United States Nuclear Regulatory Commission - Protecting People and the Environment

U.S. Nuclear Regulatory Commission

Airborne Thorium From Welding Rods

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


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


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


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

Page Last Reviewed/Updated Thursday, March 29, 2012