of the core are not spread around half the globe.

And it worked !!! It worked fine !!!  Much and much better than the russian design containment in Chernobyl ever did. Had they used a Russion doll for their reactors...........

When the fuel could not be cooled, the rods overheated and the zirconium cladding of the fuel elements reacted with the water inside the inner containment. This resulted in the formation of zirconium oxide and hydrogen gas.

To avoid over pressure the hydrogen, together with some radioactive noble gasses and LIMITED amounts of 131I were vented.

In Mark I reactors either no hydrogen igniters were present or their capacity overwhelmed by the massive release of hydrogen [Mark II containments had hydrogen igniters.

The light superstructure of the reactor building was easily knocked off during the exlposions of the hydrogen - air mixture.

[For a nice high quality picture made om march 24 2011 of the damage to reactor 4 in Fukushima: see page 14 of my article

De rol van ziekenhuizen bij de acute afhandeling van grootschalige stralingsongevallen:  Lessen uit Tsjernobyl, de Bijlmer en Japan

The role of hospitals in the acute care in case of large-scale radiation incidents: Lessons from Chernobyl, the Bijmer and Japan      ]

This was a passive safety feature: better blow of the roof of the outer building than damage the concrete containment or the inner steel vessel.

This version of the truth I have never seen in any publication for lay people.

Instead, the German weekly Der Spiegel published on their website a number of forecasts for the direction and spread of any released radioactivity. They updated their forecast.

I have taken out the images [in inter-GIF format] and on March 17 used them when giving a lecture on radiation protection for soon to be senior-radiation-protection-officers.

These images were taken out of the website by others too and I have encountered them on several anti-nuclear websites soon there after.

I give the filenames, so maybe you too can locate some of those copies:

image-191816-galleryV9-nhjp  12-18 march

image-192309-galleryV9-cnoi

image-192309-panoV9free-cnoi [1 frame of the series]

image-192399-galleryV9-ncsf [1 frame of the series]

These images described a release of 0.19E19 Bq of 131I-iodine on March 12th,which was far, far more than was actually released.

These images described [forecasted] that the plume would go predominantly eastward [ranging from north-east to straight soutward]

If one now looks up what the prevailing pattern of spread was in those early days, it is easy to see that something was wrong with the data from Der Spiegel at that time. If one now looks up what is known about the amounts released, it is easy to say that is grossly wrong too.

Was this done ON PURPOSE ???

I cannot tell.

It definitely was desinformation. And was never corrected in public.

It was one of the clearest examples of desinformation I have ever seen in any debate on nuclear energy. And certainly not the only one.

Whenever dealing with any possibly  serious radiation incident:

one has to deal with desinformation

- from the malevolent

- from the benevolent

- from the ignorant

So all measures for self-protection should take that into account.

Virtually nobody is trained for these circumstances

virtually everywhere even the military have been trained only for simulated conditions with a limited number of pointsources at most

these are not the circumstances one would likely encounter during any serious incident.

so any information obtained by anybody, any object obtained from anybody should be regarded with substantial distrust.

< end of part II >

sorry, have to go home  ;-)

If someone thinks this topic should move to a different communication channel feel free to say so. My "off" button sometimes malfunctions.

Regarding the activity levels in nuclear medcine vs a reactor accident scene. I am sure that the water samples from the basement of the damaged reactors at Fukushima was very active. I can not recall the activity level.

While it is important to be aware of the radiation levels on the site while a person works during an accident, I think it is also important to measure some key nuclides. These nuclide measurements are needed to allow someone to work out what is going on in the plant. They will also be needed to allow advice based on scientific reasoning rather than wild guess to be given to the public.

Another problem is that when a cloud of radioactivity is detected it is important to work out what it contains so that some idea of where it came from can be obtained and an idea of what will happen next can be also obtained.

I know that during the Fukushima crisis some errors were made during nuclide identification (http://www.bloomberg.com/news/articles/2011-04-21/tepco-retracts-chlorine-arsenic-findings-at-fukushima-station). What I fail to understand is why the person who detected Cl-38 did not do the simple experiment of leaving the sample to stand for a few hours before repeating the measurement. If I doing the radioanayltical work then if I had seen lots of activity due to a shortlived nuclide which has no long lived parent then I would have confirmed the result by making a measurement of the half life of the short lived nuclide.

@Mark Foreman   You are completely right about the high levels in samples from INSIDE the damaged buildings, but outside it was much, much less.

It is my opinion that measurements inside or in the direct neighbourhood should be performed by wel trained and wel qualified personel using suitable equipment. Outside that rather small area, the skills and equipment normally available on a nuclear medicine department should suffice for covering the first few hours after any large scale radiation incident.

By using these people, one can recruit from a trained and equipped staff thas is already reasonably near site and that is much larger than any specialized army unit can offer. Furthermore these are people already accustomed to dealing with frightened people [most people during work-up for a potential 'cancer-diagnosis' and experiencing their first encounter with nuclear medicine are].

Your example about Cl-38 is completely right and a very important one.

I would like to add another: These days a lot of law-enforcement officers in customs and th epolice are equiped with devices that supposedly can determine the isotopic composition automatically.

Back in 2007, as part of an advanced course in radiation protection [for senior radiation protection officers], all students had to evaluate a whole spectrum of such devices. That was a nice experiment, because this is something you wil likely not do very often in the lifetime of such an officer. So during this 'experiment' the equipment was handled by moderately experienced people with a good theoretical background. Despite this fact, more than half the identifications were grossly wrong.

So, if you have to use any equipment beyond your daily routine: distrust your results. Mistakes do occur and do occur really frequently.

This is also part of  the basis of my recommendation that in case of large scale radiation incidents: do not trust "measurements" from any-one, without validation and confirmation. Use a 'worst-case' approach with regard to self-protection. Keep with facts. Do not mix facts with interpretation, so an expert has a fair change of giving a better interpretation even if he/she is not on site.

This is just one of the kinds of desinformation, mentioned in my previous contribution. It should be taken very very seriously. Because once a public debate starts on whether or not professionals may or may not have made a mistake, mass psychological effects can be quite severe.

Such a thing happened years ago in holland after a plane crash after discussions about burned delpeted uranium. The accident ended with NO radiation victims, but over 5000 people with a post traumatic stress syndrome, because they believed to have been exposed.

Desinformation of any kind can have devastating effects. so any measure of radiation protection should include protection against  mass psychological effects too.

We might be going off on a different direction but I think that the discussion is still worthwhile.

I hold the view that if you are going to give out answers you need to be ready to explain the process by which you came to the answer. For example counting time will be important, as with a low count number the ESD will be much higher.

While it might not seem so exciting to write up your method than it is to get a number from "the machine that goes ping" which backs up your pet theroy. Without the method and access to the raw data the value of a measurement is much less.

@Mark Foreman:

Last night I looked again at all the reports [hundreds!] put on the internet after the Fukushima incident.

Not a single one described equipment or methodology in a useable manner, nor referred to a site / page where such data could be found.

In addition the majority did not report in sufficient detail which organization supervised the measurements [and could afterwards be consulted regarding such details].

Given the various professional organizations present there at that time , many if not most measurements should be reliable, but I can not beleive all the different measurements performed in the different municipalities there were all done by really wel trained people under ideal circumstances and with wel maintained and calibrated equipment.

Nor have I found a public digital repository for all the measurement data with retrospective supplementary metadata.

Your metaphore: "the machine that goes ping" is more than adequate.

Even after March 25, 14 days after the incident, the stream of data went on without explanation and without metadata.

I do not suggest it is all worthless, but its worth would have been considerably higher if a knowledgeable authoriy had [even retrospectively] reviewed the data and the sources.

This is something for a recommendation:

After an incident: have all equipment verified and have all measurements retrospectively scored by experts as to reliability of the raw data and interpretations given.

Most equipment is sufficiently linear and stable to yield usefull data even when all such corrections are being made after the fact.

An energy calibration procedure is needed to associate an energy with each channel of MCA. I.e. learning the MCA with specs of each energy.

Enegy calibration is fullfiled my the mean of standard sources, Co-57 and 60, Cs137 and Am 241 of known energy lines.The MCA is now calibrated and ready to give energy of each photopeak and able to identify radionuclides contained in a sample.