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November 8–12, 2025
Washington, DC|Washington Hilton
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DNFSB’s Summers ends board tenure, extending agency’s loss of quorum
Lee
Summers
The Defense Nuclear Facilities Safety Board, the independent agency responsible for ensuring that Department of Energy facilities are protective of public health and safety, announced that the board’s acting chairman, Thomas Summers, has concluded his service with the agency, having completed his second term as a board member on October 18.
Summers’ departure leaves Patricia Lee, who joined the DNFSB after being confirmed by the Senate in July 2024, as the board’s only remaining member and acting chair. Lee’s DNFSB board term ends in October 2027.
H. C. Claiborne, W. W. Engle, Jr.
Nuclear Technology | Volume 13 | Number 2 | February 1972 | Pages 209-215
Technical Paper | Shielding | doi.org/10.13182/NT72-A31055
Articles are hosted by Taylor and Francis Online.
Electronic components can be affected by the dose rate from gamma rays delivered during the first few shakes (10−8 sec/shake) of an exploding nuclear device. Determining such dose rates generally requires expensive time-dependent calculations. This paper demonstrates that relatively inexpensive steady-state transport calculations can be used to bracket time-dependent peak dose rates with meaningful upper and lower limits. The model configuration consisted of a sphere of air surrounded by a spherical annulus of concrete with an isotropic source of gamma rays from fissioning 235U located at the geometric center. Steady-state calculations were made with the discrete ordinates code ANISN and the time-dependent calculations with time-dependent ANISN (TDA). The upper limit dose rates were obtained by dividing the steady-state total dose by the pulse width of the device. This is equivalent to assuming that the uncollided and air-scattered fluxes arrive at the shield simultaneously. For a lower limit calculation, only the uncollided flux was considered incident on the shield. Calculations were made for a 120-cm-thick concrete shield for ranges of 500, 1000, and 5000 m and for step-function burst pulse widths of 1 through 8 shakes. The results from the steady-state calculations generally bracketed the peak time-dependent dose rates within an acceptably narrow band except for the 500-m range at the back end of the shield where the peak time-dependent dose rates were highest for all pulse widths. This apparent anomaly is explained on the basis of using a moving boundary condition in the time-dependent solution and the effect is shown to be of no consequence.