HJ 816-2016 in English
VALIDRadiochemical analysis of caesium-137 in water and ash of biological samples
- Issued on:2016-10-12
- Implemented on:2016-11-01
- File Format:PDF
- Delivery:Via email within 1~3 business days
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本标准规定了测定水和生物样品灰中铯-137的放射化学分析方法。
本标准适用于水和生物样品中灰中铯-137的测定。
本方法的测量范围为:水样10-2～10Bq/L，生物样品灰10-1～10Bq。
Introduction
Background and Significance of Standard Revision
HJ 816-2016 is an integrated revision of GB 6767-86 (water sample) and GB 11221-89 (biological ash sample). The main changes include:
| Revision Dimensions | Original Standard | HJ 816-2016 |
|---|---|---|
| Standard System | Two Independent Standards | Unified Integration into One Standard |
| Method Optimization | Traditional Calibration Method | Added Cesium-137 Detection Efficiency-Mass Curve |
| Quality Control | No explicit requirements | Mandatory blank test frequency |
Core Principle of the Method
Ammonium phosphomolybdate is used as an inorganic ion exchanger to selectively adsorb cesium ions in an acidic medium. After dissolution and conversion with sodium hydroxide, cesium iodide bismuthate precipitate is formed, and the activity is determined by a low background β meter. Key reaction process:
- Adsorption stage: Cs⁺ + (NH₄)₃PO₄·12MoO₃ → Cs₃PO₄·12MoO₃
- Precipitation stage: 3Cs⁺ + BiI₄⁻ → Cs₃BiI₅↓
Key operation points
1. Sample pretreatment
- Water sample: The pH needs to be adjusted to 3, and ammonium phosphomolybdate is added at a ratio of 1g per 5L of water sample
- Biological ash sample: Ashing in a muffle furnace at 430℃, extraction with nitric acid-hydrogen peroxide system
2. Instrument calibration requirements
A detection efficiency-quality curve must be established, using 5 standard sources of different masses (0.4-1.2ml carrier solution), and the calculation formula is:
η = RN / (A·Y) (η is the detection efficiency, RN is the net counting rate, A is the activity of the standard source, and Y is the chemical recovery rate)
Quality Control System
| Indicator Type | Water Sample Requirements | Biological Ash Sample Requirements |
|---|---|---|
| Precision | Relative standard deviation ≤10% (activity ≥1Bq/L) | Repeatability ≤15% (activity 1-10Bq) |
| Blank Experiment | Reagent replacement is required for each batch of samples ≥5% | |
Implementation suggestions
Handling of special situations
- Co-existing nuclide interference: When Cs-134/136/138 is present, it is necessary to use low background gamma spectrometer
- Radioactive iodine interference: It can be removed by adding iodine carrier to generate AgI precipitation
- Ammonium phosphomolybdate color change: Add saturated potassium permanganate solution to maintain yellow
Measurement time optimization
Calculate the optimal counting time according to the formula t=1/(N_T·E²·N_N), where E is the predetermined relative standard error
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