monitoring and measurement approaches · radon/radon progeny concentration, ... lims: laboratory...

P. Schmidt, Wismut GmbH Chemnitz, Germany Head of Department of Env. Monitoring and Radiation Protection

Monitoring and Measurement Approaches

IAEA Training Course on Remedaition Infrastructure, Chemnitz, Germany, Dec. 3-7, 2012

Vorführender

Präsentationsnotizen

Das Titelbild kann ausgetauscht werden

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Structure of module • Theory: What can we learn from IAEA / ICRP

• Strategy to develop a site-specific monitoring plan

• Life cycle of a site-specific monitoring plan • Parameters to be measured during different states of a site specific monitoring plan

• Some general principles for the development of a site specific monitoring plan

• Case study WISMUT, incl. measurement approaches and QA/QC

P. Schmidt, Monitoring and Measurement Approaches

IAEA Training Course on Remediation Infrastructure, Chemnitz, Germany, Dec. 3-7, 2012

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Theory: P. Schmidt, Monitoring and Measurement Approaches


ICRP 43 (1984): Principles of Monitoring for the Radiation Protection of the Population

IAEA (2005): Environmental and Source Monitoring for Purposes of Rad. Protection, IAEA Saftey Standard Series No. RS-G-1.8

Source Monitoring

Environmental Monitoring

Individual Monitoring

Personal-related environmental Monitoring / baseline monitoring Measurement: along environmental media at sites of the critical group

Source-related environmental monitoring (“fence” measurements)

Operation monitoring; remediation monitoring; Check of sealing functions

Dosimetry, working place measurements

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Strategy to develop a site-specific monito-ring plan

Agree on goal of the monitoring task to be solved see also life cycle of a monitoring system

Top-down approach historical research (documents) screening measurements (gamma dose rate, sampling in a coarse meshed grid, aerial gamma screening) identify the scope of contamination, the area of concern, the objects of relevance of your site



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Top-down approach (cont.) Identify critical objects (objects with relevant environmental impact) Identify the critical exposure pathways • Exposure pathway analysis

• Identification of the dominating ways of dispersion of contaminants (geological studies, hydrological modelling)

Identify the critical group of exposure Identify the best-suitable hard and software for measurement

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Top-down approach (cont.) Identify site-specific conditions that might have an impact on your monitoring system • accessibility to the sites (local infrastructure) • potential partners (external labs, QA/QC partner)

Take the natural background into account • Base line studies available ?, Bgrd measurements

Recognise the relevant regulatory conditions for implementation of a monitoring system • Laws, recommendations, requirements regarding

reporting/record keeping, QA/QC requirements

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Establish your program



Goal Description of the site Field: Measurement points, parameters to be measured Lab: Field sampling / Parameters to be measured Intervals QA/QC program Responsible person Reporting, record keeping

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Life Cycle of a Monitoring System for Existing Exposure Situations

Existing Situations Exposure situation

Site investigation; Pre-remediation Monitoring

Goal

Stage

Remediation Monitoring

Post-remediation Monitoring

• monitoring after termination of physical remediation work

• long-term monitoring

time

Number of measurement

time

• Site characterisation • data base to decide on justification of remediation • data base for modelling, identification of optimised remedial measures

• proof of remediation success (technical barriers, covers) • demonstration of long-term stability of the remedial measures) • political aspects (stakeholder expectations, concerns of the local public; epidemiological studies, etc.))

• assessment of the environm. impact of measures (environment, local public) • surveillance of workers (dosimetry etc)



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Same pictures / examples / remarks / hints / etc.



10 P. Schmidt, Monitoring and Measurement Approaches


Getting started:

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Parameters to be measured (1) Air

Ambient dose äquivalent rate H*(10) Dust / dust fallout Noise Radioactivity (ll alphas, nuclide-specific concentrations, radon, radon progenies [attached/unattached], AMAD)

Water monitoring (surface, groundwater, seepage, releases) Water levels Field parameters (T, pH, Eh, redox potential, turbitity) Radiological parameter (key nuclides, complete nuclide vector: Chemo-toxic parameters, salinity, metals (As, Ni, Cu, Mn, Fe)

Soil Specific activities, concentration of non-radioactive substances

Biota Specific activities, concentration of non-radioactive substances



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Parameters to be measured (2) P. Schmidt, Monitoring and Measurement Approaches


Operational Monitoring (water treatment plants) Releases (volumes, radioactivity [load, concentrations], other hazardous substances [load, concentrations]) Parameters governing technological processes Parameters characterizing residues

Individual dosimetry, hygienic working conditions Radiological parameters • Personal doese equivalent, penetrating Hp(10) • Radon/radon progeny concentration, equilibrium factor, AMAD, attached/unattached Rn progenies • Long-lived alpha emitters (dust-born) Air quality • Dust • Aerosols (gases) Noise

Geotechnical parameters Seismic parameters, levels, settlements,

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Some general aspects and examples of measurements a) The monitoring is site specific as well as object specific, not static

and it is subject to regular amendments/optimizations

b) Distinction has to be made between the basic monitoring (baseline measurements and person-related environmental monitoring)

and object- and/or process-related monitoring of the environmental impact of remedial measures (source monitoring, source-related environmental monitoring)

c) Distinction has to be made between controlled releases of radioactivity into the environment and the diffuse radioactivity migration into the air and into aquatic systems



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Monitoring of controlled discharges: water pathway

Controlled discharge into receiving streams or underground

Typically, such waters are collected and monitored for volume and quality.

Discharge is from specific hydraulic structures (drainage structures) or from water treatment plants.



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Monitoring of controlled discharge: air pathway

Controlled discharges of air-born radioactivity via a ventilation shaft

Typically, the air is collected and monitored for volume and quality.

Discharge is from specific structures (ventilation shafts and holes at mine sites, ventilation structures in water treatment facilities)

Ventilation shaft #382 at the Schlema site



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Monitoring of diffuse emissions - water pathway

Diffuse leakage of seepage and percolating waters into ground and surface waters

Quantity and to some extent the quality of such waters can only be evaluated by modelling. Their sources are infiltration waters percolating through mine dumps, tailings ponds, and mine workings.



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Monitoring of diffuse emissions - air pathway Radon exhalation, Dispersion of dust-born radioactivity

Here: Comparison of radon exhalation rates, summer vs. Winter

summer, with Toutside > 10 OC winter, with Toutside < 10 OC

<= 0,1 Bq/(m²s) 0,11...0,2 Bq/(m²s) 0,21...0,5 Bq/(m²s) 0,51...1,0 Bq/(m²s) > 1,0 Bq/(m²s)

Legende:



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Monitoring: The WISMUT Case Study



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Monitoring: The WISMUT Case Study P. Schmidt, Monitoring and Measurement Approaches


for a limited time rehabilitation project,

Monitoring of the

Basic monitoring Continuous surveillance

Rehabilitation monitoring Project-related measurements

Monitoring of geomechanical

stability

Monitoring of non-radioactive

components

Monitoring of radioactive components

Long-term monitoring after completion of rehabilitation

Guideline relating to emission and immission monitoring

in mining

WISMUT operates one of the largest environmental monitoring systems in Europe. 30000 samples per year (95 % water samples)are causing 300.000 database entries.

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WISMUT Monitoring: Water Pathway P. Schmidt, Monitoring and Measurement Approaches

ca. 350 monitoring points


IMMISSIONS EMISSIONS

SEEPAGE WATER

FROM HEAPS and

TAILING PONDS

MINE DRAINAGE WATER

catched

GROUND WATER

SURFACE WATER

RECEIVING STREAMS WATER TREATMENT

PLANT

ca. 50 emission points

diffuse




The monitoring network is divided into an emission and immission section to control the discharges and allow dose and risk estimates

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WISMUT Monitoring: Water Pathway P. Schmidt, Monitoring and Measurement Approaches

Over 1800 monitoring points for observation of • ground-, surface, seepage and processing waters • at 7 former uranium mining and milling sites.

Measured parameters • radionuclides (e.g.Ra-226, U-238) • non-radiological p. (As, metals, salinity, ..) • hydro-meteorological parameters

Annual work volume • 30.000 samplings • 300.000 parameter

analysis


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WISMUT Monitoring: Air Pathway (2012) P. Schmidt, Monitoring and Measurement Approaches


Basic Monitoring Air/ground pathway (295 meas. points) - Rn-222 (234 points) - dust and long-lived alphas (25 points) - Ra-226 in precipitated dust (33 points)

Plus emission points

- 2 shafts, - 3 controlled air emissions from water treatment facilities) x air, 12 x water)

Remediation monitoring many thousand measurements/a - Rn concentration, Cpot, Rn exhalation - Ambient dose rates, - dust long-lived alpha emitters

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LIMS / AL.VIS-W P. Schmidt, Monitoring and Measurement Approaches

The ALWIS system has been developed by WISMUT. It is a simple, easy to use, powerful tool to unify geographical and environmental data management.


LIMS: Laboratory Information Management System

AL.VIS-W: Technical Data Base System at WISMUT

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Legende Radonmeßstellen

Radon Monitoring at the Schlema site


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Groundwater monitoring at the Schlema-Alberoda site


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Surface water monitoring at the Schlema-Alberoda site


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Sample Taking: P. Schmidt, Monitoring and Measurement Approaches


(picture from the last sample taking ?)

.... in this way?

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Sample Taking: P. Schmidt, Monitoring and Measurement Approaches


.... or in this way?

Most of the errors are due to improper samp-ling and sample prepa-ration

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QA/QC: P. Schmidt, Monitoring and Measurement Approaches


Baseline QA/QC

I Wismut QA/QC handbook, ISO 9000 conform

I Special Department at Wismut I General Instructions, internal guidelines for measurements, accreditation of the laboratories, metrological basis (own calibration facilities), computer added QA/QC, special data bases, ... internal certification Process-related QA/QC I Assurance and control of process-specific parameters I Internal certification of successful performance of a certain process

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QA/QC: P. Schmidt, Monitoring and Measurement Approaches


Calibration – the WISMUT secondary standard calibration fields



View into the

Radon- Laboratory with 8 m³ chamber and 400 l containers

BFS - DKD - Calibration - Laboratory

8 m³ - stainless steel chamber

400 l containers incl. radon dosing system

QA/QC – the BfS (German Federal Office for Radiation Protection in Berlin) radon chambers



WISMUT monitoring: staff and responsibilities

CEO Technical Ressort

Dep. for Environmental Monitoring and Radiation

Protection (10 experts dealing with monitoring)

Department for Remediation Technology (5)

Dep. for data mane-gement, LIMS and modelling (3)

Dep. for QA/QC (1)

Project Management (5)

Service Center Env. Monitoring (35) [sampling, doimetery maintenace, ...]) 3 Labs (central lab in Seelin-

gstaädt, labs in Schlema, Königstein) (30)

Three external laboratories (VKTA, ...)

Authorities

reporting

Almost 90 experts are dealing with env. monitoring issues (6 % of the WISMUT staff [now 1400] )

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Some lessons learned by WISMUT I Importance of QA /QC (hard and software, staff [training] )

I Site specific monitoring (monitoring for what?)

I Purchase only instruments which fit into your infrastructure (robust, spare parts, data transfer, staff qualification,...)

I Realize, that most of the errors in environmental monitoring are caused by sampling and sample preparation I Data management (if more than one site centralised data bases) I Apply an intelligent combination of field and lab measurements (screening in the field, focus on key parameters, selected lab investigations, connecting calibration, statistical analysis of field data)



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Measurement approaches

Case study: Intelligent Combination of

Field and Lab Measurements for Characterisation of Large Amounts of

Uranium Production Residues at WISMUT Sites



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What is the problem ?

Need of representativ

e data

Point-wise measurement



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How to manage it? - The batch concept

• A batch is an assemblage of diverse items (elements, products, goods, but also samples taken from a certain amount of material) which are characterised by same features, or which have the same origin, or which went through similar technological processes.

• As a consequence, the elements / goods / samples are comparable to each other.

• Taking of randomly selected samples from this assemblage and analysis of the samples allows to determine parameters which are representative for the batch (charge).



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Intelligent combination between lab and field measurements

The problem

Contamination at NORM sites may be wide-spread and not homogenously distributed

The way out:

Intelligent combination of field and lab measurements, statistical data interpretation

Step 1: Sampling, determination of the nuclide vector, identification of the index nuclide (lab measurements)

Step 2: Selection of an appropriate field (in-situ) measurement method

Step 3: Problem related „connecting“- calibra-tion between field and lab measuremts.

Step 4: In-situ measurements, quality assurance by laboratory analyses

Step 5:

Statistical interpretation of the field data



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Example: Release of lowly contaminated scrap for smelting

At WISMUT

300 000 t scrap from demolition and decommissioning

Restricted release criterion: 0,5 Bq/cm² Total Alpha Surface Activity (SSK recommendation)

Scrap market price: 100 US $ per tonnes

Task: Separation of scrap for release to smelting in a steel factory



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Dominating Nuclide (=1) Material Ra-226 U-238 Th-230 Rn-222 Pb-210 Waste rocks 1 0.95 0.95 0.94 0.91 U concentrated 0.0013 1 0.0013 0.0009 0.00067 Tailings 1 0.04 0.64 0.88 0.95 210Pb/210Po 0.024 0.024 0.021 0.024 1

Step 1: - make sure that the batch concept is applicable (sorting) - sampling (scratching of rust from the surface), - determination of the nuclide vector, identification of the index (key) nuclide (gamma spectrometry)



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- determination of the Total Surface Alpha Activity TAA via measurement of the beta net count rate

- determination of the beta net count rate requires a double measurement (without shielding – Ntot; with a 3 mm Al shielding - Nbg)

- rationale behind: In the U decay chain is a fixed ratio between alphas and betas

- alpha surface activity can under the rough field conditions (climate, rust) not precisely measured.

- using hand-held portable instruments

Step 2: Selection of an appropriate field (in-situ) measurement method



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Clearance measurements on surfaces (release of equipment, machinery, scrap)

Determination of the beta netto count rate



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TAA [Bq/cm2]= kβ⋅Nβ = kβ ⋅ (Ntot- Nbg)

Step 3: Problem related „connecting“- calibration between field and lab measuremts.

Simulation of the

• self-attenuation and

• backscattering

• of alpha and beta particles in the rust surface layer

not commercially available; self-made, tailored to four different radionuclide vectors

Calibration pad



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Step 4: In-situ measurements, quality assurance by laboratory analyses

Screening:

Between 50 and 80 measure-ments for a scrap pile of 50 tonnes

1 scratch sample per pile for QA (gamma spectrometry)

On-site input of the data into a labtop running programme

Measurement termination after a certain level of uncer-tainty for the representative parameter(TAA) is reached



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Step 5: Statistical interpretation of the field data

• investigation of the type of statistical distribution (normal [i. e. Gaussian] distribution via log-normal distribution;

note: data on environmental contamination are as a rule lognormal-distributed !

• consideration of the background

• detection of non-plausible values; exclusion of these values from data interpretation

• determination of the relevant statistic parameters (Xmean, standard deviation σ, uncertainty ∆, percentile Pα ; confidence interval for a given level of confidence α)

• decision on the base of an agreement with authorities (convention) what “representative parameter” means (for instance with respect to a clearance level, or with respect to the input for a dose estimate)

0

20

40

60

80

100

120

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

[Bq/cm2]

Freq

uenc

y D

istri

butio

n

Frerquency of the DataLognorma Distribution Gaussian Distribution

5<

0

50

100

150

200

250

300

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

[Bq/cm2]

Freq

uenc

y D

istri

butio

n Frequency of the DataLognormal Distribution Gaussian Distribution

< 5



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Statistical evaluation of the measurement data For a normally distributed measurement quantity, the sample is characterised by es-timate of the mean value (E) and deviation (S2). Then the confidence limits for the true mean (µ) may be assessed by the relation

E tSn

E tSnn n− < µ < +− −α α, ,1 1

(1)

where t nα , −1 is the percentile of the Student distribution with n-1 degree of freedom for alpha error probability. Only the upper confidence limit defined in (1) is of rele-vance to check observance of the release level of 0.5 Bq/cm2, whereby an error probability of α = 0.05 is acceptable.

Evaluation of established frequency distributions for TAA data from various scrap heaps would suggest the use of lognormal or approximately lognormal distribution functions for the evaluation of measured data. The upper confidence limit for the true mean µ, which is essential to observe the release limit of 0.5 Bq/cm2, may then be estimated by the relation

{ }µ α< + +

−Max E E S

Sn

t Sn;exp( / ) exp ( / )ln lnln

, ln2

12 2 (2)

where Eln and Sln2 represent the estimate of the mean value and deviation of the log-

normal distribution.



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0

20

40

60

80

100

120

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

[Bq/cm2]

Freq

uenc

y D

istri

butio

n

Frequency of the DataLognormal Distribution Gaussian Distribution

Comparison of the TAA reference value (0,5 Bq/cm²) with the upper limit of the confidence interval (95 % confidence value)

Frequency distributions of TAA values for a heap of scrap metal of Wismut GmbH

Statistical evaluation of the measurement data

TAA mean value = 0,11 Bq/cm²

Upper confidence limit = 0,14 Bq/cm²



47 IAEA Project BRA3013, Workshop, Poços de Caldas, June 2011 P. Schmidt; Environmental Monitoring at Uranium Mining and Milling Sites

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Many Thanks For Your Attention

monitoring and measurement approaches · radon/radon progeny concentration, ... lims: laboratory...

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