The Nuclear Hazards of the Recovery of the Nuclear Powered Submarine Kursk

These two expeditions, particularly the latter, established the radiological regime in and around the Kursk. Air, sediment and seawater samples were taken and analyzed, and water samples within the submarine, from compartments № 3, 4 and 7, were collected and sealed in cans for subsequent gamma spectrometry. Similarly, the remote operated vehicles (ROV) and the diving personnel were rigged to monitor dose rates at various locations about the casing of the submarine (Amundsen Ingar, 2001).

The preliminary results from these two expeditions did not indicate the presence of radionuclides that may have been released from the submarine reactors or, potentially, from any nuclear weapons carried on board.

The presence of nuclear weapons on board the Kursk at time of the sinking was of particular concern. In 1989, another Russian Northern Fleet submarine, Komsomolets, which was lost in the Barents Sea at about 1,700m was leaking from both its single reactor and from two nuclear tipped torpedoes loaded in the bow tubes at the time of the foundering. For the Kursk, the Russian Federation Northern Fleet confirmed that at the time of the foundering no nuclear weapons were on board.

At this stage, no attempt was made to sample within the sealed reactor compartment, nor was any significant monitoring undertaken of any thermal gradients in the flood hull in the vicinity of the reactor compartment.

KURSK K141 — TYPE, CONSTRUCTION & WEAPONRY

The Kursk is a SSGN (cruise missile armed, nuclear powered) submarine, designated by NATO as an OSCAR II class, commissioned from Sevmash shipyard, Severodvinsk in 1995.

Designed by RUBIN, The Russian State Marine Engineering Design Bureau in St Petersburg, the Kursk was 154 m long and 18m beam over the casing or flood hull, with a 11m diameter internal pressure hull, and of submerged displacement 24,000 tons (surface 11,500t). The submarine structure was of double hull construction with nine interconnected watertight compartments, all being normally accessible except for the reactor compartment № 6 which is passed through via a radiation shield corridor. The outer hull casing comprised 8mm steel plates supported off the pressure hull by webs and struts. The inner pressure hull was an externally ribbed cylindrical form fabricated from 50mm thick high yield steel plate. The void between the casing and pressure hull varied from 1 to 4m within which was located ship’s equipment, sonar and the cruise missile silos. The entire outer hull and conning tower was clad with 40 to 80mm thick synthetic rubber tiles serving to both attenuate machinery noise and reduce the reflective echo from incoming sonar signals.

^{The external acoustic layer, showing noise/sonar attenuation voids revealed by the cutting of the lifting sockets}

The power plant comprised two, integrated type pressurized water reactors (OK 650b) each of ~200MW thermal output located in the sealed reactor compartment № 6. The reactors were arranged in line, in foreaft fashion, each in its own pressure sealed sub-compartment. Each reactor pressure vessel was housed within a sealed 25m³ capacity water shield tank that was resiliently mounted to absorb shock from the operational submarine when in battle situations. The steam generators were clustered immediately around the RPV with the main circulating pumps above with just over 1m head to assist in natural circulation in the event of pump failure. Fuel comprised annular elements of uranium-aluminum cermet or dispersion type fuel clad in zircaloy, zoned between 20 to 45% (core equivalent 30%) enriched U-235 of 48 assemblies, totaling about 200kg U-235 per reactor core. Gadolinium burnable poison was integrated within the fuel and control was via boron/hafnium absorbers.

Nuclear plant emergency shut down was via control rod injection by spring and pneumatic drive and core cooling was via a relatively conventional ECS with a supplementary bubble tank. As an ultimate safeguard the entire reactor compartment was capable of being flooded with seawater via valves set into the pressure hull.

The Kursk submarine had an armament capacity for 24 ship-to-ship cruise missiles (SN-19-GRANIT — NATO Shipwreck) armed with 760kg main charge conventional explosive but nuclear capable for low yield warheads. The missiles were housed in individual pressure sealed silos, pitched forward at 40° arranged in two rows of twelve, each covered by six hatches on each side of the sail (conning tower).

^{Starboard missile bank forward silo hatches open}

Torpedo munitions comprised 24 torpedoes held in open rack magazines, potentially including torpedoes of nuclear capability, firing from 2?650mm and 4?533mm torpedo tubes in the bow (№ 1) compartment. The armaments could also include ASW Harpoon-type rockets and seabed mines also deployed from the forward torpedo tubes.

Kursk was the latest and most modern attack submarine of the Russian Federation Navy, being assigned to the Northern Fleet operating out of the Northern Kola voyaging into the Barents Sea and beyond. With 49,000 shp through the two 7-blade propellers, she could make 28+ knots when running deep and 15 knots on the surface, being capable of full operations at 600m depth.

MAMMOET-SMIT RECOVERY PLANS

From about January 2001, the Russian Federation Navy and the Kursk designers, RUBIN, jointly asked a consortium of companies from the West to tender for the entire recovery of the wreck (with the exception of the totally devastated forward compartment) and, specifically to complete the salvage within the year. This was in order

to comply with the promise of President Putin to the relatives of the crew. The first consortium formed, Smit-Heerema-Halliburton, withdrew because Halliburton believed the end of the year recovery deadline could not be safely achieved. In mid May 2001, the Russian Federation and RUBIN, jointly contracted Mammoet-Smit (M-S) to recover the Kursk within the year deadline. Although the salvage plan was to be produced by M-S the Russian Federation Navy was to provide a floating dock where the submarine was to be finally berthed.

The M-S strategy was to effect the recovery in three phases, these being:

Phase 1: Preparatory activities, including surveying, radiation monitoring of the submarine, removal of silt around the area of the intended hull cutting operation, and cutting of the hull just forward of the № 1 bulkhead to sever the most damaged part of the submarine. Then, to give a stable and predictable lift and to mount the rigs, to cut 26 holes through the casing and pressure hull either side of the vertical centerline of the main hull for the subsequent insertion and clamping of the lifting fittings. The positions of these holes were selected by the RF to minimize hull bending during the lift and none were positioned in the reactor compartment. This also included the modification of the Giant 4 barge by preparing 26 tubes through the barge hull so that the strand jack system, used to lift the submarine, could be fitted.

Phase 2: Installation of the 26 lifting fittings, the lowering through the pre-inserted tubes in the barge hull and connecting of 26 sets of lifting cables, each comprising 54 strands of seven twisted wires each 6mm diameter and the raising of the Kursk using Mammoet’s strand jack system. The cables would then hold the Kursk against a pre-fitted inverted cradle under the barge during transit to a floating dock near Murmansk.

Phase 3: The fitting of two large pontoons, one under each side of the barge, to lift it entirely out of the water to give sufficient clearance of the underslung Kursk over the cradles when entering the floating dock, the lowering of the Kursk onto the cradles, followed by demobilization and withdrawal of all M-S equipment and personnel.

Severing the remains of № 1 compartment deployed a heavy cable carrying thick-walled tubular sections coated with a very coarse (~25mm) abrasive. Reciprocating motion was to be provided by two 30 tonne hydraulic rams attached by suction anchors to the seabed.