December 2025: Key Metrology Standards Update for Measurement and Physical Phenomena

The end of 2025 brings a significant series of updates within the field of metrology and measurement of physical phenomena. This fourth installment in our five-part coverage highlights five newly published international standards addressing everything from ionizing radiation measurement and nuclear bioassays to sound determination, nuclear borehole instrumentation, and low-voltage shore connections in port environments. For professionals tasked with maintaining high measurement accuracy, reliability, and safety—such as quality managers, engineers, safety officers, and researchers—these standards represent both advanced methodologies and operational best practices crucial for regulatory compliance and technological advancement.

Overview / Introduction

Metrology and physical measurement underpin quality, safety, and innovation across nearly every technical sector. Accurate measurement standards are essential for compliance with international regulations, safety of workers and the public, optimization of industrial processes, and advancing scientific discovery. This month’s standards focus on advanced procedures for radiological detection, environmental bioassays, acoustics, geophysical rock density analysis, and electrical interfacing between shore and ship systems.

In this comprehensive overview, you’ll discover:

• The latest requirements and technical updates for ionizing radiation measurements,
• Cutting-edge methods for biological assessment of radioactive materials,
• Engineering-grade guidelines for sound power level determination,
• Up-to-date specifications for nuclear borehole instrumentation, and
• Best practices for low-voltage shore connections in port applications.

Each section includes actionable guidance, compliance timelines, and practical considerations for seamless implementation.

Detailed Standards Coverage

ISO 11929-3:2025 - Applications to Unfolding Methods in Ionizing Radiation Measurement

Determination of the characteristic limits (decision threshold, detection limit and limits of the coverage interval) for measurements of ionizing radiation – Fundamentals and application – Part 3: Applications to unfolding methods

ISO 11929-3:2025 specifies advanced procedures for calculating characteristic limits—namely, decision thresholds, detection limits, and coverage intervals—in ionizing radiation measurements evaluated via unfolding methods. This standard focuses on multi-channel measurements, particularly in alpha and gamma spectrometry, where data deconvolution (unfolding) refines accuracy in complex environments.

Scope and Key Requirements:

• Applies Bayesian statistical methods and the latest ISO/IEC Guide 98-3 frameworks for uncertainty evaluation.
• Introduces nuanced guidance on handling measurement uncertainties, correlations, and covariances in unfolding quantitative models.
• Offers comprehensive methodologies for net count rate evaluations, gross/background discrimination, and calculation of coverage intervals.
• Details both the mathematical models behind the measurements and practical steps for their execution, ensuring traceability and reproducibility of results.
• Includes guidance for developing custom software or using provided codes like UncertRadio for uncertainty propagation.

Intended users:

• Laboratories conducting alpha/gamma spectrometric analyses,
• Nuclear facilities with advanced radiological monitoring needs,
• Regulatory authorities assessing compliance samples,
• Researchers developing or validating spectrometric unfolding methodologies.

Notable Changes:

• Refined statistical definitions and corrections for previous normative references.
• Enhanced procedures for handling multi-variate measurements.
• Expanded coverage for spectrometric unfolding and practical usage scenarios.

Key highlights:

• Advanced uncertainty evaluation for multi-channel unfolding methods
• Formalizes the treatment of correlations and covariances
• Provides workflow-optimized models and calculation tools

Access the full standard:View ISO 11929-3:2025 on iTeh Standards

ISO 18990:2025 - Measurement of Plutonium Radioactivity in Urine

Measurement of radioactivity in urine-238Pu, 239Pu and 240Pu – Test method using alpha spectrometry or ICP-MS

ISO 18990:2025 introduces rigorous procedures for measuring radioactive plutonium isotopes in urine using either alpha spectrometry or inductively coupled plasma mass spectrometry (ICP-MS). As exposure to Pu-238, Pu-239, and Pu-240 poses significant health risks, timely and precise assessment is vital for radiation protection programs and emergency response.

Scope and Key Requirements:

• Standardizes urine bioassay test methods for evaluating internal contamination levels among workers, emergency responders, and the general public.
• Provides full procedural guidance: sample collection, pre-concentration, chemical separation, and analytical measurement.
• Lists all essential reagents, apparatus, quality assurance controls, and calibration procedures for both detection methods.
• Clarifies detection limits, accuracy, and rapid turnaround needs for both planned monitoring and emergency situations.
• Emphasizes quality assurance, contamination prevention, verification, and analyst proficiency demonstration.

Intended users:

• Nuclear facility medical surveillance programs,
• Laboratories specializing in radiological bioassays,
• Health physics teams and occupational safety organizations,
• First responders and public health authorities handling radiological emergencies.

Notable Features:

• Incorporates both rapid screening (ICP-MS) and high-resolution (alpha spectrometry) techniques.
• Includes detailed annexes on chemical separation for varied sample sizes.
• Aligns results reporting with relevant ISO standards for medical labs and radioprotection.

Key highlights:

• Comprehensive sample preparation and separation methods
• Real-time and emergency assessment capabilities
• Full QA/QC and contamination control protocols

Access the full standard:View ISO 18990:2025 on iTeh Standards

ISO 3744:2025 - Sound Power Level Determination in Acoustic Environments

Acoustics — Determination of sound power levels of noise sources using sound pressure — Engineering methods for an essentially free field over a reflecting plane

This fourth edition of ISO 3744 details engineering-grade procedures for measuring the sound power level of machinery and equipment. Using sound pressure data collected around the noise source in an acoustically controlled environment, the standard prescribes how to calculate sound power across multiple frequency bands.

Scope and Key Requirements:

• Applicable to all types and sizes of noise sources (except for transient, impulsive events) in industrial or laboratory settings.
• Guides the selection and layout of measurement surfaces, microphone array configuration, and environmental adequacy.
• Specifies correction factors for non-ideal test settings and ensures applicability in both indoor and outdoor environments near reflecting planes.
• Addresses all necessary operational checks, verification procedures, background noise criteria, and uncertainty quantification (aligned to engineering grade, accuracy grade 2).

Intended users:

• Acoustics laboratories and test engineers,
• Manufacturer QA teams,
• Regulatory bodies overseeing noise emissions compliance,
• Facility managers engaged in occupational hearing conservation.

Notable Changes:

• Streamlined main procedures for sound level testing,
• Updated background noise conformity requirements,
• Expanded procedures for uncertainty reduction in labs,
• Reorganized annexes for easier application of specialized conditions, surfaces, and arrays.

Key highlights:

• Precision sound power determination suitable for compliance and R&D
• Refined environmental correction and measurement surface criteria
• Enhanced procedures to minimize test uncertainty

Access the full standard:View ISO 3744:2025 on iTeh Standards

IEC 61874:2025 - Nuclear Borehole Instrumentation for Rock Density Analysis

Nuclear instrumentation – Geophysical borehole instrumentation to determine rock density ('density logging')

IEC 61874:2025 applies to the design, operation, and verification of nuclear logging equipment used to determine rock density in situ through boreholes. These advanced probes are critical for applications in geology, mining, and hydrocarbons, where accurate subsurface information drives exploration and production decisions.

Scope and Key Requirements:

• Defines equipment structure: collimated gamma-source probe, detectors, hoisting/depth system, and surface hardware.
• Specifies design, safety, and technical requirements covering: radiation performance, electrical/mechanical reliability, environmental ruggedness, and calibration/testing procedures.
• Details operational checks before and after logging, and provides requirements for manufacturer documentation.
• Covers both single- and multi-detector arrangements for advanced compensated or litho-density logging.

Intended users:

• Oil and mining exploration companies,
• Geotechnical service providers,
• Environmental monitoring and research institutions,
• Manufacturers and operators of nuclear geophysical logging systems.

Notable Changes:

• Revised reference materials, terminology, and device classification,
• Enhanced accuracy in probe design/diameters, and environmental performance,
• New requirements for pre- and post-operation safety checks, and
• Expanded manufacturer documentation standards.

Key highlights:

• Comprehensive technical and operational requirements for density logging
• Detailed calibration and safety procedures
• Updated definitions and testing methodologies for field instruments

Access the full standard:View IEC 61874:2025 on iTeh Standards

IEC/IEEE 80005-3:2025 - Low-Voltage Shore Connection (LVSC) Systems for Ports

Utility connections in port – Part 3: Low-voltage shore connection (LVSC) systems – General requirements

IEC/IEEE 80005-3:2025 standardizes the provisions for designing, installing, and verifying low-voltage shore power connections in ports for vessels that draw up to 1 MVA while at berth. This is essential for reducing ship emissions, ensuring efficient port operations, and improving safety through reliable electrical connections.

Scope and Key Requirements:

• Covers all interface aspects—shore-side grid, cable management, power conversion, safety protocols, and shipboard systems.
• Defines system ratings (400–1,000 V AC, ≥250 A), applicable for three-phase connections and transformers.
• Lists design mandates regarding electrical protection, interlocking, monitoring, emergency shut-down, cooling, and routine/periodic testing.
• Excludes high-voltage systems (covered elsewhere), as well as systems for inland navigation vessels and non-professional operators.

Intended users:

• Port authorities and terminal operators,
• Ship owners, fleet logistics, marine engineers,
• Maritime equipment suppliers,
• Electrical contractors installing LVSC systems.

Notable Features:

• Emphasis on system compatibility, safety, and redundancy.
• Detailed requirements for operational documentation, testing, and verification before initial operation and after periodic maintenance.
• Guidelines for integration with shore power grids and vessel distribution systems.

Key highlights:

• Complete system design and emergency stop protocols
• Testing, verification, and performance documentation
• Enhanced safety for shore and ship operations

Access the full standard:View IEC/IEEE 80005-3:2025 on iTeh Standards

Industry Impact & Compliance

The December 2025 suite of standards impacts a wide range of industries—nuclear facilities, heavy industry, transport, energy, mining, laboratory testing, maritime operations, and more. Organizations must:

• Update operational protocols and training per new requirements.
• Ensure laboratory and field equipment are calibrated and validated to the revised specifications.
• Revise documentation, QA/QC, and traceability procedures especially for regulated and accredited contexts.
• Address cybersecurity, safety, and interoperability for connected systems, especially in sensitive environments (e.g., ports, nuclear sites).

Compliance Considerations and Timelines:

• For newly published standards, regulators may set adoption delays—verify with national/international authorities.
• Risk of non-compliance includes legal penalties, reputational risk, and compromised safety or accuracy.

Benefits:

• Improved measurement accuracy, reliability, and international harmonization.
• Enhanced protection for personnel handling radioactive and electrical equipment.
• Streamlined operations in industrial, research, and logistics settings.

Technical Insights

Across these standards, a few technical themes and best practices emerge:

• Uncertainty Evaluation: Bayesian and Monte Carlo approaches, as highlighted in ISO 11929-3, are becoming the norm for advanced uncertainty analysis.
• Sample and Calibration Integrity: Both ISO 18990 and IEC 61874 highlight stepwise verification, contamination control, and calibration.
• Engineering-Grade Acoustic Measurement: ISO 3744 moves end-users toward best-in-class uncertainty reduction and reporting.
• Integrated System Safety: IEC/IEEE 80005-3 emphasizes comprehensive protection schemes, interlocking, and physical/electrical separation.

Implementation Best Practices:

1. Stay current on documentation and versioning—many standards replace or supplement previous editions.
2. Roll out comprehensive staff and contractor training before the standards become mandatory.
3. Leverage available tools and templates (such as UncertRadio for uncertainty calculation, prescribed QA/QC forms, or test routines) to streamline compliance.

Testing and Certification:

• Conduct validation studies, round-robin or proficiency testing where required.
• Maintain calibration and operational records per standard mandates and regulatory requirements.

Conclusion / Next Steps

The December 2025 release cycle marks a significant advance in metrology and measurement of physical phenomena, driving technical and compliance excellence in radiation, acoustics, geotechnical logging, and maritime systems. Organizations should:

• Review the full text of each standard to map exact changes to their operational context.
• Prioritize early adoption to minimize compliance risks.
• Monitor for future updates—especially as Part 5 will complete this series next month.

Stay ahead of compliance and technological change:

• Explore the latest standards in metrology and measurement on iTeh Standards
• Subscribe for real-time updates and implementation resources.

By implementing these new standards, your organization will not only ensure regulatory compliance but also achieve new heights of reliability, safety, and measurement excellence.