UK Nuclear Industry First Wireless Applications

Abstract

Magnox Ltd^® and Sellafield Sites Ltd^® have both installed modern wireless instruments. This paper discusses the challenges and benefits.

I. Introduction

While undertaking nuclear decommissioning, both Sellafield and Magnox still need to install considerable quantities of instrumentation. This is used for monitoring during plant closure and subsequent decommissioning. Common sense says installing items in a plant we wish to dismantle is counter intuitive. Installation work in parts of nuclear sites is often costly, difficult and time-consuming. Decommissioning often means legacy installed Control & Instrumentation (C&I) is no longer appropriate nor in the correct location. For C&I in remote locations, or where access is difficult (stacks, chimneys, furnaces, areas with higher background radiation, atmospheres explosive (ATEX; an area with a flammable atmosphere) hazardous areas, environmental monitoring, etc.), cable infrastructure costs dominate C&I project budgets.

II. Sellafield’s Requirements

Sellafield has a number of piped services distributed around the site. These include high pressure (hp) steam, low pressure (lp) steam and electrical power. For 40 years, Sellafield was in the fortunate position of having its own nuclear power station on-site, thus steam and electricity were always available and essentially “free.” The replacement of the Calder Hall station with a combined heat and power (CHP) station changed the use of steam. It was apparent that

• Sellafield had limited measurement information about piped services, particularly steam. Historical views on steam use were often “guestimates”!

• Steam was widely distributed geographically across site, including remote areas;

• A legacy of historical problems was reported by steam consuming plants;

• Almost no means of measuring the benefit of recent decommissioning, energy efficiency, asset care nor environmental improvements;

• A changing future need for energy, materials and environmental metering.

Sellafield decided to concentrate first on steam measurement, so three new steam metering locations were identified. These were

1. The pipes from the CHP to the site hp and lp steam mains (the CHP),

2. A steam pipework junction (the Junction),

3. A recent steam mains extension (the Extension),

4. Displays at two existing Utilities Buildings (Buildings 1 and 2).

III. Sellafield’s First Application

A. Location 1, the CHP

There are two hp and two lp steam pipes. Legacy instruments on the hp and lp pipes measured pressure (only) by existing 4~20 mA pressure transmitters, wired to the CHP. Sellafield now wanted to measure both pressure and temperature for each hp and lp steam pipe (i.e. eight new measurements on four pipes). Rather than scrap the legacy instruments, Sellafield routed the existing wired signals into a new Yokogawa^® Transmitter MultipleXer (YTMX; a wireless multiplexer) that connected by wireless to a new Yokogawa DX2000 chart recorder.

Details are shown in Figure 1 and consist of

• Four off new H & B Sensors Ltd^® resistance temperature detector (RTD) temperature sensors (T1 to T4) wired directly to a Yokogawa YTMX,

• Four off legacy ABB^® 260T pressure transmitter measurements 4~20 mA (P1 to P4) wired to CHP plant and now with extended wiring into the YTMX,

• One off new Yokogawa YTMX (an 8 input wireless multiplexer) with an extended aerial to enable reliable communication with the Utilities Buildings.

Figure 1.

Location 1, the CHP, installed instruments, all T and P are wired

B. Location 2, the Junction

There is one hp and one lp steam line. Temperature and flow was already measured by existing (4~20 mA) transmitters. Sellafield now wanted to measure pressure, temperature and flow. New wireless Yokogawa EJX530Bs pressure transmitters were added for the pressure measurements.

Details are shown in Figure 2 and consist of

• Two off legacy H & B Sensors Ltd temperature sensors (T1 and T2) now wired directly into a Yokogawa YTMX,

• Two off new Yokogawa EJX530B (P1 and P2) pressure transmitters communicating via wireless to the YTMX,

• Two off legacy ABB differential pressure (dP) flow meters (F1 and F2) wired directly into a Yokogawa YTMX,

• One off new Yokogawa YTMX (8 input unit) with an extended aerial communicating to the Utilities Buildings.

Figure 2.

Location 2, the Junction, installed instruments, all F and T are wired, all P are wireless

C. Location 3, the Extension

There are two hp and two lp steam lines. There was no legacy instrumentation. Sellafield now wanted to measure pressure and temperature. Sellafield fitted four off Yokogawa EJX530Bs pressure transmitters, communicating via wireless to a Yokogawa YTMX.

Details are shown in Figure 3 and consist of

• Four off new H & B Sensors Ltd RTDs (T1 to T4) wired directly into the YTMX,

• Four off new Yokogawa EJX530B wireless pressure transmitters (P1 to P4),

• One off new YTMX (8 input unit) with a standard aerial communicating with the Utilities Buildings.

Figure 3.

The Extension, installed instruments, all T are wired, all P are wireless

D. Location 4, Utilities Building 1

Utilities Building 1 ( Figure 4 ) consists of

• One off new Yokogawa field gateway system (YFGWS) gateway unit on the roof. The YFGWS communicates via Ethernet with …

• One off new Yokogawa DX2000 DAQStation recorder/data-logger inside the buildings.

Figure 4.

Utilities Building 1, installed instruments

The YFGWS Gateway will accept 50 devices, and so this system has plenty of spare capacity. The DX2000 reads the data from the YFGWS Gateway via Modbus. DX2000 display supervisory control and data acquisition (SCADA) screens were customised to suit. In addition, on separate “engineers pages,” Sellafield displayed data such as wireless signal status, instrument battery warnings and so on. The DX2000 is capable of pushing data (via Object Linking and Embedding for Process Control (OPC)) onto a future wired network and comes with both Ethernet and serial communications functionality. At present data are removed via a compact flash (CF) card in the front of the DX2000 once per month.

E. Location 5, Utilities Building 2

Utilities Building 2 ( Figure 5 ) consists of

• One off new Yokogawa YFGWS Gateway unit on the roof. The YFGWS communicates via Ethernet with …

• One off new Yokogawa DX2000 DAQStation recorder/data-logger inside the building.

Figure 5.

Utilities Building 2, installed instruments

F. Installation, commissioning and training

Conscious this was Sellafield’s first application of this technology, Sellafield adopted a risk-reduction strategy. This consisted of the following:

• All equipment was purchased from a single supplier (Yokogawa) so as to avoid any program or technical interfaces.

• All equipment was configured and pretested at the supplier’s works. This included tests as interesting as placing a transmitter in the back window of a car and slowly driving away until communication was lost!

• Installing the equipment in Utilities Buildings 1 and 2 first: This enabled them to be used as an aid during the installation and commissioning of the field instruments.

• Training was done using a series of workshops on-site in small teams to begin to transfer a good working knowledge to Sellafield Ltd staff.

IV. Magnox’s Early Applications

Wireless applications at Magnox include

• Temperature monitoring of a reactor pile-cap crane,

• Wind speed and air humidity monitoring,

• The monitoring of surface rainwater drainage and collection in sumps and bunds,

• Fire alarm communications to remote buildings.

Also under consideration at Magnox are

• A feasibility study for off-site plant monitoring,

• Temporary wireless monitoring of defueled reactor’s legacy thermocouples,

• Wireless SCADA (i.e. on a tablet computer) for mobile plant monitoring.

V. Cost and Time Savings

Installation time for all applications was pleasantly short, there being no cables or cable trunking to run. While difficult to estimate accurately, Sellafield estimate time savings of at least 16 weeks for the steam project. Project costs were the most notable benefit. Sellafield estimate a saving of around £185,000 on the steam project. Indeed, if ISA100 Wireless ¹ technology had not been available, this project would simply not have been viable.

VI. Conclusion

All applications thus far have been successful. The Sellafield application discussed above is Phase 1 of the site plan; discussions are taking place for Phase 2 applications. Phase 2 may have further flow measurements, the monitoring of relief-valve and steam-trap positions and some vibration monitoring. Equipment would be supplied by several ISA100 Wireless partners,; showing it is a truly open and interoperable standard.

Sellafield also plan to install wireless instrumentation on other piped services (e.g. water and compressed air) giving better coverage on-site.

Magnox plan to look at wireless instruments using solar power, wind power and external power scavenging (i.e. from vibration or temperature changes and so on).

For their part, the ISA100 Wireless suppliers are looking at improvements in aerial technology (i.e. directional antennae giving range extended from about 600 m max at moment to +1000 m), also, improvements to wireless “backhaul” using high frequency radio and laser to transmit a large amount of data over long distances (+2 km). Following this is “Duo-cast,” a very interesting feature which means rather than relying on an instrument’s router function to “rescue” data from a disconnected device, we can have multiple backbone routers per system and thus the potential for doubling battery life.