DOSIMETRÍA DEL RADÓN EL RADÓN: EL ENEMIGO INVISIBLE (CURSO BASICO) - Estudios Propios de Posgrado, Universidad de Cantabria - El Radón
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
EL RADÓN: EL ENEMIGO
INVISIBLE (CURSO BASICO)
Estudios Propios de Posgrado,
Universidad de Cantabria
DOSIMETRÍA DEL RADÓN
Carlos Sainz Fernández & Luis S.Quindos Poncela
Catedráticos de la
Universidad de Cantabria
Rn PROGENY
218Po 214Po 210Po
3.05 m 1.6 10-4 s 138 d
214Bi 210Bi
6.00 5.31
19.7 m 7.69 5.0 d
214Pb 206Pb
210Pb
26.8 m Estable
22.3 a
solids
Chemically active
Half period < 30 min
Complex behaviour
Radiological Impact
RADON PROGENY
Size (nm)
Radon exhalation
Disintegración
RADÓN
0.5 - 1 Depósito
Unattached progeny
”Plate out”
+ 88 %
Neutro 12 %
Adherence
WALL,
Recoil
Solo 218Po FLOOR
10 - 1000 Depósito
Descendiente adherido
Deposition
Vargas 2004 Aerosol Particle
Porstendorfer 1994
K. Kozak, Polonia
RADON PROGENY
Transformation/removal mechanisms (typical values)
Disintegración = 1.6 – 14 h-1
Ventilation = 0.5 – 1.0 h-1
= 0.1 h-1 (aerosoles)
Surface deposition
= 20 h-1 (libres)
Main mechanism
Deposition speed inverse to particle size
Disequilibrium cause radon/progeny
Deposition rate increases as S/V increases
ICRP 66
Human respiratory
tract model
Vias extratorácicas
Bronquial
Bronquiolar
Alveolar
Porstendorfer 1994
Harrison 2017
Porstendorfer 1994
Porstendorfer 1994
Porstendorfer 1994
MAGNITUDES
AND UNITS
(Wassily Kandinsky, 1944)Rn PROGENY
218Po 214Po 210Po
3.05 m 1.6 10-4 s 138 d
214Bi 210Bi
6.00 5.31
19.7 m 7.69 5.0 d
214Pb 206Pb
210Pb
26.8 m Estable
22.3 a
ENERGÍA ALFAPRINCIPAL MAGNITUDES
Concentration (Bq m-3 , pCi l-1 ,Bq l-1)
(1Ci = 3,7 E10 Bq)
Equilibrium
Exposure (Bq m-3 h)/ Factor / WLM
Dose Coefficients (mSv/WLM)
Equivalent/Effective
(mSv, mSv/y, etc…)
doseMAGNITUDES AND UNITS (ICRU 2012)
UNA ATMÓSFERA CON RADÓN Y DESCENDIENTES
ES ACTIVA (ALFA, BETA Y GAMMA)…
POTENTIAL ALPHA ENERGY es la energía alfa total emitida en la desintegración
de los descendiente de vida corta del radón
(of a progeny atom) en su cadena de desintegración hasta llegar al 210Po
PAE (MeV, J)
1 átomo de 218Po 13.69 MeV (6,11 + 7,83)
¿y un Bq?
PAE (MeV) = 13.69 NPo-218 + 7.69 (NPb-214+ NBi-214) )+ 7.69 NPo-214
4MAGNITUDES AND UNITS
… CONCENTRACIÓN DE ENERGÍA ALFA POTENCIAL
PAEC(J m 3 ) E aj C j
POTENTIAL ALPHA ENERGY j
CONCENTRATION of any mixture of short-lived radon
progeny in air is the sum of the potential alpha energy ç
(PAEC) of these atoms present per unit
(MeV/m3, J/m3) volume of air, expressed in the SI-unit J m-3
PAEC (MeV/m3) = 3615 CPo-218 + 17840 CPb-214+ 13250 CBi-214
Traditional Unit: WL (working level): Every progeny combination which deliver
1.3 108 MeV of alpha energy in one cubic meter of air
1 WL = 2.08 10-5 J m-3MAGNITUDES AND UNITS
… CONCENTRACIÓN DE ENERGÍA ALFA POTENCIAL
PAEC(J m 3 ) E aj C j
POTENTIAL ALPHA ENERGY j
CONCENTRATION of any mixture of short-lived radon
progeny in air is the sum of the potential alpha energy ç
(PAEC) of these atoms present per unit
(MeV/m3, J/m3) volume of air, expressed in the SI-unit J m-3
PAEC (MeV/m3) = 3615 CPo-218 + 17840 CPb-214+ 13250 CBi-214
Traditional Unit: WL (working level): Every progeny combination which deliver
1.3 108 MeV of alpha energy in one cubic meter of air
1 WL = 2.08 10-5 J m-3OJO!
MAGNITUDES AND UNITS
concentración de gas radón
CONCENTRACIÓN EQUIVALENTE que estando en equilibrio con sus descendientes
DE RADÓN EN EQUILIBRIO tiene la misma PAEC
(EEC, Bq m-3 ) que los descendientes en el aire
EEC ( Bq m 3 ) 0.105 C218 Po 0.516 C214 Pb 0.379 C214 Bi 6 108 C214 Po
Related with PAEC
¿Cuál ES LA EEC CORRESPONDIENTE A 1 WL?
EEC ( Bq m 3 )
PAEC (WL)
3750MAGNITUDES AND UNITS
Equilibrium Factor Relationship between EEC
and real radon gas concentration
EEC
F
C
In terms of PAEC
WL 3700
F
C ( Bq m 3 )
TYPICAL VALUES:
F = 0,4 INDOOR F = 0,8 OUTDOORS
UNSCEAR 2000 www.radon.comMAGNITUDES AND UNITS
EXPOSICIÓN Time integral of the radon gas/progeny concentration
extended to the inhalation period
Traditional unit WLM (working level month):
On activity (Bq m-3 h) Exposure to 1 WL during a working month (170 h)
On PAEC (J m-3 h) 1 WLM = 3.54 mJ h m-3
1 WLM = 3750 Bq/m3 X 170 h = 6.37 105 Bq m-3 h de EEC
UNATTACHED Proportion of radon progenies not attached to aerosols
FRACTION
EEC p 414 DCF 8.4 64 * fp
fp fp
EEC Z
DOSIMETRIC APPROACH, ICRP 66
Porstendorfer 1996WL
E WLM DCF DCF
170
C ( Bq m 3 ) F t
E ( mSv ) DCF ( mSv / WLM )
170 3750DOSE CONVERSION
Continuous radon (and progeny) inhalation
provoques alpha irradiation of the respiratory tract
TWO WAYS FOR RISK
ASSESSMENT
-DOSIMETRIC MODELS
-EPIDEMIOLOGYDOSIMETRIC APPROACH
Respiratory model based dose estimation
Progeny retention period
Alpha radiation weighting factor
Lung tissue sensitivity
Tissue weighting factors
Probability density functions
Applied to miners conditions (Birchall 1994) 15 mSv WLM-1
Applied to residential conditions (Marsh 2002) 12 mSv WLM-1EPIDEMIOLOGICAL
APPROACH
STUDIES IN COHORTS OF MINERS
High exposure rate
Tobacco influence
Presence of other pollutants
Specific exposure conditions
(tasas de respiración, variedad concentración de partículas, etc)
Difficult extrapolation of CASE CONTROL STUDIES
risk factors to residential environmentEPIDEMIOLOGICAL
APPROACH
ICRP 65 (1993) DOSE CONVERSION FACTOR
Detriment due to radon exposure (A)
mSv WLM-1 =
Detriment per effective dose unit (B)EPIDEMIOLOGICAL
APPROACH
THEN
Detriment per radon exposure (A) Miners population
“NOMINAL RISK COEFFICIENT”
3 10-4 WLM-1
Data Hiroshima Nagasaki
Detriment per effective dose unit(B)
Animal Experiments
Public 7.3 10-5 mSv-1
Workers 5.6 10-5 mSv-1
DCF (ICRP Pub 65, 1993)
Public 3.88 mSv WLM-1 = 6.09 nSv por Bq m-3 h
workers 5.06 mSv WLM-1 = 7.95 nSv por Bq m-3 h
Para convertir a exposición a gas radón hay que conocer F (medida/bibliografía)
Ej. F = 0.4 2.4 nSv por Bq m-3 h (público)EPIDEMIOLOGICAL
APPROACH
NOW
DCF (ICRP Pub 115, 2010)
Detriment per radon exposure (A) CASE CONTROL STUDIES
DWELLINGS
5 10-4 WLM-1
Public 9 mSv WLM-1
workers 12 mSv WLM-1HEALTH RISKS
Epidemiological Dosimetric
approach approach
Factor 3??
Change in weighting factors ICRP
-Lung (0.12 a 0.04)
- Alpha particles(20 a 7)
-Lung regions
LESS DIFERENCE…
SIGNIFICANT CHANGES IN PREVENTION STRATEGIES!NOW
ICRP 137 (2018)
The dose coefficients for inhalation of radon are calculated
using BIOKINETIC AND DOSIMETRIC MODELS
Underground miners and buildings
3 mSv per mJ h m-3 (10 mSv WLM-1 )
Workplaces with substantial physical activity
and tourist caves
6 mSv per mJ h m-3 (20 mSv WLM-1 )
SIGNIFICANT IMPACT ON RISK ESTIMATION AND
RADIOLOGICAL PROTECTION SYSTEMEpidemiological Dosimetric
approach approach
AGREEMENTYou can also read
