If q is very small, then co0 is also small and less than the smallest A,-. Thus e = (l*co0/keS) + o,0 £ (ft/A,) = К (1.13)

І-1

Thus the stable period, co0 — q/1, is inversely proportional to the mean ef­fective neutron lifetime / where:

/=(/*/*«*) +SOTO 0-14)

»-l

For a fast reactor l* is between 10~® and 10-8 and thus the terms of the right hand side of the equation for / are of the order of 10-e or less and 40 X 10-3 so that l* is not important here. For small reactivity changes then the delayed neutron characteristics are most important and

/ — E (AM«)

i-l

This is true also for thermal systems where І* ~ 10-3.