jgd@gatech.edu (John G. De Armond) (11/04/89)
From: rsiatl!jgd@gatech.edu (John G. De Armond) In article <10851@cbnews.ATT.COM> mamba@csd4.csd.uwm.edu (Paul A Deisinger) writes: >That reminds me, take a look at this story off of the AP newswire: > >"An Energy Department laboratory in Tennesee lost a significant amount of >radioactive tritium in a test shipment between two lab buildings, raising the >possibility of foul play, governmental records show. To inject a bit of fact, the media raised the "foul play" issue. The DOE accurately attributed the probable "shortage" to instrumentation problems in the shipping container filling apparatus. The actual ammount reported unaccounted for is about 4 grams, or in more ordinary terms and assuming the physical form to be tritium oxide, about a thimble-full. I am personally familiar with the facilities at the DOE lab in Oak Ridge, having bought thousands of curies of radioactive gas for my work. A description of the handling apparatus is in order. High concentration gaseous radioisotopes are handled and shipped in partial vacuum in order to ensure that any leakage will result in air dilution of the specimen rather than release of the isotope. Shipment is normally in DOT class 7A radioactive gas shipping cylinders. These containers pass a set of physical abuse tests quite similiar to those required of nuclear fuel shipping containers. A typical filling operation is as follows. A manifold assembly is used to measure the shipment and contain it. Typically, the gas is condensed in LN or activated charcoal traps and the quantity is measured indirectly by means of partial pressure measurements and a knowledge of the volume of the system. The shipping container is evacuated and flushed with helium (used because it will not condense in cold traps) several time to ensure an inert and dry atomosphere in the cylinder. A final mechanical hogging pumpdown leaves the pressure >29 in Hg in the cylinder. Next, the manifold is opened and the isotope gas is allowed to flow by differential pressure into the cylinder. The quantity delivered is determined by measuring the rise in pressure in the cylinder and by knowing the internal volume. If the quantity of isotope dictates, helium is used to flush the manifold of isotope. Then the cylinder is filled with helium to leave the pressure a few mm below atomspheric. After the cylinder is capped and sealed, the residual isotope is purged either to a waste gas stack or to a recovery unit, depending on the value of the gas. Kr-85 with is plentiful to the point of being a waste gas is typically purged. H-3 or Xe-133 would be salvaged for the most part. This technique make for quite simple and safe handling and makes it easy for the end-user to extract the sometime microgram quantity of isotope. All he has to do is condense the isotope gas in a cold trap. The helium remains a gas and is purged. The DOE preliminary report attributes the descrepancy between shipped and received quantities (4 grams, remember) to an air leak in the manifolding. An air leak would lead the operator to believe that more isotope had been transfered than what had actually been delivered. If calculations showed that a sufficiently small quantity of gas remained in the manifold that recovery was not justified, the contents would be purged to the stack. The difference between what was thought to be delivered and what actually was delivered would go up the stack. >Ironically, the secret test was done as a part of an internal investigation >into troubling discrepancies in the amount of tritium shipped from the Oak >Ridge National Laboratory at Oak Ridge, Tenn., to commercial buyers. Troubling descrepancy mostly because of the anticipated media grandstanding which they got. BTW, QA testing and verification is a routine aspect of radioactive and SNM materials handling. The safeguards practiced by the recipient of the material caught the descrepancy and prompted the additional testing of the transfer apparatus. > >Tritium supplies are classified by teh government. The material is produced >in Energy Department reactors in South Carolina for use in nuclear warheads, >although small amounts are sold to domestic and foreign companies. Kinda makes sense that the government would classify our stockpiles, especially in light of the problems in the production reactors. Knowledge of what we have would be an important barganing tool for the Soviets in weapons reduction talks. >No explanation could be found for the tritium lost in the test shipment, >according to a report Wednesday." Only in the popular media. Preliminary scientific reports are very credible and offer very likely explainations of what happened. >Wonderful, just wonderful. Yeah, I thought so too. Nice to see the safeguards system works! >Paul Deisinger Just to put this thing into perspective relative to possible sinister involvement in diversion, consider that the quantity involved here is of the same magnitude as the tritium contained in the self-luminous emergency exit signs in airplanes and public buildings. If I were intent on collecting tritium for weapons use, I'd simply steal some emergency signs. There is no accountibility at this level which is in sharp contrast to the safeguards involved in delivering the raw material. It would be just plain stupid to try to steal from a DOE facility when the stuff is so readily available elsewhere. John -- John De Armond, WD4OQC | Manual? ... What manual ?!? Radiation Systems, Inc. Atlanta, GA | This is Unix, My son, You emory!stiatl!rsiatl!jgd **I am the NRA** | just GOTTA Know!!!