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Re: [Fwd: IH- 2% Thoriated Tungsten]
NRC, HHPOS-255 provides useful information regarding thorium in welding
rods.
A copy is pasted, below.
The opinions expressed are strictly mine.
It's not about dose, it's about trust.
Bill Lipton
liptonw@dteenergy.com
HPPOS-255 PDR-9308020142
Title: Airborne Thorium From Welding Rods
See the memorandum from L. J. Cunningham to J. H. Joyner
(and others) dated June 18, 1993. This memo addresses a
question from a corporate health physicist at a nuclear
utility that had found airborne thorium in a nuclear power
plant. Although this regulatory position is presented
quite clearly in 10 CFR Part 40, it is being issued as a
health physics position to call attention to an exemption
that might otherwise be overlooked by Part 50 licensees.
A response was requested as to whether there are any NRC
regulatory requirements that apply to airborne thorium
caused by grinding the tips and using welding rods
containing thorium. The response stated that 10 CFR 40,
"Domestic Licensing of Source Material", in subsection
40.13 (c) (1) (iii), provides that any person is exempt
from the regulations in Part 40 and from requirements for
an NRC license to the extent that the person receives,
possesses, uses, or transfers any quantities of thorium
contained in welding rods. Therefore, there are no NRC
regulatory requirements that apply to airborne thorium
caused by grinding and using welding rods that contain
thorium.
Additional technical information concerning the
considerations for the 10 CFR Part 40 exemption for
thoriated welding rods does not include any information on
the radiological hazards associated with their use.
However, some information on the radiation doses associated
with the use of these rods can be found in the following
references:
1. NUREG / CR-1039, "Estimated Radiation Doses from
Thorium and Daughters Contained in Thoriated Welding
Electrodes," December 1979.
2. NUREG / CR-1775, "Environmental Assessment of
Consumer Products Containing Radioactive Material," October
1980.
3. NCRP Report No. 95, "Radiation Exposure of the U.S.
Population from Consumer Products and Miscellaneous
Sources," 1987.
4. E. M. Crim and T. D. Bradley, Abstracts of Papers
Presented at the Thirty-Eighth Meeting of the Health
Physics Society, Atlanta, Georgia, 11-15 July, 1993, Health
Physics, Vol. 64, Supplement 1, p. S85, June 1993.
Reference 2 includes the following summary statement
concerning radiation doses:
The maximum individual fifty-year dose commitment to bone
for welders was estimated at between 55 mrem and 2 rem for
a one-year exposure. Welders not engaged in welding at
home and occasional welders were estimated to receive a
bone dose commitment of 16 to 575 mrem and 1.3 to 115 mrem,
respectively. A maximum individual bone dose commitment
range between 30 and 230 mrem was estimated for nonwelders.
External doses for all group members were estimated to be
less than 1 mrem.
Reference 4 includes the following statement concerning
airborne thorium (Th-232) from welding rods:
The results for the grinding and welding operations to
date, show that all personal and area air samples are below
the maximum permissible concentration for Th-232 as well as
below the derived air concentration.
Regulatory references: 10 CFR 40.13
Subject codes: 7.2, 8.4
Applicability: Reactors
I understand your concerns. The radiation levels for a 2% thoriated welding
rod(s) are extremely low. Badges are not required for use during welding.
The health concern is airborne particles or fumes. An air sample would
provide you with adequate data as to air quality.
I would consult your state health departments Radiation Safety office for
guidance.
Good luck,
David Romaine
RASI Health Physics
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