Nuclear Facility Lighting Recommendations and Guidelines|
Article - February 10, 2016 By LarsonElectronics.com
Nuclear Facility Lighting Recommendations and Guidelines
Nuclear power plants have very strict lighting requirements due to the delicate nature of work conducted in such facilities. Operators typically avoid experimental or untested luminary designs; and opt for traditional lighting options that have been tried and tested for safety and reliability.
This article expounds on the complex requirements of nuclear power plant fixtures and medical cyclotron vaults. The post below also specifies the type of lighting technologies commonly used during operations.
Nuclear Lighting Design Considerations
Luminaries for nuclear power plants must be designed carefully in order to reduce risks during operations. When choosing fixtures for such facilities, it is important to ensure that the units adhere to new, post-Fukushima nuclear guidelines. One of the most common features of nuclear fixtures include rounded, smooth surfaces for streamlined decontamination. Enclosed corners are difficult to clean during hose down sessions and require workers to spend more time performing decontamination-related tasks. Another reason rounded edges are preferred is due to risks related to accidental exposure. Sharp features could easily tear a worker’s protective suit or gloves during handling.
For underwater nuclear fixtures, stainless steel is the industry standard due to its ability to withstand corrosion. Lexan polycarbonate is the ideal choice for protective covers, because it is up to 30 times more impact resistant, compared to mainstream safety glass. Moreover, it offers up to 300 percent more protection from radiation than acrylic. Lenses that are highly resistant to radiation is needed to ensure optimal transitivity and illumination. The application of glass and PMMA is not recommended, as exposure to radiation will cause such materials to turn brown. This can cause a rapid decline in transmissivity, from 92 percent to 56 percent or lower. Crystalline-based materials are recommended, such as quartz or fused silica, due to their ability to withstand high levels of radiation.
Another crucial feature of nuclear power plant lighting is holistic design. Most operators avoid fixtures with small parts, such as small screws and bolts. Should a tiny screw fall into the pool, individuals would have to drain the area to properly locate and dispose the part. Ideally, such luminaries should not require meticulous maintenance. If re-lamping is needed, workers should be able to complete the process without tools (by hand). To ensure protection against earthquakes and other unforeseen natural disasters, compliance with IEEE-344 (IEEE Recommended Practice for Seismic Qualification of Class 1E Equipment for Nuclear Power Generating Stations) must be observed.
Light Sources and Technologies
Most nuclear plants rely on tungsten-halogen and high-pressure sodium vapor luminaries during operations. These technologies have been thoroughly tested and have been proven superior in supporting various tasks around a nuclear power plant. When using the latter option (high-pressure sodium vapor), the bulbs should contain very low levels of mercury (as low as 0.01 mg). In the worst case scenario, the tube could break, releasing mercury in the pool or storage areas. Reacting with other active elements in the facility could create a highly corrosive mixture.
LEDs, although extremely promising, still needs to be thoroughly tested for use in nuclear power plants. Some facilities use LEDs for emergency lighting (ELFs) and in-air applications.
Fixtures for Medical Cyclotron Vaults
Cyclotrons are capable of producing large amounts of radiation at high voltages. Because this, they are typically located in a vault with very thick concrete walls and buried underground (up to one meter). These precautions ensure that radiation does not escape the facility. Workers in cyclotron facilities typically observe ALARA (“As Low As Reasonably Achievable”) guidelines when mitigating exposure to radiation. This ensures that radiation doses are minimal, but also effective. In the medical field, isotopes are needed during nuclear medical imaging protocols and cancer treatments. Medical isotopes are highly unstable and very radioactive (derived from a stable atom). These atomic particles (over 200, including medical isotopes, such as Fluorine-18 and Carbon-11) are artificially produced in cyclotron facilities and nuclear reactors.
In all rooms of the facility, colored lamps are not recommended and solid white (CRI rating of 85 and color temperature ratings of 4,100K) is preferred to ensure detection of contamination. Furthermore, lights should be enclosed to prevent dust accumulation. Battery supported emergency lighting systems must be installed in all areas of the building. For general lighting (in control, electrical and storage rooms), ceiling mounted units are recommended. For technical sections of the building (cyclotron and treatment rooms) wall mounted fixtures should be used. Most cyclotron medical scanning rooms apply fluorescent fixtures (recessed) with F32T8 tubes that adhere to the National Energy Policy Act of 1992.
In the cyclotron’s surroundings, fixtures must be installed over the cyclotron catwalk and pit at a height of 125 cm. Control rooms that monitor the machine should be able to provide 700 lux of lighting. While in general rooms, 500 lux is sufficient (for storage areas, 200 lux).