HFIR

Initiating events, in this study, initiate plant scram or setback. Other initiators, such as refueling discharge accidents, do not necessarily cause a reactor shutdown but may lead t< minor fuel damage and radioactive releases. The list of initiators for nuclear power plants has litf ance for HFBR because of size and design differences. A list of HFBR-specific initiators was developed from " st prepared with the HFBR staff, the FSAR, the plant design manual, the procedures manual, techn specifications, monthly operating reports, and the HFIR PRA (Johnson, 1988). 

Clicvcrton, R. D. ct ai 1987, Evaluation of HFIR Pressure Vessel Integrity Considering Radiation Embrittleiiiciit, ORNL/TM-10444, September. 

Os-191 is produced by neutron irradiation of isotopically enriched 0s-190 (isotopic composition 0s-190, 97.8 o Os-188, 0.47 o Os-192, 1. 02 o). Irradiations are currrently performed at the Oak Ridge National Laboratory in the High Flux Isotope Reactor (HFIR) at a neutron flux of 2.5 x 10 n/cm -s. The routes to the various nuclides produced during irradiation of the 0s-190 target and the neutron cross-section values (2 ) are summarized below (Scheme I). 

The discovery of fermium (also einsteinium) was not the result of very carefully planned experiments, as in the cases of the other trans uranium elements, bill fermiuni and einsteinium were found in Ihe debris of an atomic weapon lest in the Pacific in November 1952. Researchers, using the Oak Ridge High Flux Isotope Reactor (HFIR) which produced 3.2-hour " Fm. determined ihe magnetic moment of the atomic ground state of the neutral fermium atom with a modified atomic beam magnetic resonance... 

All of this would not be possible without the High Flux Isotope Reactor (HFIR) to serve as a source of neutrons to carry out the transmutation of the elements. Since first reaching full power (100 MW) on October 21, 1966, the HFIR has logged 4148 equivalent full power days through December 31, 1979, for an overall operating efficiency of 86%. During many years, this figure has run 93% or more. 

The purpose of this paper is to indicate the capabilities of the HFIR for transplutonium element production and particularly to dwell on the mathematical techniques involved in forecasting the composition of irradiated target materials. Also described are some of the uses to which such forecasts are put. Early work along this line was published by Burch, Arnold, and Chetham-Strode (6), providing the basis for design of HFIR and TRU. 

The axial distribution was measured in early experiments in the HFIR. The data were very well fit by the usual chopped cosine distribution with a small amount of reflector peaking (Fig. 4). We generally calculate the target compositions at... 

Figure 3. Radial flux distribution in HFIR target island...

For the HFIR, this ratio is 0.839, and for calculational purposes, the thermal fluxes described in the preceding section were multiplied by this quantity before use in computing reaction rates. 

All of these models must now be combined to yield a useful approximation for the reaction rate of a nuclide with the neutrons in the HFIR. 

Table I. Neutron cross section parameters used to compute transmutations in HFIR target irradiations...

Table II. Comparison of Calculated and Measured Isotope Yields for 13 HFIR Targets Processed During TRU Campaign 59.

Figure 5. Californium-252 production efficiency for HFIR feed of two compositions...

HFIR) Experiment Facilities and Capabilities, ORNL Brochure available from K. J. Foust, Bldg. 7910, Oak Ridge National Laboratory, P. 0. Box X, Oak Ridge, TN 37830. 

Chapman, T. G. HFIR Target Design Study, ORNL-TM-1084... 

Analysis of Failure of HFIR Target Elements Irradiated in SRL and HFIR - An Interim Status Report, ORNL-TM-2236, (February 1972). 

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