[ RadSafe ] DOT versus DOE 5400.5 and Other Authorized Limits

[Redmond, Randy (RXQ)]

Radsafers and IRP,

How are you reconciling the difference between DOT, DOE, NRC Reg. Guide 1.86 surface contamination values?

Question 1

The 49CFR173.403 definition of "contamination" is more restrictive than the Department of Energy (DOE) Order 5400.5 limits to free-release an item to the public and the NRC Regulatory Guide 1.86 surface contamination values [5000 dpm/100 cm2 (0.8 Bq/cm2) fixed plus non-fixed for uranium].  Additionally, if authorized limits are obtained for certain materials/items, the authorized limits may be substantially higher than the values specified in 49CFR173.403.

For example: A table is monitored for radioactive contamination and the monitoring results indicate 0.7 Bq/cm2 fixed plus non-fixed beta-gamma.  The monitoring results exceed 0.4 Bq/cm2 fixed plus non-fixed beta-gamma, but are less than the DOE 5400.5 free-release limit of 0.8 Bq/cm2 fixed plus non-fixed beta-gamma.  The table can be free-released to the public under the DOE 5400.5 limits; however, since 0.7 Bq/cm2 exceeds 0.4 Bq/cm2 , it appears that the table may be considered a Surface Contaminated Object (SCO-1) under 49CFR173.

Is an item that is free-released under DOE 5400.5 limits, or other authorized limits, and exceeds the 49CFR173.403 contamination values, regulated under 49CFR173, OR are there other 49CFR173 criteria (for example: 49CFR173.436 173.436  Activity Limit for Exempt Consignment) must be exceeded that must also be met for the item to be considered a Surface Contaminated Object?

Question 2

If an item is released under DOE or other authorized limits, does DOT even apply?

Reference

49CFR173.403 - "Contamination means the presence of a radioactive substance on a surface in quantities in excess of 0.4 Bq/cm\2\ for beta and gamma emitters and low toxicity alpha emitters or 0.04 Bq/cm\2\ for all other alpha emitters. Contamination exists in two phases.
    (1) Fixed radioactive contamination means radioactive contamination that cannot be removed from a surface during normal conditions of transport.
    (2) Non-fixed radioactive contamination means radioactive contamination that can be removed from a surface during normal conditions of transport."

49CFR173.403 - "(1) SCO-I: A solid object on which:
(ii) The fixed contamination on the accessible surface averaged over 300 cm\2\ (or the area of the surface if less than 300 cm\2\) does not exceed 4 x 10\4\ Bq/cm\2\ (1.0 microcurie/cm\2\) for beta and gamma and low toxicity alpha emitters, or 4 x 10\3\ Bq/cm\2\ (0.1 microcurie/cm\2\) for all other alpha emitters;

Question 3

The 49CFR173.403 definition of low toxicity alpha emitters does not include enriched uranium; however, it includes uranium-235. Uranium-235 always has uranium-234 present. The 49CFR173.403 definition of uranium includes enriched uranium and makes a point in stating that uranium-234 is present in depleted, natural and enriched.

Is enriched uranium considered a high toxicity alpha emitter?  If so, given the definitions, why?

Reference

49CFR173.403 -  "Low toxicity alpha emitters means natural uranium; depleted uranium; natural thorium; uranium-235 or uranium-238; thorium-232; thorium-228 and thorium-230 when contained in ores or physical and chemical concentrates; and alpha emitters with a half-life of less than 10 days."

Uranium--natural, depleted or enriched means the following:
    (1)(i) ``Natural uranium'' means chemically separated uranium containing the naturally occurring distribution of uranium isotopes
(approximately 99.28% uranium-238 and 0.72% uranium-235 by mass).
    (ii) ``Depleted uranium'' means uranium containing a lesser mass percentage of uranium-235 than in natural uranium.
    (iii) ``Enriched uranium'' means uranium containing a greater mass percentage of uranium-235 than 0.72%.
    (2) In all cases listed in this definition, a very small mass percentage of uranium-234 is present.

Regards,

Randy Redmond
B&W Y-12
Radiological Engineering
865.574.5640