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A large measure of the successfil operation of the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL) for over a decade can be attributed to the cleaning of its UHV components during and after construction. A new UHV cleaning process, which had to be environmentally and personnel safe, was needed to replace the harsh, unfriendly process which was still in use. Dow Advanced Cleaning Systems was contracted to develop a replacement process without the use of harsh chemicals and which must clean vacuum surfaces as well as the existing process. Acceptance of the replacement process was primarily based on Photon Stimulated Desorption (PSD) measurements of beam tube samples run on NSLS beam line UIOB. One meter long beam tube samples were fabricated f?om aluminum, 304 stainless steel and oxygen free copper. Initially, coupon samples were cleaned and passed preliminary testing for the proposed process. *Work performed under the auspices of the U.S. Department of Energy, under contract DE-AC02-7GCH000 16 and W-3 1-109-ENG-3 8. Next, beam tube samples of each material were cleaned, and the PSD measured on beam line UlOB using white light with a critical energy of 487ev. Prior to cleaning, the samples were contaminated with a mixture of cutting oils, lubricants, vacuum oils and vacuum grease. The contaminated samples were then baked. Samples of each material were also cleaned with the existing process after the same preparation. Beam tube samples were exposed to between IO" and1023 photons per meter for a PSD measurement. Desorption yields for H,, CO, CO,, CH, and H,O are reported for both the existing cleaning and for the replacement cleaning process. Preliminary data, residual gas scans, and PSD results are given and discussed. The new process is also compared with new cleaning methods develolped in other laboratories.

The LMFBR Debris Coolability Program at Sandia National Laboratories investigates the coolability of particle beds that may form following a severe accident involving core disassembly in a nuclear reactor. The D series experiments utilize fission heating of fully enriched UO2 particles submerged in sodium to realistically simulate decay heating. The D13 experiment is the first in the series to study the effects of bottom cooling of stratified debris, which could be provided in an actual accident condition by structural materials onto which the debris might settle. Additionally, the D13 experiment was designed to achieve maximum temperatures in the debris approaching the melting point of U02-The experiment was operated for over 40 hours and investigated downward heat removal at specific powers of 0.22 to 2.58 W/g. Channeled dryout in the debris was achieved at powers from 0.94 to 2.58 W/g. Maximum temperatures approaching 2700°C were attained. Bottom heat removal was up to 750 kW/m^ as compared to 450 kW/m^ in the DIO experiment.

No abstract

A large measure of the successful operation of the National Synchrotron Light Source ͑NSLS͒ at Brookhaven National Laboratory ͑BNL͒ for over a decade can be attributed to the cleaning of its ultrahigh vacuum ͑UHV͒ components during and after construction. A new UHV cleaning process, which has to be environmentally and personnel safe, is needed to replace the harsh, unfriendly process which is still in use. Dow Advanced Cleaning Systems was contracted to develop a replacement process without the use of harsh chemicals and which must clean vacuum surfaces as well as the existing process. Acceptance of the replacement process was primarily based on photon stimulated desorption ͑PSD͒ measurements of beam tube samples run on NSLS beam line U10B. One meter long beam tube samples were fabricated from aluminum, 304 stainless steel, and oxygen-free copper. Initially, coupon samples were cleaned and passed preliminary testing for the proposed process. Next, beam tube samples of each material were cleaned, and the PSD measured on beam line U10B using white light with a critical energy of 487 eV. Prior to cleaning, the samples were contaminated with a mixture of cutting oils, lubricants, vacuum oils, and vacuum grease. The contaminated samples were then baked. Samples of each material were also cleaned with the existing process after the same preparation. Beam tube samples were exposed to between 10 22 and 10 23 photons per meter for a PSD measurement. Desorption yields for H 2 , CO, CO 2 , CH 4 , and H 2 O are reported for both the existing cleaning and for the replacement cleaning process. Preliminary data, residual gas scans, and PSD results are given and discussed. The new process is also compared with new cleaning methods developed in other laboratories. After modification, the new UHV cleaning process was accepted by BNL.