# Electromagnetic Testing of Rod Cluster Control Assemblies in Pressured-Water Reactor Power Plants
## 3 Experimental Setup
### Sensor and System Prototype  
According to the diameter of the control rods, EHaS probes were designed with an inner diameter of 10.2 mm and an outer diameter of 22.0 mm. Each EHaS probe has 16 Hall sensor elements arrayed around an 11.2 mm cylindrical supporter at an interval of 22.5\({}^{\circ}\) (2.2 mm). The bobbin coil is placed outside of the EHaS, which has 168 turns, with a width of 13 mm, using a 0.1 mm copper wire. The inner diameter of the bobbin coil is 13.8 mm. The sensor signal cable length is 10 m from the inspection stage to the signal processing units. The prototype of the EHaS probe is shown in Figure 4.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Type** & **No.** & **Depth** & **\%W.T** & **Degree** & **Width** & **Type** & **No.** & **Depth** & **\%W.T** & **Degree** & **Width** \\ \hline \multirow{4}{*}{Short-circumferential grooves (SCGs)} & \# 1 & 0.047 & 10 & & & & & \# 1 & 0.047 & 10 & \\ \cline{2-10}  & \# 2 & 0.117 & 25 & & & & & \# 2 & 0.094 & 20 & \\ \cline{2-10}  & \# 3 & 0.188 & 40 & & & & & \# 3 & 0.141 & 30 & \\ \cline{2-10}  & \# 4 & 0.235 & 50 & & & & & & \# 4 & 0.188 & 40 & 360\({}^{\circ}\) & 0.2 \\ \cline{2-10}  & \# 5 & 0.282 & 60 & & & & (FCCs) & \# 5 & 0.235 & 50 & \\ \cline{2-10}  & \# 6 & 0.329 & 70 & & & & & & \# 6 & 0.282 & 60 & \\ \hline \multirow{4}{*}{Sliding wears (SWs)} & \# 1 & 0.141 & 30 & - & & & & \# 7 & 0.329 & 70 & \\ \cline{2-10}  & \# 2 & 0.235 & 50 & - & & & & & \# 1 & 0.094 & 20 & 45\({}^{\circ}\) \\ \cline{2-10}  & \# 3 & 0.47 & 100 & - & & & & & \# 2 & 0.188 & 40 & 90\({}^{\circ}\) \\ \cline{2-10}  & \# 4 & 0.141 & 30 & - & & & & & \# 3 & 0.188 & 40 & 90\({}^{\circ}\) & 0.2 \\ \cline{2-10}  & \# 5 & 0.235 & 50 & - & & & & & \# 4 & 0.188 & 40 & 180\({}^{\circ}\) & \\ \cline{2-10}  & \# 6 & 0.47 & 100 & - & & & & & \# 5 & 0.188 & 40 & 270\({}^{\circ}\) & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Shapes and sizes of the artificial defect (unit: mm, degree; W.T = wall thickness (0.47 mm)).  
Figure 3: Different artificial defects on the control rods: (**a**) Short-circumferential groove (SCG), (**b**) sliding wear (SW), (**c**) full-circumferential cracks (FCC), and (**d**) partial-circumferential cracks (PCC).  
For inspection of the entire RCCA, the construction of the EHaS probes, signal processing units, and a prototype of the system is designed as shown in Figure 5. The system is divided into two central units: Unit-1 is mainly for signal processing, and Unit-2 is predominantly for signal acquisition and control. The 24 EHaS probe signal is simultaneously processed by the HPFs (fc = 300 Hz), the 1 st stage amplifiers (59.7 dB), and the RMS circuits before arriving at the multiplexer, as shown in Figure 2. The multiplexer extracts the signals from four EHaS probes in the four groups (A, B, C, and D) at the same time. For instance, A-1, B-1, C-1, and D-1 probes operate at the same time. In total, 64 channel signals (4\(\times\)16) will be outputted at each loop of the multiplexer. The signal is then amplified in the 2 nd stage amplifiers (6 dB), digitized by an analog-to-digital converter (NI USB 6255), and stored in a notebook. The software is built based on the LabVIEW program. The 24 EHaS operation takes approximately 72 ms for each data acquisition cycle. For demonstration in this paper, the system is operated at 20 mm/s with a scan step of 1.72 mm and the bobbin coil current is 200 mA-15 kHz.