* China tests "Yanlong" dedicated nuclear reactor
* Each 400-MW unit can heat 200,000 homes
* Hurdles remain: money, approvals, public safety anxiety
* Potential to help north shift away from polluting coal
SHANGHAI, Dec 10 (Reuters) - With its smog-prone north desperate to slash coal consumption, China is looking to deploy nuclear power to provide reliable winter heating, raising public safety concerns - though developers say the risks are minimal.
State-owned China National Nuclear Corp (CNNC) recently conducted a successful 168-hour trial run in Beijing for a small, dedicated "district heating reactor" (DHR) it has named the "Yanlong".
With the north facing natural gas shortages as cities switch away from coal, CNNC presented the "DHR-400" as an alternative heat supplier for the region, with each 400-megawatt unit capable of warming 200,000 urban households.
The model - which consists of a reactor core immersed in a water-filled tank around the same volume as an Olympic swimming pool - will require 1.5 billion yuan ($226.7 million) in investment and take just three years to build, a crucial advantage in a sector plagued by construction delays.
As a small and relatively simple "swimming pool" design, the low-pressure reactor is expected to be safer than conventional models, with temperatures not exceeding 100 degrees Celsius, and it could be plugged directly into existing heating networks.
The technology is ready, said Gu Shenjie, deputy chief engineer with the Shanghai Nuclear Engineering Research and Design Institute (SNERDI), part of the State Power Investment Corp (SPIC).
"They (CNNC) have supplied heat to their institute and office buildings and have successfully done that for three years," Gu told Reuters on the sidelines of the INNCH New Nuclear Build Conference in Shanghai, adding that commercialisation was the next stage.
"I think it's workable. The parameters are very low and it's easy to maintain operations," he added.
While the use of conventional nuclear plants to provide heating is common in Russia and Eastern Europe, China aims to be the first country to build reactors dedicated to the task of warming its cities.
China is pumping billions of yuan into advanced nuclear technology that will not only boost domestic capacity but also strengthen its global presence. It aims to develop a portfolio of reactors capable of powering cities, remote islands, ships, cars and even aeroplanes.
With northern China still relying on "centralised" heating systems, a DHR in every city could be an ideal solution, said Cheng Huiping, a CNNC technical committee member.
The firm said the technology would use only 2 percent of the radioactive sources used in a conventional 1-gigawatt nuclear power plant, but winning public acceptance remains a hurdle.
"We will have to face 500-600 million ordinary people in northern China and tell them that swimming pool reactors are absolutely safe," Cheng told a conference earlier this year.
The government is keen on the technology, but cautious about deploying it too quickly, especially amid widespread public anxiety about the risks of nuclear power.
Late last month, Liu Hua, director of China's National Nuclear Safety Administration, acknowledged the DHR was of "great significance" and could help resolve northern China's energy and environmental problems. But he also urged CNNC to do its utmost to prove safety and reliability.
Cost will also be a major factor.
CNNC said that, at an estimated 30-40 yuan per gigajoule, it could end up cheaper than gas, but a nuclear industry consultant told Reuters the economics of the DHR was difficult to predict.
The approval process also remains a long one, said Gu at the SNERDI, with each project expected to undergo a battery of environmental impact and conceptual design assessments.
"I don't think it can be done within five years," he said.
($1 = 6.6173 yuan) (Reporting by David Stanway; Editing by Ian Geoghegan)