6th International Summer School 2014, Ispra, Italy Methods for radiological characterisation 6th International Summer School on Operational issues in radioactive waste management and nuclear decommissioning, JRC Ispra, 8 – 12/9/2014 Dr. Petr Londyn, Petr Kovarik 10.9.2014 1
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6th International Summer School 2014, Ispra, Italy
Methods for radiologicalcharacterisation
6th International Summer School on Operational issue s in radioactive waste management and nuclear decommissioning, JRC Ispra, 8 – 12/9/2014
Dr. Petr Londyn, Petr Kovarik10.9.2014
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6th International Summer School 2014, Ispra, Italy
Presentation outline
� Radiological characterisation
� Methods for radiological characterisation
� Measuring systems - examples
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6th International Summer School 2014, Ispra, Italy
Radiological characterisation
What is the radiological characterisation?
The radiological characterisation is the knowledge of:
where is the activity?on the surface of components, structures?
fixed?can be wiped (lose)?
inside the material?contamination (how deep, distribution ...)induced radioactivity (how deep, distribution ...)can be easy release by mechanical dividing (tritium )?
which nuclides?
dose rate in the vicinity of the contaminated materi al / device (radiation safety)?
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6th International Summer School 2014, Ispra, Italy
Radiological characterisation
The radiological characterisation includes:• collection and review of historical file
• performing calculation of radionuclide inventory from historical information
• in situ measurement
• sampling
• laboratory measurement
• review and evaluation of the data obtained
• comparison of the calculated result with measured value etc.
Why we need the radiological characterisation?Radiological characterisation is very important for each decommissioning and waste management project.
It is relevant for all phases of decommissioning an d should be started as early as possible.
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6th International Summer School 2014, Ispra, Italy
1. For assembling the decommissioning plan2. For radiological protection3. For selection of suitable methods
• of disassembling the equipment• of cutting objects (most suitable segmenting techni ques)
4. For continuous refinement of the decommissioning plan5. For estimation the quantity, form and activity of waste6. For cost estimation
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Timeline of radiological measurements:
1. Before decommissioning2. During the decommissioning3. After decommissioning
area + radioactive waste measuring (for storing / r eleasing)
6th International Summer School 2014, Ispra, Italy
Documents
Several documents that describe the sampling and me asurement methods, evaluation procedures, quality assurance and other relevant issues:
� Multi Agency Radiation Survey and Site Investigatio n Manual (MARSSIM), � Multi-Agency Radiation Survey and Assessment of Mat erials and Equipment
Manual (MARSAME) � Environmental Radiation Survey and Site Execution M anual (EURSSEM)
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International Atomic Energy Agency (IAEA) Safety St andards for decommissioning:
� The Joint Convention on the safety of radioactive w aste management – 1 (2)� Decommissioning of Nuclear Power Plants and Researc h Reactors – WS-G-2.1� Decommissioning of Medical, Industrial and Research Facilities – WS-G-2.2� Decommissioning of Nuclear Fuel Cycle Facilities – W S-G-2.4� Safety Assessment for the Decommissioning of Facili ties Using Radioactive Material – WS-G-5.2� Decommissioning of Facilities Using Radioactive Mat erial – WS-R-5� Decommissioning of Facilities Using NORM (planned)
........
6th International Summer School 2014, Ispra, Italy
3. Gamma scanning4. Gamma imaging camera (distribution activity with picture)
5. Gamma spectrometric measurement (nuclide specific measurement)
For example, a simple radiation dose rate measurement will give an indication of the total quantity of gamma emitting radionuclides, but will not identify the individual radionuclides or their concentrations.
Gamma spectroscopy will identify the individual radionuclides and, when properly calibrated, their quantities as well.
complexity
6th International Summer School 2014, Ispra, Italy
Dose rate measurement
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Especially for the radiation protection of the work ers, localization of hot-spots
Measuring range: from background to 1 Sv/h (10 Sv/h )
Teleprobe (up to 4 meters distance) for difficult accessible placesfor sources with high activity (with high dose rate )
Frequently used monitors:Dose Rate Meter 6150AD, FH 40 G
6th International Summer School 2014, Ispra, Italy
Dose rate measurement
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6150D
FH 40 G
6150D with external probe
IF 104
6th International Summer School 2014, Ispra, Italy
Surface contamination measurements
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Measurement of surface contamination is an importan t aspect of the decommissioning. From the measured data, it is poss ible to decide on the protection of workers and to prevent the unacce ptable discharges to the environment.
Hand held instruments are mainly used for direct me asurement of:gross alpha surface activitygross beta / gamma surface activity
Detectors: Proportional counter tube Gas flow counting tube - butan, counting gas P10 (A r + methan)Xenon counter tube - permanent fillingScintillation detectors – thin layer plastic scintil lator with ZnS/Ag-coating
Important parameters: counting sensitivity for alpha and betadetection area (100 – 170 cm2)distinguish between alpha and beta particles (gamma radiation)very low sensitivity to gamma radiationsmall massdetector resistance against damage (tearing of foi l detector)
6th International Summer School 2014, Ispra, Italy
Surface contamination measurements - monitors
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Measurement of surface contamination is an importan t aspect of the decommissioning. From the measured data, it is poss ible to decide on the protection of workers and to prevent the unacce ptable discharges to the environment.
6th International Summer School 2014, Ispra, Italy
Surface contamination measurements - monitors
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FHT 111M – Contamat CoMo 170 – troley for floor measurement
Electra – survey meter DP6 Alpha-beta probe
Large area alpha / beta detector + GPS
6th International Summer School 2014, Ispra, Italy
Surface contamination measurements - monitors
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Large-area gamma detector PL 525
Detector surface: 525 cm2 Basic versi on detector lift Maximum high approx. 5 m
6th International Summer School 2014, Ispra, Italy
Gamma scanning
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Gamma scanning provides relevant information to the contamination of the object.
A scintillation detector is usually used.
Its sensitivity (the size of a crystal in the detector) is chos en so as thestatistical error by counting of impulses will be sufficien tly small.
When performing gamma scanning:
a) the detector moves in a specified height by a fixed speed above the surfaceb) the detector is gradually placed into individual points of measurement
For reducing the impact of surrounding radioactive sources the detector is inserted into shielding (most commonly lead collima tor).
6th International Summer School 2014, Ispra, Italy
Gamma imaging – RadScan 800
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RadScan 800
Detection head, pan / tilt unit, tripod Look inside the detection head
6th International Summer School 2014, Ispra, Italy
Gamma imaging – RadScan 800
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detector NaI(Tl)10 x 16 mm
photomultiplier
Shielded scintillation detector of RadScan 800angle 2 degrees
for high angular resolution
Kolimátor - 2 stupně - EN.vsd
steel collimator2 degrees
tungsten shieldingro = 19,3 g/cm3
angle 2 degrees
6th International Summer School 2014, Ispra, Italy
Gamma imaging – RadScan 800
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The gamma imaging system collects data on a predefined array of measurementpoints. The detection head is moved to appropriate pan and ti lt position, gammaspectrum is acquired for the user defined dwell time.
6th International Summer School 2014, Ispra, Italy
Gamma imaging – RadScan 800 – gamma snaps
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Measurement at EC JEC Ispra – building: 20a pipe line: L0008 8001 BS0020 above the tank VB0020 range: 4,5 m collimator: 3 degree scan time = 200 s count rate for Cs-137: max. 1,9 cps,
contact dose rate: 1 010 µSv/h
6th International Summer School 2014, Ispra, Italy
Gamma imaging – Cartogam
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Gamma imaging camera CARTOGAM uses the results of the development of the gamma camera in nuclear medicine.
6th International Summer School 2014, Ispra, Italy
Gamma imaging – Cartogam
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6th International Summer School 2014, Ispra, Italy
Gamma imaging – Cartogam
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New generation – model GAMPIX:� less weight� higher sensitivity� lower price
6th International Summer School 2014, Ispra, Italy
Gamma spectrometric measurement - info
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In-situ gamma spectrometric method takes advantage of the f act that manyradionuclides during its conversion emit gamma photons. Th ese gammaphotons have energy typical for each radionuclide.
It is possible to determine the activity of gamma r adionuclides
• in solid and liquid substances• on a surface of the objects (from simple to rela tively complex shapes)• inside materials• on large surfaces (on the floor, on the walls, in t he open field ....)
Stage of measurement: 1st stage uncollimated detector2nd stage collimated detector
6th International Summer School 2014, Ispra, Italy
Gamma spectrometric measurement - hardware
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In-situ gamma spectroscopy system consists of:� detector (scintillation, semiconductor)
� shielding (collimator)
� electronic unit (high voltage power supply, preamp lifier ....)
� analog to digital converter (ADC) / digital signal processing (DSP)
� multichannel analyzer
� evaluation unit (NB, PC) with gamma spectrometry S W
6th International Summer School 2014, Ispra, Italy
Gamma spectrometric measurement - calibration
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The calibration is performed using:• radioactive standards• calculations (SW: MicroShield, ISOCS, Monte Carlo – MCNP)
Gamma spectrometric measurement ranks among the so-called relativemeasurements. For each geometry of the measurement, a calib ration shouldbe performed.
6th International Summer School 2014, Ispra, Italy
Low resolution gamma spectrometry
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As the name says, by low resolution gamma spectrometry, dete ctors with
relatively low energy resolution are used. That brings prob lems with the
interpretation of the measured data, but on the other hand, i t is a cheap and
commercially available device.
For the detection of gamma photons, so called scintillation detectors are
used. The most widespread is the detector with NaI/Tl (CsI/T l).
Recently, new scintillation materials (lanthan bromide - L aBr3/Ce, cadmium
zinc telurid - CdZnTe, ...) begin to be used. They have a better energy
resolution, but the disadvantage is their high price.
6th International Summer School 2014, Ispra, Italy
6th International Summer School 2014, Ispra, Italy
High resolution gamma spectrometry
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Comparison of HPGe detector with scintillation detectors:• Better energy resolution• Needs cooling to the temperature of liquid nitrogen (-196 de gree of C)• Less sensitive (small volume of the crystal)• More expensive
Using in-situ high resolution gamma spectrometry, almost a ll theradionuclides emitting gamma photons can be detected.
For the measurement a semiconductor detector is used (today almostexclusively from high purity germanium - HPGe).
Equipment cost:HPGe detector (high efficency, small Dewar, liquid nitrogen cooling), multichannel analyzer, SW cca 60 k€
Cooling:For cooling of HPGe detector, liquid nitrogen is mainly used. Recently, detectors with electrically cooledHPGe crystal are more and more used (the most commonly by Stirling´s cooler).
6th International Summer School 2014, Ispra, Italy
High resolution gamma spectrometry - example
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In-situ object counting system (ISOCS):
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High resolution gamma spectrometry – Micro-DEtective HX
6th International Summer School 2014, Ispra, Italy
Radiological laboratory analysis
(Destructive analysis – DA)
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Methods for radiological characterisation
6th International Summer School 2014, Ispra, Italy
Radiological laboratory analysis
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Some examples:
In the vicinity of the measured object is another o bject with significantly higher activity (it cannot be removed, shielded).
We want to determine the distribution of activity i nside the material.
A number of radionuclides emit during its conversio n such a radiation that cannot be measured directly, and it is necessary to perform the radioc hemical separation. These radionuclides are called "hard to detect” radionuclides – HTD or “difficult t o measure” - DTM.
There are several reasons why it is necessary to ma ke some measurements
in the laboratory:� high radiation background in the place where you wa nt to determine the
concentration of radionuclides
� bad geometry for measurement
� inaccessible place for in-situ measurement
� in-situ measuring systems do not measure some radio nuclides
6th International Summer School 2014, Ispra, Italy
Radiological laboratory analysis – important radionuclides
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Laboratory destructive analyses for common radionuc lides
Mass spectrometry U-233, U-234, U-236, U-238, Pu-238, Pu-239, Pu-241, Pu-242
Typical preparation time before measurement: from hours to daysTypical counting time: from hours to daysPrice to detect one radionuclide between 100 and 300 €
6th International Summer School 2014, Ispra, Italy
Radiological laboratory analysis – alpha emitters
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The most commonly used instruments to detect of alp ha radiation is alpha spectrometer:
� silicon detector� evacuated counting chamber� power supply� amplifier� analog to digital converter� multichannel analyzer� computer� SW
Measurement often requires:� complex chemical separation � special sample preparation before alpha counting
6th International Summer School 2014, Ispra, Italy
Radiological laboratory analysis – beta emitters
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The most commonly used instruments to detect of beta radiati on is a liquidscintillation spectrometer.
Usually, it is necessary to carry out the chemical separatio n of theradionuclide.
6th International Summer School 2014, Ispra, Italy
Radiological laboratory analysis – low energy gamma emitters
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Some radionuclides emit gamma photons with very low energy d uring theirconversion.
For the detection of these photons it is necessary to use a spe cialsemiconductor detector (entrance window is made from a mate rial with asmall absorption – carbon fiber, ion-implantated contact o n the HPGecrystal).
6th International Summer School 2014, Ispra, Italy
Radiological laboratory analysis – gamma emitters
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Gamma spectroscopy:Gamma spectrometry in laboratory is used to define isotopic composition of materials.
The sample together with the detector is inside the high-quality shielding.
The advantage of this method is that a very low det ection limit can be reached.
6th International Summer School 2014, Ispra, Italy
Radiological laboratory analysis – ICP-MS
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Inductively Coupled Plasma – Mass Spectrometry (ICP-MS)
Principle:
The solution with the isotopes is sprayed into flowing inert gas (argon) and passedinto a torch which is inductively heated to approximately 10 000 ºC.
At this temperature, the gas and almost all components are at omized and ionized,forming a plasma which provides a rich source of both excited and atomized atoms.
Positive ions in the plasma are focused down a quadrupole mas s spectrometer.
Data can be obtained for almost the entire periodic table jus t in minutes with detectionlimit 0,1 µg/L (0,1 ppb).
It is possible to measure radioactive and stable elements.
The measurement of some elements is complicated by interfer ence.
For some elements, calibration standards are not available .
6th International Summer School 2014, Ispra, Italy
Scaling factor - SF
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Laboratory methods are much time consuming and more expensi ve thandirect methods. Therefore, it is an effort to reduce the amou nt of laboratoryanalyses.
The SF method was developed from operating experiences at nu clear powerplants for low and intermediate level radioactive waste.
The SF method is a technique for evaluating the concentratio n of difficult tomeasure (DTM) nuclides which are typically represented by b eta and alphaemitting nuclides, such as C-14, Ni-63, Pu-240 ......
The scaling factor is the ratio of the concentration between DTM nuclide andeasy to measure (ETM) nuclide (key nuclides: Co-60, Cs-137)
Other information in the document: IAEA No. NW-T-1.18 “Determination and Use of Scaling Factors for Waste Characterizationin Nuclear Power Plants”.
6th International Summer School 2014, Ispra, Italy
Scaling factor - SF
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The use of scaling factor:
1. the determination of the scaling factor (correla tion factor)2. determine the concentration of easy to measure n uclide 3. calculate the concentration of radionuclide diff icult to measure
CDTM = SFDTM * CETM
Scaling factor – Ni-63 to Co-60 – NPP Dukovany
sludge steel
6th International Summer School 2014, Ispra, Italy
Measurement ofwaste packages
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Methods for radiological characterisation
6th International Summer School 2014, Ispra, Italy
Measurement of waste package
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The reason for the measurement:
Prevent the release of material with significantly higher activity than the other material.
Gamma Excavation Monitor (GEM)
Gamma Excavation Monitor (GEM) is a gross gamma system capab le of real-time assay ofexcavated materials in support of clearance initiatives. T he bulk monitoring system has gainedEnvironment Agency approval for effective material segreg ation of volumes up to 1m 3.
6th International Summer School 2014, Ispra, Italy
Measurement of waste package – total gamma measuring
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Total gamma measuring
You need a good knowledge of nuclide composition (different gamma photons emissions forindividual nuclides, different energy of photons).
Measuring systems with 24 plastic scintillations detector s.
6th International Summer School 2014, Ispra, Italy
Measurement of waste package – nuclide specific measurement
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High Resolution Assay Monitor (producer NUKEM UK)
This trailer-mounted system is designed for the on-site ass ay of waste materials, is easilytransportable and can remain on site during the measurement campaign.
6th International Summer School 2014, Ispra, Italy
Measurement of waste package – nuclide specific measurement
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HiRAM – result of measurement, using of scale factor for difficult to measure nuclides
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Measurement of waste package – nuclide specific measurement
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Drum measuringOne HPGe detector – scanning systemMeasuring before sending to disposal site at NPP Dukovany
6th International Summer School 2014, Ispra, Italy
Measurement of waste package – nuclide specific measurement
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Drum measuring3 HPGe detectorsMeasuring before sending to Radioactive waste depository a t NPP Dukovany
6th International Summer School 2014, Ispra, Italy
Measurement of waste package – nuclide specific measurement
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Characterization of Waste at NPP Dukovany Prepared F or Incineration(at Studsvik, Sweden)
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The reason for the measurement:
Prevent the release of the material with an activity that exceeds the free release level.3 HPGe detectors – 10 cm lead shielding - measuring before sending to landfill disposal
Measurement of waste package – free release measurement
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MUM – advanced free release measurement facility
Prototype of unified Europe wide FRM methodology system.
� Low-background measuring tunnel;
� 4 HPGe Interchangeable Detector Modules with lead collimators;
� Conveyor for moving the measuring container;
� 4 measuring containers;
� Air-conditioning and filtration unit for measuring tunnel.
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MUM – advanced free release measurement facility
Key advantages: � Easy, dry and clean construction.
� Modular construction system.
� Self-supporting construction.
� Cheap production
Internal content of
radionuclides:
K-40 10.6 Bq/kg
Ra-226 1 Bq/kg
Th-228 0.7 Bq/kg
Low – background concrete like shielding material.High density material – bulk density in the interval 2 300 – 3 250 kg/m3
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Metrology for decommissioning nuclear facilities
EMRP SRT-v19 project
Start in the half of 2014.
�Radionuclide characterization of materials present on decommissioning sites, automatedradiochemical analysis
�Preselection of waste into streams (repository or potential free release)
�Implementation of ‘free release measurement facility‘ on decommissioning site, scanning ofheterogeneous wastes
�Monitoring in radwaste repositories and decommissioning sites
�Calibration reference materials and standard sources
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