NUCLEAR STUDY OF CONTROL POISONS FOR S3G/S4G
8 ( 2 B 9 = ? = all of those materials which would be acceptable control materials for pressurized water reactors from the nuclear standpoint. Estimates have been made of the quantities required for 19 cruciform- shaped 3/16 in. thick control rods. A material was considered unacceptable if the 3/16 in thick blade was not ''black'' to thermal neutrons with the material at full density. Acceptability for any particular application would depend on the ability of the material to absorb epithermal as well as thermal neutrons. However, this survey is confined to consideration of thermal neutron absorption only. The loss of blackness due to non-uniform burnup of poison was treated in some detail for beron-containing rods and for europium-gadolinium rods, The minimum acceptable concentration of poison for boron-containing rods is about 0.027 grams B/sup 10/cm/sup 2/. for europium-containing rods the recommended concentration is 0.46 grams Eu/cm/sup 2/ (15 volume percent Eu/sub 2/O/sub 3/ in 3/16 in. rod). A number of materials such as hafnium, rhodium, silver, rhenium, and gold are required in large quantities for rod ''blackness'' and as a result are only slightly aftected by non-uniform burnup during operation. These materials are, therefore, desirable from the standpoint of nuclear design simplicity, and the absence of undesirable burnout of the red tips. (auth) l6299 By means of measurements with a double ionization chamber, the average fission cross section of U/sup 238/ for neutrons from the fission of U/sup 235/ was determined in terms of nu , the average number of neutrons per fission of U/sup 235/ The number of fissions of U/sup 238/ was measured in one of the ionization chambers while the number of fissions from the fission neutron source of U/sup 235/ was measured in the other chamber. In the nine runs made to determine the cross section, a variety of different methods was used to determine the number of fissions and the mass of U/sup238/. The weighted average of these runs gives sigma (bar)/sub f/(28) = (0.756 plus or minus 0.008)/ nu barn or, if the most recent value nu = 2.48 plus or minus 0.03 is used, sigma (bar/sub f/ (28) = 0.305 plus or minus 0.005 barn. (auth) l6300 The purpose of this program is to determine the feasibility of using Sr/sup 90/ as the heat source in a thermoelectric generator which is to have an unattended life expectancy of up to 10 years under the most extreme environmental conditions. Designs for 100-w generators for land, sea, and undersea applications arc being de veloped. The most suitable compound form of Sr/sup 90/ and the most corrosion resistant alloy for both land and sea applications were selected, and biological shield requiremeats were determined. The land application design was completed, and fabrication problems of such a unit were analyzed. In selecting the most suitable compound form of Sr/sup 90/, eight compounds were tested for insolubility, thermal conductivity, fabricability, high compound density, high strontium density, and structural stability. Of these eight, only strontium titanate exhibited the qualities required. The corrosion box for heat element compound evaluation was fitted with a water reservoir system to provide constant volume during long term studies. The heat element fabricating dry box was fitted with rubber glove ports and an automatic air sampling device to assure safe operating conditions for fabricating test pellets containing Sr/sup 90/. Stable strontium titanate pellets as large as 2 5/8 in. in diameter were successfully fabricated. Thermal conductivity of strontium titanate and cermets of this compound are being measured from room temperature to operating temperatures of the proposed generator. (First quarterly
- Research Organization:
- Knolls Atomic Power Lab., Schenectady, N.Y.
- DOE Contract Number:
- W-31-109-ENG-52
- NSA Number:
- NSA-13-016298
- OSTI ID:
- 4244100
- Report Number(s):
- KAPL-M-WAN-8(Rev.)
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-59
- Country of Publication:
- United States
- Language:
- English
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