冷戦時代の核実験や民間防衛をめぐるカルチャー

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Operation Castle (1954)


Operation Castleは1954年3月〜5月に、Bikini atollの島や、艀に搭載して環礁内の海上で行われた、米国の水爆実験シリーズである。

60%含まれるLi-7が反応に参加しないと仮定して、1発目のBravoの出力を6Mtと推定されたが、実際には15Mtの爆発となった。このため、放射性降下物が想定外の領域にまで及び、現地住民や第五福竜丸が放射性降下物に被曝する事態を招いた。

これにより、出力推定の見直しや、爆発延期などが行われた。
Predicted, Modified, Actual yields, Scheduled and Actual dates
Test NameDevice NameOriginal Predicted Yield/RangePost-Bravo Predicted Yield/RangeActual YieldSchedule DateDate
BravoSHRIMP6 Mt (4-8 Mt)-15 Mt1 Mar1 Mar
RomeoRUNT I4 Mt (1.5-7 Mt)8 Mt (1.5-15 Mt)11 Mt15 Apr27 Mar
UnionALARM CLOCK3-4 Mt (1-6 Mt)5-10 Mt (1-18 Mt)6.9 Mt11 Mar26 Apr
KoonMORGENSTERN1 Mt (0.33-2.5 Mt)1.5 Mt (0.33-4 Mt)110 kt22 Apr7 Apr
Yankee (I)JUGHEAD8 Mt (6-10 Mt)-Cancelled (post-Bravo)22 Mar-
Yankee (II)RUNT II-9.5 Mt (7.5-15 Mt)13.5 Mt-5 May
EchoRAMROD125 kt (65-275 kt)-Cancelled (post-Koon)29 Mar-
NectarZOMBIE1.8 Mt (1-2.5 Mt)2-3 Mt (1-5 Mt)1.69 Mt5 Apr14 May

軍の解説動画は、この威力推定ミスに言及しつつ、成功裏に終了したと述べている。

[ Operation Castle ]

このBravoの失敗により、マーシャル諸島の住民たちが被曝。放射線の人体への影響調査が可能となったため、急遽、調査プロジェクト"Project 4.1が編成・開始された。このブラボー爆発(1954)によるマーシャル諸島住民の被曝をめぐっては、「意図的に被曝させた」という主張がなされているが、それを示す証拠はない。


なお、島・環礁の位置は...






Transcript

Operation Castle (1954)

0:30 Operation castle, the fifth in a series of tests at the Pacific proving grounds.
0:36 Another accumulation of men, of machines, another meeting of ships and aircraft, and troops
0:44 It was the best of physics, metallurgy, and electronics
0:49 During the months after, the historic might detonation preparations for a new series of tests, to solve the problems of a deliverable Megaton weapon, went ahead at an accelerated pace throughout the country.
1:02 Operation castle became a reality and is now successfully concluded
1:08 The report, which follows is a summation of what occurred at the Pacific proving grounds, during that operation in 1954
1:16 Here, the lead off record is General Clarkson, Task Force Commander
1:20 Operation castle was concluded on the 14 of May 1954
1:27 Castle was an all thermal nuclear test, a test basically of devices in the Megaton range.
1:35 We feel that the report of this important test should give the failures as well as the successes should reflect the changes in thinking that occurred during the test.
1:47 We hope this treatment will help you understand the problems that we experienced during the course of the operation
1:54 This program encompass them three shots on land and four shots on barge.
2:01 Our main base camp on bikini was located in the same island complex.
2:05 The firing station to be used on all bikini shots was located on Eniwetok island, Eniwetok island at Eniwetok atoll.
2:17 Again functioned as the center of man-based operations
2:24 This then was the weapon schedule and the operational plan for castle on March 1.
2:33 Parry island at Eniwtok atoll, this is the third time this island has been used as the headquarters of a specific task force
2:37 For this operation, our weapons assembly area was constructed at the southern tip of this valuable piece of real estate.
2:48 This is the first time on any operation that weapons were assembled on Parry and then moved out to the firing site.
2:53 Weapon development would be impossible without diagnostic instrumentation
3:03 But such instrumentation is expensive very expensive at this distance from home.
3:09 For this reason extensive instrumentation was limited to a few shots and each diagnostics experiment was carefully considered before being included in the program.
3:19 Instrumentation while more elaborate than that of other shots is representative of the type of diagnostic studies made.
3:22 Recorders to read the yield of the primary bomb from its rate of neutron multiplication.
3:33 Cloud sampling for Radiochemical determination of fission yield and to assist in determination of total yield.
3:39 High-speed cameras & photo towers quialify photography to indicate total yield of the device.
3:48 Scopes recording electromagnetic radiation and cameras both to obtain the time interval between primary and secondary bomb detonations.
3:59 other cameras to look directly into the open door of the cab
4:03 A great mass of information was gathered as a result of an array of 12 evacuated pipes
4:10 These pipes are like peoples looking at portions of the weapons case to pick up gamma and neutron emission from many stages of the reaction.
4:19 Starting at each - 48 hours, all personnel at Bikini Atoll were evacuated from the scattered islands and moved aboard taskforce ships
4:30 The only men to remain where the members of the firing party protected in their bunker on Enyu island.
4:37 Once more for the first time since operation crossroads in 1946 bikini took its place in this story of atomic testing.
4:46 The date was Mar 1, 1954
4:55 This photograph was taken from an airplane at 50 miles.
4:58 The width of the fireball, at this time about three seconds after detonation, was 4 miles.
5:06 The frame size of the picture is 6 by 8 miles.
5:35 The top of the fireball, at this time 40 seconds after detonation, was 5 miles above sea level.
5:50 Prove that we can have a high-yield weapon weighing less than 10 tons.
5:55 The tremendous field resulted in a serious fallout situation at bikini and certain another attols downwind from ground zero.
6:03 This was the forecast wind direction. The actual wind was in this direction
6:15 Some 10 degrees less favorable than forecast.
6:19 Even so the winds were within the area of acceptable fallout.
6:24 However the unexpected high-yield caused significant fallout occur on Rongelap atoll, 110 miles distant, on Rongerik , 150 miles from Bikini and on Utrik, 280 miles out.
6:43 after the natives were evacuated, radiation survey teams were flown back to the exposed atolls where studies were made and water and soil samples taken.
6:56 Rongelap had an 80 population of 82. Evacuation was carried out on the second morning after the shot.
7:50 Rongerik had no native population, but was occupied by 28 men of the taskforce.
7:12 Eight men were evacuated by air at H + 28 hours and the remaining men soon after
7:20 Utrik had 150 natives and they were also evacuated, although radiation levels here were relatively light.
7:30 The removal of personnel from the contaminated atolls was done mainly by destroyers.
7:37 These destroyers were attached to the taskforce primarily for security purposes, but were easily adapted for use as evacuation vessels.
7:48 All of those exposed were taken to Kwajalein, where complete physical examinations were carried out.
7:56 every effort was made to ensure their comfort and well-being.
8:01 Fallout on bikini temporarily rendered that atoll unusable.
8:06 25 R/hour was recorded on Eniman, a port of entry.
8:13 On Enyu, the side of our control station, 35 R/hour was recorded.
8:20 100s of R/hour measured on Aomoen and Bikini islands.
8:26 Even if radiation had not been a factor, blast damage on Eniman was considerable.
8:32 It would have taken a sizable effort to make that island again usable as the base camp.
8:39 The ground shock and fallout experienced by a firing party on Enyu, forced us to give up the idea of a man station.
8:50 The necessary electronic systems were installed on the USS Estes to permit firing remotely by radio.
9:00 The possibility of further damage to previously prepared shot sites at bikini, cause us to change our schedule at this point.
9:10 Back in the states at about the same time castle was an operation, the results of these drops plus tested fusing and firing systems made it possible to have a deliverable weapon ready, a weapon approximately 19 feet in length and 5 feet in diameter.
9:27 While the case is made of aluminum, this is by no means a light weapon, since it weighs 43,000 pounds.
9:35 It was put aboard its firing barge.
9:39 This was the first time that the barge method of firing was used.
9:44 It was felt that a firing could be done from a barge on open water.
9:47 It would result in an appreciable reduction of fallout as well as a considerable simplification of operational problems.
9:55 Approval to difficult shot to get off, we had to postpone 14 days from the schedule date firing because of weather.
10:04 The winds continue to swing around going to the south and then to the west.
10:10 This took 10 days.
10:11 Then for 16 days, the winds remained in this sector. Since Eniwetok is in this area, this area it might receive fallout if the winds were too close to a borderline condition
10:26 At 7am on the 26 of March, the forecast was for a favorable wind in the right direction.
10:33 The shot was set for 630 the next morning the 27th in Mar
10:40 On this rather unimpressive barge, floating in the Bikini lagoon, rest of the device which carried the hopes for a large step forward in the weapons development program.
10:58 The distance of the camera aircraft is 50 miles.
11:01 The frame size of the picture is 14 x 18 miles.
11:06 The film is running at normal speed.
11:24 Look from Eniwetok atoll, 200 miles away.
11:38 Daily commuting from ship to shore for several working hours for man each day.
11:44 We had to watch the radiation doses received by the people working on the test island.
11:51 Maximum of 3.9 R/man was set for the operation, and with minimum ratings of approximately 100 mR/hour the men had to work fast.
12:05 As on previous tests the armed forces took advantage of the castle series to broaden their knowledge of the effect produced by high yield weapons.
12:15 As an example, there has been much uncertainty in specifying the minimum safe distance for aircraft delivering high yield weapons.
12:24 blast and thermal effects were measured on B-36 & B-47 aircrafts, position so that some damage was expected.
12:34 This data will help us to specify the yield at which parachute drops are required for delaying a detonation, as well as providing us with answers to many questions which arise when positioning for multiple drops is considered
13:47 The whole picture of fallout contamination becomes of increasing importance with high-yield weapons.
12:53 In one program drone ships were sent into fallout areas to evaluate the worth of a washdown system for ship decontamination.
13:03 We found we could measure fallout even in large ocean areas by making aerial surveys using extremely sensitive to radiation detection equipment, and with surface craft such as tugs and destroyers.
13:17 As a result of these measurements, we were able to document for the first time fallout data from high yield detonations.
13:25 It is now known that fallout from the larger castle shots blanketed areas of more than 5,000 square miles with radioactive material that would have been lethal to unprotected personnel.
13:38 This one result gives a new insight into a method for using high yield weapons in both strategic and tactical situations
13:47 It is now around ahead of april and recap of our story of Castle, 3 shots down and 3 to go.
13:55 The weather continued to work against our keeping firm firing schedule.
14:00 During the Middle two weeks of april we were faced with the same situation.
14:06 The winds above 10,000 feet were again in an unsafe direction.
14:11 Under these conditions populated area are directly in line of fallout.
14:16 Again we postpone awaiting a favorable forecast.
14:21 This occurred on the 25th of april at noon
14:26 Anchored in his location of the island of Yurochi, zero hour approached
14:32 The time of firing 610 on the 26 th of April.
14:42 Camera position 50 miles at 10,000 feet, size of a picture 14 x 18 miles, photographed at normal speed.
14:54 The yield with 7 Mt.
15:31 The weapon was scheduled for firing on 5th of May,
この爆弾は5月5日に起爆が予定された。
15:36 This was 10 days since the last shot
15:39 For the first time in the operation we had what could be considered in normal interval between shots.
15:47 On the 16th of April a strategic air command B-36 landed on Eniwetok island.
16:17 camera position 50 miles at 10,000 feet, size of picture 14 x 18 miles, photographed at half normal speed.
17:13 The sixth and final shot of operation castle.
17:18 This device was also thrown out to the forward area for final assembly at Parry island.
17:24 Barge was thrown directly to zero point at Eniwetok Atoll
17:28 Here over the spot, that was once the island of the Elugelab and is now a might creator, was anchored in position.
17:38 At 0620 on the morning of May 14 the smallest device of the operation was ready.
17:44 This test initiated an investigation of small lightweight, thermonuclear weapons in the Megaton class.
17:53 Size of picture is 14 x 18 miles, the yield was about 1.7 megatons essentially as predicted
18:06 From this firing, we learned that we have the capability of developing Megaton weapons weighing less than 10,000 pounds.
19:10 Castle was by far the most complex and significant operation, and the short but impressive history of nuclear testing.
19:22 And in my opinion, absolutely vital to national security and the security of the free world.
19:38 We will be set by operational problems of a magnitude not encountered previously.
19:44 Degree of flexibility attained by the task groups and by the task force of the whole, and meeting these problems is only one example of the spirit of cooperation evidenced by all members of the 3 services and by the members of the Atomic Energy Commission and its contract
20:00 To the man who made operation Castle success, to the same men who were asked to undergo many personal hardships, I have already expressed my gratitude.
20:15 I'm sure that these men also deserve the sincere appreciation of the Department of Defense, the Atomic Energy Commission, and the people of the United States.
20:26 This concludes the report on operation castle.


Transcript: Trinity and Beyond

Castle Bravo (Trinity & Beyond)

0:00 Welcome high yield hydrogen bombs had progressed from Operation Ivy
0:05 Culminating in the spring of 1954 with castle bravo, the largest device ever detonated in atmospheric testing by the United States.
0:20 Bravo was a hydrogen bomb, using solid thermo nuclear fuel
0:25 Confirming the designs of Edward Teller and standing room and paving the way to producing aircraft deliverable hydrogen bombs and more effective weapons
2:53 Significantly exceeding its expected yield by two and a half times, Castle Bravo with an explosive power 15 megatons stripped islands clean of vegetation and took the scientists by surprise.
3:11 The huge explosion released large quantities of radioactive debris into the atmosphere.
3:18 This resulted in the exposure and contamination of some servicemen, natives, and the crew of the Japanese fishing boat which had gone unnoticed in the security zone around the blast.
3:28 This incident push the dangers of fallout from nuclear weapons clearly into the public mind





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