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Shortly thereafter, the DOE Office of Science provided funds for a pilot more » study that confirmed the feasibility of the Million Worker Study (MWS), and then additional resources were provided (with other agencies) to extend the follow-up of many populations, not just DOE workers, but also atomic veterans, industrial radiographers, nuclear power plant workers and medical radiation workers (the Million Persons Study (MPS)). In the early 2000s, the Office of Health, Safety and Security authorized access to specific DOE worker datasets. Since the early 1940’s DOE has supported the conduct of epidemiologic studies of practically every DOE (AEC) facility and collected these data, now managed by the Oak Ridge Associated Universities (ORAU), in remarkable detail. The goal is to ensure that workers are adequately protected from the various radiological hazards associated with DOE sites and operations. Radiation health issues have been an important aspect of DOE's Worker Safety and Health programs. and attributed to the disappearance of the second hump of the double-humped fission barrier and a weakening of the 152-neutron subshell.
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Our measurements support a shift in the spontaneous fission half-life systematics at element 104, first proposed by Flerov and Oganessian et al. Contrary to other observations, we have not found any indication for an 80-ms spontaneous fission activity, earlier credited to the spontaneous fission decay of /sup 260/Rf, in reactions in which we expected to produce this isotope. Presently we are unable to assign several other new spontaneous fission activities with half-lives of approx.15 ms, approx.22 ms, approx.100 ms (Z<104), approx.1.6 s, approx.5 s, approx.5 s, approx.30 s, and approx.47 s. The following tentative assignments are based on several cross bombardments and comparisons between experimental and calculated production cross sections: /sup 256/Rf(9 +- 2 ms), /sup 257/Rf(3.8 +- 0.8 s, 14 +- 9% SF), /sup 258/Rf(13 +- 3 ms), /sup 259/Rf(3.4 +- 1.7 s, 9 +- 3% SF), /sup 260/Rf(21 more » +- 1 ms), and /sup 262/Rf(47 +- 5 ms). Their half-lives and production cross sections have been measured by collecting recoils on a moving nickel or steel tape and transporting them past stationary mica track detectors at known velocities. We have found several new spontaneous fission (SF) activities and suggested assignments for some of them to rutherfordium (element 104) isotopes. For this purpose the spontaneous fission decay constants , On this project spontaneous fission has been studied for the past several years in an effort to obtain a complete picture of the phenomenon. Bohr and Wheeler have given a theory of the effect based on the usual ideas of penetration of potential barriers. Subsequently, extensive experimental work on the subject has been performed by several investigators and will be quoted in the various sections. In 1940, Petrzhak and Flerov, using more sensitive methods, discovered spontaneous fission in uranium and gave some rough estimates of the spontaneous fission decay constant of this substance. The first attempt to discover spontaneous fission in uranium was made by Libby, who, however, failed to detect it on account of the smallness of effect.