1 Radiological protection, dosimetry & environmental monitoring National Training Course on...

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Radiological protection, dosimetry & environmental monitoring

National Training Course on Radiopharmacy, Radiochemistry and

Radioisotope Production Site Management

Dr. Radu Vasilache

Canberra Packard

IAEA TC project ROM/6/0172

Overview

1. Quantities and standards

2. What to survey? Pathways of exposure

3. Radiation protection planning

4. Specific instruments and methods for radiation monitoring

5. Conclusions


Standards and regulations

Law 11/1996 & Basic Radiological Protection Norms

Set up the dose limits for exposed personnel (20 mSv/year)

and population (1 mSv/year)

IAEA Basic Safety Standards


Quantities to be measured / calculated

Doses:

Absorbed dose D = dE/dm, measured in Gy (1 Gy = 1 J/kg)

Equivalent doses (used in practice for external radiation,

measured):

Personal equivalent dose (penetrating) Hp(10), measured in Sv (1 Sv = 1 Gy for photons), for personnel monitoring

Ambient equivalent dose H*(10), measured in Sv, for area monitoring

Effective committed doses (used in practice for internal

exposure, calculated): the dose that an individual will

receive over a number of year, resulting from the intake of

radiaoctive substances


Quantities to be measured

Activity (measured in Bq):

External contamination of equipment & personnel

Internal contamination (WBC)

Effluents (gaseous & liquid)

Waste


Radiation protection planing

Steps for building up a proper RP management plan:

1. Identify all possible pathways / sources of exposure specific to the site (e.g.: external exposure at the cyclotron site, in the hot-rooms, etc., internal exposure possibilities, ways of discharging effluents, etc.)

2. Identify all possible accidents via a fail chart, set up emergency response plan

3. Identify points of continuous monitoring and what needs monitored


What to survey?

Survey targets in a cyclotron production site & paths of exposure:

Protection of the working personnel:

Direct exposure to external radiation – dose monitoring

Internal exposure through inhalation & ingestion – internal

contamination (activity) monitoring, doses are calculated

External contamination

Protection of the public

Gaseous effluents

Liquid effluents

Waste disposal


Dosimetry – personnel monitoring

Quantities to be measured:

Hp(10) – personal equivalent dose, penetrating: doses due to

external penetrating radiation (above 60 keV), the point of interest

is considered as 10 mm below the surface of the skin

Hp(0.07) – personal dose equivalent, superficial: doses to to low

energy external radiation (photons below 60 keV, beta radiation)

Instruments:

Electronic alarm dosemeters

Film dosemeters

TLDs

Glass dosemeters


Examples of personnel dosemeters


Personnel dosimetry – internal contamination

Whole Body Counting

Spectroscopic measurement of intake

Measures the activity and calculates

committed dose per radionuclide

Adds up to the external dose


Personnel contamination


Dosimetry – area monitoring

Ambient equivalent dose H*(10)

Measured directly, usualy the dose, time stamp and location are logged in

Usually applies to photons (gamma & X) and neutrons

Area monitoring normally involves network monitoring, with detectors sending remotely the data, combined with periodic surveys performed by operators


Dosimetry for area monitoring - examples


Area monitoring – hand held units


Details to be observed

Dose ranges: in areas where the dose rate could have significant fluctuations, a matter of concern should be the saturation of the probes

TTC methods is the answer


Time – to – count principle

Conventional GM Tube Operation

TIME

TIME

TIME

PULSE

DISCR.

WAVE FORMS

+HV

BIAS



“Time to Count” Operation

HV

HV

2

t ont on

t off

t off

GM TUBE WAVEFORMS

TIME

Time Totalizer

Pulse Totalizer

÷ Average Time to Count

RATE = K

TIME TO COUNT



“Time to Count” Behaviour

HV

+HV

2

SHORT TIME

2 mSec.

TIME

HIGH FIELD

HV

+HV

2 LONG TIME

2 mSec.

TIME

LOW FIELD


Effluent & waste monitoring

Should be integrated in the same RMS software as the dose area monitoring

Involves gas & liquid discharges

Waste (solid & liquid) are to be measured and categorised according to the activity

Can be done via radiometric and / or spectrometric measurements

The architectures of GEM & LEM are similar


Gaseous and liquid effluent monitors

P1

PLC SV1

P2

SV2

F

FE/FT 3

LAN Server

MCR Workstation HP Workstation

MAR

MONITORUL DEEFLUENTI GAZOSI

#1

MIR MGN

PANOUL LOCALDE CONTROL ALMONITORULUIDE EFLUENTI

GAZOSI #1 & #2

CONDUCTA TEHNOLOGICA DE EVACUARE

F

FE/FT 2

F

FE/FT 1

V3 V1

V2V4

PLCPLC control debit

MCA “UNISPEC” & 3" NaI(Tl) detector

F

FE/FT 2 Senzor / Traductor debit

SV1

Electrovana reglaj debit

Comunicatie seriala (port USB)



Semnal analogic

Semnal analogic

Semnal analogic

Semnal analogic

Sem

nal a

nalo

gic

Com

unic

atie

ser

iala

LAN

MONITORUL DEEFLUENTI

GAZOSI #2


Gaseous Effluent MonitorSPING CP/GNS/SCN-1

Two monitors (reactor hall and stack), with 3 channels each – MGN (noble gas), MIR (iodine), MAR (aerosol)

Each channel has a NaI 3x3 inch with UniSpec (can be replaced with any other combination of detector & MCA)

New architectures can combine stabilised NaI or LaBr with Osprey, or HPGe coaxial detectors with electrical cooling and Lynx MCA, thus making totally useless the usage of local computing stations

Result of the combined work of CPRO, GNS and SCN Pitesti


Gaseous effluent monitor (cont.)


Control software


Gaseous effluent monitors – non spectrometric


Liquid effluent monitors

On-line / in-line


Waste assay & objects contamination monitors

Radiometric / spectrometric


Conclusions

From the point of view of the radiological protection, one must observe the following in the site planing:

Plan for the possible incidents and the pathways of

exposure

Insure proper monitoring of personnel exposure /

contamination

Monitor the environmental releases and keep them under

control (limit population exposure)

Monitor waste production

Decide for the best technological solution applicable to the

site to achieve the above objectives


Mulțumesc!

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