Q1. POCO stands for:
(a) Pre Operational Construction Order (b) Pre Operational Certification Order (c) Post Operational Clean Out (d) Post Operational Conditioning Order
Answer: (c) — POCO stands for Post Operational Clean Out. It is carried out at facility shutdown and involves removing operational radioactive materials and waste, ensuring continuation of site infrastructure and essential safety provisions. POCO is traditionally considered to be outside the actual decommissioning operation proper and may be carried out under the operational licence.
Q2. According to the IAEA waste classification, high level waste is defined as:
(a) Heat-generating waste (b) Waste generating more than 2 kW/m^3 (c) Waste with activity above 400 Bq/g (d) Waste with a half-life greater than 1000 years
Answer: (b) — Under the IAEA classification, HLW is waste with thermal power above about 2 kW/m^3. While (a) “heat-generating waste” is the UK definition, the IAEA uses a specific quantitative threshold. Note that (d) relates to the distinction between short-lived and long-lived waste, not the HLW classification specifically.
Q3. A sample has a beta/gamma activity of 10^9 Bq and a mass of 1 kg. In the UK system of waste classification this would be:
(a) Out of Scope Waste (b) LLW (c) ILW (d) HLW
Answer: (c) — Activity concentration = 10^9 Bq/kg = 10^12 Bq/te = 1000 GBq/te. The LLW limit for beta/gamma is 12 GBq/te. Since 1000 GBq/te far exceeds 12 GBq/te, and the waste is not described as heat-generating, this is classified as ILW.
Q4. A sample has a beta/gamma activity of 10^4 Bq and a mass of 1 kg. In the UK system of waste classification this would be:
(a) Out of Scope Waste (b) LLW (c) ILW (d) HLW
Answer: (b) — Activity concentration = 10^4 Bq/kg = 10^7 Bq/te = 0.01 GBq/te. The LLW limit for beta/gamma is 12 GBq/te. Since 0.01 GBq/te is well below 12 GBq/te, and the waste is radioactive (above clearance levels), this is classified as LLW.
Q5. In the UK, the greatest fraction of radioactive waste activity is in the form of:
(a) Out of Scope Waste (b) LLW (c) ILW (d) HLW
Answer: (d) — Although HLW has the smallest volume, it contains the greatest fraction of radioactive waste activity. HLW contains the highly concentrated fission products from spent fuel reprocessing, which account for the vast majority of total radioactivity.
Q6. The greatest fraction of UK radioactive waste volume is in the form of:
(a) Out of Scope Waste (b) LLW (c) ILW (d) HLW
Answer: (b) — LLW accounts for the greatest volume of radioactive waste. This includes lightly contaminated miscellaneous waste from operations and maintenance (plastic, paper, metal) as well as soil, building materials and metal plant from decommissioning.
Q7. Out of Scope Waste (formerly VLLW) is usually disposed of:
(a) By fly tipping (b) At a Local Authority landfill site (c) At the LLWR Drigg site (d) After storing on site until the activity is negligible
Answer: (b) — Out of Scope Waste can be disposed of at permitted landfill sites operated by Local Authorities, subject to certain conditions. It does not require the specialised disposal facilities used for higher categories of waste.
Q8. LLW is usually disposed of:
(a) At a Local Authority landfill site (b) At the LLWR Drigg site (c) After storing on site until the activity is Out of Scope, then at LA landfill (d) Deep underground storage
Answer: (b) — Most LLW from nuclear licensed sites is currently disposed of at the Low Level Waste Repository (LLWR) near Drigg in Cumbria, although other disposal facilities are now permitted to receive such waste.
Q9. Which form of waste may NOT be dealt with by bituminisation?
(a) Low level waste (b) Intermediate level waste (c) High level waste
Answer: (c) — Bituminisation is not suitable for HLW because it can only be used for very low heat-producing concentrates. Restrictions also apply to high alpha-bearing materials, biodegradable materials and soluble salts. HLW requires vitrification (incorporation into borosilicate glass at ~1100 degrees C).
Q10. The annual dose constraint to a member of the public from a single source is:
(a) 0.1 mSv (b) 0.3 mSv (c) 0.5 mSv (d) 1.0 mSv
Answer: (b) — The source-related dose constraint is 0.3 mSv per year. This was recommended by NRPB following ICRP Publication 60. Option (c) 0.5 mSv is the site-related constraint (from all operations on a site). Option (d) 1.0 mSv is the overall dose limit for a member of the public. Option (a) 0.1 mSv is the maximum dose from waste disposal.