REGDOC-2.6.4, Chemistry Control for Reactor Facilities

Preface

This regulatory document is part of the CNSC’s fitness-for-service series of regulatory documents, which also covers reliability and maintenance programs, and aging management. The full list of regulatory document series is included at the end of this document and can also be found on the CNSC’s website.

Regulatory document REGDOC-2.6.4, Chemistry Control for Reactor Facilities, clarifies the requirements for, and provides guidance on, developing, implementing and maintaining a chemistry control program for a reactor facility. A chemistry control program is essential for the safe operation of a reactor facility (including nuclear power plants, advanced reactor designs, small modular reactors (SMRs) and research reactors).

This document is the first version.

The chemistry control program is a key element in ensuring the integrity, reliability and availability of the facility’s structures, systems and components (SSCs) important to safety, in accordance with the intent of the design. The program contributes to ensuring the safe operation of the reactor facility, the long-term integrity of SSCs, and the integrity of the fuel; minimizing the buildup of radioactive material; and ensuring all releases to the environment are as low as reasonably achievable (ALARA).

Given the wide range of reactor facilities – especially of advanced reactor designs and small modular reactors – and given that reactor facilities have risk profiles that vary significantly depending on the particular characteristics of the activity or facility, the proponent, applicant or licensee may propose addressing requirements and guidance in a risk-informed manner commensurate with the level of risk of the regulated activity, or may propose alternative approaches to meet regulatory requirements, as described in REGDOC-1.1.5, Supplemental Information for Small Modular Reactor Proponents, and REGDOC-3.5.3, Regulatory Fundamentals.

For information on the implementation of regulatory documents and on the risk-informed approach, see REGDOC-3.5.3, Regulatory Fundamentals.

1. Introduction

1.1 Purpose

This regulatory document clarifies the requirements for, and provides guidance on, developing, implementing and maintaining a chemistry control program for a reactor facility.

Note: In this document, the term “licensee” refers to proponents, applicants and licensees.

1.2 Scope

This regulatory document applies to new and existing reactor facilities, including nuclear power plants (NPPs), advanced reactors, small modular reactors (SMRs) and research reactors.

This regulatory document is based on operational experience (OPEX), best practices developed from currently licensed reactor facilities, and vendor design reviews. The information in this regulatory document will be updated as additional information is gathered from experience with advanced reactors and SMRs. Licensees should apply the information and concepts from this regulatory document to the extent practicable and as best applicable to other reactor designs.

Given the wide range of reactor facilities – especially of advanced reactors and SMRs – and given that reactor facilities have risk profiles that vary significantly depending on the particular characteristics of the activity or facility, the licensee may propose addressing requirements and guidance in a risk-informed manner commensurate with the level of risk of the regulated activity, or may propose alternative approaches to meet regulatory requirements, as described in REGDOC-1.1.5, Supplemental Information for Small Modular Reactor Proponents ^{Footnote 1} and REGDOC-3.5.3, Regulatory Fundamentals ^{Footnote 2}.

Licensees may propose alternative ways to meet a requirement. Any proposed alternative (including the use of other codes and standards) should appropriately address the complexities and hazards of the proposed activities, and the licensee must demonstrate, by providing supporting information, that the proposed alternative meets an equivalent level of safety.

1.3 Relevant legislation

The following provisions of the Nuclear Safety and Control Act (NSCA) and the regulations made under it are relevant to this document:

• NSCA, subsection 24(5)
• General Nuclear Safety and Control Regulations, paragraphs 3(1)(j) and 12(1)(c) and (f)
• Class I Nuclear Facilities Regulations, paragraphs 5(e) and 6(d)
• Radiation Protection Regulations

1.4 National and international standards

Key principles and elements used in developing this document are consistent with national and international standards.

In CSA N286:12, Management system requirements for nuclear facilities ^{Footnote 3}, clause 7.9.11 applies to any high energy reactor facility (that is, with an output greater than 10 megawatts thermal (MWt)) and states that “system chemistry shall be maintained in accordance with requirements related to:

• “a definition of chemistry specifications;
• “chemistry parameter monitoring; and
• “data trending and evaluation.”

The following documents are relevant to this regulatory document:

• International Atomic Energy Agency (IAEA), SSG13 (Rev. 1), Chemistry Programme for Water Cooled Nuclear Power Plants ^{Footnote 4}
• IAEA, TECDOC-1942, Coolant Chemistry Control and Effects on Fuel Reliability in Pressurized Heavy Water Reactors ^{Footnote 5}
• IAEA, SSG-48, Ageing Management and Development of a Programme for Long Term Operation of Nuclear Power Plants ^{Footnote 6}
• CSA Group, CSA N286:12, Management system requirements for nuclear facilities ^{Footnote 3}
• CSA Group, CSA N290.20, Aging management requirements for nuclear power plants ^{Footnote 7}

Other documents that contain information that may be relevant to chemistry control for reactor facilities are listed in the Additional Information section of this regulatory document.

2. Overview of a Chemistry Control Program

A chemistry control program is a series of documents, processes and procedures that define chemistry specifications with the goals of controlling the degradation of SSCs important to safety, reducing sources of radiation in the facility as low as reasonably achievable (ALARA), and reducing releases to the environment. The program is a key component in ensuring the integrity, reliability, and availability of the facility’s structures, systems and components (SSCs) important to safety, in accordance with the intent of the design. It provides effective control of the degradation process of SSCs and of the impurities and corrosion products that hinder safe operation, contributes to ensuring that SSCs are fit for service, and interfaces with the maintenance and aging management programs.

Depending on the reactor facility, the chemistry control program may require more or less detail. For example, an NPP requires a full chemistry control program; however, by applying a risk-informed approach, other reactors (especially research reactors) may need a subset of the full program.

Optimization of chemistry control contributes to minimizing the generation of activated corrosion products and minimizing the release and redeposition of activated corrosion products from the core to outside the core.

For any new reactor design, the licensee should apply additional rigour to the chemistry control program to account for any factors that may not be fully demonstrated during design and development. The licensee should have additional capacity (trained and knowledgeable personnel; emergency equipment and services; physical barriers) to respond to any of these factors.

2.1 Goals of a chemistry control program

The main goal of a chemistry control program is to support the safe operation of the reactor facility and the safety of persons on the site, by:

• ensuring SSCs remain fit for service (for example, by minimizing all forms of corrosion of SSCs influenced by the chemistry regime)
• preserving the integrity of the fuel
• reducing the buildup of radioactive material (enabling lower occupational radiation exposure)
• limiting the release of chemicals and radioactive material to the environment, and contributing to ensuring that releases are as low as reasonably achievable (ALARA) and use the best available technology and techniques economically achievable (BATEA)
• contributing to the reactivity management
• ensuring that industrial safety standards are implemented and maintained

An effective chemistry control program accomplishes this goal through consideration of:

• chemistry regimes (which are defined by the reactor type, its design, and the materials used in its construction)
• chemistry monitoring (which ensures that the facility is operated in accordance with the chemistry regimes, and defines the parameters to be measured, their measurement frequencies, the action levels and the corrective actions to be taken when necessary)
• chemistry data monitoring, trending and decision making; which include:
  • measurements (to provide information about the actual chemistry conditions in the systems, and provide the basis for decisions on the safe operation of SSCs that rely on chemistry control as part of the safe operating envelope (SOE))
  • surveillance and monitoring (to ensure that measurements are taken and analyses are performed according to procedures)
• quality control and assurance (to contribute to ongoing safety, safe handling of nuclear and hazardous materials, and continual improvement)

An effective chemistry control program brings additional benefits to the efficient operation of a reactor facility. Some examples are:

• ensuring thermal efficiency of the heat transport system
• minimizing the buildup of sludge and scale
• monitoring the intrusion of non-conforming chemicals or other substances into facility systems, which can result in deviations in the chemistry regime (leading to component and system damage or increase of dose rates)
• monitoring the use of uncontrolled materials on the surfaces of components, which may induce damage

Some examples of how chemistry control contributes to radiation protection are:

• minimization of dose rates in the reactor facility over time
• support of the facility’s radiation protection program; some areas where chemistry control may affect the radiation protection program are:
  • the facility’s radiological source term
  • verification of the adequacy of the facility’s radiological source term monitoring tools and techniques
  • verification of the adequacy of the facility’s radiological source term reduction initiatives
  • verification of the adequacy of the facility’s dosimetry program

For more information on fitness for service, maintenance and aging management, see:

• REGDOC-2.6.2, Maintenance Programs for Nuclear Power Plants ^{Footnote 8}
• REGDOC-2.6.3, Aging Management ^{Footnote 9}

2.2 Corporate organization related to the chemistry control program

Implementing an effective chemistry control program affects other safety and control areas (SCAs) in the CNSC’s SCA framework. The licensee is not required to adhere to the CNSC’s SCA framework, but must address all aspects in their own corporate organization.

An effective chemistry control program takes all of the following areas into account:

• management system
• human performance for personnel training
• safety analysis, especially for research and development (R&D)
• physical design
• radiation protection
• environmental protection
• waste management

Requirements

As described in REGDOC-2.5.2, Design of Reactor Facilities ^{Footnote 11}, SSCs must be designed to limit the activation of corrosion products by proper specification of materials. The material choices must be consistent with the design, operation and expectations of the chemistry regime, applied with conservative decision-making.

The licensee shall ensure that the effect from any changes to the chemistry regime or chemistry control program are adequately analyzed to manage and control any adverse effects on radiation exposures to facility personnel and on releases of radioactive and hazardous substances to the environment.

Before implementing changes to the chemistry program, the licensee shall ensure that processes are in place to provide adequate support for the identification and characterization of radioactive or hazardous waste generated at the reactor facility (including waste from decontamination).

When developing and maintaining the chemistry control program, the licensee shall incorporate any relevant national or international operational experience (OPEX) and research and development (R&D).

Guidance

As described in SSG-13 (Rev. 1), Chemistry Programme for Water Cooled Nuclear Power Plants ^{Footnote 4}, some examples of corporate functions and responsibilities related to the chemistry control program are:

• management of resources
• chemistry control
• dose management
• chemistry and radiochemistry control, measurements, surveillance and data management
• quality control
• reviews of results
• staff training and qualification
• approval of procedures (including change control)

The licensee should ensure that representatives of the chemistry department regularly obtain OPEX from national and international organizations, that research results, lessons learned, good practices and standards are analyzed and incorporated into the chemistry control program, and that procedures are updated accordingly. This process supports knowledge transfer and information exchange, and ensures that the chemistry control program is kept up to date with best industry practices.

The licensee should ensure that basic training in chemistry and chemistry control is provided to all operational personnel, using a systematic approach to training (SAT). Staff involved in receiving, storing, transporting, and using chemical substances should be trained to understand storage compatibility, labeling requirements, handling, safety, and effects on SSCs. Initial training for chemistry staff should include on-the-job training. The initial training should also cover chemistry-specific topics during normal operation, shutdown, start-up, and potential transient scenarios.

Training courses should include techniques for:

• recognizing unusual conditions during sampling
• establishing appropriate and effective corrective actions
• recognizing malfunctions of measurement equipment
• recognizing adverse trends in measurement results
• reviewing the chemistry of inaccessible SSCs

Staff who work with chemicals should be trained in the proper handling and storage of hazardous, flammable and poisonous chemicals.

For training programs and emergency exercises, chemistry staff should take part in any training programs or emergency exercises where internal or external releases of chemicals and radioactive material are involved. The programs or exercises should use emergency chemistry procedures, emergency equipment and expected chemistry values, to ensure correct responses by chemistry staff.

The licensee should ensure that design changes to the facility or the SSCs are reviewed for relevance to chemistry and to the chemistry control program. If design changes relevant to chemistry or to the chemistry control program are planned, the licensee should ensure that the chemistry department is included in the facility’s design authority process. Chemistry management and supervisors should understand and approve the design basis documentation relevant to the chemistry control program and they should either be responsible for the management of this information or have easy access to it. If design changes are implemented, the chemistry should be monitored; if the changes affect the chemistry, the affected areas of the chemistry control program should be reviewed and revised.

For more information, see:

• CSA N286:12, Management system requirements for nuclear facilities ^{Footnote 3}
• REGDOC-2.2.2, Personnel Training ^{Footnote 10}
• REGDOC-2.5.2, Design of Reactor Facilities ^{Footnote 11}
• REGDOC-2.7.1, Radiation Protection ^{Footnote 12}
• REGDOC-2.9.1, Environmental Principles, Assessments and Protection Measures ^{Footnote 13}
• REGDOC-2.9.2, Controlling Releases to the Environment ^{Footnote 14}
• CSA N288.6, Environmental risk assessments at nuclear facilities and uranium mines and mills ^{Footnote 15}
• REGDOC-2.11.1, Waste Management, Volume I: Management of Radioactive Waste ^{Footnote 16}

3. Developing and Implementing a Chemistry Control Program

Requirements

The licensee shall ensure that a suitable chemistry control program has been developed and implemented for the reactor facility. The program shall consider the original design and structural materials, and any modifications shall be taken into account.

The licensee shall ensure that the chemistry control program addresses the following elements:

• corrosion is controlled or reduced to the extent possible
• radioactive material and hazardous substances within the monitored systems is prevented from increasing beyond acceptable limits
• SSCs remain fit for service

Guidance

To support the overall requirements of the chemistry control program, the licensee should ensure that:

• any deviations from normal operational limits are addressed in a timely manner, and that the effectiveness of the methodologies used is evaluated regularly and improved where necessary
• the chemistry control program supports the reliable operation of SSCs and does not compromise design assumptions during the lifecycle of the operating facility (including decommissioning)
• self-assessments and independent assessments of the chemistry control program are conducted regularly
• the chemistry control program includes participation in a recognized analytical certification and intercomparison program (that is, a “comparison lab” program that includes both chemistry and radiochemistry measurements)
• identified non-conformances are reported, analyzed, and addressed with effective corrective actions in a timely manner through the facility’s corrective action program, including relevant significance level
• the effectiveness of corrective actions is reviewed and addressed regularly before closure of the actions

To support the corrosion control element, the chemistry control program should:

• include a process for timely reporting of evaluation results to management at the responsible level and to other users of such results from the chemistry program
• include a process for a timely response to correct any deviations from normal operational status
• ensure that methodologies for diagnosis and treatment of deviations are used and are kept up to date

To support the element of preventing radioactive material from increasing beyond acceptable limits (that is, to support source term management and reduction), the licensee should consider the following:

• The chemistry control program should effectively control and minimize the buildup of radioactive material from the transport and accumulation of fission products and activated corrosion products on the internal surfaces of the SSCs. The program should also consider all materials used in the primary cooling circuit to prevent fuel cladding failure and any detrimental effect on the primary cooling circuit or the environment. The program should also consider the impact that the addition of chemical agents may have on liberating radioactive material within the monitored systems such that mobility of previously fixed radioactive material may pose increased risk to personnel, equipment, or the environment.

As appropriate to the nuclear facility’s technology, the licensee should ensure their chemistry control program and chemistry regime interface with their source-term reduction program, in order to evaluate replacement materials and to monitor and control the impacts to radiation fields from the fission products and activation products present within the water systems.

To support the fitness-for-service element (including maintenance and aging management), the licensee should ensure that:

• the chemistry program supports the facility’s aging management program
• staff from the chemistry department contribute to maintaining the availability of the SSCs (for example, ensuring appropriate chemistry to minimize equipment degradation)
• processes are in place to prevent the use of substances and reagents that may adversely affect the integrity of SSCs
• the presence of easily activated elements is minimized in SSCs and, if necessary and possible, specifically removed from the coolant during reactor shutdown by the selection of a proper shutdown chemistry regime with an adequate purification system
• the chemistry control program includes requirements to perform a review of the chemistry of inaccessible SSCs whenever they become available (for example, during maintenance shutdowns)
• for SSCs important to safety, the chemistry control program is designed to ensure fitness for service throughout the SSCs’ intended design life

To support the overall chemistry control program, the licensee should also consider the information below.

Before making any changes to the chemistry control program, or performing problem resolution on unknown phenomena, the licensee should ensure that either well-documented R&D work is conducted or results from OPEX are analyzed, and that an adequate technical basis for the changes is demonstrated.

The licensee should ensure that any measures to shorten the scheduled shutdown period and to accelerate facility startup activities will not affect the chemistry control program. Some examples of procedures that should be considered are:

• efficient use of purification systems during shutdown and startup phases
• maintaining suitable wet or dry conservation conditions in equipment during shutdown periods

The chemistry control program should provide chemistry staff and radiation protection staff with information on fission products, coolant activation products, and activated corrosion products.

3.1 Chemistry regimes

Chemistry control includes the correct application of the appropriate chemistry regime taking into account each SSC important to safety. The appropriate chemistry regime depends on the design of the reactor facility and on the construction materials used.

Requirements

The licensee shall establish a suitable chemistry regime for each SSC important to safety, under all facility states.

The licensee shall establish specifications for all important chemistry parameters and shall ensure that any deviations from these specifications are addressed in a timely manner.

The licensee shall establish adequate lay-up chemistry regimes to preserve equipment during outages.

The licensee shall maintain the chemistry regimes of active and passive safety systems that contain liquid neutron absorbers, in accordance with design standards.

The licensee shall fully understand the impact on the reactor facility’s lifecycle of continuing to operate the reactor facility with impaired chemistry parameters.

The licensee shall specify action levels in advance for control parameters. When deviations occur, the licensee shall take action to restore the control parameters.

Guidance

For each chemistry regime, the licensee should define detailed chemistry control parameters to be followed in all operating conditions. These parameters should be developed according to their potential importance to safety, in accordance with the risk-informed approach. All parameters should be based on adequate technical knowledge and OPEX.

The licensee should define the chemistry parameters and their corresponding action limits, in chemistry procedures or other relevant facility documentation for the following facility states:

• transition from construction to commissioning
• commissioning
• start-up
• normal operation
• transients
• shutdowns (both short and extended)
• outages
• accident conditions
• transition from operation to decommissioning
• decommissioning

The control parameters selected for the chemistry regime for each facility state should be the most important parameters for monitoring that regime, including those parameters that:

• are known to negatively affect material integrity, fuel cladding corrosion and fuel design performance
• have a direct effect on reactivity control, radiation fields or the environment
• can be used for monitoring the presence of impurities

If deviations from action levels occur, the licensee should initiate corrective actions within a predefined period of time. Further corrective actions should be applied until the control parameters are restored (until facility shutdown, if necessary).

The licensee should establish sampling points, set out the scope and periodicity of chemistry monitoring activities (sampling and analysis), and ensure that defined procedures are in place.

The licensee should define diagnostic parameters to provide information on the chemistry status of the facility. The licensee should select parameters that enable the chemistry staff to react proactively on chemistry deviations.

The licensee should define a chemistry regime for each auxiliary system that is in accordance with the design specifications, and with the intent of preserving the system’s full integrity and availability.

During outages, the licensee should ensure that lay-up parameters are monitored and corrective actions for deviations are implemented. The chemistry regime during lay-up should minimize material degradation and allow for an effective return to service of the SSC.

If liquid neutron absorbers are present, the licensee should establish a chemistry regime of systems that contain those absorbers. The licensee should take into account that, generally, correction of the liquid chemistry within these reservoirs can be made only infrequently and at specified times.

When developing or updating the chemistry regimes, the licensee should ensure that:

• the primary cooling circuit chemistry regime is appropriately selected, with account taken of its potential impact on:
  • uniform corrosion and stress corrosion cracking of circuit materials
  • fuel cladding corrosion
  • activation and transport of corrosion products
  • dose rates
  • power shifts induced by circulating corrosion products
  • localized corrosion induced by circulating corrosion products (local conditions are an important consideration when assessing corrosion threats, as compared to only the bulk; the corrosion threats should be graded on the basis of safety significance, likelihood and potential severity)
• if applicable (depending on the reactor technology), for the secondary and tertiary cooling circuits:
  • the construction materials inside the containment are compatible with the coolant chemistry conditions
  • the chemistry regimes are designed to:
    • minimize corrosion in the integrated system, concentration of deleterious compounds in crevices of areas with restricted flow, and condenser leaks in both coolant and air parts
    • increase the effectiveness of the steam generator blowdown purification system (if used) and of the condensate cleaning system (if used)
• for auxiliary systems:
  • the chemistry regime defines the minimum quality (for example, concentrations of permitted impurities) of all oils that are used for each system important to safety or for the availability of systems important to safety
  • lubricants and hydraulic oils from operating systems important to safety, or used for the availability of backup systems important to safety, are analyzed regularly to check the control parameters that characterize the condition of the lubricant or hydraulic oil
• if applicable (depending on the reactor technology), for the steam generator and heat exchanger:
  • the concentrations of impurities detrimental to the integrity of steam generator heat transfer tubes are kept as low as possible, and the levels are monitored
  • local corrosion due to sludge formation in the steam generator is minimized by the application of appropriate secondary and tertiary side chemistry regimes
  • use of a blowdown system to remove impurities is considered

3.2 Chemistry monitoring

Chemistry monitoring verifies the effectiveness of chemistry control in facility systems and verifies that SSCs important to safety are operated within the specified chemical limit values.

Effective chemistry monitoring is achieved through:

• a chemistry surveillance program
• chemistry facilities and equipment
• radiochemistry measurements
• a post-accident sampling system

For more information on each of these aspects of chemistry monitoring, see the following subsections.

3.2.1 Chemistry surveillance program

The objectives of a chemistry surveillance program are:

• to verify compliance with control and diagnostic chemistry limits and conditions
• to maintain the availability of SSCs
• to detect any abnormal chemistry condition and apply early corrective action before it becomes a consequence that is significant for safety
• to ensure compliance with regulatory release limits

Requirements

The licensee shall establish and implement a chemistry surveillance program to:

• verify the effectiveness of chemistry control in the facility’s systems
• verify that chemical parameters for SSCs important to safety are within the specified action levels
• detect trends in chemistry parameters
• discover and eliminate undesirable effects and consequences of out-of-range chemistry parameters

document chemistry specifications for all stages of the lifecycle of the facility, including commissioning, shutdown and start-up, and when systems are taken out of operation for prolonged periods

The licensee shall ensure that:

• appropriate chemistry controls and diagnosis parameters are applied to verify safe and reliable operation
• practices are in place to confirm that coolant cleanup systems and sampling systems are operated effectively
• adequate and reliable continuous monitoring and laboratory systems for measurement of chemistry parameters are in proper operation; continuous monitoring instruments and equipment in the laboratory are regularly inspected, calibrated and maintained

Guidance

For more information on timely calibration of chemistry instruments and equipment being used for radiation measurements, see REGDOC-2.7.1, Radiation Protection ^{Footnote 12}.

The licensee should ensure that:

• the procedures for selecting the chemistry regime include an identification of the relative importance to safety of each chemistry parameter
• the level of chemistry control and monitoring is tailored such that greater attention is paid to those systems most important to safety, according to the graded approach
• the chemistry surveillance program uses all available sources of information, including chemistry data and other technological data related to chemistry

The licensee should ensure that provisions are in place to ensure that:

• the continuous monitoring and data acquisition systems accurately measure and record data and provide alarms for key chemistry parameters
• the measurement ranges of analytical instruments extend beyond the operating ranges and safety limits of the facility
• reagents and sources used for calibration are valid (for example, all standards should be traceable to certified standard solutions or reagents)
• calibration points are chosen such that their measurement ranges overlap and they are as close as possible to the expected measurement value
• “check standards” (that is, measurements made at specified time intervals) are analyzed and control charts are maintained to show that the methods applied continue to give accurate results; the establishment of an interlaboratory comparison program may be considered

The licensee should consider the use of continuous monitoring of control parameters as the preferable monitoring method for evaluating chemistry conditions in facility systems. Laboratory analysis complements the diagnosis of chemistry issues, verifies the accuracy of continuous monitoring equipment, and identifies when it is not practicable to implement continuous monitoring. Selection of analytical methods should also take into account the doses likely to be accrued by intrusive sampling.

In determining the analytical methods to be employed, the licensee should consider the expected concentration levels for the chemistry parameter of interest. The method chosen should provide sufficient sensitivity in the expected concentration range. The matrix effect (the effect of other components in the sample) should be determined and corrected if necessary.

Chemistry staff may apply other methods for ensuring that the collected data is accurate and reliable; some examples include:

• comparison of results from continuous monitoring equipment and laboratory equipment
• comparison of data from different sampling points or comparison of different parameter measurements from the same sampling point for evaluating the plausibility of the data measured

When developing the chemistry surveillance program, the licensee should:

• ensure the program provides support for the development of methodologies, taking the requirements of the chemistry control program and appropriate standards into consideration
• ensure software for calculations of chemistry processes important to safety is verified and validated by a third party or another appropriate independent organization, or by experts
• take into account typical physical conditions (such as temperature or flow rate) at the measuring location
• ensure a calibration and maintenance program is established and applied to all continuous and laboratory monitoring

For example, the intrusion of non-conforming chemicals or other substances into facility systems can result in deviations in the chemistry regime, leading to component and system damage or increase of dose rates. The use of uncontrolled materials on the surfaces of the components may induce damage.

3.2.2 Chemistry facilities and equipment

Requirements

The licensee shall ensure that adequate chemistry facilities, sampling and laboratory equipment (including laboratory instruments and continuous monitoring instruments) are provided.

Guidance

The licensee should ensure that adequate facilities, sampling and laboratory equipment (including laboratory and continuous monitoring instruments) are available for chemistry measurements and analysis. The licensee should also ensure that predefined acceptance criteria and specifications are in place to check that the chemistry equipment and related systems are ready to return to service after maintenance and modifications.

When establishing the chemistry facilities and equipment, the licensee should ensure that:

• redundant or equivalent laboratory facilities are always available
• instrumentation and equipment are validated, along with the methods to be applied
• the adequacy and accuracy of procedures and of equipment performance:
  • are checked regularly by means of intra- and inter-laboratory tests to verify analytical interference, proper calibration, analytical techniques and instrument operation
  • these test results are evaluated to determine the cause of unexpected differences and deviations, with both short- and long-term effects taken into account
  • if necessary, corrective action are taken to improve laboratory performance
• results of the analysis of standards are used to verify instrument accuracy based on specified acceptance criteria
• if instrument performance shows significant deviation from expected values, an investigation is performed to determine the cause of the deviation, and repair or recalibration of an analytical instrument is done as necessary
• appropriate consideration is given to the need for correct sampling conditions; account is taken of:
  • delays in obtaining samples when using data obtained through continuous monitoring or laboratory measurements
  • specific sampling issues associated with obtaining representative soluble and particulate corrosion products
  • representative grab samples are ensured by appropriate flushing of sampling lines, proper determination of the flow rate, cleanliness of containers, and minimization of the risk of chemical contamination and loss of dissolved gases or volatile substances during sampling

The licensee shall ensure that hazardous chemicals are managed safely, and that a set of material safety data sheets is available. Note that reasonably small amounts of chemicals can be stored in other controlled environments within the workshops or operational department.

3.2.3 Radiochemistry

Requirements

The licensee shall ensure that primary coolant activity is monitored in support of:

• measurement of fission product activity (as a means of evaluating the fuel integrity, identifying fuel cladding leaks, and estimating the type and number of cladding defects)
• measurement of the activities of corrosion products to ensure good representative data
• measurement of other activated species as a means of verifying or cross-checking the results of chemical analyses and for early warning of low concentrations of possibly unknown impurities

Guidance

The licensee should ensure that specifications for all important radiochemistry parameters are established and applied during different operational modes to fulfill dose limits and maintain radiation exposures ALARA. During an outage, and if possible also during operation, dose rates from systems and components should be measured regularly for trending purposes. This data should be complemented by nuclide-specific measurements to identify which nuclides are the main contributors to the dose rates.

The licensee should ensure that radiochemistry measurements are carried out for fluid-based systems for early detection of leaks in material barriers.

When monitoring measurement of fission product activity (as part of primary coolant activity monitoring), the licensee should consider:

• using good-quality, well-maintained and calibrated gamma spectrometry instrumentation, a sufficient variety of calibrated measurement geometries, and effective, verified radiochemical separation procedures
• applying the results of such measurements as input data for validated calculations to evaluate fuel leaks, with sufficient sensitivity to enable the early detection of fuel leaks through activity measurements of key fission products
• monitoring of power transients
• proper selection (as part of the above actions, and depending on the type of fuel) for analysis of both volatile and non-volatile radionuclides, such that both small and large cladding defects can be detected

proper selection (depending on the type of reactor) of radionuclide activity ratios to assess the burnup of leaking fuel rods (to facilitate their identification during operation or outages)

If applicable (depending on the reactor technology), the licensee should ensure that radioactivity of the secondary cooling circuit is monitored to detect pipe breaks in the interface between primary and secondary coolant and between secondary and tertiary coolant.

The licensee should ensure that:

• radiochemistry measurements are part of all fuel handling operations, to monitor fuel integrity and the possible propagation of defects
• radiochemistry measurements are applied in monitoring the performance of purification systems (especially when the main purpose of operating the purification system is removal of radioactive material)
• measurement of the activities of relevant radionuclides should be carried out while monitoring the efficiency of decontamination processes (especially in the decontamination of large components) to optimize treatment time and minimize radioactive waste generation; the monitoring practices should be in accordance with ALARA principles and objectives
• radiochemistry methods are applied to provide the results necessary for the characterization of radioactive waste with regard to its treatment, conditioning and disposal:
  • effective and validated radiochemical separation methods are developed to measure the activity of difficult-to-measure radionuclides
  • for the radionuclides specified for each disposal facility, and as defined in the safety analysis report, the activities should be determined repeatedly in a defined set of waste streams, so that sufficient data is accumulated from which mathematical correlations can be derived between difficult-to-measure radionuclides and key (reference) radionuclides (that is, fingerprinting)
  • these mathematical correlations are then used for the calculation-based characterization of newly generated waste; however, periodic checks of their correctness are carried out by new radiochemical analyses
• the activities of radioactive effluents, both liquid and gaseous, are monitored regularly by appropriate methods
• radiochemical methods that rely on radiochemical separation methods and properly calibrated liquid scintillation counters are applied to monitor liquid and gaseous releases of tritium and carbon14 as specific low-energy beta emitters

3.2.4 Chemistry data trending and evaluation

Evaluation and trending of data enables the licensee to assess the efficiency of chemistry control, to identify inconsistencies in analytical data and adverse trends in chemistry conditions, and to help optimize chemistry in the SSCs.

Requirements

The licensee shall ensure that analytical data is reviewed to verify its completeness, accuracy and consistency. To identify actual and potential deviations in chemistry parameters, an assessment of chemistry data shall be performed promptly after the data has been recorded. Depending on the importance and potential consequences of any deviation, the chemistry staff shall inform relevant operational personnel according to the facility’s procedures.

In the case of deviations or anomalies in measurement results, a qualified chemistry staff member shall check and verify the analyses and proper, prompt corrective actions shall be taken and documented.

The licensee shall compare the chemistry data with operational limits, and shall carry out evaluation and trending of data.

Guidance

The chemistry staff should be assigned primary responsibility for reviewing chemistry data.

When reviewing the analytical data, chemistry staff should:

• compare the current data with previously obtained data and:
  • investigate situations where the results obtained are outside the expected range of the system operating conditions
  • identify recent additions of chemicals or recent operational changes
  • regularly evaluate the results of laboratory quality control tests
• compare the data with operational limits and carry out evaluations and trending of the data to:
  • assess the efficiency of chemistry control
  • identify inconsistencies in analytical data and adverse trends in chemistry conditions
  • help to optimize chemistry in the systems
• give particular attention to data that deviates from operational limits

The licensee should ensure that chemistry data trending is performed to identify and correct adverse trends on chemistry where those trends challenge the goals of the chemistry control program. Some examples of trends are transients of short duration caused by operational changes in the facility, and slower long-term changes occurring during steady-state operation.

Some examples of data trending and evaluation are:

• trends in chemical data should be correlated to operational parameters (such as thermal power, changes in chemical injection rates and so on)
• trending of relevant chemistry parameters should be carried out to obtain an adequate picture of chemistry conditions and to facilitate correlations between related chemistry parameters and the status of SSCs
• trends should be reviewed soon after data has been recorded, in order to identify problems that may need corrective action before a parameter exceeds its specified limit
• the expected values should:
  • be used to detect a parameter approaching its specified limit
  • have sufficient margins to control limits

The chemistry staff should proactively report significant deviations in chemistry analysis results to the appropriate level of management. The chemistry staff should communicate with other relevant groups at the reactor facility when analytical data indicates the need for prompt action to correct chemistry-related problems.

3.3 Post-accident monitoring system

In addition to normal operating conditions and standard shut-downs, an effective chemistry control program supports post-accident management through monitoring of chemistry parameters. Timely post-accident monitoring capability establishes if the reactor fuel is damaged, and the extent of the damage. An early determination of chemicals and their levels provides knowledge of the state of the reactor facility.

Requirements

The licensee shall ensure that a post-accident monitoring system or other adequate sampling facility is ready to operate when required by emergency procedures and is considered for use in taking regular samples from facility systems.

The licensee shall ensure that the following items are provided:

• operating procedures for the post-accident monitoring system, including periodicity for taking measurements
• radiation protection measures for personnel who carry out sampling and analysis; such measures should be evaluated in advance (for more information, see REGDOC-2.10.1, Nuclear Emergency Preparedness and Response ^{Footnote 19})
• a program for preventive maintenance of the post-accident monitoring system
• regular checks of the operability of the post-accident monitoring system
• regular training of personnel designated for operation of the post-accident monitoring system
• specification of the chemistry parameters to be monitored

Guidance

The licensee should ensure that results of the post-accident monitoring (such as chemistry and radiochemistry reports) are communicated in a timely manner to the chemistry management team and to those parts of the organization who need such information.

If a post-accident monitoring system does not exist, other approaches should be adopted for:

• core damage evaluation
• estimation of the inventory of fission products released into the containment

3.4 Performance evaluation

Requirements

The licensee shall develop and implement quality control and quality assurance for the chemistry control program.

The licensee shall periodically evaluate the performance of the chemistry control program.

Guidance

The licensee should establish performance indicators, including relevant operational indicators (both chemistry and radiochemistry) to monitor the effectiveness of the chemistry control program. The results of performance indicators should be regularly communicated by the chemistry staff to other applicable departments and senior management. The licensee should ensure that chemistry performance indicators are trended, and preventive or corrective measures are undertaken when necessary.

The licensee’s conventional health and safety program addresses industrial and chemical safety risks to workers, while their radiation protection program addresses radiological risks. To set the overarching goals for quality control and quality assurance in these areas, see:

• the licensee’s management system
• REGDOC-2.8.1, Conventional Health and Safety ^{Footnote 17}
• REGDOC-2.7.1, Radiation Protection ^{Footnote 12}.

As a best practice, the reagents and ion exchange resins used for any safety-related systems should be tested before use, to verify they are within the required specifications for impurities.

Glossary

For definitions of terms used in this document, see REGDOC-3.6, Glossary of CNSC Terminology, which includes terms and definitions used in the Nuclear Safety and Control Act and the regulations made under it, and in CNSC regulatory documents and other publications. REGDOC-3.6 is provided for reference and information.

The following terms are either new terms being defined, or include revisions to the current definition for that term. Following public consultation, the final terms and definitions will be submitted for inclusion in the next version of REGDOC-3.6, Glossary of CNSC Terminology.

chemistry control program (programme de contrôle chimique)

A series of documents, processes and procedures that define chemistry specifications with the goals of controlling the degradation of SSCs important to safety, reducing sources of radiation in the facility as low as reasonably achievable (ALARA), and reducing releases to the environment. The program defines the chemistry parameters to be measured, the means to measure them, the measurement frequencies, the action levels and the corrective actions to be taken when necessary. It ensures that the facility is operated in accordance with the chemistry regime. Chemistry control includes the correct application of the chemistry regime, and also relates to the ability to manage the chemistry regime, including the ability to detect and rectify deviations. “Control” is not restricted to instrumentation and control (I&C) systems, but extends to all operations that provide a degree of control over the operating chemistry, such as sampling and analysis. The chemistry control program may include procedures for the selection, monitoring and analysis of the chemistry regime (that is, instructions for operations involving chemistry processes and evaluation of operating results, with determination of the operation and reference limits for chemistry parameters and action levels and possible remedial actions).

chemistry regime (régime chimique)

The set of chemical conditions (parameters) that are maintained and monitored within a reactor facility to ensure safe operation. The chemistry regime is guided by the type of nuclear fuel (some examples are cladded oxide solid fuel, molten salt, and tri-structural isotropic particle fuel), the coolant (some examples are water, molten salt, liquid metal, and inert gas), and the structural materials used for the reactor and associated systems. The specifications are chosen to meet the requirements (in terms of chemistry) of the overall chemistry control program, and are identified for each SSC important to safety. Some examples are the determination of pH range and of concentrations of chemicals and contaminants. Also referred to as a chemistry control regime.

References

The CNSC may include references to information on best practices and standards such as those published by CSA Group. With permission of the publisher, CSA Group, all nuclear-related CSA standards may be viewed at no cost through the CNSC webpage “How to gain free access to all nuclear-related CSA standards”.

Additional Information

The CNSC may recommend additional information on best practices and standards such as those published by CSA Group. With permission of the publisher, CSA Group, all nuclear-related CSA standards may be viewed at no cost through the CNSC webpage “How to gain free access to all nuclear-related CSA standards”.

The following documents provide additional information that may be relevant and useful for understanding the requirements and guidance provided in this regulatory document:

• CSA Group, CSA N293, Fire protection for nuclear power plants, 2023.
• CSA Group, CSA N393, Fire protection for facilities that process, handle, or store nuclear substances, 2022.
• International Atomic Energy Agency (IAEA), Safety Reports Series No. 106, Ageing Management and Long Term Operation of Nuclear Power Plants: Data Management, Scope Setting, Plant Programmes and Documentation, Vienna, Austria, 2022.

Organisation for Economic Co-operation and Development (OECD) – Nuclear Energy Agency (NEA), NEA/CRPPH/R(2014)2, Radiation Protection Aspects of Primary Water Chemistry and Source-term Management, 2014.

The following documents provide additional information that is relevant and useful for understanding the requirements and guidance for chemistry control at specific phases of a reactor facility’s lifecycle:

• Canadian Nuclear Safety Commission (CNSC), REGDOC-1.1.2, Licence Application Guide: Licence to Construct a Reactor Facility, Ottawa, Canada.
• CNSC, REGDOC-1.1.3, Licence Application Guide: Licence to Operate a Reactor Facility, Ottawa, Canada.

CNSC Regulatory Document Series

Facilities and activities within the nuclear sector in Canada are regulated by the CNSC. In addition to the Nuclear Safety and Control Act and associated regulations, these facilities and activities may also be required to comply with other regulatory instruments such as regulatory documents or standards.

CNSC regulatory documents are classified under the following categories and series:

1.0 Regulated facilities and activities

2.0 Safety and control areas

3.0 Other regulatory areas

Note: The regulatory document series may be adjusted periodically by the CNSC. Each regulatory document series listed above may contain multiple regulatory documents. Visit the CNSC’s website for the latest list of regulatory documents.