Underwater Search for the Lost Radioisotope Device in the Hard-To-Reach Region of the Sea of Okhotsk

Underwater Search for the Lost Radioisotope Device in the Hard-to-Reach Region of the Sea of Okhotsk

Accidental drop of IEU-1 type RTG during its transportation to the lighthouse site of Maria Cape of the Sakhalin island as external load with Mi-8t helicopter belonging to Nickolayevsk flight took place not in the vicinity of the Cape from the height of 100 meters on the 8-th of August 1997 at 5 PM. Radioisotope power generators convert the heat energy generated during fission of the active part of the radionuclide source into electric energy due to the semiconductor thermoelectric converter, store it and supply it to the consumer – navigation equipment. This allows operating the equipment for a long period of time without additional servicing of it. Strontium-90 with the half-life of 28.4 years is the radionuclide source. Activity of radionuclide by the time of the generator decommissioning was 12.95x1014 Bq. The radionuclide itself is located inside the sealed cylindrical container of stainless steel. Gamma radiation presenting potential threat of external radiation does not exceed 200mR/h. Radiation shielding of the device consists of the lead, tungsten-nickel alloy, depleted uranium, and of alloys on its basis. Transportation of RTG is allowed in a special steel transportation container. The sizes are – 1.8x1.3x1.7 m, its weight is 2800 kg. Manufacturing plant guarantees integrity if IEU-1 RTG when it falls from one hundred meters. Search for the sunken RTG was started by the Hydrographic service of the Pacific Fleet, which is in charge of the navigation equipment, in August 1997 and was carried out practically every year. The search area was defined by the observations of witnesses and the photo-picture of the “dropping spot” of the RTG made from the coast after the accident. This location is at the distance of 1000- 2200 m from the lighthouse, according to the bearing its area is approximately 1.500.000 m2. The depth in the region is 20-30 m. The region was studied by magnetometric (using magnetic properties of the steel transportation container) and sonar (using the sizes of the device) equipment. Several tens of the supposed items were found. Later some of the most probable items were studied by the divers in the heavy three-bolt diving-suits.

Fig.1a. Lighthouse at Cape Maria, close to which IEU-1 RTG was Fig. 1b. IEU-1 RTG similar to the lost one. lost

Fig.2. Map of the region.

It is difficult to conduct the search in this region from the standpoint of hydrometeorology. The time of carrying out the work is limited to 2-3 months a year (July – September); it is only possible to use divers for 3-4 hours a day because of the strong (up to 4 knots) tidal currents. They can work in low and high tides. Underwater visibility is 20-50 cm. With consideration of the errors in item positioning it was not always possible for the divers to contact the item and to identify it. Sea-bed geomorphology is characterized by the basement rock yield with the chines of underwater mountain ridges of 5-6 m high from the bottom, and by stone fragments (comparable in sizes with the looked for item) spread in the region. Krasnoarmeysk Scientific and Research Institute of Mechanization possessing side-scan sonar devise “Gidra” was engaged into the work in 2004 and 2005, four divers in the light diving-suits participated in identification of contacts. The Ministry of the Russian Federation for civil defense, emergencies, and mitigation of consequences of natural disasters (EMERCOM of RF) joined the work upon the request of the Pacific Fleet. In the course of the missions to find and inspect underwater potentially hazardous items in the Far Eastern seas the work

3 was performed jointly with the hydrographic and rescue ships of the fleet with the use of modern equipment for the underwater work. In the framework of the RF EMERCOM mission the work was carried out by the experts of ZAO “Altair- NTPZ). Research ship (SRS) “Professor Khromov” of DVNIGMI, “HS-404” (with “MGK-975” on board) PF was involved into the work in August 2005. The following devices and equipment were used by the expedition to help with the search of the lost radioisotope source: - side-scan sonar device – Klein System 3000 (SSSD S-3000); - underwater remote-controlled survey devise – Sea Lion; - underwater gamma-spectrometer; - special equipment for accommodation of the searching equipment on the floating vessel of small displacement. It was assumed that SSSD S-3000 and remote-controlled device would be used for the search of the lost generator, and gamma-spectrometer would help identifying (indicate that the item is the radioactive source) it. Reconnoitring with the use of the photo-picture of the “dropping spot” was carried out on the coast close to the lighthouse. Slide of the photo-picture of the falling process was put into the specially fabricated photolens (sort of “Obscure chamber”), and superpositioning of the coastal objects in the picture with the real ones in the locality was performed. When the direction from photographing location to the “spot” was identified, the leading beacons were installed on the coast. These leading beacons showed the direction for the ship with the GPS receivers. When the ship was passing the “dropping spot” the buoy was put, coordinates were measured, and the “spot” location was identified on the map.

Fig.3. Photo-picture of the witness. Dropping location (light spot on the water surface) is Fig.4 Direction-finding of dropping location encircled with red. with the help of projecting camera

5 Falling location was found to be at the distance of 950-1000 meters from the lighthouse. According to the assumed dropping location and with consideration of potential examination errors, the search region was defined as the square 300 meters on side. With the help of SSSD S-300 mounted onto MGK triple (in different directions) examination of the selected region was carried out. Figure 5 presents examples of the contacts, which can be interpreted as the looked for item from the standpoint of the size. Example of the ship mechanical trajectory during single scanning with the help of SSSD is presented in fig. 5a.

Fig.5. Examples of echo contacts obtained with the help of SSSD.

Fig.5a. Example of the ship mechanical trajectory during single scanning with the help of SSSD

Totally 13 contacts to be examined for being the RTG were found (Fig. 6). All of them are located in a certain region. It is possible that there are less than 13, as if some were found twice. Reasons for that can be: difficult towage that was mentioned above (impossibility of getting into the water at the same location twice), and navigation capabilities in this region. GPS fixation accuracy for Maria Cape is approximately 30 meters. It is not comparable with the sizes of the looked for item, therefore, it is necessary to improve the accuracy to meters, i.e. it is necessary to set up special navigation devices. The attempts were made to identify the found underwater items with the help of remote-controlled examination device (fig. 7) and submerged gamma- spectrometer (fig. 8). Unfortunately these attempts were unsuccessful. Even technically it was impossible to use the remote-controlled device at the depth exceeding 10 meters due to very bad underwater visibility and high current velocities. Points of placing gamma-spectrometer on the sea-bed happened to be aside from the found (due to complicated hydrology) contacts. The measured values were 51-55 mR/h, which is in compliance with the background values. In order to register radiation from RTG gamma-spectrometer is to be at the distance of no more than 1.5 m from the RTG.

Fig.6. Schematic of the search in 2005.

Fig.7. Underwater remote-controlled device - Sea Lion. Fig.8. Submerged gamma- spectrometer.

9 The results of the work indicated clearly that in order to be successful in finding the RTG next year it was necessary to achieve accurate positioning comparable with the results of the item. It is also necessary to involve highly qualified divers in the light diving-suits (the item is at the depth of only 18-20 m) with special equipment allowing orientation in the muddy troubled water. Measurements of Sr-90 and Cs-137 content in the probes of soil close to the Cape of Maria indicated concentrations of 1-3 Bq/kg (concentrations in the sea water are by an order of magnitude less). This testifies to the fact that there is no radioactive contamination of the marine environment in the region, because these values agree well with the average values at the same depth in all the regions of the great oceans. Participants of the 2006 expedition as well as the equipment of the RF Emercom were located on board the research ship “Pavel Gordiyenko” of DVNIGMI. Pacific fleet was represented by the hydrographic ship “HS-404” from Sovietskaya Harbor, and rescue towboat “SB-521” from Petropavlovsk- Kamchatsky. Along with the previously used equipment the expedition possessed: - underwater acoustic system - Sonardyne Scout (fig.9) to identify positioning of the divers and items under the water; - underwater hydro-acoustic device – ARMA (sound-imaging device) (fig. 10); - light diving-suits to work at the depth of up to 25 meters (2 sets).

Fig.9. Sonardyne Scout - underwater acoustic system for positioning divers and items under the water

Fig.10. AKMA - underwater hydro-acoustic device (sound-imaging device).

On the site of the lighthouse at Cape Maria specialists of the Head department of the navigation and oceanography (HDNO) of the RF MoD deployed the mobile station for differential corrections with three portable systems for global positioning (GPS) for accurate (up to 1-3 meters) determination of coordinates during the work. Witnesses of the RTG falling down that were on the coast by the lighthouse stated that it happened at the distance of 400-500 meters from the coast. Some uncertain time after the RTG fell down (approximately from 3 to 6 minutes) the photo-picture of the spot, left on the surface of the sea water after the RTG fell down, was made. Taking into consideration the North-Western direction of the

11 underwater currents the search region was shifted to the South-East off the “spot” by the distance of 150-200 meters. Long-term study of the currents in this region allowed making the following statements. Low-tide current is the prevailing and most powerful; during the expedition it was of great significance since early morning to 3-4 PM. Velocity – of up to 4 knots, direction – from 350 to 10 degrees, i.e. practically to the North. This is the time of the muddiest water brought from the Amur firth. Unfortunately the most severe characteristics – high current velocities, change of the current directions, muddy troubled water fall exactly for the search region. Analysis of results of achievements of the previous expeditions indicated that in order to avoid working in these severe conditions they searched for the RTG much farther from the coast, i.e. in the locations the RTG was never in. Low-tide gives place to high- tide approximately at 4-6 PM. High-tide current comes from the central part of the Sea of Okhotsk, its velocity does not exceed 1.5-2 knots, water clarity is much higher (~1.5 m), it is of South-Western direction. It is possible for the divers to work in the time interval when the currents change or at the beginning of the high- tide, but this is the time when they are lacking light. Besides, the currents are of different-variable character in the layers: 0-5 m, 5-10 m, 10-15 m, and 15-20 m; they meander depending on the presence of compensation current from the North- West. Therefore, specific conditions of the Cape of Maria allowed to efficiently using highly-qualified divers in light diving-suits, only. They worked in turns using compressed air, autonomously according to the method of no decompression descending. Divers carried out examination of the region while moving along the guiding halyard 120 m long going through the marker buoys (with the load on the sea-bed) put with high accuracy owing to the GPS. Triple examination of the region was carried out at the very beginning of the work with the help of “Klein S-3000” side-scan sonar device. Using the results of this examination divers started working from the North-Eastern part of the site, where the largest number of items (corresponding to the looked for item in size) were found. All of the above-mentioned equipment was tested in the first days after the work started. Under real hydrological conditions of the site, and with consideration of the technical capabilities of the remote-controlled underwater device – “Sea Lion” it could move aside from the ship at anchor for 15-20 meters in the unknown direction (because it has no system of orientation) and identify the outline of items at the distance of 1-1.5 meters when there were no current whatever. It is clear that in real hydrological conditions the attempt of using the underwater device to identify the items was unsuccessful. Results of testing AKMA equipment indicated that the device identifies unclear outlines of the items at the distance of 5-10 meters. The device is located at the vertically suspended cable fastened to the board of the ship at anchor. It is impossible to use the AKMA device during towing (neither of the small boat, nor of the research ship), besides the quality of image is insufficient to identify the

12 RTG lying on the sea-bed, as there are many rocks of the similar size in this region. When the distance between the detector and antenna exceeded 40 meters, underwater acoustic positioning system gave out incorrect data, probably because of the complicated hydrology of the region. Attempts of involving divers in the heavy 3-bolt diving-suits from the board of “SB-521” indicated that they could not carry out the search in the above region. “SB-521” could not anchor so close to the coast as was necessary. The divers could not moved away for more than 10-12 meters from the descending place, because the air hose was greatly influenced by the underwater currents of various directions (often the divers got entangled). Muddy troubled water (visibility of 20-50 cm) and lack of any orientation did not allow any examination of the sea-bed. During the whole period of work the divers were involved for only 8 days, they carried out 22 inefficient descending. Divers in the light diving-suits were more efficient. After the first experimental descending attempts it was found out that in low tides when the Sea of Okhotsk tide with the more clear water in the close to the bottom layer (50-100 cm thick) was prevailing, the underwater visibility became better – 1.5-3.0 meters. Therefore, it is possible to efficiently look for the RTG while moving in this layer. The most important is to coordinate the work of examining the underwater sectors. The mode of behavior at the depth like this is – 20 minutes under the water for each diver, 2-3 hour break, and 20 more minutes under the water if the light conditions and hydrology permit. Descending was carried out from the board of inflatable motor boat of the “Zodiac” type. Head of the expedition was in charge of the work. In the course of the search the divers found seven plates (#1-7) of the cooling radiator of IEU-1 RTG (five large, and two small), two of which (#5, 6) were lifted up and identified (fig. 11).

Fig.11. Divers in light diving-suits with the found and lifted plate of IEU-1 radiator.

14 Altogether 15000 m2 of the sea-bed were examined. The lifted plates (they were spread in the region at the distance of up to 130 meters from each other) allowed making the following conclusions: - the region for search was defined correctly, its size can be limited to approximately 100x100 meters; - being dropped IEU-1 RTG was damaged when bumped against the water surface; transportation container was not used; - some parts of the RTG moved around when dropped to the sea-bed due to the influence of initial impulse, and subsequent influence of the stratified different-direction current; - dimensions of the remaining radiation-hazardous part of the RTG diminished and are equal to 770 x 760 x 1200 mm (probably even less); - it is impossible to find this part of RTG with the help of SSSD because of the existing geomorphology of the sea-bed – number of “contacts” increases tens of times (several hundred). The most important finding of the work carried out in 2006 – location of dropping the RTG is identified correctly, region for search of the RTG is identified, the work order and conditions of the work are thought over. The work in 2007 was totally oriented to the use of the divers in light diving-suits. They were to work on the specially produced portable site. The previous experience indicated that in the conditions of drastically variable tide currents intensified by the wind currents success of the work depended on very prosaic things – weight of the anchor holding the buoy, length and strength of the halyard connecting them, accuracy of anchoring, etc. Schematic of the adjustable site is developed.

ВС ГС Страховочный фал Удаление 100-300 м.

I водолазный пост II водолазный пост «Гусёк» P=35 кг Направляющий P=80 кг фал

Направление перемещений Направление направляющих фалов движения водолазов

Направляющие Район поиска фалы длиной 110м. 3 м.

Ширина полосы просмотра L=30 м

Направление на точку Стальные 10 мм тросы длиной фотографирования 100 м., метки через 3 м.

15 HS; Distance of 100-300 m; I-st diver post; II-nd diver post; “Ogee”; Movement direction of the guiding halyard; Diver movement direction; Guiding halyards 110 m long; Region for search; Steel 10-mm thick, 100 m long hawsers, marks every 3 m; Direction to the photographing point; Safety halyard; Guiding halyard; Width of the examination zone.

Description of the site: Two steel 10-mm thick, 100-m long hawsers are tightened to loads weighing 80 kg. These hawsers are marked with red buoys at 30- m long halyards. There are marks in every 3 meters of these halyards. Accuracy of anchoring was observed with the mean-square error of no less than 1 meter. Distance between the hawsers – 100 meters. Two guiding halyards 110-m long were laid between the hawsers. Ends of the guiding halyards tightened to the loads weighing 35 kg were marked with white buoys. Loads for greater holding strain at the 5-m long halyards have additional anchors – “ogees”. Setting of the site was executed from “MGK-975” equipped with the “Starfix-HP 8300” receiver; it took 3-4 hours. Diver posts on the rubber boats of “Zodiac” type are tightened to the white buoys. Diver descends along the halyard to the load and then moving along the guiding halyard from the first to the second steel hawser examines the sea-bed on both sides of the halyard. When he approaches the second hawser, he carries the load of the guiding halyard along the steel hawser at the distance equal to two ranges of vision (~3m), and goes back along the guiding halyard examining the sea-bed. When he approaches the steel hawser, he carries the load of the guiding halyard to the middle of the site to the distance of 6 meters, and ascends. Usually it takes the diver 15-20 minutes to walk this distance of 200 meters and to do the above work, i.e.- one submergence with the air tank for 200 atm. Before starting the work to draw up the bathymetric chart for the region 300 x 300 meters with regard to the “dropping spot” the specialists of the Moscow OOO “Svarog” performed the work on bathymetric survey of the region with the multibeam echo-sounding device “SeaBat 8125” located on “HS-200”. Work positioning was carried out based on particular locations with the discreteness of 1 second of radio signals of standard and high frequency in the L1 and L2 frequency range of the “Navstar” satellite navigation system. Special 2-frequency “Starfix- HP 8300” receiver was used. Along with the satellite signal recept high-accuracy signal of differential correction from the controlling-corrective station “Noglicks” came to the same receiver. Calibration of the system in the differential mode in the port of “Sovietskaya Gavan” indicated the accuracy of 0.82 of a meter. In the region for search the receiver operated in the navigation mode with CKO = 0.22m. Electron registration of the incoming digital navigation information was carried out with the discreteness of 1 time per second with the help of “Starfix Suit 7.2” software installed into the navigation computer. As a result 3-D electron map has been developed for the whole region of search with all the possible contacts resembling RTG. Divers studied the electron map of the region to be examined in every detail – location of the underwater mountain ridges, ravines, and similar contacts.

Fig.12. Bathymetric chart of the site mad with the help of multibeam echo-sounding device “SeaBat 8125”.

Fig.13. Research ship “Lugovoye”.

18 Positioning of the carried out diving job was also performed with the above method. Research ship “Lugovoye” of the Far Eastern branch of the Russian Academy of Sciences (diving boat) was involved to ensure safety of the diving job (fig. 13). The work was supported by “HS-404”. Six qualified divers from Primorye participated in the search of RTG. Taking into consideration spreading of the RTG cooling system and the contacts obtained with the help of the multibeam echo-sounding device, the site was initially set up to the South-East of the “dropping spot”. It took the divers 3 days to examine the site. Each diver descended twice a day in the period of low tides since 2 to 6 PM. The attempts were also made to identify the contacts according to the bathymetric chart, but they gave no results, and after 4 contacts were examined this type of searching was rejected. The first site was removed and the new one was put into place. Selection of the new location for the site was based on the following assumption. Two plates of the RTG cooling system were found during examination of the first site. One of them is lifted (#4 was not lifted last year), the second one (#8) found to be blocked up under the stone, as well as one of the last year plates (#7). Both of the plates (#7 and #8) got under the stones from the North-West. That is why the site was moved there, to the direction of the “dropping spot”. During the first day of the work at the new site one more plate (#9), as well as a short strap of the same metal of up to 3-cm thick that presumably broke off the fixing part of the RTG housing were lifted. Metal frame of the capsule top fixation with eyebolts and a fragment of the trailing line were found on the second day. They were at the distance of 40 meters from the center of the “spot” (fig. 14). Two more plates (#10, #11) were found that day, but they were not lifted. Next day before descending the divers were especially attentive in studying the electron map of the remaining part of the site.

Fig.14. Lifted part of fixturing of the IEU-1 damaged during falling down.

At night of July 27 the anchor started crawling, it was impossible for the ship to stay in the region and it found shelter at the other side of the nearest cape, but it came back by lunch time and the work continued. The divers were instructed to examine very carefully two ravines in the region of the “spot” and the hills close to them. To the North of the lifted frame two screw couplings fixing the frame to the RTG bottom support (screws 1 and 2) were found. At 3 PM when the diver was completing examination of the site he found the RTG itself. It was at the distance of 3 meters to the North from the site in the examined ravine, lying on the side, with practically no biofouling. Its coordinates are: Latitude = 54019/00//.86 N; Longitude = 142015/14//.80 Ost (fig.15). Two divers put a sling circuit to the RTG and connected it to the buoy. “HS-404” anchored close to the RTG and lifted on board with its own crane. RTG was practically ruined except for the capsule with the isotope; its dimensions were 760 x 760 x 900 mm (fig. 16). Radioactive radiation of RTG corresponded to the operating value. Onboard the ship the damaged IEU-1 RTG was put into sarcophagus and transported to the port of “Sovietskaya Gavan” for the subsequent transportation of it for disposal. Thus, further degradation of the RTG and, therefore, radioactive contamination of the water area close to the Sakhalin Island is prevented.

20 0 10m 20m 30m 40m 50m 60m 70m 80m 90m100m 90m 54.317 80m ИЭУ 70m винт2 60m 50m 40m 54.3165 Крышка Пл2 30m винт1 Пл1 Пл3 20m Пл11 10m 0 Пл10 54.316 Обломок Пл9 Пл6

54.3155 Пл5 Пл7 Пл4

Пл8 54.315 142.254 142.2545 142.255 142.2555 142.256 142.2565 - Предположительное место падения.

- Районы поиска водолазами 2006 года. - Районы поиска водолазами 2007 года - Объекты, обнаруженные ГБО. - Обнаруженные обломки установки. - Поднятые обломки установки. - Место обнаружения и подъёма установки. Fig.15. Schematic of the search in 2007.

21 Presumable dropping location; Regions examined by divers in 2006; Regions examined by divers in 2007; Items found due to SSSD; Found fragments of the RTG; Lifted fragments of the RTG; Location, where the RTG was found and lifted.

Fig.16. State of IEU-1 RTG lifted from the sea-bed.

22 The following conclusions can be made based on the analysis of the location, where the RTG was found and lifted: - The RTG was not identified with any of the modern devices used for the underwater search because of the complicated structure of the sea- bed. - Finding of the RTG at the distance of 40 meters from the “dropping spot” (defined from the coast) testifies to the great significance of the initial investigation of all the circumstances of the event. This was not done in 1997 and, therefore, led to the 10-year long search for the RTG. Initial radiation level of the RTG was standard for IEU-1 type – approximately 21mR/h. After the RTG was lifted from the water its initial radiation level was 10.5mR/h. During transportation to the port of “Sovietskaya Gavan” its radiation level started increasing and from 10.6mR/h it reached 30mR/h, the RTG heated up greatly, so the situation was reported to the headquarters. The specialists of VNIITFA suggested putting the RTG into the reservoir with water. The scow of “MHS-404” was tightened from inside, filled with the sea water, and RTG was put into it. Heating up receded. Radiation level stopped growing. Special sarcophagus with fresh water was constructed in the port of “Sovietskaya Gavan”. When the RTG was brought to the port it was put into the sarcophagus (fig.17), where it stays till now. It is necessary to manufacture special container with water for transporting the RTG for disposal, but no finance is allocated for these purposes. The financial issue has not been solved yet.

Fig.17. Temporary sarcophagus with fresh water.