Research Papers

Level Dynamics Monitoring of a Once-Through Steam Generator: A New Method Using the Reflectometric Technique

[+] Author and Article Information
Francesco Cordella

ENEA FSN-FUSPHY-SAD—Frascati Research Center, Via E. Fermi, 45, Frascati 00044, Italy e-mail: francesco.cordella@enea.it

Mauro Cappelli

ENEA FSN-FUSPHY-SCM—Frascati Research Center, Via E. Fermi, 45, Frascati 00044, Italy e-mail: mauro.cappelli@enea.it

Massimo Sepielli

ENEA FSN—Casaccia Research Center, Via Anguillarese, 301, Rome 00123, Italy e-mail: massimo.sepielli@enea.it

Manuscript received August 27, 2015; final manuscript received May 19, 2016; published online October 12, 2016. Assoc. Editor: Jovica R. Riznic.

ASME J of Nuclear Rad Sci 2(4), 041003 (Oct 12, 2016) (10 pages) Paper No: NERS-15-1181; doi: 10.1115/1.4033696 History: Received August 27, 2015; Accepted May 19, 2016

We present here some theoretical and experimental results about the application of the time-domain reflectometry (TDR) technique to a once-through steam generator (OTSG) bayonet-type, which is considered here, from a new point of view, as a coaxial transmission line and used as a level monitoring device for its own dynamics. This original approach leads to the design of a new kind of sensor, employable as a general-level measuring system in harsh conditions as well. This sensor may offer some interesting features for the design of control systems for nuclear facilities as well as for oil and gas plants. In order to experimentally verify the theoretical part, a mockup has been designed and built, so as to be used as a level control for a dedicated hydraulic loop system both in static and dynamic conditions. The purpose of the hydraulic loop system is to implement a short-/medium-term transient-level dynamics requiring fast sensor response, online measurement, and some nonlinearity features that are crucial for its control. The obtained results show that the TDR application on the OTSG is feasible at standard ambient temperature and pressure (SATP) conditions, paving the way for tests at the operating pressure and temperature ranges of a real plant.

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Fig. 1

Pictorial view of the heat-transfer regions in a general OTSG

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Fig. 2

Simulation results for different physical parameters: (a) pressure, (b) L1 level, and (c) L2 level response to a step of flow rate and thermal flux

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Fig. 5

Hydraulic loop for “dynamic” level measures

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Fig. 4

Level sensor geometries, details, and simplified model

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Fig. 3

Schematic view of the experimental configuration for “static” level measurements

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Fig. 6

Experimental data and fitting curve of the step function response

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Fig. 7

Different “static” level measurements (from right to left: baseline in air, 10.5×10−2  m, 20.5×10−2  m, 40×10−2  m of water at 293.15 K)

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Fig. 9

Level-detection algorithm block diagram

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Fig. 10

rs–bs (dashed black line), rs–bs piecewise linear approx. (thick dashed line), rs–bs first derivative (dashed-dotted thin line)

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Fig. 11

Zoom of the level-point determination algorithm with the complete rs–bs curve (inset)

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Fig. 12

Data streaming viewed with ML



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