Radioactive waste treatment and disposal Which set correctly lists recognised methods for treatment and disposal of radioactive wastes from nuclear or radiological activities?

Introduction / Context:
Radioactive wastes span a wide activity range and physical/chemical forms. Treatment aims to minimise volume, immobilise radionuclides, and ensure long-term isolation from the biosphere. Multiple unit operations—physical, chemical, and solidification—are used before final disposal according to national regulations and international guidance.

Given Data / Assumptions:

• Mixed low- to intermediate-level wastes, aqueous streams included.
• Focus on principle methods rather than country-specific policy nuances.
• Historic practices are listed; some are restricted or phased out in certain jurisdictions.

Concept / Approach:
Evaporation concentrates aqueous wastes; chemical precipitation/co-precipitation removes radionuclides into a smaller sludge volume; ion exchange selectively captures ionic species; biological methods can assist certain organics or complexants; and solidification (cementation/bituminisation/vitrification) immobilises radionuclides for safe handling and storage. Historically, some nations practised ocean disposal (sinking packages in the deep sea), though modern treaties increasingly restrict or prohibit it; nevertheless, as a method it is part of the historical canon covered in many exam syllabi.

Step-by-Step Solution:

Verification / Alternative check:
Standard nuclear waste management texts enumerate these processes; country regulations determine which are currently permitted for final disposal.

Why Other Options Are Wrong:

• Each individual option is a subset; the comprehensive answer is the combination.
• None of these: Incorrect since several listed methods are indeed used or historically used.

Common Pitfalls:
Assuming modern policy bans equate to “not a method”; exam contexts often include historical or general-method listings.

Final Answer:
All (a), (b) and (c).