Overview

Reuter-Stokes, a Baker Hughes business, leads in providing nuclear instrumentation for Boiling Water Reactors (BWR), delivering highly reliable detectors, sensors and equipment to the nuclear industry. Reliability ensures no unplanned shutdowns, supports timely startups, resolves problems and aligns timely delivery with outage schedules and goals.  Most importantly, an innovative design reduces dosages to personnel during replacement.

For decades Reuter-Stokes has developed solutions for the nuclear industry, focused on maximizing life cycle equipment while minimizing the potential exposure of personnel to radiation. Reuter-Stokes achieves this goal by simplifying installation, removing probes and reducing the time under vessel.

A leading supplier of source and intermediate range detectors for plant startup, Reuter-Stokes offers hardware that reduces time spent swapping probes. As well, wide-range neutron detectors simplify operation by eliminating the need for two separate probes, boosting one probe to 10% power.

Please review these product features and assess your nuclear instrumentation and control needs to learn what supplemental solutions we can provide or design to suit your needs.

Product Features
LPRM Power Range Detectors

Reuter-Stokes has more than 45 years’ experience designing and manufacturing our LPRM detectors. We were the first to introduce miniature in-core fission chambers and the breeder LPRM concept. With more than 5,000 LPRM installations for nearly 75 boiling water reactors (BWRs), our operating experience is unsurpassed in all phases of BWR LPRM technology including design, manufacture, in-reactor performance and performance surveillance.

Our LPRM system consists of a number of fission chambers, which operate in a range from ~1 to 125% of the rated reactor power on a linear scale.

The individual LPRM assemblies consist of four sensors located at predetermined elevations, and a calibration tube for the traversing in-core probe (TIP). The entire assembly is enclosed in a stainless steel cover tube equipped with interface features that correctly mate with the reactor core’s support plates and grid.

radiation measurement
Wide Range Neutron Detectors

Reuter-Stokes designed its wide range detector (WRNM) to perform the functions of both the source range monitor (SRM) and the intermediate range monitor (IRM) during reactor startup. Our WRNM detectors operate in a dry tube inside the reactor core. The detectors are permanently fixed within the reactor core—even when operating at full-power—throughout the entire fuel cycle.

Single, stationary sensors replace moveable SRM and IRM instrumentation, eliminating excess mechanical drive systems:

  • Hands-off operation
  • Continuous power indication for entire startup period, requiring no range selection switching
  • Long-life detector
  • Nominal lifetime of 1.2 x 10^22 nvt
  • Operational experience has exceeded an average life of 1.7 x 10^22 nvt, or approximately 10 full-power years
  • Reduced under-vessel activities, maintenance and exposure during outages
  • Environmentally and seismically qualified, meeting requirements of U.S. NRC Reg Guide 1.97 for post-accident monitoring
nuclear instrumentation
Source & Intermediate Range Detectors

Reuter-Stokes is a technological leader in reactor startup instrumentation sensors. A typical reactor has four source range (SRM) sensors and eight intermediate range monitor (IRM) sensors that are used during the startup phase of reactor operations. Our Reuter Stokes SRM and IRM sensors operate inside a dry tube installed within the reactor core designed to be moved in and out of the dry tube.

  • The SRM is a fission-counting device that operates from below the source level to 109 nv, or approximately 10E-3 percent of the rated power
  • As the reactor power level exceeds the range in which the SRM can individually count neutrons, a drive mechanism withdraws the detector from the reactor core to a storage location below the active fuel region. The IRM then begins to generate output and is used to control the reactor operation up to approximately 10% of rated reactor power. After the power level exceeds the range of the IRM, it is also withdrawn and stored 
  • The IRM is a fission chamber that uses the voltage variance (Campbell) method and operates from 108 to 1.5 x 10^13 nv, or approximately 10% of the rated reactor power
  • The IRM is a fission chamber that uses the voltage variance (Campbell) method and operates from 108 to 1.5 x 10^13 nv, or approximately 10% of the rated reactor power
  • Able to withdraw detectors as the reactor flux exceeds startup, intermediate ranges prolong sensor life and lengthen overlap between the SRM and IRM channels and between the IRM and LPRM channels, respectively
  • The IRM sensor's lifespan averages eight years based on 1 x 10^17 nvt per startup/shutdown cycle and five cycles per year
Traversing In-Core Probes (TIPs)

Reuter-Stokes offers two types of our traversing in-core probes (TIPs): the gamma TIP and the neutron TIP. TIP sensors are inserted in the calibration tube of the LPRM assemblies to perform periodic calibration of the four LPRM sensors. These DC ion chambers measure gamma and neutron flux, respectively, at the elevation of each LPRM sensor. Sensors operate in a neutron flux range from 1.5 x 10^13 nv to 1.5 x 10^14 nv, or from about 10 to 100% of rated reactor power. Both styles of TIP sensors are driven in or out of the calibration tube by a drive mechanism that engages a helical drive cable, forming the outer sheath of the sensor signal cable. Between calibrations, the TIP sensor is withdrawn to a storage location outside primary containment. Several LPRMs can be calibrated with a single TIP sensor guided to the LPRM calibration tubes by an indexing mechanism.

Traversing In-Core Probes
Dry Tube Assemblies for BWR

Reuter-Stokes manufactures SRM/IRM, WRNM, LPRM and universal dry tubes for the boiling water reactor fleet. The dry tube assemblies provide housing for the sensors and position the sensors in the active core region of the reactor. All our dry tube assemblies form part of the pressure boundary of the reactor pressure vessel. Their design, manufacture and factory-testing conforms to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section III, Nuclear Power Plant Components.

  • All components are manufactured from stainless steel types 304, 304L, 316 or 316L 
  • Components are manufactured from low carbon (0.035 % maximum) and low cobalt (0.05 % maximum) materials to improve component-joining methods and reduce activation, resulting in lower disposal costs and dosage
  • Welds are designed to reduce residual stress and heat sensitization
  • All welds are crevice-free, which significantly increases the resistance to IGSCC and IASCC and decreases the frequency of in-vessel visual inspections by 50% compared to older creviced dry tubes
In Core ECP Detection Probes

Electro-chemically active elements such as excess oxygen that dissolve in the coolant stream can cause inter-granular stress corrosion cracking (IGSCC) in the reactor vessel and piping systems, resulting in additional outage time and increased costs for reactor internal replacements or repairs. The start of this IGSCC disintegration can be mitigated by both injecting hydrogen to neutralize the free oxygen and by monitoring the electrochemical corrosion potential (ECP) in various locations. Reuter-Stokes recommends that BWRs use detectors that accurately monitor ECP when hydrogen injection is inactive, as well as when hydrogen is being injected. At present, many plants utilize a system that can monitor data from two different types of probes:

  • An iron/ iron oxide ECP probe for measurement without hydrogen injection
  • A platinum ECP probe for measurement during hydrogen injection
ECP Probes

Electro-chemically active elements such as excess oxygen that dissolve in the coolant stream can cause inter-granular stress corrosion cracking (IGSCC) in the reactor vessel and piping systems, resulting in additional outage time and increased costs for reactor internal replacements or repairs. The start of this IGSCC disintegration can be mitigated by both injecting hydrogen to neutralize the free oxygen and by monitoring the electrochemical corrosion potential (ECP) in various locations.

  • A stainless steel ECP probe for measurement without hydrogen injection
  • A platinum ECP probe for measurement during hydrogen injection
  • Additional ECP probes have been designed and manufactured for special applications, such as stainless steel and carbon steel
ECP Probes
CRD Position Indicator

The Reuter-Stokes position indicator probes (PIPs) maximize plant operation and reliability, saving time and huge ALARA savings. Our PIPs compare the position of the control rod drive (CRD) to the reactor protection information system (RPIS) to control reactor power. 

Advantages of our PIPs include:

  • Rugged design prevents damage during undervessel activities
  • Significant time and ALARA savings via reduced PIP troubleshooting and replacement activities
  • Fewer occurrences of double flashing and intermittent/absent position indications
  • PIP-equivalent measurements and test repeatability through automated collection of test data; reduced operator-specific variability in test setup, performance and collection methods
  • Pre-installed stand-offs on locating strips and switch-locating fixtures ensure accurate, fixed-switch location
Mechanical Drive Equipment

Reuter-Stokes provides quality, technology-driven support equipment for its SRM and IRM detectors, including drive mounts, motor modules, flex shafts, drive tubes and shuttle tubes. In addition, we offer TIP support equipment such as drive mechanisms, indexing mechanisms, TIP tubing and guide tube/valve assemblies.

  • A DC motor module drives the moveable sensors in or out of the reactor’s active fuel region
  • SRM and IRM drive gears’ interface to the drive tubes enclosing the sensor signal cables
  • TIP systems’ helical-wrapped drive cable surrounding the sensor signal cables are driven by a worm gear
Mechanical Drive Equipment
Nuclear Undervessel Equipment

Reuter-Stokes offers a variety of products that save time, eliminate personnel exposure and reduce costs during undervessel work on our SRM, IRM, LPRM and WRNM detectors.


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