A debris filter useable in a nuclear reactor, the filter comprising: a first plate having a plurality of peaks and valleys alternating in a transverse direction; and a second plate having a plurality of peaks and valleys alternating in the transverse direction, wherein, the peaks of the first plate touch the valleys of the second plate so as to form a plurality of channels between the first and the second plates, and at least one of the first plate and the second plate include cut-out features (241, 242) that permit fluid coolant flow between the channels and entrap debris, wherein the cut-out features (241, 242) have diamond-like shapes; and the first plate and the second plate are arranged in a lower section, the filter further comprising: an upper section joined to the lower section, wherein the upper section includes, a third plate having a plurality of peaks and valleys alternating in a transverse direction, and a fourth plate having a plurality of peaks and valleys alternating in the transverse direction, wherein the peaks of the third plate touch the valleys of the fourth plate so as to form a plurality of channels between the third and the fourth plates; the filter characterised in that the upper section is joined to the lower section by a plurality of ligaments extending vertically between the upper section and the lower section in a gap section, wherein the ligaments include a twist in their profile, turning as they extend axially so as to impart a swirl to fluid coolant flow between said sections (201, 202). a first plate having a plurality of peaks and valleys alternating in a transverse direction; and a second plate having a plurality of peaks and valleys alternating in the transverse direction, wherein, the peaks of the first plate touch the valleys of the second plate so as to form a plurality of channels between the first and the second plates, and at least one of the first plate and the second plate include cut-out features (241, 242) that permit fluid coolant flow between the channels and entrap debris, wherein the cut-out features (241, 242) have diamond-like shapes; and the peaks of the first plate touch the valleys of the second plate so as to form a plurality of channels between the first and the second plates, and at least one of the first plate and the second plate include cut-out features (241, 242) that permit fluid coolant flow between the channels and entrap debris, wherein the cut-out features (241, 242) have diamond-like shapes; and the first plate and the second plate are arranged in a lower section, the filter further comprising: an upper section joined to the lower section, wherein the upper section includes, a third plate having a plurality of peaks and valleys alternating in a transverse direction, and a fourth plate having a plurality of peaks and valleys alternating in the transverse direction, wherein the peaks of the third plate touch the valleys of the fourth plate so as to form a plurality of channels between the third and the fourth plates; the filter characterised in that the upper section is joined to the lower section by a plurality of ligaments extending vertically between the upper section and the lower section in a gap section, wherein the ligaments include a twist in their profile, turning as they extend axially so as to impart a swirl to fluid coolant flow between said sections (201, 202). an upper section joined to the lower section, wherein the upper section includes, a third plate having a plurality of peaks and valleys alternating in a transverse direction, and a fourth plate having a plurality of peaks and valleys alternating in the transverse direction, wherein the peaks of the third plate touch the valleys of the fourth plate so as to form a plurality of channels between the third and the fourth plates; a third plate having a plurality of peaks and valleys alternating in a transverse direction, and a fourth plate having a plurality of peaks and valleys alternating in the transverse direction, wherein the peaks of the third plate touch the valleys of the fourth plate so as to form a plurality of channels between the third and the fourth plates; the filter characterised in that the upper section is joined to the lower section by a plurality of ligaments extending vertically between the upper section and the lower section in a gap section, wherein the ligaments include a twist in their profile, turning as they extend axially so as to impart a swirl to fluid coolant flow between said sections (201, 202).