Regulations on Radiation Safety Design of Nuclear Fuel Reprocessing Plants
2Expert Interpretation
An in-depth interpretation of the EJ 849-94 nuclear industry standard, covering the radiation safety design requirements for nuclear fuel reprocessing plants, including key technical points such as site selection, zoning layout, shielding design, and waste treatment, and providing professional implementation suggestions that meet national standards.
Analysis of the core content of the standard
As a programmatic document for the radiation safety design of nuclear fuel reprocessing facilities in my country, this standard systematically stipulates the protection requirements for the entire process from site selection to accident emergency for the first time. Its technical framework is based on the three-principle system of GB 8703 "Radiation Protection Regulations", and has formulated enhanced measures specifically for the special risks of high-level waste liquid and airborne pollutants in the reprocessing process.
Radiation Protection Grading System
| Building Type | Radioactivity Concentration(Bq/L) | Partition Requirements | Shielding Thickness Benchmark |
|---|---|---|---|
| Weak Radioactivity Building | <4×103 | 2 Zone System | No Special Requirements |
| Low Radioactivity Building | 4×103-4×105 | 3 Zone System | 25cm Concrete |
| Medium-level radioactive plant | 4×105-4×107 | 4-zone system | 80cm concrete |
| High-level radioactive plant | >4×107 | 4-zone system+hot chamber | Pre-shielding≥1m |
Key technical requirements
1. Three-level closed system
The standard innovatively proposes a three-level closed structure of equipment-operating box-building:
- First level: process equipment body negative pressure 200-300Pa
- Second level:>Hot chamber/glove boxMaintain 100-150Pa negative pressure
- Level 3: Building airtightness detection leakage rate ≤1.5h-1
2. Waste treatment specifications
Specify the disposal paths for different forms of waste:
- Liquid waste: Implement trough emission monitoring, effective dilution factor＞2×103
- Airborne waste: Exhaust tower height ≥1.5-2.5 times of the building
- Solid waste: Combustible incineration reduction rate ≥10:1
Implementation suggestions
Design optimization direction
1. Modular layout: high-level radioactive equipment is concentrated in the central island area, and a circular maintenance passage is set up on the periphery
2. Intelligent monitoring: deploy an online gamma dose rate monitoring system at key points (such as EJ/T 1206-2017)
3. Decommissioning reserve: the equipment foundation adopts a detachable structure, and the wall covering uses a peelable coating
Standard evolution analysis
This standard systematizes the radiation safety requirements for the back-end of the nuclear fuel cycle for the first time. Compared with the early specifications:
- Added special control for α aerosol (Article 9.7)
- Strengthen the dose control under accident conditions (the limit value of Article 6.3.4 is stricter than that of IAEA GSG-8)
- Introduction of the application of optimization principle in dose limits (clause 6.3.2)