RU2387964C1 - Method for detection of leaks at reservoir bottom - Google Patents

Abstract

FIELD: testing equipment.

SUBSTANCE: invention relates to means of testing for tightness of large-sized reservoir bottoms, in particular at NPP. Technical result is achieved due to the fact that powdery indicator substance that consists of discrete particles is filled into reservoir liquid in the area of controlled section. At the same time size of discrete particles is selected based on condition of their suspended state provision for a specified period of time to quasi-even submersion onto reservoir bottom. Actual location of defect is detected by disappearance of powder on section surrounded with a settled indicator substance. For stainless steel vessel indicator substance may be represented by a ground chalk. Monitoring may be carried out with the help of endoscope or underwater video equipment. In both cases it is desirable to use illumination.

EFFECT: creation of cheap and simple-to-operate method, which does not require usage of external surface of bottom and does not affect corrosion resistant of reservoir material and does not require reservoir emptying.

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Description

The invention relates to a method for testing tanks for leaks on the bottoms of large tanks, mainly stainless steel with one-way access, in particular at nuclear power plants.

The problem is that such a procedure must be carried out promptly and without emptying the pool. Leaks can occur both due to fatigue deformations, and due to mechanical deformations, for example, due to the accidental fall of objects into the pool. However, as a rule, these leaks are very small and require the use of leak indicators.

A known method using indicator dyes according to the author's certificate of the USSR No. 1439427 dated 14.04 87 IPC G01M 03/04. According to this method, a solution of manganese-acid potassium solution is supplied under a certain static pressure to the outside of the bottom of the controlled reservoir, previously freed from the working fluid, and the location of the leaks is detected by the penetration of the control fluid through the bottom into its internal volume.

As follows from the description, quite complex preparatory operations are required that precede the direct detection of leaks, which is a disadvantage of this method.

As a prototype, the method according to A.S. USSR No. 1582813 dated 04.10.88, IPC G01M 03/20. According to this method, a layer of powdered indicator composition is applied to the inner surface of the bottom, which is used as a mixture of discrete particles of chalk, soda ash and methyl orange, and a control liquid is used outside, which is used as a weak solution of nitric acid. In the presence of through defects, the control fluid interacts with the indicator composition with the formation of brightly colored foamy caps over the defect.

The disadvantage of this method for detecting leaks is, firstly, the need to provide access to the outer part of the bottom, i.e. to the space between the tank and the lined wall of the canyon in which it is installed, and, secondly, means for introducing control fluid into this space. In addition, as follows from the description, the application of the indicator composition on the inner surface of the bottom is carried out in a tank freed from liquid.

The objective of the present invention is to provide an inexpensive and easy to use method that does not require the use of the outer surface of the bottom and does not affect the corrosion resistance of the material of the tank, and most importantly, does not require the release of the pool from liquid, i.e. without decommissioning it.

The problem is achieved in that in the method for detecting leaks at the bottom of the tank, which consists in using a powdered indicator substance consisting of discrete particles, according to the invention, the indicator substance is poured into the liquid of the tank in the region of the controlled area, while the size of the discrete particles is selected from the condition of finding they are in suspension for a predetermined time until quasi-uniform immersion at the bottom of the tank, and the exact location of the defect is judged by powder in the area surrounded by the settled indicator substance.

The technical essence consists in sucking the indicator substance into a defect causing a leak, leaving a small but sufficiently noticeable area surrounded by settled particles that are different in color and light reflection from the stainless steel of the tank. The size of the particles does not allow them to sink too quickly, and they perceive the movement of liquid in the place of the leak until they settle to the bottom.

As a powdered indicator substance for a stainless steel tank, pure crushed chalk is selected.

In addition, the search for a defect can be carried out both visually with the help of an endoscope, and with the help of a video camera, using the backlight in either case.

In practice, a conventional tooth powder was used to implement the method, although the degree of chalk grinding can be selected experimentally for maximum effect. Manipulations were carried out without releasing the pool from the working fluid and separately in each of the controlled areas. As indicated above, the location of the leak was determined both visually using a surveillance tool, such as an endoscope, and backlight, and using an underwater video camera, also with backlight. In the second case, mathematical processing of the image was carried out in order to accurately localize the leakage site. Due to the fact that near the defect due to leakage, the fluid velocity is maximum, the smoothly settling indicator substance is “blown away” as if by the flow of the expiring fluid, not having time to sink to the bottom precisely in the zone where the defect is located. At some small distance, deposition occurs more or less evenly. Therefore, the defect is clearly visible especially with the use of video monitoring equipment (video cameras), which searches for contrasting areas on a quasi-uniform background. This effect is not affected by the movement of fluid in the pool itself, for example, the influx of fluid into the pool, as this leads only to a smooth non-uniformity of the settled indicator substance, while the liquid outflow through the defect causes a clearly noticeable sharp non-uniformity.

The inventive method is applicable for the rapid search for leaks at the bottom of the pool, designed to store ampoules with spent nuclear fuel at nuclear power plants, moreover, both in the case of a loaded pool and without placing the ampoules in it.

Claims (4)

1. A method for detecting leaks at the bottom of the tank, which consists in using a powdered indicator substance consisting of discrete particles, characterized in that the indicator substance is poured into the liquid of the tank in the area of the controlled area, while the size of the discrete particles is selected from the condition of ensuring they are in suspension for a specified time until quasi-uniform immersion at the bottom of the pool and the exact location of the defect is judged by the disappearance of the powder in the area surrounded by settled ndikatornym substance. 2. A method for detecting leaks at the bottom of the tank according to claim 1, characterized in that pure powdered chalk is selected as a powdered indicator substance for the stainless steel tank. 3. The method for detecting leaks at the bottom of the tank according to claim 1, characterized in that the search for the defect is carried out visually using an endoscope and backlight. 4. The method for detecting leaks at the bottom of the tank according to claim 1, characterized in that the search for the defect is carried out using a video camera and backlight.