[Michael Homchick]

I wrote last night that we found a pretty hot (Gamma) slab. I emaild a state rad expert asking about it.

“

Hello,

I found your email address of a federal nuke site. I have a question about a material that is reading 99 micorRoentgens per hour, with the PM1703 meter laid against the material.

Is this high enough to be of concern? The meter will read in the low forties or high thirties at four feet or so.

Is there any website that carries info like this, something that will help me understand what levels of radiation are safe and what are dangerous, expressed in milliRoentgens or microRoentgens? That is all my meter will read, except cpm.

Thanks,

Al”

And his first response:

“ I wouldn’t expect 99 microR/hour to be a health hazard for a reasonable period of time. State and federal rules prohibit exposing the public (including non-radiation workers) to more than 2,000 microR/hour, and to more than 100,000 microR in a year’s time. If you have a device that is leaking radiation, such as an old Radium watch or aircraft instruments sometimes do, it could present a problem by ingesting radioactive materials. What sort of material do you have?

M.B.

Program Manager

Oklahoma DEQ

Radiation Management Section”

I replied back:

“

It is a Bordeaux granite slab that we have been requested to fabricate into countertops. We are using 4 to 5 times background levels as our highest recommended level granite for inside countertops, purely arbitrary, but with so many opinions out there on the subject, we feel it is best to be over cautious.

I’m thinking five hours a day close in exposure to a countertop, times 365 days would mean 180,675 microR/year. Again that might be over cautious, but we will decline the job if there is the slightest worry. I am no way close to being an expert, probably know enough to get me in trouble, but if kids and pregnant women are at risk, I’m not working the slab.

The slab read 1.4 milliroentgens on our Geiger-Mueller counter. It is a new Leni unit, about five or six weeks since calibration. Strictly amateur’s measuring, but I am assuming most of the 1.4 is Alpha.

Does your department have a website with any info on these matters? I take it that there are state rules that I could read on this matter, are they available online?

Thanks for your help on this,

Al

“

He replied back:

“

Granite typically contains Uranium and daughter products. In practice, this means mostly Uranium-238 and Radium-226. There is some “external hazard” from radiation of the type you are measuring, but the biggest avenue for concern is internal exposure after the material is inhaled or ingested. I doubt there is a major health hazard from doing this on a one time basis, but I’d still advise trying to arrange things to minimize inhalation of dust from any grinding or cutting, and cleaning up the dust afterwards. As an absolute minimum, a well-ventilated area. If it doesn’t create a bigger safety hazard, I’d consider respiratory protection. I suspect you do these protective measures for normal stone dust, but have no experience for sure.

The official rules that will be of most concern as far as exposure are 10 CFR 20 Parts C and D, Occupational Dose Limits and Dose limits for Individual Members of the Public. They are available on the internet here:

http://www.access.gpo.gov/nara/cfr/waisidx_05/10cfr20_05.html

If you have any waste material, you are not supposed to dispose of it in a solid waste landfill in the state. You may want to send any waste material (trimmings, etc.) back to the person who gave you the slab rather than keep them around yourself.

To repeat, the main thing I’d be concerned about is if you do any grinding or cutting that generates particulates.

Is there any doubt left that some granites are hazardous?

[Chris Goore]

Using the 100,000 per year max exposure level, a person could spend no more than 2.7 hours per day in or near that kitchen, if they received no other radiation from other sources.

Anyone know how many hours per day a normal kitchen is used?

[robin@oystra]

Found one reference on the subject

” Women reported that they spent about 2.1 hours per day on cooking food, about 1.1 hour on cleaning the household and utensils.”

[CalinB]

That site mentioned in the Rad experts email said that pregnant women were allowed only 500 milliRoentgens, .50 of a Rem.

That would be around 350 hours if one had that Bordeaux in their kitchen. After that, the woman would be allowed only 35 hours more for the remainder of the pregnancy.

Let’s all say it together,

“No pregnant women around granite countertops.”

Here are the actual NRC rules:

(a) Each licensee shall conduct operations so that —

(1) The total effective dose equivalent to individual members of the

public from the licensed operation does not exceed 0.1 rem (1 mSv) in a

year, exclusive of the dose contributions from background radiation,

from any medical administration the individual has received, from

exposure to individuals administered radioactive material and released

under Sec. 35.75, from voluntary participation in medical research

programs, and from the licensee’s disposal of radioactive material into

sanitary sewerage in accordance with Sec. 20.2003, and

(2) The dose in any unrestricted area from external sources,

exclusive of the dose contributions from patients administered

radioactive material and released in accordance with Sec. 35.75, does

not exceed 0.002 rem (0.02 millisievert) in any one hour.

The level allowed, .1 rem would be 100milliRoentgens per year. Bordeaux can pump out as much as 1.7 milliRoentgens per hour, so 58 hours would max out your exposure.

Uh, oh. Read part (2), it restricts you to .002 of a rem (2 milliRoentgens) per hour. 1.7 milliRoentgens is too close for comfort in my opinion.

[Gail Chase]

“To repeat, the main thing I’d be concerned about is if you do any grinding or cutting that generates particulates.”

I’m glad we went all wet from the start and pay Jose to spray the floors down daily as an added precaution…

[Andy Graves]

Posted By Kevin Noel on 04/22/2008 6:51 PM

“To repeat, the main thing I’d be concerned about is if you do any grinding or cutting that generates particulates.”

I’m glad we went all wet from the start and pay Jose to spray the floors down daily as an added precaution…

Smart move. Not only will this protect your employees, but it should insulate you from furture lawsuits if an employee decides to sue for some lung related injury.

[Mike]

Heard back from the state Rad expert on disposal of any scraps of Bordeaux.

“There isn’t an approved way to dispose of “NORM” (Naturally-Occurring Radioactive Material) such as this in an Oklahoma facility. An effort we made several years ago to establish a regulation to cover this sort of situation failed due to controversy. People who’ve had to deal with it tell me that the cheapest way they’ve found is with a company called Waste Control Services that has a facility in Andrews County, TX. “

I would bet that a drum of scraps would run $500 or more to dispose of. Some universities that are closing down their physics labs are stuck with storing the radioactive samples due to the cost of disposing of them. Same thing with some of the machinerry for measuring radiation, some of which has radioactive check sources.

Granite, the only countertop material that I know of that can require haz mat disposal.

One of the radiation field guys on one of the radiation groups I belong to mentiond that our reading of 99 microRoentgens per hour meant that the slab was putting out 5,940 counts per minute. That is only on the small pager sized detector, a person would be exposed to over 600 times more hits.

[Author]

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