RADON FILM-BADGES BY RADIATORSWITH NANOHOLES VERSUS EXISTING

PASSIVE MONITORS

L. TommasinoTHL, Via Cassia 1727, 00123 Roma, Italy

ltommasino@gmail.com

Rn atoms are nanoparticles .4 nm wide for entering nanoholes with .4 nm aperture

Rn nanoparticles move through nanoholes in liquids and solids (Eyring, 1936)

Rn-monitors by diffusion chambers

Absorber Thickness Part. Coeff. α

CR-39 1 mm 0.06

Polycarbonate 0.3 mm 8

Holder-plastics 3 mm 0.5-0.75

(From More and Hubbard, 1997)

(From Pressianov and others)

LIQUID–LIKE POLYMERS (T>Tg)(Rubber, polyethylene)Transient nanoholes

GLASS–LIKE POLYMERS (T< Tg)(Polycarbonate) Frozen nanoholes

THERMOSETS-(CR-39)

Frozen nanoholes as sorptive sites

Diffusion by molecular-induced jumps

EQUILIBRIUM SAMPLING:

Fast Rn-absorption time

Equilibrium time (Barrer, 1939): T=d2/6D

d the film thickness D the diffusivity

For a 300-μm-thick PC-film (CD)T=~ 30 days

Non-equilibrium sampling

For a PC-film thickness < 50 μmT < 5 hours

Equilibrium sampling

CR-60 absorptive radiatorswith bulk-distributed nanoholes for:

- obtaining compact and easy-to-deploy radon film-badges - increasing the response linearity of passive monitors

-measuring soil-radon under equilibrium conditions-measuring radon directly in water.

CR-60 Definition respectively for:- having a radon-diffusion length of about 60 μm at environmental temperature

- being a Carbonate Radiator (CR) with a solubility of 60 ± 20 (i.e. in the range 40-80)-degrading maximum alpha-particle energy by a 64 μm-thick film

- having a film-thickness not greater than 60 μm.

CR-60 Characteristics depend on: - the polymer structure and morphology

- the manufacturing processes - the shelf-life

- the thermal history, etc.

Radiator

(facing CR-39)

Thickness

(µm)

Response[Tracks.m3/

(cm2. kBq.h)

Metal ----------- 0.010±0.002

CR-60 (1 Makrofol N; Low solubility, S=40)

20 0.20 ± 0.02

CR-60 (2 Makrofol N) 40 0.34 ± 0.04

CR-60 (3 Makrofol N) 60 0.45 ± 0.05

CR-60 (4 Makrofol N) 80 0.42 ± 0.06

Two responses in one monitor

Response Tracks.m3/

(cm2.kBq.h)

Passive chambers 2.8 ± 0.7 (with CR-39)

CR-60 (20 µm Makrofol N) 0.2 ± 0.03

Two Radiators

PE Bag CR-39

Radon film badge for in-soil and in-water measurements

Large tubes are conducive to errors (Tanner, 1991)

Different volumes-Same responses

α

(T)

[C]Rn

[C]Rn

[CRn]water =α (T) [CRn]air

For large exposure measurements:

Film-badges by absortpive radiators with bulk-enclosed nanoholes

For low exposure measurements of one week or less:

Film-badges by adsortpive radiators with surface-distributed nanoholes

ADSORPTION

Non-equilibrium sampling-activated-charcoals

Equilibrium sampling-solid layers with surface-distributed

nanoholes having very large surface to volume ratio.

CR-2000 adsorptive radiatorswith surface-distributed nanoholes for:

- measuring indoor radon-exposures for one week or less.

CR-2000 Definition:-equilibrium Rn-adsorption of radon up to a concentration

2000 times of that present in the surrounding air.

CR-2000 Characteristics depend on:- the manufacturing processes

- the shelf-life - the storage environment

Sampler Response Tracks.m3/(cm2.kBq.h)

- CR-2000 (Adsorptive radiator) 20 ± 4

-Passive chambers 2.8 ± 0.7 (with CR-39)

Uniquely-compact radon-film-badges with absorptive- and/or adsorptive-

radiators for:

- indoor measurements for days, months, and years

- using as a back-up monitor

- correct soil-measurements

- direct-in-water measurements

CR-0 bags for storing all types of monitors prior to and after

the exposure are:

- radon-proof bags

-radon-free bags

-bags sealable by pressure-type devices

CR-60, CR-2000, CR-0 available through a centralised distribution because of the:

- need of custom-made radiators with desired characteristics

- large cost of minimum-orders consisting of stocks up to 1000 kg

- difficulty in handling and storing large volumes of materials in suitable low-radon environments

Luigi Tommasino

THL, Via Cassia 172700123 Roma, Italy

ltommasino@gmail.com