UK GAS-Prompt prices soar as Norwegian outage cuts supplies

* Outage at Norway's Kollsnes cuts supplies

* Gas flows to Britain via Langeled around 30 mcm/d

April 2 (Reuters) - Prompt British gas prices soared on Thursday after an unplanned outage at a Norway's Kollsnes gas processing plant led to lower imports.

Prices for within-day delivery were at 53.55 pence per therm at 0805 GMT, up 3.20 pence, or 6.4 percent pence since their last settlement..

The Kollsnes processing plant was unexpectedly shut on Wednesday, reducing gas flows by 60 million cubic metres (mcm), or about a fifth of Norway's output.

By Thursday morning gas flows from Norway to Britain via the Langeled pipeline were around 30 mcm/day, National Grid (LSE: NG.L - news) data showed, down on its full capacity of 70 mcm/day.

Langeled is Britain's main sub-sea gas import pipeline, and the cuts from Norway led to an undersupplied system.

With total gas flows at about 186.6 million cubic metres (mcm) per day on Thursday and demand expected to be about 256 mcm, Britain's gas system was 69.4 mcm undersupplied, National Grid data showed.

"We expect a recovery (in Norwegian flows) by tomorrow and into next week but prices are likely to rise during the outage period," analysts at Thomson Reuters Point Carbon said in a daily research note on Thursday.

Kollsnes operator Gassco said on Wednesday evening the outage would last between 12 and 24 hours.

British gas prices for day-ahead delivery were flat at 50.00 pence per therm.

Further along the curve, gas for May delivery was 0.75 pence higher at 47.56 pence per therm.

Europe's benchmark carbon price dipped 0.03 euros to 7.16 euros a tonne on ICE Futures Europe. (Reporting by Susanna Twidale; editing by Jason Neely)