| (3) The radiation dose rate at 1 m from the shield of a dry-source-storage panoramic irradiator when the source is shielded may not exceed 2 mrem (0.02 mSv) per hour and at 5 cm from the shield may not exceed 20 mrem (0.2 mSv) per hour. (k) Fire protection. (1) The radiation room at a panoramic irradiator shall have heat and smoke detectors. The detectors shall activate an audible alarm. The alarm shall be capable of alerting a person who is prepared to summon assistance promptly. The sources shall automatically become fully shielded if a fire is detected. (2) The radiation room at a panoramic irradiator shall be equipped with a fire extinguishing system capable of extinguishing a fire without the entry of personnel into the room. If water is used, the system for the radiation room shall have a shut-off valve to control flooding into unrestricted areas. (l) Radiation monitors. (1) Irradiators with automatic product conveyor systems shall have a radiation monitor with an audible alarm located to detect loose radioactive sources that are carried toward the product exit. If the monitor detects a source, an alarm shall sound and product conveyors shall stop automatically. The alarm shall be capable of alerting an individual in the facility who is prepared to summon assistance. Underwater irradiators in which the product moves within an enclosed stationary tube are exempt from the requirements of this paragraph. (2) Underwater irradiators that are not in a shielded radiation room shall have a radiation monitor over the pool to detect abnormal radiation levels. The monitor shall have an audible alarm and a visible indicator at entrances to the personnel access barrier around the pool. The audible alarm may have a manual shut-off. The alarm shall be capable of alerting an individual who is prepared to respond promptly. (m) Control of source movement. (1) The mechanism that moves the sources of a panoramic irradiator shall require a key to actuate. Actuation of the mechanism shall cause an audible signal to indicate that the sources are leaving the shielded position. Only one key may be in use at any time, and only operators or facility management may possess it. The key shall be attached to a portable radiation survey meter by a chain or cable. The lock for source control shall be designed so that the key may not be removed if the sources are in an unshielded position. The door to the radiation room shall require the same key. (2) The console of a panoramic irradiator shall have a source position indicator that indicates when the sources are in the fully shielded position, when they are in transit, and when the sources are in the fully exposed position. (3) The control console of a panoramic irradiator shall have a control that when activated, shall return the source to its fully shielded position within its normal transit time. (4) Each control for a panoramic irradiator shall be clearly marked as to its function. (n) Irradiator pools. (1) For licenses initially issued after August 1, 1996, irradiator pools shall either: (A) have a water-tight stainless steel liner or a liner metallurgically compatible with other components in the pool; or (B) be constructed so that there is a low likelihood of substantial leakage and have a surface designed to facilitate decontamination. In either case, the licensee shall have a method to safely store the sources during repairs of the pool. (2) For licenses initially issued after August 1, 1996, irradiator pools shall have no outlets more than 0.5 m below the normal low water level that could allow water to drain out of the pool. Pipes that have openings more than 0.5 m below the normal low water level and that could act as siphons shall have siphon breakers to prevent the siphoning of pool water. (3) A means shall be provided to replenish water losses from the pool. (4) A visible indicator shall be provided in a clearly visible location to indicate if the pool water level is below the normal low water level or above the normal high water level. (5) Irradiator pools shall be equipped with a purification system designed to be capable of maintaining the water during normal operation at a conductivity of 20 microsiemens per centimeter or less and with a clarity so that the sources can be seen clearly. (6) A physical barrier, such as a railing or cover, shall be used around or over irradiator pools during normal operation to prevent personnel from accidentally falling into the pool. The barrier may be removed during maintenance, inspection, and service operations. (7) If long-handled tools or poles are used in irradiator pools, the radiation dose rate on the handling areas of the tools may not exceed 2 mrem (0.02 mSv) per hour. (o) Source rack protection. If the product to be irradiated moves on a product conveyor system, the source rack and the mechanism that moves the rack shall be protected by a carrier or guides to prevent products and product carriers from hitting or touching the rack or mechanism. (p) Power failures. (1) If electrical power at a panoramic irradiator is lost for longer than 10 seconds, the sources shall automatically return to the shielded position. (2) The lock on the door of the radiation room of a panoramic irradiator shall not be deactivated by a power failure. (3) During a power failure, the area of any irradiator where sources are located may be entered only when using an operable and calibrated radiation survey meter. (q) Design requirements for irradiators. The following are design requirements for irradiators that have construction beginning after August 1, 1996. (1) Shielding. For panoramic irradiators, the licensee shall design shielding walls to meet generally accepted building code requirements for reinforced concrete and design the walls, wall penetrations, and entrance ways to meet the radiation shielding requirements of subsection (j) of this section. If the irradiator will use more than 5 million curies (2 x 1017 becquerels) of activity, the licensee shall evaluate the effects of heating of the shielding walls by the irradiator sources. (2) Foundations. For panoramic irradiators, the licensee shall design the foundation, with consideration given to soil characteristics, to ensure it is adequate to support the weight of the facility shield walls. (3) Pool integrity. For pool irradiators, the licensee shall design the pool to assure that it is leak resistant, that it is strong enough to bear the weight of the pool water and shipping casks, that a dropped cask would not fall on sealed sources, that all outlets or pipes meet the requirements of subsection (n)(2) of this section, and that metal components are metallurgically compatible with other components in the pool. (4) Water handling system. For pool irradiators, the licensee shall verify that the design of the water purification system is adequate to meet the requirements of subsection (n)(5) of this section. The system shall be designed so that water leaking from the system does not drain to unrestricted areas without being monitored. (5) Radiation monitors. For all irradiators, the licensee shall evaluate the location and sensitivity of the monitor to detect sources carried by the product conveyor system as required by subsection (l)(1) of this section. The licensee shall verify that the product conveyor is designed to stop before a source on the product conveyor would cause a radiation overexposure to any person. For pool irradiators, if the licensee uses radiation monitors to detect contamination in accordance with subsection (w)(2) of this section, the licensee shall verify that the design of radiation monitoring systems to detect pool contamination includes sensitive detectors located close to where contamination is likely to concentrate. (6) Source rack. For pool irradiators, the licensee shall verify that there are no crevices on the source or between the source and source holder that would promote corrosion on a critical area of the source. For panoramic irradiators, the licensee shall determine that source rack drops due to loss of power will not damage the source rack and that source rack drops due to failure of cables (or alternate means of support) will not cause loss of integrity of sealed sources. For panoramic irradiators, the licensee shall review the design of the mechanism that moves the sources to assure that the likelihood of a stuck source is low and that, if the rack sticks, a means exists to free it with minimal risk to personnel. (7) Access control. For panoramic irradiators, the licensee shall verify from the design and logic diagram that the access control system will meet the requirements of subsection (i) of this section. Cont'd... |
