# Radioactive Waste Management and Transportation

## Introduction

Nuclear medicine departments generate radioactive waste from diagnostic and therapeutic procedures, radiopharmaceutical preparation, and contaminated materials. Proper waste management and transportation of radioactive materials are regulated by the NRC under 10 CFR Parts 20 and 30 and the Department of Transportation under 49 CFR Parts 171 through 178. Compliance with these regulations protects workers, the public, and the environment from unnecessary radiation exposure.

## Categories of Radioactive Waste

### Dry Solid Waste

Dry solid waste includes gloves, syringes, absorbent pads, tubing, and vials that are typically contaminated with short-lived isotopes such as Tc-99m, F-18, and Ga-68. This waste is segregated by half-life to enable efficient decay-in-storage management. Sharps must be placed in approved sharps containers before being added to radioactive waste streams.

### Liquid Waste

Liquid waste consists of residual radiopharmaceutical solutions, wash solutions, and patient excreta. Liquid waste may be discharged to the sanitary sewer under specific conditions outlined in 10 CFR 20.2003, provided the monthly average concentration at the point of discharge does not exceed specified values. Annual total release limits are 185 GBq (5 Ci) for tritium, 37 GBq (1 Ci) for carbon-14, and 37 GBq (1 Ci) for all other radionuclides combined.

### Biological and Mixed Waste

Biological waste includes animal carcasses and tissues from research protocols and pathological waste from therapy patients such as surgical specimens. Mixed waste, which contains both radioactive and hazardous chemical components, requires dual regulation and presents particular disposal challenges. Special handling and dedicated disposal pathways are required for these waste categories.

### Sealed Sources

Sealed sources include check sources, calibration sources, and brachytherapy sources. These must be leak-tested every 6 months or as specified by license conditions. Disposal is accomplished by returning sources to the manufacturer or through a licensed waste broker. Continuous inventory and accountability are required for all sealed sources.

## Decay-in-Storage (DIS)

### Regulatory Basis

Under 10 CFR 35.92, decay-in-storage is permitted for waste containing radionuclides with half-lives less than 120 days. After sufficient decay, waste may be disposed of as ordinary non-radioactive waste provided that background radiation levels are indistinguishable from ambient, all radioactive labels and markings have been removed or defaced, and the waste has been held for a minimum of 10 half-lives.

### Practical Implementation

Effective decay-in-storage programs require segregation of waste by radionuclide and half-life category. Containers must be labeled with the isotope, date of storage, and expected disposal date. The waste is stored in a designated, shielded, and secured area. Before release, each container is surveyed with an appropriate radiation detector to confirm background levels. Records of all waste held for decay and subsequent disposal must be maintained.

| Radionuclide | Half-Life | Time for 10 Half-Lives | Practical DIS Duration |
|---|---|---|---|
| F-18 | 110 minutes | ~18 hours | 1 day |
| Tc-99m | 6 hours | ~60 hours | 3 days |
| Ga-67 | 78 hours | ~33 days | ~5 weeks |
| I-131 | 8.02 days | ~80 days | ~3 months |
| Tl-201 | 73 hours | ~30 days | ~5 weeks |
| In-111 | 2.83 days | ~28 days | ~4 weeks |

### Common DIS Timelines

The time required for 10 half-lives of decay varies significantly among common nuclear medicine radionuclides. Tc-99m, with its 6-hour half-life, requires approximately 60 hours and can be disposed of within 3 days. F-18, with its 110-minute half-life, decays sufficiently in about 18 hours. I-131, with its 8-day half-life, requires approximately 80 days. Ga-67, with its 78-hour half-life, needs about 33 days. This variation in decay timelines makes segregation by half-life category essential for efficient storage management.

## Sewer Disposal of Liquid Waste

### Requirements (10 CFR 20.2003)

Liquid radioactive waste may be disposed of through the sanitary sewer provided the material is readily soluble or dispersible in water. The monthly average concentration at the point of discharge must remain within the limits specified in Appendix B, Table 3 of the regulations. Annual quantity limits apply for each isotope, and records must be maintained for each disposal event including the date, isotope, activity, and volume discharged.

### Patient Excreta Exemption

An important regulatory provision is that patient urine and feces are exempt from NRC sewer disposal limits. No activity limits apply to excreta from patients who have been administered radiopharmaceuticals. However, contaminated items such as bedding and clothing are not exempt and must be managed as radioactive waste through appropriate disposal pathways.

## Transportation of Radioactive Materials

### Regulatory Oversight

Transportation of radioactive materials falls under the jurisdiction of the Department of Transportation under 49 CFR Parts 171 through 178, which regulates the transport of hazardous materials including radioactive materials. The NRC under 10 CFR Part 71 regulates packaging for quantities exceeding Type A limits. Internationally, the IAEA Transport Regulations form the basis for national regulatory frameworks.

### Package Types

Packages for radioactive material transport are classified by the quantity and form of material they contain. Excepted packages are used for very low activity items such as empty containers and limited quantities. Type A packages contain up to A1 quantities for special form sources or A2 quantities for normal form material and are designed to withstand normal transport conditions. Type B packages are required when quantities exceed Type A limits and are engineered to withstand severe accident conditions, requiring NRC approval for their design.

### Labeling Requirements

DOT radioactive material transport labels are assigned based on surface dose rate and transport index. White-I labels indicate a surface dose rate below 0.005 mSv per hour and a transport index of 0. Yellow-II labels indicate a surface dose rate below 0.5 mSv per hour and a transport index between 0 and 1. Yellow-III labels indicate a surface dose rate below 2 mSv per hour and a transport index between 1 and 10. All labels must include the radionuclide identity, activity, and transport index.

### Shipping Documentation

Proper shipping documentation includes shipping papers listing the proper shipping name, UN number, hazard class, and activity of the material. Emergency response information must accompany the shipment, and the shipper must certify that the package has been properly prepared, packaged, and labeled. Drivers transporting radioactive materials must meet specific DOT training requirements.

## Package Receipt Procedures

When radioactive packages are received, they must be inspected for damage or contamination. A wipe test of the package surface must be performed within 3 hours of receipt during business hours, or within 3 hours of the next business day if received after hours. External radiation levels must be monitored. The removable contamination limit is 6,600 dpm per 300 cm2 for beta-gamma emitters. Receipt must be documented including the date, time, carrier, package condition, and survey results.

## Records and Documentation

Comprehensive records must be maintained for all aspects of radioactive waste management and transportation. Waste disposal records must include the date, isotope, activity, and method of disposal. Decay-in-storage records must include survey results confirming background levels before disposal as ordinary waste. Sewer disposal logs must track monthly and annual tallies. Transportation records must document both shipments and receipts. All records are retained per license conditions, typically for 3 years or until license termination.

## Clinical Pearls

Decay-in-storage is the most practical waste disposal method for nuclear medicine departments and is applicable to radionuclides with half-lives under 120 days. Waste must be held for a minimum of 10 half-lives and surveyed to confirm background radiation levels before it can be disposed of as ordinary waste.

Patient excreta are exempt from NRC sewer disposal limits, but contaminated items such as clothing and linens are not exempt and must be managed as radioactive waste through appropriate channels.

DOT radioactive material transport labels, designated White-I, Yellow-II, and Yellow-III, are assigned based on surface dose rate and transport index. Correct labeling is a legal requirement, and errors in labeling can result in regulatory citations.

All radioactive packages must be wipe-tested within 3 hours of receipt during business hours to detect any contamination that may have occurred during transport. The removable contamination action level is 6,600 dpm per 300 cm2.

## References

1. U.S. Nuclear Regulatory Commission. "10 CFR 20.2001 -- General Requirements for Waste Disposal." NRC Regulations.
2. U.S. Department of Transportation. "49 CFR Parts 171-178 -- Hazardous Materials Regulations." DOT.
3. U.S. Nuclear Regulatory Commission. "10 CFR 35.92 -- Decay-in-Storage." NRC Regulations.
4. IAEA Safety Standards Series No. SSR-6. "Regulations for the Safe Transport of Radioactive Material." 2018 Edition.