Management of Low and Intermediate Level Waste

Abstract

Low and intermediate level wastes (LILW) are generated from nuclear power plants, industrial processes, research laboratories, and hospitals. Although low in radioactivity contents in comparison to high level waste, LILW, with widespread presence of its generators in various sectors of society, demands foresight and careful planning and coordination for its safe management and disposal. This chapter describes an overview of LILW management approaches including their characterization, classification, treatment, packaging, and disposal. The issue of mixed hazardous and radioactive waste is also discussed.

Homework

• Problem 13.1: Discuss the pros and cons of current U.S. nuclear waste classification scheme. If we ought to make any changes for improvement, what would be your suggested changes?

• Problem 13.2: Based on the US LLW classification scheme, determine the class of the LILW with the following mix of nuclide concentrations.

  • (a) ⁶³Ni at 15 Ci/m³ & ⁹⁰Sr at 50 Ci/m³

  • (b) ⁶³Ni at 30 Ci/m³ & ⁹⁰Sr at 100 Ci/m³

• Problem 13.3: In a nuclear power plant, 5 kg of wastes with a total activity of 2 μCi was accumulated of which 1 μCi was from ²⁴¹Am. The rest of the activity is due to isotopes with Z < 92. What is the class of this waste according to the US LLW classification scheme?

• Problem 13.4: The steady state (saturation) concentration of the fission production ¹³¹I (t_1/2 = 8.07 day) in PWR fuel during irradiation is 0.023 Ci/watt of thermal power. During normal operation, 0.1% of the fuel rods in a PWR core fail each year. Assume that the entire inventory of iodine in each failed fuel rod is discharged into the primary reactor coolant. It has been proposed to install an anion exchange column to remove the iodine from the primary coolant. The column would process a side-stream of 5% of the total primary coolant flow and would achieve a decontamination factor of 20 (i.e., 95% of the iodine entering the column would be sorbed on the ion exchange resin).

Calculate the amount by which the steady-state iodine concentration in the primary coolant would be reduced if the column were installed. Base your calculation on a 1000 MWe PWR. Use the following reactor parameters: Thermal efficiency = 0.33; Primary coolant volume = 375 m³; Primary coolant circulation time = 12 s.

• Problem 13.5: A 55 gallon (200 liter) drum containing ion-exchange resins is labeled LLW and is found to have a total of 100 Bq/g activity concentration emitting 1 MeV gamma-rays. Determine the dose rate at the measurement location at 50 cm from the surface of the container. Assume a resin density of 0.8 g/cm³, mass absorption coefficient of air for 1 MeV gamma-ray is 0.0280 cm²/g, mass attenuation coefficient of air for 1 MeV gamma-ray is 0.0636, and density of air is 0.001225 g/cm³.

• Problem 13.6: By using the information given in Table 13.13, determine the total fee to pay at each of the U.S. LLW disposal facilities for the disposal of the following LILW. (Use $6/ft³ for Atlantic Coast Compact administration charge at the South Carolina facility)

  • (a) Ten of 20 ft. Sea land container (B-25 Steel Boxes, 92.86 ft³ each)

    • Dose rate on container: 210 mR/hr. on each box

    • Total activity: 1000 mCi

    • ¹⁴C activity: 1 mCi

    • Density of waste: 50 lbs./ft³

    • Total weight of S/L: 48,000 lbs.

  • (b) One High Integrity Container (HIC) in Type A Cask (120 ft³)

    • Dose rate: 5 R/hr. on HIC contact, 100 mR/hr. on Type A cask contact

    • Total activity: 10 Ci

    • 14C activity: 100 mCi

    • Waste weight: 10,000 lbs.

    • Density of waste: 84 lb./ft³