'The signs on the beach used to read: 'Danger, no entry for 24,000 years,'' reflects Fred Iban as he plows his skiff through the turquoise shallows and onto the gleaming white sands. 'Welcome to Runit,' says the old fisherman. 'Remember the radiation - don't stay long.' Runit lies on the north side of Enewetak atoll. The site of at least eight nuclear tests, the 36-hectare islet is now home to one of the world's largest radiation dumps, Runit Dome (left). Built in the 1970s by the US military, the concrete dome is the resting place for a fraction of the radioactive detritus amassed from the 43 Enewetak nuclear tests. Following a tip-off that it is beginning to crack, Post Magazine can confirm Runit Dome is showing signs of structural deterioration. The remote sarcophagus - inside of which is interred 200,000 tonnes of concrete-embalmed radioactive waste - has fissures so large birds have laid eggs in them (above). Professor Nick Buenfeld, head of the Concrete Durability Group at Imperial College London, warns: 'Cracking of the containment structure is a concern and should be investigated ... as soon as possible.' The US Department of Energy (DOE) is sending a team to investigate. A spokeswoman says: 'Based on a survey in 2005 ... there appears no discernible evidence of any leakage of radioactive waste.' However, she insists the department has no custodial responsibility for the edifice - a mantra repeated by any US agency that might be called upon to pay for repairs. 'We are the only population ever to have been resettled on a nuclear test site,' states Enewetak senator Jack J. Ading. 'Our message to the DOE is that they establish a long-term monitoring regime, as would be required for any similar waste site in the US.'