THE Government and Chinese authorities have yet to reach an agreement on contingency plans in case of an accident at the Daya Bay nuclear power station, despite one of the $3.7-billion twin reactors becoming operational in July. The second reactor is expected to be completed by summer, and the plant will be fully operational in September or October. Reflecting widespread concern on the safety measures for the mainland's largest nuclear reactor, just a few kilometres over the border from Hongkong, the Legislative Council's Environmental Affairs Panel yesterday pressed the Government to reveal detailsof its discussion with Chinese authorities. But their request was turned down by officials, who maintained that such a disclosure would make any future talks difficult. Principal Assistant Secretary for Security, Mr Frankie Lui Kin-fun, said: ''While the talks are going on, I don't think it would be wise to disclose where we disagree with each other.'' But he said the Government would seek a direct on-line communication link with Guangdong nuclear authorities so that they would be simultaneously informed of any emergency situation at the plant. Dr Leong Che-hung, the Legco representative for the medical profession, queried the necessity to keep the discussion secret. His view was shared by Miss Emily Lau Wai-hing, who said: ''It is obvious that their suggestion does not match up with the standards for our contingency plans. That is why you still need to talk it over.'' Mr Lui said: ''The talks are about some technical points, and I believe the Chinese side are still considering our proposals.'' United Democrats legislator Mr Man Sai-cheong joined in, demanding to know what were the outstanding points of disagreement. But Mr Lui said: ''In any talks, both parties are bound to have different views.'' But Dr Leong pressed on, saying the answer should be a simple yes or no from China. Miss Christine Loh Kung-wai said a direct communication link was an absolute must. ''I am sure members agree that it should be the bottom line, rather than the opening position for us. This is non-negotiable,'' she said. But members were told that the Government had not brought this condition into discussions with China. Mr Lui said they would strive to strike a deal with the Guangdong nuclear authorities during their next meeting in mid-May. Legislators were told that the Government would stage a rehearsal of its contingency plans next month. This involved the adoption of counter-measures which would minimise the risks to the public from radiation, including staying indoors and shutting all doors and windows for a few hours, the washing of food, or banning the consumption of some foodstuffs. When the plan is activated, radiation scanning of arriving passengers and their personal effects will be conducted at border control points. Monitoring centres will also be opened for people who require decontamination treatment. The measures, drawn up by Security Branch and the Royal Observatory, are based on standards set by the International Atomic Energy Agency (IAEA). A team of 15 IAEA safety inspectors arrive at Daya Bay on Monday for a two-week review of the plant in preparation for its first delivery of uranium fuel rods. Approval of the plant's operations is needed before plant engineers can begin loading the nuclear fuel into the reactors, according to sources.