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- since 1996 -

Sonotron NDT
Original developer and manufacturer of advanced ultrasonic instruments
2115 views
Technical Discussions
Conrad
Other, QA Manager
Swepco Tube, USA, Joined Feb 2014, 2

Conrad

Other, QA Manager
Swepco Tube,
USA,
Joined Feb 2014
2
14:35 Feb-21-2014
RT

Can someone help with this question, I am prepping for my ACCP/ASNT Level 3 RT renewal.
Assume you are standing three feet from a a 15 Curie cobalt-60 source. How many mR/hr dosages are you getting?

 
 Reply 
 
Frank Lund
R & D,
United Kingdom, Joined Apr 2005, 222

Frank Lund

R & D,
United Kingdom,
Joined Apr 2005
222
15:08 Feb-21-2014
Re: RT
In Reply to Conrad at 14:35 Feb-21-2014 (Opening).

My background is not in RT, but I would have thought that knowledge of strength of sources would be fundamental for a Level 1 in view of its impact on Radiological Safety.

 
 Reply 
 
Gerald R. Reams
Engineering,
Industry, USA, Joined Aug 2012, 181

Gerald R. Reams

Engineering,
Industry,
USA,
Joined Aug 2012
181
15:23 Feb-21-2014
Re: RT
In Reply to Frank Lund at 15:08 Feb-21-2014 .

A word of advice for taking Level III examinations: You need to be very familiar and comfortable with equations that are basic to the NDE method. You need to understand which equation applies to the question asked and how to properly complete the calculations.

I assume that since you are preparing for your Level III renewal examination, you have successfully passed the initial Radiography Level III examination. If so, you should be capable of working the equation.


Regards,
Gerald R. Reams
ASNT NDT Level III

 
 Reply 
 
Conrad
Other, QA Manager
Swepco Tube, USA, Joined Feb 2014, 2

Conrad

Other, QA Manager
Swepco Tube,
USA,
Joined Feb 2014
2
16:43 Feb-21-2014
Re: RT
In Reply to Gerald R. Reams at 15:23 Feb-21-2014 .

Wow, my first time posting here and I get hammered. I expect it from the Brit, but et tu Gerald? I should be use to NDT egos by now, I guess. OK, I did work out the problem and got 23.2 mR/H but it wasn't an answer on the multiple choice exam. So, I came here for a consensus.

 
 Reply 
 
Frank Lund
R & D,
United Kingdom, Joined Apr 2005, 222

Frank Lund

R & D,
United Kingdom,
Joined Apr 2005
222
17:32 Feb-21-2014
Re: RT
In Reply to Conrad at 16:43 Feb-21-2014 .

Conrad,

There's no need for that "Brit" comment. Experts everywhere should know the basics.

We see a lot of questions on here that are worrying. Beginners/students ask basic questions as we could expect, but it often seems that people are just going on inspection with very little understanding of their kit.

Frank

 
 Reply 
 
Gerald R. Reams
Engineering,
Industry, USA, Joined Aug 2012, 181

Gerald R. Reams

Engineering,
Industry,
USA,
Joined Aug 2012
181
18:13 Feb-21-2014
Re: RT
In Reply to Conrad at 16:43 Feb-21-2014 .

I am American by birth. My Mother's family is Welsh and my Father's famly is English by way of Normandy. That probably makes me a mixture of Celt and Viking.

My only intent was to caution an individual in regards to the rigors of the Radiographic method Level III examination. Still, it is a basic inverse sqare law equation using the proper emissivity values.

Gerald,

 
 Reply 
 
Uli Mletzko
R & D, Retired
Germany, Joined Nov 1998, 89

Uli Mletzko

R & D, Retired
Germany,
Joined Nov 1998
89
11:56 Feb-22-2014
Re: RT
In Reply to Conrad at 16:43 Feb-21-2014 .

Hallo Conrad,

I think, your calculation was O.K., but in your answer you did a mistake of factor 1000 (thousand), because the question should be answered in mR/h (milli-Roentgen per hour) and not in R/h (Roentgen per hour).

Nevertheless, I'm surprised that in the year 2014 ACCP/ASNT is still using the units ROENTGEN (R) and CURIE (Ci), which at least in Europe since some decades are replaced by SIEVERT (Sv) and BEQUEREL (Bq).

The law is
(dose rate) = (specific dose rate) * activity/distance^2 .

The specific dose rate for Co 60 in metric units is either 0.354 (mSv*m^2)/(h*GBq) or 1.32 (R*m^2)/(h*Ci). If I use a distance of 3 feet = about 0.91 meter and an activity of 15 Ci, this will result in a dose rate of about 23.9 R/h or 23900 mR/h (if I have made no mathematical errors).

Regards
Uli

 
 Reply 
 
Pablo
Engineering,
ASNT Level 3, Argentina, Joined Sep 2007, 10

Pablo

Engineering,
ASNT Level 3,
Argentina,
Joined Sep 2007
10
13:18 Feb-23-2014
Re: RT
In Reply to Conrad at 14:35 Feb-21-2014 (Opening).

Hello Conrad, the dose rate is 23.2 R/h or 23200 mR/h.

Regards,
Pablo.

 
 Reply 
 

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