QUALITY ASSURANCE OF RADON MEASUREMENTS IN PORTUGAL

FILIPA DOMINGOS (M.Sc)

LABORATORY OF NATURAL RADIOACTIVITY

QA SYSTEM FOR RN MEASUREMENTS INDOORS AND IN WATER IN LNR (UC)

• LABORATORY OF NATURAL RADIOACTIVITY

• ESTABLISHED IN 1999 IN THE EARTH SCIENCES DEPARTMENT, UNIVERSITY OF COIMBRA

• ACCREDITED AS A TESTING LABORATORY (COMPLIANT

WITH ISO/IEC 17025) SINCE 2019:

Assay ISO Method Product

Radon 13164-4:2015 Liquid scintillation Water

Gross alpha and beta 11704:2018 Liquid scintillation Water

Ra-226 13165-1:2013 Liquid scintillation Water

U-238 and U-234 13169:2018 Liquid scintillation Water

Po-210 13161:2011 Alpha spectrometry Water

Sample collection - Internal method Water

Radon 11665-4:2012 Passive detectors (CR-39) Indoor

Ra-226, Th-232 and K-40 18589-3:2015 Gamma spectrometry Solid

QA SYSTEM FOR RN MEASUREMENTS INDOORS AND IN WATER IN LNR (UC)

• ELEMENTS OF THE QA SYSTEM

• INTERNAL QUALITY CONTROL:

• BLANK TESTS (INDOOR: UNEXPOSED DETECTORS; WATER: SCINTILLATION COCKTAIL)

• CERTIFIED REFERENCE MATERIALS (WATER)

• DUPLICATES (WATER)

• STANDARDS WITH KNOW ACTIVITY (INDOOR: DEMOSLIDE; WATER: BLANK, C-14 AND H-3)

• EXTERNAL QUALITY CONTROL:• PROFICIENCY TESTING:

• INTERCOMPARISON EXERCISES (BILATERAL ASSAYS)

• STATISTICAL ANALYSIS (INTERNAL/EXTERNAL DATA):• SHEWHART CHARTS (BLANKS, STANDARDS)

• WARNING AND ACTION LEVELS

• ESTIMATION OF THE ANNUAL PRECISION CRITERIA

Periodicity: for each batch of samples

QC in Sampling (contamination during sampling & transport)

and Sample preparation

QA SYSTEM FOR RN MEASUREMENTS INDOORS AND IN WATER IN LNR (UC)

• ELEMENTS OF THE QA SYSTEM

• INTERNAL QUALITY CONTROL:

• BLANK TESTS (INDOOR: UNEXPOSED DETECTORS; WATER: SCINTILLATION COCKTAIL)

• CERTIFIED REFERENCE MATERIALS (WATER)

• DUPLICATES (WATER)

• STANDARDS WITH KNOW ACTIVITY (INDOOR: DEMOSLIDE; WATER: BLANK, C-14 AND H-3)

• EXTERNAL QUALITY CONTROL:• PROFICIENCY TESTING:

• INTERCOMPARISON EXERCISES (BILATERAL ASSAYS)

• STATISTICAL ANALYSIS (INTERNAL/EXTERNAL DATA):• SHEWHART CHARTS (BLANKS, STANDARDS)

• WARNING AND ACTION LEVELS

• ESTIMATION OF THE ANNUAL PRECISION CRITERIA

Periodicity: for each batch of samples; 5 % of

all samples collected

QC in Sampling (contamination during transport) and Sample preparation; Estimation

of precision

QA SYSTEM FOR RN MEASUREMENTS INDOORS AND IN WATER IN LNR (UC)

• ELEMENTS OF THE QA SYSTEM

• INTERNAL QUALITY CONTROL:

• BLANK TESTS (INDOOR: UNEXPOSED DETECTORS; WATER: SCINTILLATION COCKTAIL)

• CERTIFIED REFERENCE MATERIALS (WATER)

• DUPLICATES (WATER)

• STANDARDS WITH KNOW ACTIVITY (INDOOR: DEMOSLIDE; WATER: BLANK, C-14 AND H-3)

• EXTERNAL QUALITY CONTROL:• PROFICIENCY TESTING:

• INTERCOMPARISON EXERCISES (BILATERAL ASSAYS)

• STATISTICAL ANALYSIS (INTERNAL/EXTERNAL DATA):• SHEWHART CHARTS (BLANKS, STANDARDS)

• WARNING AND ACTION LEVELS

• ESTIMATION OF THE ANNUAL PRECISION CRITERIA

Periodicity: according to the verification plan (ex. monthly); exceptionally

Check the equipment (drift and fitness to use);QC in data acquisition

(measurement)

QA SYSTEM FOR RN MEASUREMENTS INDOORS AND IN WATER IN LNR (UC)

• ELEMENTS OF THE QA SYSTEM

• INTERNAL QUALITY CONTROL:• BLANK TESTS (INDOOR: UNEXPOSED DETECTORS;

WATER: SCINTILLATION COCKTAIL)

• CERTIFIED REFERENCE MATERIALS (WATER)

• DUPLICATES (WATER)

• STANDARDS WITH KNOW ACTIVITY (INDOOR: DEMOSLIDE; WATER: BLANK, C-14 AND H-3)

• EXTERNAL QUALITY CONTROL:

• PROFICIENCY TESTING:

• INTERCOMPARISON EXERCISES (BILATERAL ASSAYS)

• STATISTICAL ANALYSIS (INTERNAL/EXTERNAL DATA):• SHEWHART CHARTS (BLANKS, STANDARDS)

• WARNING AND ACTION LEVELS

• ESTIMATION OF THE ANNUAL PRECISION CRITERIA

Periodicity: variable; depends on available

exercises/entities willing to do bilateral assays

QA SYSTEM FOR RN MEASUREMENTS INDOORS AND IN WATER IN LNR (UC)

Decision rules:• 1 value surpasses the

action level (AL);• 2 out of 3 consecutive

values surpass the warning level (WL);

• 6 consecutive values increase/decrease;

• 9 consecutive values in the same side of the mean;

• ELEMENTS OF THE QA SYSTEM

• INTERNAL QUALITY CONTROL:• BLANK TESTS (INDOOR: UNEXPOSED DETECTORS;

WATER: SCINTILLATION COCKTAIL)

• CERTIFIED REFERENCE MATERIALS (WATER)

• DUPLICATES (WATER)

• STANDARDS WITH KNOW ACTIVITY (INDOOR: DEMOSLIDE; WATER: BLANK, C-14 AND H-3)

• EXTERNAL QUALITY CONTROL:• PROFICIENCY TESTING:

• INTERCOMPARISON EXERCISES (BILATERAL ASSAYS)

• STATISTICAL ANALYSIS (INTERNAL/EXTERNAL DATA):

• SHEWHART CHARTS (BLANKS, STANDARDS, CRM)

• WARNING AND ACTION LEVELS

• ESTIMATION OF THE ANNUAL PRECISION CRITERIA

Periodicity: calculated with 20 results; updated

upon new data;

CALIBRATION OF RN MEASUREMENT INSTRUMENTS IN LNR (UC)

• CALIBRATION SYSTEM

• ALL EQUIPMENT WITH DIRECT INFLUENCE ON THE TEST RESULTS IS SUBJECT TO PERIODIC CALIBRATION/VERIFICATION/MAINTENANCE, ACCORDING TO PRE-DEFINED PLANS;

• THE PERIODICITY IS ESTABLISHED BY:

• MANUFACTURER'S RECOMMENDATIONS;

• TREND ANALYSIS OF QC DATA (EX: INSTRUMENTAL SHEWHART CHARTS, INTERLABORATORY COMPARISONS);

• PREVIOUS EXPERIENCE;

• FREQUENCY, TYPE AND CONDITIONS OF USE OF THE EQUIPMENT;

• ENVIRONMENTAL CONDITIONS (TEMPERATURE, HUMIDITY, VIBRATION, ETC.);

• DESIRED DEGREE OF ACCURACY/THE MAXIMUM ALLOWABLE ERROR;

• ACCEPTANCE/EVALUATION OF CALIBRATION CERTIFICATES;

• ORGANIZATIONS RESPONSIBLE

• CALIBRATION CERTIFICATES;

• CERTIFIED REFERENCE MATERIALS (EX. DEMOSLIDE, H-3, C-14 & BLANK)

EXPERIENCE OF INTERCOMPARISON OF PASSIVE OR ACTIVE MEASUREMENT INSTRUMENTS

• WHEN PARTICIPATED IN WHICH INTERCOMPARISON

External quality control Year Assay Product Type Organiser

Proficiency testing 2017 Radon Indoor Passive PHE, England

Interlaboratory comparison 2018 Radon Indoor Passive MetroRadon, Spain

Interlaboratory comparison 2018 Radon Indoor Active NRPI, Czech Republic (IAEA)

Proficiency testing 2019 Radon Water - IPROMA, Spain

Proficiency testing 2019 Radon Indoor Passive BfS, Germany

Interlaboratory comparison 2020 Radon Water - LARUC

Interlaboratory comparison 2020 Radon Indoor Passive LARUC

Proficiency testing 2020 Radon Water (Sampling) Relacre, Portugal

EXPERIENCE OF INTERCOMPARISON OF PASSIVE OR ACTIVE MEASUREMENT INSTRUMENTS

• HOW DO YOU USE THE RESULTS OF INTERCOMPARISON :

• ASSESS ACCURACY;

• MONITOR/DETECT SYSTEMATIC ERRORS;

• IDENTIFY THE NEED FOR EQUIPMENT MAINTENANCE/VERIFICATION;

• MONITOR HUMAN ERRORS (EX. SAMPLE PREPARATION/HANDLING);

• EVALUATE/COMPARE THE LABORATORY PERFORMANCE;

• INTERNAL QUALITY CONTROL;

• ASSESS THE PERFORMANCE OF LABORATORY TECHNICIANS;

• QUALIFICATION OF LABORATORY TECHNICIANS (ANNUALLY);

EXPERIENCE OF INTERCOMPARISON OF PASSIVE OR ACTIVE MEASUREMENT INSTRUMENTS

• PROFICIENCY TESTING SCHEME AS AN ORGANISER:

• ASSAY: RADON IN WATER SAMPLES;

• OBJECTIVE: QUALITY CONTROL IN SAMPLING;

• STRATEGY: SAMPLE COLLECTION OF SPRING WATER AT THE SAME LOCATION BY ALL PARTICIPANTS

• ORGANISER: RELACRE (ASSOCIATION OF PORTUGUESE ACCREDITED LABORATORIES)

• RESPONSIBILITIES OF LNR AS A PROFICIENCY TESTING PROVIDER:

• STABILITY AND HOMOGENEITY STUDIES FOR THE SELECTION OF THE SAMPLING LOCATION;

• STABILITY AND HOMOGENEITY STUDIES ON THE DAY OF SAMPLE COLLECTION;

• DETERMINATION OF RADON IN ALL WATER SAMPLES COLLECTED AND DELIVERED BY THE PARTICIPATING LABORATORIES;

• PROTOCOL: SAMPLING ACCORDING TO THE RECOMMENDATION 1/2017 (ERSAR), DECREE-LAW 152/2017 (7TH DECEMBER), AND ISO 5667-5:2006;

• PARTICIPATION OF 18 LABORATORIES (54 WATER SAMPLES COLLECTED);

CHALLENGES FOR GOOD LABORATORY PRACTICES AND QUALITY ASSURANCE OF RN MEASUREMENT INSTRUMENTS IN LNR (UC)

• METHODS FOR SAMPLING FOR RADON IN WATER SAMPLES (SOURCE OF VARIABILITY/ UNCERTAINTY)

• SAMPLING OF INDOOR RADON IN REAL CONDITIONS (INTERCOMPARISON EXERCISES ARE HELD IN “IDEAL” CONDITIONS)

• EXECUTION OF INTERCOMPARISON EXERCISES DEPENDS ON AVAILABILITY (LOW PERIODICITY AND LONG WAIT FOR RESULTS)

• CONTAMINATION DURING TRANSPORT IN INTERCOMPARISON EXERCISES:• RESPONSIBILITY IDENTIFY

• HOW TO INTERPRET/ANALYSE THE DATA?

• DECISION RULES IN SHEWHART CHARTS/ACCEPTABILITY CRITERIA ARE SUBJECTIVE;

• FUTURE CHALLENGE FOR THE LNR: COMPLY WITH THE REQUIREMENTS OF ISO/IEC 17043 FOR THE COMPETENCE OF PROVIDERS OF PROFICIENCY TESTING SCHEMES, THEIR DEVELOPMENT AND OPERATION