Interpretation of Pulsed-Source Experiments in the Peach Bottom HTGR

Fort St. Vrain startup test A-3: pulsed-neutron experiments

“…a pulsed-neutron source, 2. three neutron detectors, 3. an external timer, and 4. the Fort St. Vrain data logger programmed as a multichannel analyzer.…”

“…1 and 2), eight with rods withdrawn in the normal sequence (Confs. 3,6,7,8,9,10,llA,and IIB), and three with high worth rods withdrawn (Confs. 4, 5, and 12 Note: The predicted rod worths were obtained using a 4-group, hexagonal geometry core model, not the seven-group, r-z geometry model discussed in Section 7.…”

“…If C. is the number of raw counts in channel i, then the number of counts in channel i corrected for the detector dead time is C, This is the same as Eq. (2)(3)(4) …”

“…Moreover, the magnitude of F is nearly 1 in most cases so that the correction is small. However, for the more subcritical configurations (1)(2)(3)(4)(5)(6) , the effect of higher harmonics leads to considerable error in the calculation of F by Eq. (9).…”

“…5 and 8). For the six distinct control rod configurations for which two runs of data were taken, those designated by 2A, 3,4,5,6, and 7 were predicted to be optimum, while 2B, 3A, 4A, 5A, 6A, and 7A were reasonable alternates. In all but one of these configurations (6 + 6A), there was less scatter in the three a values for the optimum detector locations than in the three a values for the alternate detector locations.…”