Is a radioactive level gauge using Na22 as a radiation source effective?
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We have several horizontal tanks, and it has been decided to use external radioactive level gauges to measure the liquid level. The wall thickness of both the tank body and the jacket is around 12.5 mm, the diameter of the tank body is 1.5 m, and the medium is molten polymer. Cs-137 or Co-60 sources were considered, and it was determined that they could meet the requirements for use. However, given the various strict regulations regarding prior registration, subsequent maintenance, and daily management, I felt hesitant before making a decision:P:P Recently, I learned that there is a radioactive level gauge on the market from a brand named “Ecophyspribor,” which uses Na22 as its radiation source. Thanks to the very high sensitivity of its receiver, the radiation dose emitted by this source can be kept extremely low (as low as 1‰ of that of ordinary sources, i.e., below 0.1 mCi). It is claimed to be environmentally friendly and allows for **exemption from registration requirements. It seems very attractive! If I choose this Na22 source, my main concerns are as follows: (1) I am not aware of the actual performance of this product, nor of how users actually use it ； (2) Can a γ-ray source with such a low dose penetrate such thick steel plates? If it cannot penetrate, no matter how sensitive the converter is, it is of no use ； (3) Since the receiver is so sensitive, will it respond to background radiation or environmental interference? Will it be unstable when running? Have seafarers used Na22 level gauges in their work? I wonder how effective it is for you guys? I hope you can share your experience. Those who are familiar with Na22 are also welcome to leave comments. Your insights and opinions will be of great help to the choices we are about to make.
I know that Na22 has a very short half-life, which is shorter than that of Co60 and Cs137. But the intensity of Co60 radiation is quite high.
Thank you, expert, for your reply! The half-life of Na22 is indeed short; as a source for level gauges, it is said to need to be replaced every 5 years, which makes it worthwhile compared to the subsequent maintenance requirements of Cs137 or Co60. But it’s not known whether the industrial application of Na22 is stable and mature
Background radiation does have an impact; previously, during inspections of adjacent devices, it caused fluctuations in the readings of the E+H radiation level gauge. . . Now, with new projects, there are also difficulties in selecting level gauges. For some special operating conditions, using radiation-based sensors is indeed a good option, but as you mentioned, the strict regulations regarding preliminary approval, subsequent maintenance, and daily management make it hard to make a decision.
After communicating with E+H, their experience is that when performing gamma ray inspection within a 50-meter radius, it is essential to turn off the power to the probe; otherwise, it is prone to damage. However, the power supply must not be turned off for more than 20 days; otherwise, once the internal lithium-ion battery is depleted, the instrument will no longer function properly (perhaps the internal calibration data will be lost?) ).
This post was last edited by denghl on 2020-6-4 at 11:16. Thank you all for your active participation, especially @qugd, for providing professional technical assistance selflessly and consistently over the long term. After calculations by various manufacturers and technical exchanges, the comparison of key parameters is as follows (the wall thickness throughout is approximately 50 mm). No judgment is made here on the advantages and disadvantages of products from various manufacturers; each has its own strengths, and one should choose based on their needs.
May I ask, which type of radiation source was ultimately chosen?
This gauge is quite good; it is exempt from environmental regulations. The manufacturer holds the necessary exemption documents, so there is no need for the user to file any registrations or obtain any permits. Since it belongs to a radiation source of category V or lower, it poses no harm to the human body. Moreover, such radiation sources do not require storage in specialized warehouses or special protection equipment, which saves a significant amount of money in the long run. It is also installed by clamping it onto the pipeline, without the need for drilling holes; therefore, this type of gauge has seen quite good sales performance so far. The wall thickness of both the tank body and the jacket is around 12.5 mm, with the tank diameter being 1.5 m. Therefore, the total wall thickness is 12.5 mm for the tank body plus 12.5 mm for the jacket, which equals 25 mm per side; multiplying this by 2 gives 50 mm, which is quite thick. This might indeed lead to the issue of inability to penetrate as you mentioned. This watch receiver features advanced capabilities for detecting weak gamma rays, boasts good stability, and outperforms traditional instruments such as Cs-137 or Co-60 in terms of sensitivity and response speed. If there are any further questions, we can discuss them in detail.
The irradiation distance for the Na-22 source is only 300 mm; plates thicker than 80 mm cannot be irradiated with this source. Its half-life is also only about 2 years, and it is quite expensive – the cost of replacing the source is enough to purchase several sets of other radioactive sources. Otherwise, with low activity and being of a lower grade, they would have long been replaced by nuclear instruments using other radiation sources.