18.08.2015   NUCLEAR CHEMICAL ENGINEERING

HIGH-LEVEL WASTE

Liquid HLW is the concentrate of the aqueous raffinates from the reprocessing extraction cycles. This means that up to 1 percent of the uranium and plutonium and practically all of the

t For brevity, the Barnwell Nuclear Fuel Plant is referred in this chapter as the AGNS plant, an abbreviation for the plant owner, Allied General Nuclear Services.

Table 11.1 Annual amounts of wastes ready for intermediate storage prior to final conditioning generated by a 1400 MT/year reprocessing plantt

Type of waste

Volume

(т3/ут)

Radioactivity after 1 yr collecting time, Ci/m3

Plutonium-

concentration,

kg/m3

Type of

intermediate

storage

High-level

Liquid concentrate

600

<4 X 106

<0.07

Tank with cooling

Dissolver sludge

80

<6X 10s

<0.45

Tank

Cladding hulls

800

<1 X 104

<0.09

Container

Medium-level

Liquid concentrate

1500

<2 X 103

<10’3

Tank; 400 g/liter salt

Tritiated water

3000

<200 tritium, 0.1 others

<10’5

Tank

Solids

(noncombustible +

ash)

800

<1

<3 X 10‘4

Fixed in concrete

Krypton

2

<8 X 106

Pressurized steel bottles

^ Fuel elements cooled 1 year before reprocessing.

Source: Deutsche Gesellschaft fur Wiederaufbereitung von Kembrennstoffen (DKW): “Bericht iiber das in der Bundesrepublik Deutschland geplante Entsorgungszentrum fiir ausgediente Brennelemente aus Kernkraftwerken,” Hannover, 1977.

fission products, neptunium, and the transplutonium elements produced in nuclear reactors end up in the HLW. It is therefore a reservoir of radioactivity that will not reach a steady state as long as nuclear power is generated, and its hazard potential will last much longer than the use of nuclear energy. Therefore, a reliable technology for long-term isolation of high-level wastes from the environment is a key to environmental protection against the consequences of nuclear power, and it is also a key to the public acceptance of nuclear power.

HLW arising in solid form, mainly cladding hulls, has activity concentrations more than two orders of magnitude lower than liquid HLW. It presents somewhat different technical problems, which will be discussed briefly in this chapter.