The Whitehaven News
KRYPTON TRAPPING PLANT WAS BUILT
Thursday, February 01, 2001
SIR - I was surprised to read the report in The Whitehaven News (January 25) about BNFL's statement that "To date, there is no system available or which could be developed capable of safely removing and storing Kr-85 on an industrial process scale."
I fear that the company has forgotten that a krypton-85 trapping plant was actually built and installed in the first reprocessing plant (B204) at Sellafield in the early 1950s (around 1950/51). This used a cryogenic method of separation and ran successfully for several months before being shut down, presumably because the health physicists had shown that the gas had no environmental significance.
The company also seems to be ignorant of the sterling work done by the Volatile Fission Product Study Group (VFPSG), a Harwell-based committee set up in the early 1970s by Sir John Hill, who at that time was a chairman of both BNFL and the Atomic Energy Authority. The committee was asked to look into industrial methods of trapping and storing volatile fission products (chiefly tritium, carbon-14, krypton-85 and iodine-129) and to carry out research on developing new methods.
The committee was chaired by Dr H A Mckay, a senior research chemist at Harwell, and after he retired, by Mr M J S Smith. The committee had two representatives from Sellafield (Dr M W Wakerley and myself) and Dr Watson Clelland (the Head of Waste Management in the company) from Risley. Several papers on different ways of trapping krypton were produced, but the preferred method was the cryogenic method which uses existing technology. Subsequently detailed flowsheets and cost estimates were prepared for a full scale krypton removal plant suitable for use in future reprocessing plants such as THORP.
The committee then went on to develop a novel method of storing krypton by a process known as ion-implantation. In this technique, the krypton is ionised and then bombarded by means of a strong electric field onto a metal foil resulting in the ions being implanted into the metal matrix where they are held fast. This process was fully developed in the laboratory, written up in AERE reports and was the subject of a patent.
The VFPSG papers were given a wide distribution within Sellafield and Risley at the time, but most of the recipients have long since retired or have moved on to other jobs, and in all probability the papers have by now been consigned to the waste bin! Meanwhile BNFL appears to be trying to reinvent the wheel!