The Munch Museum in Oslo, where Edvard Munch's masterpiece ''The Scream'' and another painting were stolen by armed robbers on Aug. 22, will remain closed until next summer while the museum spends up to $7.8 million on a security upgrade. Security measures recommended by Det Norske Veritas, an Oslo-based consulting firm, include improving the museum's video surveillance system and enclosing its most famous paintings in glass cases bolted to the wall. The company also recommended that the museum install metal detectors and build a labyrinthine passage in the lobby area to slow the escape of any future robbers. In a statement, city officials said they would ''follow the recommendations from Veritas and start the necessary work immediately.'' Norwegian police have conducted a high-profile investigation of the robbery, but there have been no arrests, and neither ''The Scream'' nor the other stolen painting, Munch's ''Madonna,'' has been recovered.