UK GAS-Prices rise on undersupplied system

* System undersupplied by 15 mcm/day

* Hunterston B-7 nuclear unit shut down

LONDON, June 2 (Reuters) - British prompt gas prices were higher on Tuesday, as short supply and lower imports drove the market up.

Gas for within-day delivery was up 0.3 percent at 44.00 pence per therm at 0754 GMT, while gas for day-ahead delivery was up 0.4 percent at 43.70 pence.

National Grid (LSE: NG.L - news) data showed supply was forecast at 177 million cubic metres (mcm) on Tuesday, while demand was seen at 192 mcm, showing the system was undersupplied by 15 mcm.

Meteorologists forecast temperatures rising above normal levels on the weekend which should help ease demand for gas.

Norway's Langeled pipeline is nominated at 15 mcm, down from 22 mcm Monday as some gas has been rerouted to the Continent, Thomson Reuters Point Carbon analysts said.

Nuclear power generation was lower after Britain's 500-megawatt Hunterston B-7 nuclear unit shut down late on Monday in an unplanned outage with operator EDF Energy expecting the unit to remain offline until June 3.

Gas for delivery in the third quarter was up 0.7 percent at 42.03 pence per therm.

In the Netherlands, day-ahead gas at the TTF hub was down 0.2 percent at 20.48 euros per megawatt-hour.

"The NBP (Britain's benchmark gas price) premium at this time of year comes as the NBP (Shanghai: 601018.SS - news) has had colder weather in comparison to the TTF, seeing the system open a bit shorter. With temperatures expected to climb over the rest of the week, we would expect the NBP to shift back to being at a discount," consultancy Energy Aspects said.

The benchmark European Union carbon price was trading 0.1 percent lower at 7.27 euros a tonne on ICE Futures Europe. (Reporting by Sarah McFarlane; editing by Jason Neely)