1

Special technique at KRB A:

Decontamination of

stainless steel parts with

phosphoric acid

• quick processing time• reliability• less secondary waste• maximal recycling effect

Electropolishing

2

Principle of electropolishing

Oxide skin

Base material

before after

+

-

H2PO4

6000 A

at low voltage

chemical or

electrochemical

bath with phosphoric acid

3

Stainless Steel in Acid Bath

4

Stainless Steel after Electropolishing

5

Regeneration of Phosphoric Acid

• Recycling of Phosphoric acid by

• Reuse acid for decontamination

• Thermolysis of iron oxalat

- adding oxalic acid

- precipitate the dissolved iron as

- iron oxalate

- extracting the iron oxalate

- vaporization

- heating the iron oxalate

- transformation into iron oxid for final storage

6

Schematic principle of Regeneration

7

Thermolysis plant for iron oxalate

8

Technical Data of the thermolysis

9

Example „Secondary Steam Generator“

Vessels of three Steam Generators

decontaminated from 20,000 Bq/cm²

to free release

producing only 1,5% radioactive waste