UK GAS-Prompt prices rise on strong demand, lower imports

LONDON, May 2 (Reuters) - Prompt British wholesale gas prices rose on Tuesday morning, as lower imports from Norway and strong demand led to an undersupplied system. * The British day-ahead gas price rose 1.36 pence to 42.36 pence per therm by 0847 GMT. * The within-day contract was up by 1.20 pence at 42.50 p/therm. * The system was undersupplied by 26 million cubic meters (mcm),with demand forecast at 246.2 mcm, and flows at 220.2 mcm/day, National Grid (LSE: NG.L - news) data showed. * Imports from Norway through Langeled were at 37 mcm/day, down from around 45 mcm the previous day. * Traders said demand from gas-fired power stations was strong due to outages at some of the country's nuclear power plants and expectations of low output from wind farms. * Britain's Hartlepool 1 nuclear reactor began planned maintenance, meaning four of the country's 15 nuclear reactors are currently offline. * Peak wind power output is forecast at 3.8 gigawatts (GW) for Tuesday, rising to 5.4 GW on Friday, National Grid data showed. * Gas demand was almost 10 percent above the seasonal norm of 224 mcm, National Grid data showed. * The June gas contract was up by 1.00 pence at 39.50 p/therm. * Day-ahead gas price at the Dutch TTF hub was down by 0.14 euro at 16.58 euros per megawatt hour. * Benchmark Dec-17 EU carbon contract was down by 0.06 euro at 4.51 euros per tonne. * Thomson Reuters (Dusseldorf: TOC.DU - news) analyst view: http://emea1.apps.cp.extranet.thomsonreuters.biz/cms/?pageid=united-kingdom-gas (Reporting by Susanna Twidale, editing by Louise Heavens)