On a lightly floured surface, roll out pastry into a 14-in. circle. Spread preserves to within 2-inches of edges. Transfer to a parchment paper-lined baking sheet; set aside.
In a large bowl, combine the rhubarb, oranges, 1/2 cup sugar, tapioca and cinnamon; let stand for 15 minutes. Spoon over pastry to within 2 in. of edges; sprinkle with almonds. Fold edges of pastry over filling, leaving center uncovered.
Beat egg white and water; brush over folded pastry. Sprinkle with remaining sugar. Bake at 375° for 30-35 minutes or until crust is golden and filling is bubbly. Using parchment paper, slide tart onto a wire rack to cool.
In a microwave, melt white chips and shortening; stir until smooth. Drizzle over tart.