The level of 235 U in uranium ore (< 1%) is generally not sufficient for use in
ID: 925224 • Letter: T
Question
The level of 235U in uranium ore (< 1%) is generally not sufficient for use in nuclear reactors; the uranium in the ore is mostly 238U and must be enriched to approximately 4% 235U for use as a nuclear fuel. In the 20th century (and to a lesser extent today) this enrichment was achieved by chemical transformation of the uranium in the ore to uranyl hexafluoride, UF6. Effusion of gaseous UF6 through a semipermeable membrane slightly enriches 235U on the far side of the membrane because the relative effusion rates of 235U and U are proportional to the inverse square roots of their masses,
The level of 235U in uranium ore (< 1%) is generally not sufficient for use in nuclear reactors; the uranium in the ore is mostly 238U and must be enriched to approximately 4% 235U for use as a nuclear fuel. In the 20th century (and to a lesser extent today) this enrichment was achieved by chemical transformation of the uranium in the ore to uranyl hexafluoride, UF6. Effusion of gaseous UF6 through a semipermeable membrane slightly enriches 235U on the far side of the membrane because the relative effusion rates of 235U and U are proportional to the inverse square roots of their masses
How many passes through the semipermeable membrane would be required to prepare UF6 gas enriched to 4% 235U?
Explanation / Answer
Calculate the amount of 235 U which should be present as 4% 235 U in UF6 = [( 352 x 4 ) /100] =14.08 parts by wt.
According to the given relation , the rate of enrichment of 238 U with 235 U is inversely proportional to square root of the mass ratio of 238 U & 235 U = SQRT 238 / 235 = 1.0063 which means that a single pass of UF6 would enrich U238 with U235 by 1 / 1.0063 = 0.9937 parts by weight
Therefore for enriching to 14.08 parts of U235 the number of passes required = ( 14.08 /0.9937 ) = 14.17
which is practically equal to 14 passes.
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