This is coolbert:
Han class down!
During that period of the Cold War it was not only American and Soviet submarines colliding underwater. Others too!
Continuing with extracts and commentary from the book: : "K-19, The Widowmaker" by the American author Peter Huchthausen.
"Pacific Fleet Victor III-class SSGN, K-324 from the Pacific Base of Rakushka collided with the Chinese Han-class SSN . . . the Han sank to a depth of one Km [about 3,000 feet] near Ashkold Island with the loss of its entire 70-man crew. A Soviet survey in 1989 . . . commissioned by the Pacific Fleet, detected extremely high radiation levels measuring 1,000 roentgen per hour [877 rad/hour] within a five-mile radius of the broken hull of the Han SSN."
An exposure of 500 rads per hour a lethal dose to a human for which there is no remedy! A dose of 250 rads per hour not necessarily lethal but enough to instantly incapacitate a human!
"OBITUARIES APPEARING IN CHINESE NEWSPAPER CONFIRMED THAT MANY CHINESE SENIOR SUBMARINE DESIGNERS WERE LOST IN A SUBMARINE ACCIDENT IN 1983."
[all bold my emphasis]
Further regarding the Han class Chinese nuclear submarine:
"The Han-Class is well known for having a noisy reactor and poor radiation shielding, which causes health hazards for her crew as nuclear radiation levels are higher than they should be aboard the submarine."
Again, the loss of so many senior design personnel their specialty submarine design creating a problem not easily remedied. Institutional memory and experience not easily replaced!