Co-60 source , a few non technical questions

[arunmrao]

Co60 is the recommended source for thick section castings/forgings etc. However, I am interested in knowing the availability of this source compared to Ir192,in other countries as there are limited cameras in India.

The waiting period for testing is long and quite often the transportation cost over rides the radiography charges.Also if one can provide a cost ratio between Ir192 and Co60.I shall be thankful.

" All that is necessary for triumph of evil is that good men do nothing".
Edmund Burke

 

[rustbuster]

Co60 is rare from my experience. What are you trying to examine? Would ultrasonics and or advanced UT as in phased array give you acceptable results?

 

[Rjeffery]

1 Curie of Co60 is about equivalent to 75-100 Curies of Ir192 (in quantity not quality). if your total thickness of steel is less than an inch [2.54 cm] then a long exposure with Ir 192 "may" work. other NDE/NDT methods may be more expedient.

 

[JR97]

Rjeffery,

I must take exception to part of your post. We successfully achieve 2-2T sensitivity with Ir-192 at thicknesses up to 2". The exposure times range up to 1/2 hour depending on the activity of the source.

Co-60 can be effectively used for thicknesses up to about 4". The difference being a Co-60 exposure of the 2" thick part will be on the range of 5 minutes (versus 30 for Ir-192).

Depending on the part geometry an option may be a portable X-ray unit. Energies well into the MeV range can be achieved with portable units.

JR97

 

[Rjeffery]

Sorry, I didn't have my exposure wheel out and was estimating using my 53 year old brain that has CRS [Can't Remember Stuff] but you are correct! (I found the exposure calculator)

 

[IRstuff]

Co60 is commonly used for gamma radiation sourcing in testing electronics for radiation tolerance.

TTFN

FAQ731-376

 

[unclesyd]

Ir192 is much better personal safety wise than Co60 when it come to radiation safety.

Since distance is your friend the area required for a Co60 exposure is at a minimum of twice the distance for IR192.

I been around two very serious radiation exposures from a Co60 source.

The thickness numbers given above for each source a little conservative. I have went to 3.25 thick material with Ir192 with intensifying screens and got acceptable radiographs.

 

[arunmrao]

Thanks for the various inputs. I was advised by one of my vendors to provide radiography reports for outermold casting used in a die casting machine. Normally UT is adequate,but this time the engineer refused to qualify without adequate reports.I explained to him the cost and logistic difficulties,but he was not convinced.

"Ours is a multi national company and cost is not a criteria."

This statement prompted me to pose the few questions especially the cost. I hope someone fills in this request too.
Thanks once again for taking your time to read this long post.

" All that is necessary for triumph of evil is that good men do nothing".
Edmund Burke

 

[unclesyd]

I miss the cost part of your post.
I checked with an inspection company that is doing some Ir192 work will I compose this. The supervisor of the crews working stated that the last numbers he saw were that Co60 was approximately 4 times the cost per film compared to Ir192 film. These number were for a large turnaround where there was a lot of radiography being accomplished. From my last experience this numbers seems low.

He also stated that Co60 sources are not as available as they were sevral years ago so mobilization could be a big added cost.

I'll call Monday and see if I can get some actual hard numbers for a better comparison.

 

[unclesyd]

Just got the return call from the local supervisor for an inspection company and got the following information.

With Co60 the technician hourly rate is double.
His company doesn't house a Co60 source anymore so they have to rent one for the duration of the job. The rental fee is an adder to the bill. He states that not many companies are housing Co60 sources anymore so rental is becoming standard practice.

He checked his last three jobs where Co60 was used and after all was said and done the cost was 3-4 times the cost of Ir192 Radiography. He had 2 at 3 times the cost and 1 at 4 times the cost.

 

[arunmrao]

Thanks Unclesyd for the input. The cost is determined by opportunity cost. It ranges anywhere between 6-10 times Ir192 cost and the smug feeling that you are beng served!!.

Is there no way out from this trap?

" All that is necessary for triumph of evil is that good men do nothing".
Edmund Burke

 

[nickt1960]

I too work for a multinational oil & gas company and you should tell your client that we normally prohibit using Co-60 for NDT work as the sensitivity is so low it is not worth the radiation risk to all and sundry. You should ask him whether he truly wants to find defects or does he just want to spend money? UT is the most cost effective option for large wall thicknesses. If UT is not practical for some reason (eg austenitic casting) then it is more practical to transport the casting to a lab with a linear accelerator (high MeV Xray unit). This can penetrate wall thicknesses of 300 mm plus very quickly and has extremely good sensitivity. Cost will be about the same as for C0-60. Nevertheless if your client knows anything about NDT he would realise that UT is always prefereable for thick components if he is serious about finding defects. Another note is that you cannot easily transport Co-60 around the country side. You cannot fly it so unless there is a source within reasonable trucking distance from your casting he should forget this whole idea!