7.1.4 History

Anchors come in many shapes and sizes, from domestic rawlplugs to heavy load anchors carrying several tons.

The first industrially made anchors were invented by John Joseph Rawlings in 1910. The UPAT company first made similar anchor of hemp string with metal sleeves in 1926. Fritz Axthelm of NIEDAX applied for the first patent for a metal spreading anchor two years later (DRP 555 384).

In building nuclear power plants, metallic anchors were also an essential structural element right from the start for attaching light to moderately heavy system parts and components. Path-controlled spread anchors of the Spit-Gold, TiFiX and Hilti-HKD types were installed in large numbers in accordance with the manufacturers’ guidelines. The Liebig company supplied the Liebig safety anchor the first force-controlled force — spread heavy-load anchor used in German nuclear power plants. The first precursor of a General Technical Approval was issued by what was then the IFBt, today’s DIBt, in 1972. This was the first anchor ever to have a General Technical Approval, issued in 1975. The Liebig safety anchor was first used in nuclear power plants in 1973, due to the particular requirements involved for attaching safety-related anchorings, based on approvals on a case-by-case basis. Liebig then released the Ultraplus, the first displacement-controlled anchor on the market. Together with the FZA anchor devel­oped by the Fischer company, these two path-controlled anchor types were a major step forward in attachment systems in nuclear power plants.

Static verification for the anchoring with anchors was made until then as per approvals or consents on a case-by-case basis, but the so-called Kappa-method from 1988 and the introduction of the DIBt Guideline ‘Design methods for anchors for anchoring in concrete’ [87] based on the so-called CC method in 1993 revolutionised the verification of attachments in concrete.

In 1998, with the aim of creating a uniform evaluation basis for awarding consents in all German Federal States, the DIBt published the guidelines on ‘Using anchors in nuclear power plants and nuclear installations’ [63]. These guidelines recommended that only form lock anchors should be allowed for attaching safety-related components and system parts. Based on these guidelines, the first General Technical Approvals were issued, for Fischer’s Zykon-Bolzenanker FZA-K [88] in 1999 and for Hilti’s HDA undercut anchors [89] in 2000. These two approvals, and their current versions, provide a uniform design basis for the respective anchor models for all German nuclear power plants.

In June 2010, the DIBt published new guidelines entitled ‘Guidelines for anchor attachments in nuclear power plants and other nuclear installations’. This supersedes the 1998 version, and provides more differentiated details of the tests to be conducted, methods of verification and handling for anchors and anchoring to be approved for safety-related attachments subject to particularly high requirements in the event of accidental actions. It does not limit itself to undercut anchors so that other types of anchors may be approved for use in nuclear installations.

A KTA status report on allowing for the particularities of nuclear installations is expected in the near future.