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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 40439 | 7 January 2004 08:00:00 | Agreement State | Agreement State Report - Lack of Posting and Access Restrictions to Radiation Area | During an inspection of the licensee facility by RHB (State) on 1/7/04, a potential radiation problem was indicated by a high neutron radiation level above a shield assembly used to store Cf-252 neutron sources. Directly above the shield, the neutron dose rate was measured as approximately 5 rem/hr using a rem-ball. This area was not controlled as a high radiation area, nor were controls effective at the time of the inspection to preclude unrestricted access to the room. On the roof, directly above the shield assembly, the neutron dose rate was measured as approximately 25 mrem/hr, in an area of approximately 1 square foot. The roof area was not controlled as a restricted area. (Both neutron measurements were made by the licensee because of the lack of neutron survey instrumentation by the RHB inspector.) The licensee was directed to remeasure the neutron dose rate on the roof because it was inconsistent with the room dose rate, to add shielding to reduce the roof dose rates, and to provide high radiation area controls to the room containing the stored neutron sources. The second measurement of the roof dose rate found 250-260 mrem/hr in the highest area (approximately 1 square foot). The licensee representative reported he had incorrectly read the instrument scale during the previous measurement. Polyethylene sheets and a container of hydrogenous material were placed on the top of the shield assembly to act as temporary neutron shielding. This reduced the neutron dose rate directly above the shield assembly to 8-10 mrem/hr, and the roof dose rate to less than 2 mrem/hr. Locks were installed on the doors accessing the laboratory area where the Cf-252 sources are stored. The licensee is in the process of constructing a permanent safe storage inside of this shield assembly, with additional shielding to conservatively ensure that individuals in unrestricted areas won't exceed 100 mrem/year dose (and unrestricted area dose rates will be less than 2 mrem in any hour). The shielding design will ensure that the shielding cannot be removed by an unauthorized person and accidentally recreate the high radiation area and unrestricted area dose rate problems. This construction is expected to be completed by 1/15/04. The state (RHB) will continue to investigate this matter to evaluate the potential for exposures to personnel as a result of the elevated dose rates and lack of access controls. No personnel overexposures, worker or public, are known to have occurred at this time. |