Customer benefits

The effects of interference radiation on radiometric measurements can be considerable and must therefore be controlled. As neither when interference radiation will be present, nor how much the impact of a distant NDT testing on a nucleonic measurement is predictable, customers need a reliable system that automatically deals with such events.
Berthold offers sophisticated products that manage interference radiation and provide the customer with a stable and reliable measurement that ensures a continuous process and avoids unscheduled shutdowns. The features XIP (X-Ray Interference Protection) and RID (Radiation Interference Discrimination) are used for this. We help plant operators to get “RID” of problems caused by interference radiation and in doing so, we make sure they are always in control.

NDT, X-Ray, and the consequential interference radiation

Interference radiation is a common issue for any radiation-based measurement, as non-destructive testings (NDT) are routinely performed in industrial facilities. These are typically weld or vessel integrity inspections. NDT uses gamma sources with very strong activities. Such interferences could cause a significant increase of count rate and therefore a misinterpretation of the level. Therefore, Berthold has the standard XIP feature, as well as the special LB 470 RID model to minimize NDT impacts.

Development stages to deal with such unpredictable events

In the following, the handling of interference radiation in relation to radiometric measurements and their further development will be explained in more detail.

A) Informing the control room

In the past, when there were no systems for the detection of interference radiation, it was necessary for the control centre to be informed of upcoming weld inspections well ahead of time. The weld inspection had to be carried out in close coordination with the control center and control was done manually, blindly so to speak, during this period. This gave rise to the following difficulties:

  • The control room was not always informed of weld inspections.
  • It was not uncommon for weld inspections to affect measurements that were thought to be out of their reach. The corresponding control centres were therefore not informed.

B) Separate X-ray detector

As weld inspections, particularly in chemical and petrochemical sector, became more and more common, the detection of interference radiation became more and more significant. The increased use of rod detectors, whose gamma-sensitive volume is significantly larger than that of point detectors, and is therefore more easily influenced by interference radiation, increased the need for an automatic response. For this purpose, additional X-ray detectors were added, which had the task of detecting an increase in radiation in the vicinity of the measurement, and were placed in the vicinity of the measurement. The idea was that the control room would be informed of an increased radiation level, and radiometric detectors would be switched off. This method involved the following difficulties:

  • Personnel in the control room must act immediately
  • An additional detector ultimately increases the costs for each individual measuring point

C) XIP (X-ray Interference Protection)

This feature freezes the output on the last reasonable measurement when NDT is detector. This is typicaclly of great help to the control room, as the level in the vessels only changes very slowly. An optional digital output can let the control room know when the feature is engaged. In most cases, it is sufficient to continue with the frozen value and intervention by the control room is not necessary at all.

D) RID (Radiation Interference Discrimination)

The LB 470 RID takes advantage of the fact that the radioactive isotopes used for weld inspection tests, such as iridium, selenium and X-rays, have a different radiation energy than the sources used by Berthold for the measurement itself. Berthold detectors use this energy difference to detect the interference radiation and to suppress it. This means that measurements can continue even under the influence of interference radiation.

Whitepaper “Radiation Interference Discrimination (RID)”

A whitepaper sharing the common sources of interference radiation, how they affect radiometric measurements, and how to minimize or avoid their impact. The paper explains how Berthold's radiation interference detection (RID) feature helps plant operators maintain a reliable and repeatable measurement, even as NDT occurs.

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DuoSeries LB 470 with RID option

DuoSeries LB 470 is now also available with radiation interference discrimination (RID). The level measurement system with RID consists of a Co-60 source, an LB4700 detector with PVT scintillator, and a separate LB 470 RID transmitter for display, calculation, and operation. The detector mounted at the measuring point is connected to the LB 470 RID transmitter via a two-wire cable. If Cs-137, Ir-192, or St-90 sources are being used for NDT at or near your plant, and you have a critical measurement that requires continual monitoring, the LB 470 RID is the right choice for you.

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