Prob. F.9 The cross section of a cylindrical fuel element in a nuclear reactor i

Question

Prob. F.9 The cross section of a cylindrical fuel element in a nuclear reactor is shown below. The element is designed to operate surrounded by a 200 F coolant. An average heat-transfer coefi cient between the cladding and the coolant is 1200 Btu/hr-ft The reactor safeguards committee is con- cerned about safety duringstart up ofthe reactor. When the control rods are suddenly pulled, and generation begins in the thorium, there is the possibility that if the rods are accidentally pulled too far and/or too fast there may not be time to correct the trouble before melting of either the thorium or the aluminum occurs. NELG is about to run a test program in which such a fuelelement is suddenly exposed to a neutron source so that generation begins suddenly. The test exposure flux will produce a heat generation rate of 40,000 Btu/hr-in 3. The test will be controlled so that the ambient remains constant at 200 F (with h 1200 Btu/hr-ft2.eF and the fuel ele. ment will be initially at 200 F. You have been called in to estimate the length of time before Thin aluminum cladding 1 in. Thorium fuel rod

Explanation / Answer

Solution:

The computation are expressed below using heat conduction for the given data,

t = ((130+25)/2)*1*(3300-1200)) / (1*40,000)

t = 4.07 hrs for complete meltdown.

Hence nuclear meltdown is highly dangerous which cannot controlled if rapid shutdown system fails, most advanced safety systems are implemented each year but cannot able to control nuclear meltdown once it crosses its threshold limit.

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