Minimizing Exposure: RVI Videoscopes Take Radiation Exposure to a New Low
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Source: Olympus IMS
For personnel in nuclear power plants, time and distance are critical measurements when it comes to safe inspections. When workers need to enter a high-radiation area to examine a potential problem or make a routine inspection, proximity to radiation and the length of time the inspection takes can increase their effective radiation dose.

Suspected corrosion or blocked conduits or vessels in the containment area need to be handled immediately to help avoid accidental radiation leakage. In some cases, the reactor may need to be shut down so that workers outfitted in full-body protective gear can carry out the inspection. However, remote visual inspection (RVI) offers an alternative to this method, helping avoid costly shutdowns, saving time and operational costs, and reducing the risk of a harmful radiation dose for workers.

Radiation Exposure, Limits, and Risks

Exposure to radiation in the workplace is strictly regulated by safety standards, with the annual effective dose limit set at 5 rems (0.05 sieverts (Sv)). For comparison, the average person is exposed to less than 0.003 sieverts of naturally occurring radiation in a year. Workers in nuclear plants are generally exposed to less than 0.01 Sv annually. According to the standards, this level is considered reasonably safe.

As Low as Reasonably Achievable: How Low Can You Go?

Despite the general safety of working in a nuclear power plant, the as low as reasonably achievable (ALARA) principle dictates that workplace radiation safety programs should minimize employee exposure as much as possible. RVI methods can enable these workers to make their inspections from a sufficient distance to help decrease their annual effective dose level.

What RVI Can Do to Reduce Radiation Exposure

Water is essential to nuclear energy production and how the water is used can vary depending on the plant and type of technology, but generally, water is used in three stages.

Stage 1: In the radiation containment building, water helps cool the uranium rods in the nuclear reactor; during this process, the water is heated by the reactor.

Stage 2: The radioactive (or "dirty") water from the reactor is sent in a loop to heat a reservoir of fresh, clean water.

Stage 3: Once the clean water is heated, it turns into steam, which powers the generator’s turbine.

Minimizing Exposure: RVI Videoscopes Take Reasonably Achievable Radiation Exposure to a New Low

Source: nrc.gov.

The pipes and vessels located within the containment structure are in a high-radiation area. Even with anticontamination suits and other personal protective equipment (PPE), workers who perform inspections in this area will inevitably be exposed to higher doses of radiation.

RVI offers a way for workers to carry out inspections in hazardous locations without physically entering the area. As well as letting workers maintain a safe distance from high-radiation areas, a videoscope equipped with a long insertion tube can enable the inspection of difficult-to-access locations, such as water conduits. The longer the insertion tube, the farther away the workers can be from the radiation.

Videoscope Durability in Radioactive Conditions

Unfortunately, even the best videoscope equipment doesn’t come out completely unscathed when exposed to radiation. If the insertion tube is used to inspect dirty-water-filled pipes, contamination is inevitable, and damage is also a possibility.

For example, with long-term exposure, the clear fiberoptic material used in insertion tubes for illumination can begin to turn yellow. This yellowing causes it to absorb light, reducing the intensity at the tip. The tube’s image sensor is more susceptible to damage from short, high doses of radiation, which can result in a noisy, or milky, image on the videoscope screen.

When the equipment is used in high-radiation areas, in some instances, decontaminating the equipment may be considered too costly and risky for the health of the workers. The plant may opt to sacrifice the insertion tube, leaving it permanently in the radiation area. Regardless, the insertion tube and the videoscope need to be robust enough to satisfy the requirements and expectations of the nuclear plant’s safety inspection and maintenance programs. That’s why we build systems with features that enable them to survive longer in radiation areas.

5 Advantages of the IPLEX™ YS Videoscope in Nuclear Power Plants

Resistant to radiation damage

We tested the IPLEX YS videoscope’s insertion tube and found that, even after being exposed to 200,000 rad (a unit that measures an absorbed radiation dose), the laser illumination and CCD image sensor still work. Depending on the type of radiation, 1 rad is roughly equal to between 0.01 to 0.2 sieverts. So, that means that the insertion tube can withstand many times more radiation than the established safe limits for workers: around 40,000 to 800,000 times a person's annual exposure limit.

Inspect from a safe distance

The IPLEX YS videoscope has an extra-long insertion tube that enables workers to make inspections from a safe distance. The 30-meter (100-foot) tube can be fed into dirty water pipes in the radiation containment area, and workers can control and maneuver it from afar.

Tough tube

With such a long insertion tube, there’s a lot of potential for damage. However, the IPLEX YS videoscope’s insertion tube is engineered to resist abrasion with a protective tungsten braided outer layer.

See the light

A powerful light source that provides enough illumination to inspect the inside of a pipe or vessel from far away is essential. The IPLEX YS videoscope uses a powerful laser illumination system coupled with our WiDER® (wide, dynamic extended range) image processing to deliver bright, contrast-balanced images across the entire depth of field.

Keep it clean

Imagine inspecting the inside of a vessel 100 feet away. You navigate the insertion tube into the vessel and are about start your inspection when, suddenly, a piece of dust lands on the lens and obscures your view. Instead of starting all over again, the IPLEX YS videoscope has an air-powered lens cleaning system that can be used to blow away dust and drip residue from the tip, so operators can have a clear view, even in dirty pipes.