based upon an arbitrary scale in which 100 per cent corresponds to 300 Mwd/t at the center of the rod.nThe reason for expansion of the rods in one case and contraction in another is not yet known, nor is it known whether the rods which shrink are all from the same fabrication batch....
Either (a) the reactor must certainly remain below critical after withdrawal of the rods or (b) more shut-off rods are available for rapid insertion than are being raised at any time. To make start-up possible more than one rod must satisfy criterion (a) and not (b).W. B. Lewis...