120 operates at a pressure of at least 2 bars gauge and at a temperature of at least 130 u00b0 c these are cooking conditions under which the thin chips are processed in the digester vessel the single digester vessel cooking system shown in fig1 may be embodied as a two or more vessel cooking system configured for thin chip cooking and to operate under similar cooking conditions as are disclosed herein the flow of the thin chips e g the chip column through the digester vessel 120 may be a unidirectional downward flow and a uniform chip flow across the entire cross section of the chip column the digester vessel may not have cooking liquor recycle loops cooking liquor countercurrent flow or extraction cooking screens at multiple elevations in the vessel the cooking zone 121 of the vessel may be cylindrical with smooth and uniform cylindrical walls which may expansion rings 123 where the diameter of the vessel expands the interior walls of the cooking zone 121 may be free of screens nozzles and other devices to add or extract fluid to the cooking zone the digester vessel 120 may further include one or more inlets for wash liquid which may be water the wash liquid mixes passes through the chips pulp in a wash zone 125 in a lower section of the digester vessel wash liquid may be added to the digester vessel via wash lines 148 146 and 144 to the digester vessel 120 wash liquid enters the system 100 via line 136 where it is optionally pressurized a pump 180 may move the wash liquid towards the wash zone and may pressurize the wash liquid optionally the wash liquid may be thermally adjusted e g heated or cooled via a heat.