[ RadSafe ] DOT versus DOE 5400.5 and Other Authorized Limits

Glenn R. Marshall GRMarshall at philotechnics.com
Mon Aug 22 09:13:23 CDT 2011


Question 1:  The table might meet SCO, but only if it the activity exceeds the limits of 49 CFR 173.436 for both activity concentration and toatl activity per consignment.  If it doesn't exceed both of those limits, then it's not Class 7 material and would not be shipped as SCO.

Question 2: Yes.  An item could meet DOE or Reg Guide 1.86 contamiantion limits and be unconditionally released, but could, I suppose, have enough activity to be considered DOT Class 7 material.  I would have to think for while to come up with an example, but it could happen.  Maybe a very large, thin sheet of plastic that was just below the Reg Guide 1.86 limits; but if you added up all the activity it would exceed 49 CFR 173.436.

Question 3:  Most of the activity in enriched uranium is U-234.  My first reaction is to assume the people who wrote the regulations intended for U-234 to also be a low-toxicity alpha emitter.  But it doesn't make sense to risk a DOT violation because we thought we knew what the regulator who wrote that definition was thinking.  Because neither enriched uranium nor U-234 is listed in the definition, you should assume it's high toxicity.

Glenn Marshall

From: radsafe-bounces at health.phys.iit.edu [radsafe-bounces at health.phys.iit.edu] On Behalf Of Redmond, Randy (RXQ) [redmondrr at y12.doe.gov]
Sent: Monday, August 22, 2011 8:33 AM
To: The International Radiation Protection (Health Physics) Mailing List
Subject: [ RadSafe ] DOT versus DOE 5400.5 and Other Authorized Limits

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?


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?


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.


Randy Redmond
B&W Y-12
Radiological Engineering

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