AW: [ RadSafe ] What's a "T unit?"

Franz Schönhofer franz.schoenhofer at
Thu Oct 19 15:54:56 CDT 2006


To find out about the unit "TU" you only need to make a 30 seconds Google
search. 1 TU is one tritium atom in 10E18 H-1 atoms. This corresponds to
0.118 Bq/L or for the old fashioned US and not SI-units 3.19 pCi/l. 

Hope this helps.


Franz Schoenhofer
PhD, MR iR
Habicherg. 31/7
A-1160 Vienna
phone -43-0699-1168-1319

> -----Ursprüngliche Nachricht-----
> Von: radsafe-bounces at [mailto:radsafe-bounces at] Im
> Auftrag von Strom, Daniel J
> Gesendet: Donnerstag, 19. Oktober 2006 19:54
> An: radsafe at
> Betreff: [ RadSafe ] What's a "T unit?"
> I need to interpret a declassified report dated June 15, 1944 concerning
> a company called (at the time) Metal Hydrides. Here's what one finds at
> :
> -------------*------------
> Ventron Corporation
> Also Known As: Metal Hydrides Corp.
> Also Known As: Ventron Div., Morton Thiokol, Inc.
> State: Massachusetts Location: Beverly
> Time Period: AWE 1942-1948; Residual Radiation 1949-1995; DOE 1986;
> 1996-1997 (remediation)
> Facility Type: Atomic Weapons Employer Department of Energy
> Facility Description: From 1942 to 1948, Metal Hydrides Corp. was under
> contract to the Manhattan Engineer District and the Atomic Energy
> Commission to convert uranium oxide to uranium metal powder. This work,
> as well as later operations to recover uranium from scrap and turnings
> from a fuel fabrication plant at Hanford, was conducted at a foundry at
> the site. During this period, Metal Hydrides was the AEC's primary
> uranium scrap recovery contractor.
> Cleanup activities at this location included the removal of an
> underground storage tank in 1986. Further remediation was performed
> between May 1996 and August 1997 by Bechtel National Inc. and a number
> of local subcontractors as part of the Formerly Utilized Site
> Remediation Action Program (FUSRAP).
> The plant is currently owed by the Ventron Division of Morton
> International.
> ----------*-----------
> The report gives one pair of readings as "0.04 r/8-hr. day (gamma)" and
> "0.5 T units (beta and gamma)" at "1/2 foot from 14000 pounds of scrap
> metal." For measurements reported in "T units," the report states,
> "Shield was removed from chamber, hence both beta and gamma radiation,
> if present was measured with no differentiation possible."
> In those days, the "Tolerance Dose" was 0.1 "r/day." It is possible that
> a "T unit" was simply a fraction of the tolerance dose, when the beta +
> gamma [open window or shield off] reading was interpreted as simply the
> r/d divided by 0.1.
> The limit for extremities was evidently 5 times higher, because there
> are a whole series of readings inside of a left glove and a right glove
> from 10 Apr. 1944 such as "Beta Rad. R/8 hr." of 0.15 and "Times
> Tolerance" of 0.3, indicating a Tolerance Dose for the hands of 0.5 r/d
> (usually one sees "r" and sometimes "R", as in a column heading where
> all words or abbreviations began with an uppercase letter). I would
> infer that these measurements must have been made with film, the only
> contemporary technology that would fit into a glove. "Times Tolerance"
> values ranged from 0.1 ("inside-back of hand") to 0.5 ("inside-base of
> 3rd and 4th fingers").
> Intriguingly, a paragraph states, "The above figures indicate that these
> gloves were not contaminated beyond the tolerance limit with beta
> radiating materials as of 21 March 1944 or within a week prior to that
> date. Corrections for the decay of radioactive materials were made to
> the 21st of March, because that is when the gloves were shipped, but if
> most of the radioactive contamination was accumulated two or three weeks
> before the 21st, the beta radiation to the hands of the wearer at that
> time was in the neighborhood of tolerance." This would imply a half-life
> of a few weeks. The material in question may have been U-238 alpha decay
> product Th-234, with a 24.1-day half-life, if it had been chemically
> separated from uranium for some reason.
> I would be grateful for any references to information that can confirm
> what a "T unit" was.
> - Dan Strom
> The opinions expressed above, if any, are mine alone and have not been
> reviewed or approved by Battelle, the Pacific Northwest National
> Laboratory, or the U.S. Department of Energy.
> Daniel J. Strom, Ph.D., CHP
> Environmental Technology Directorate, Pacific Northwest National
> Laboratory
> Mail Stop K3-56, PO BOX 999, Richland, Washington 99352-0999 USA
> Overnight: Battelle for the U.S. DOE, 790 6th St., Richland WA 99354
> ATTN: Dan Strom K3-56
> Telephone (509) 375-2626 FAX (509) 375-2019 mailto:strom at
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