GB/T 9224-2025 in English

《GB/T 9224-2025直流周期计》由TC30（全国核仪器仪表标准化技术委员会）归口，TC30SC1（全国核仪器仪表标准化技术委员会通用核仪器和辐射探测器分会）执行，主管部门为国家标准委。

Introduction

GB/T 9224-2025, "DC Periodometer," is the second revision of the 1998 edition. This revision fully addresses the digital and intelligent development needs of nuclear power plants, as well as the increased measurement accuracy requirements resulting from over two decades of technological advancement. The standard was proposed and coordinated by the National Technical Committee for Standardization of Nuclear Instruments (SAC/TC30), with key drafting organizations including China National Nuclear Corporation Control Systems Engineering Co., Ltd. and Tsinghua University.

Analysis of Major Technical Changes

Compared with the 1998 edition, the 2025 edition of the standard has made important adjustments in technical content and structure:

Detailed explanation of key technical requirements

Measurement performance indicators

DC periodometer's core performance indicators include:

• Range: Period measurement range is -∞～-50s and 5s～∞, input current range is 10⁻¹¹A～10⁻³A
• Measurement error: Under standard test conditions, the measurement error of the period output value should be better than 5%
• Response time: When the initial current is 10⁻¹¹A and the shortest period is 5s, the response time is ≤15s
• Zero swing: When the input current is the most sensitive range, the output swing is ≤3%

Environmental adaptability requirements

The standard specifies detailed environmental adaptability indicators:

Test methods and implementation points

Standard test conditions

Requirements for key test equipment

• Low-noise DC current generator (10⁻¹²A to 10⁻³A, accuracy better than 1%)
• 4.5-digit digital voltmeter
• 1500V withstand voltage tester
• 500V megohmmeter
• Millivolt recorder

Inspection Rules and Quality Control

Factory Inspection Requirements

Each DC periodometer must undergo a comprehensive inspection before shipment, including visual inspection, measurement error testing, and response time testing, to ensure product quality consistency.

Type Inspection Conditions

Type inspection is required in the following circumstances: new product development, major process changes, resumption of production after a long shutdown, and quality supervision requirements, to ensure continued compliance with standard requirements.

Implementation Suggestions and Application Guidance

Equipment Selection Suggestions

When selecting a DC periodometer, focus on:

• Whether the measurement accuracy meets the 5% error requirement
• Whether the environmental adaptability meets the on-site use conditions
• Whether the electromagnetic compatibility performance meets Class A requirements
• Whether the stability meets the 72-hour continuous operation requirement

Key Points for Installation and Commissioning

Pay attention to the following during installation and commissioning:

• Ensure that the test equipment accuracy meets the requirements
• Test in strict accordance with standard test conditions
• Pay attention to the warm-up time requirements to ensure measurement stability
• Take good electromagnetic shielding measures to reduce external interference

Maintenance Requirements

Regular maintenance should include:

• Perform insulation resistance tests regularly
• Inspect the appearance and mechanical properties
• Verify measurement accuracy
• Re-check environmental adaptability

Significance of standard implementation

The implementation of GB/T 9224-2025 will have a significant impact on the nuclear instrument industry:

• Unify the technical requirements and test methods of DC periodometers
• Improve the reliability and safety of nuclear reactor measurement systems
• Promote technological progress and industrial upgrading in the nuclear instrument manufacturing industry
• Provide technical support for the safe operation of nuclear power plants

This standard will be issued and implemented in 2025, replacing the 1998 version of the standard. All relevant units should update their technical documents in a timely manner to ensure that their products meet the latest standard requirements.