Reactivity excess prompt

The quantity k t) is the excess prompt reactivity and I is the prompt generation time. The small time variation of Z will be ignored throughout. The assumptions that all power is in the fundamental mode shape and that I is independent of time seem unlikely to lead to serious error, but do represent potential weaknesses in the argument. The equation for the time variation of power when a neutron source is present can be written ... 

A further set of definitions is convenient. We decompose the excess prompt reactivity as follows ... 

Justify that the expression dn/dt = nkex/l describes correctly the change of neutron density n with time t on the microsecond time scale. Here kg is the excess prompt reactivity and 1 is the neutron lifetime. 

Various reactive oxygen species (ROS) are generated from enzymatic and nonenzymatic processes during the normal metabolism in cells. If excessive ROS are not eliminated promptly, the accumulated ROS will induce cytotoxicity, which plays important role in pathophysiology of... 

Prompt negative coeflScient of Triga fuel is well known, and for fuel having higher uranium content, they use Erbium as the burnable poison to compensate excess reactivity. 

Based upon past Hanford experience and taking into consideration additional factors unique to B Beactor, an upper limit for error in a reactivity prediction prior to startup is 1 per cent k If rods are withdrawn at the maximum rate possible (l U per cent k/sdn) beyond the point of criticality, approximately 30 seconds of rod withdrawal would be required to reach prompt critical and approximately ko seconds to attain an excess reactivity equal to the prediction error ... 

The FUJI MSR has very low excess reactivity, and even in the case of a malicious action of control rod withdrawal, the reactor would have no prompt criticality accidents with a release of radioactivity to the environment. 

Here is taken to be the excess reactivity above delayed critical, /3 is the fraction of neutrons delayed/prompt neutron, and t is the effective lifetime. 

Thus prompt critical may, in some cases, be as little as 0.1% excess reactivity. 

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