HW18-7a7b

HW18-7a7b - in Table C.1 aIj20 = 2aIj + ar; = 2a~ + a~ = 2...

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10-4 Chap. 10 Principles of Nuclear Reactors 5::- L- a -I-J u nI 4- C a "jjj U! i;: ""iV E L- QI .c I- A soluble salt of fully enriched uranium is dissolved in water to make a solution containing 1.5 x 10-3 atoms of 235U per molecule of water. (a) Explain why lOp ~ 1 for this solution. (b) What is koo for this solution? Neglect any neutron absorption by other elements in the uranium salt. (c) This solution is used to fill a bare spherical tank of radius R. Plot keff versus R and determine the radius of the tank needed to produce a critical reactor. Solution: We will need the microscopic thermal absorption cross section aIj20 for water. Treating water as being composed of 1 Hand 160 only, we find from the data
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Unformatted text preview: in Table C.1 aIj20 = 2aIj + ar; = 2a~ + a~ = 2 x 0.333 b + 0.00019 b = 0.666 bfmolecule. Other needed cross section data are obtained from Ta-ble 10.1. The diffusion length for pure water, Lk2o = 8.1 cm2, and the Fermi age rH20 = 27 cm2 are taken from Table 10.2. (a) Almost all of the neutron absorption during slowing down in a uranium fueled reactor is due to 238U. Similarly, almost all fast fission is caused by fission neutrons interacting with 238U. Thus, without any 238U, fp ~ 1. (b) From Eq. (10.3) July 24. 2002...
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This note was uploaded on 02/01/2010 for the course ECE 4130 taught by Professor Cady during the Spring '06 term at Cornell.

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