Overview
ISO 18990:2025 - Measurement of radioactivity in urine - specifies standardized approaches for determining plutonium isotopes 238Pu, 239Pu and 240Pu in urine using alpha spectrometry or inductively coupled plasma mass spectrometry (ICP‑MS). The standard addresses sample preparation, measurement and result expression for urine bioassay in both routine (planned exposure) and emergency exposure situations. It focuses on analytical procedures and quality assurance; it does not cover when to monitor or how to interpret results in terms of dose or health effects.
Key topics and technical requirements
- Analytical methods: Procedures for two measurement technologies - alpha spectrometry and ICP‑MS - with guidance on preparing sources for each technique.
- Sample preparation: Pre‑concentration, organic decomposition and chemical separation steps; annexed example procedures for 20 ml, 100 ml and 24‑hour urine samples.
- Source preparation methods: Electrodeposition and lanthanide‑fluoride co‑precipitation procedures are provided in informative annexes.
- Measurement and expression of results: Guidance on counting, activity concentration reporting and uncertainty treatment for both alpha spectrometry and ICP‑MS.
- Quality assurance and quality control: Requirements for laboratory QA/QC programs, instrument verification, contamination and interference control, method verification and demonstration of analyst capability.
- Performance context: Applicability to monitoring where detection limits must meet occupational dose limits (planned exposures) or enable rapid reporting in emergency response scenarios (higher acceptable detection limits but shorter sample turnaround time).
- Terminology and symbols: Definitions (e.g., sample turn‑around time, sample preparation volume) and symbols consistent with ISO measurement standards.
Practical applications and users
ISO 18990:2025 is intended for organizations performing urine bioassay for plutonium, including:
- Occupational health and radiation protection laboratories monitoring workers who handle plutonium.
- Emergency response teams and public health labs performing rapid screening after potential exposures.
- Environmental and nuclear facility laboratories that require validated methods for internal contamination assessment.
- Accreditation/quality managers implementing ISO/IEC 17025 or ISO 15189 compliance for radiobioassay services.
Use cases:
- Routine monitoring to detect exposures relevant to regulatory dose limits.
- Rapid emergency bioassay workflows requiring short sample turnaround and pragmatic detection limits.
- Method validation, staff competency demonstration and laboratory QA program development.
Related standards
ISO 18990:2025 references and aligns with standards such as ISO 11929 (detection limits), ISO 28218 (radiobioassay performance criteria), ISO 20553 (monitoring of workers), ISO 17294 / ISO 20899 (ICP‑MS guidance), and ISO/IEC 17025 / ISO 15189 (laboratory competence).
Keywords: ISO 18990:2025, plutonium isotopes, 238Pu, 239Pu, 240Pu, alpha spectrometry, ICP‑MS, urine bioassay, radiological protection, chemical separation, sample preparation, quality assurance.