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Technical Discussions
John kal
John kal
18:52 Feb-23-2019
RT gamma ray ir safty distance

Good noon all

I am john i m basically mechanical engineering . In our plant we are planning to perform RT gamma ray source-Ir going to be used dosage 30curie.

Any one pls tell what is the safety distances.
Is some calculations pla tell . And standards pls tell

Hks Al
Kal

Sathiyaraj
Engineering,
TOSHIBA JSW POWER SYSTEMS PVT. LTD.,, India, Joined Apr 2013, 14

Sathiyaraj

Engineering,
TOSHIBA JSW POWER SYSTEMS PVT. LTD.,,
India,
Joined Apr 2013
14
12:22 Feb-25-2019
Re: RT gamma ray ir safty distance
In Reply to John kal at 18:52 Feb-23-2019 (Opening).

Dear John Kal,

Regards
Sathiya

Ricardo Andreucci
FATEC - Technological University of Sao Paulo, Brazil, Joined May 2018, 36

Ricardo Andreucci

FATEC - Technological University of Sao Paulo,
Brazil,
Joined May 2018
36
14:23 Feb-25-2019
Re: RT gamma ray ir safty distance
In Reply to Sathiyaraj at 12:22 Feb-25-2019 .

Hi Mr. Kal

The calculation of dose rate at a distance depends on what kind of radioisotope are you going to use.
So, for a simple calculation you can use the following formula:
2
Dose rate = (Gamma Factor x Activity ) / d in miliSivert per hour (mSv/h)

where:
Gamma factor for Iridium ( Ir-192)= 0,13 mSv/h x GBq at 1m
Activity = 30 Ci = 1110 GBq (Giga Becquerel)
d = source distance

Example:
Which is the dose rate at 5 m distance, due a 30 Ci (1110 GBq) of an Ir-192 radioactive source ?

Dose rate = 0,13 x 1110 / 5 x 5 = 5,772 mSv/h

The International standard considers maximum dose about 20 mSv/year for operators. But you have to check this information in the Nuclear Regulation Authority of your Country
So, if the operators work for 2000 hours per year, we can calculate the maximum dose rate per hour, as follows:
Max. Dose rate = 5,772 /2000 h = 0,0029 mSv/h or 2,9 uSv/h
You can use the portable Geiger-Muller detector in order to ensure the maximum dose at the workplace.

Regards
R.Andreucci

ricardo andreucci
FATEC - Technological University of Sao Paulo, Brazil, Joined May 2018, 36

ricardo andreucci

FATEC - Technological University of Sao Paulo,
Brazil,
Joined May 2018
36
20:38 Feb-25-2019
Re: RT gamma ray ir safty distance
In Reply to Ricardo Andreucci at 14:23 Feb-25-2019 .

Mr. Kal

I`m so sorry. There is a mistake in my above calculation.

Dose rate = (gamma factor x activity) / d²

Where:
- Gamma factor for Ir-192 = 0,13 mSv/h x GBq at 1 m
- Source Activity: 30 Ci (1110 GBq)
- d = source distance

The International standard considers maximum dose about 20 mSv/year for operators. But you have to check this information in the Nuclear Regulation Authority of your Country
So, if the operators work for 2000 hours per year, we can calculate the maximum dose rate per hour, as follows:
Max. Dose rate acceptable = 20 mSv/year = 20 mSv/h/2000h = 0,010 mSv/h or 10 uSv/h
You can use the portable Geiger-Muller detector in order to ensure the maximum dose at the workplace.

The safety distance "d" for operators due 30 Ci of Ir-192 radiation source shall be :

0,010 mSv/h = (0,13 x 1110) / d²

d² = 14430 = > d = 120,12 meters

Best regards

R.Andreucci

Vivek Mehta
,
India, Joined Feb 2017, 2

Vivek Mehta

,
India,
Joined Feb 2017
2
06:23 Mar-04-2019
Re: RT gamma ray ir safty distance
In Reply to ricardo andreucci at 20:38 Feb-25-2019 .

Ricardo Andreucci
FATEC - Technological University of Sao Paulo, Brazil, Joined May 2018, 36

Ricardo Andreucci

FATEC - Technological University of Sao Paulo,
Brazil,
Joined May 2018
36
13:17 Mar-04-2019
Re: RT gamma ray ir safty distance
In Reply to Vivek Mehta at 06:23 Mar-04-2019 .

Hi Mr. Kal

I live in Brazil, and the National Commission on Nuclear Energy follows the international standard for limits of radiation dose.
For workers or radiographic operators the limit is 20 mSv/year, for body
For non workers, public and people that live or work around the radioactive device is 1 mSv/year, for body.

Best regards

R.Andreucci

ASHOK KUMAR PATRA
,
Saudi K-KEM Engineering service co, Saudi Arabia, Joined May 2018, 55

ASHOK KUMAR PATRA

,
Saudi K-KEM Engineering service co,
Saudi Arabia,
Joined May 2018
55
14:27 Mar-05-2019
Re: RT gamma ray ir safty distance
In Reply to John kal at 18:52 Feb-23-2019 (Opening).

Barication = root over (Ci X 0.55 X 1000 X 0.054/ 0.75 mr/hr)

0.054 use when you are using tungsten collimator otherwise don't use it.

0.55 RHM for Iridium 1000 for milliroentgen

you can use occupancy factor also.

Ricardo Andreucci
FATEC - Technological University of Sao Paulo, Brazil, Joined May 2018, 36

Ricardo Andreucci

FATEC - Technological University of Sao Paulo,
Brazil,
Joined May 2018
36
22:38 Mar-06-2019
Re: RT gamma ray ir safty distance
In Reply to ASHOK KUMAR PATRA at 14:27 Mar-05-2019 .

Hi Mr. Ashok

I understanding that you are using the old radiation units.
The conversion of old units by the usual units in radiation protection is:

a) 1 mSv/h = 100 mR/h
b) 37 GBq = 1 Ci
c) The gamma factor : 0,13 mSv/h/GBq at 1 m = 0,55 R/h/Ci at 1 m
d) The maximum dose rate according to International Standard: 0,010 mSv/h = 1 mR/h = 0,001 R/h

So, for a radiation source Ir-192 with activity 30 Ci , the safe distance "d" will be:

d² = (0,55 x 30) / 0,001 = > d = 128 meters (without any collimator)

Note: If you are using 0,75 mR/h (0,075 R/h) as the maximum dose rate permitted in your Country , the safe distance will be:

d² = (0,55 x 30) / 0,075 = > d = 14,83 meters (without any collimator)

Best Regards

R.Andreucci

ASHOK KUMAR PATRA
,
Saudi K-KEM Engineering service co, Saudi Arabia, Joined May 2018, 55

ASHOK KUMAR PATRA

,
Saudi K-KEM Engineering service co,
Saudi Arabia,
Joined May 2018
55
08:12 Mar-10-2019
Re: RT gamma ray ir safty distance
In Reply to Ricardo Andreucci at 22:38 Mar-06-2019 .

Yes . Thanks

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