By this point in the history of the venting controversy, the State Department was getting better at controlling information. It was not until October 1967 that the Washington Post got wind of the meeting the previous January, which it reported as a "secret protest" of Russia's December venting. Thereafter, newspaper coverage of U.S. government inquiries about venting incidents dried up, probably because nothing was leaking from the State Department or perhaps because the incidents were no longer news.
One venting that became a major news story, reaching the front pages of the U.S. press, was the Baneberry nuclear test on December 18, 1970. Everything went wrong geologically at the Nevada Test Site. The 10 kiloton test produced a "prompt, massive venting" of radioactive particles and gases, the worst such incident in the history of U.S. underground testing. The cloud reached 8,000 feet in height and radioactive particles were detected across the Canadian border. Owing to an error by the test controller, a warning was not issued quickly enough and radiation reached Camp 12 where hundreds of workers were stationed. The incident led to a six-month moratorium on underground testing accompanied by a significant effort to apply resources to containment procedures so that nothing like Baneberry happened again. Canadian diplomats cited the detection of radioactive particles but they did not make a formal protest, although relations with Canada were already strained because of U.S. underground testing at Amchitka, Alaska.
Dobrynin brought up the Baneberry venting but Assistant Secretary Martin Hillenbrand, in a tit-for-tat fashion, handed him a note about Soviet tests in December 1970 that had caused venting and the collection of radioactive debris outside of Soviet borders. As usual, Dobrynin denied that the December 1970 tests had released any radioactive debris. In the reporting cable, the State Department informed the U.S. Embassy in Moscow that it was following the "practice" of not publicizing "the nature of this exchange," but did not refer to a mutual understanding with the Soviets.
Moscow, of course, kept its media under tight control and thus did not face a major public opinion problem. Venting incidents continued; no major resources were expended to minimize them. Thus, the venting on September 27, 1971, became the subject of another exchange with Moscow. As had become the practice, Washington consulted with the British, the other original signatory of the LTBT, whenever it was about to lodge a protest. State Department official Holsey Handyside told British diplomat Christopher Makins that the United States did not bring up every venting incident with Moscow but that there had been six in the last year -- and the September 27 incident was the "worst" since October 1966.
In response to Makins's query about what the United States hoped to gain by protesting, Handyside explained that Washington wanted to build a "firm record" to respond to congressional inquiries, to encourage the Soviets to improve their containment practices -- not only to minimize atmospheric radioactivity but also to avoid encouraging opposition to "all nuclear testing." Moreover, Washington wanted to counter any Soviet "propaganda" charges about U.S. testing or its infrequent venting incidents. Summing up, Handyside explained that Washington "wished to remind the Soviets that the continuation of the existing gentlemen's agreement against publicizing venting incidents was to the advantage of both the US and the USSR."
Handyside was probably not referring to an explicit agreement, but to practices that both sides had been following for mutual convenience since the mid-1960s in response to the political problems raised by venting incidents.
The next day, Acting Assistant Secretary of State George Springsteen handed off an aide memoire about the venting to Soviet diplomat Yuli Vorontsov. Replying on January 10, the Soviets stuck to their customary story that venting had not occurred and riposted by asking about a U.S. test that occurred on November 24, 1971. As Dobrynin had done in February 1967, diplomat Viktor Isakof asked the United States to stop bringing up the incidents. Whatever the nature of the agreement about venting, tacit or explicit, Isakof interpreted it as meaning to keep silent: "he thought an understanding had been reached not to keep making reference to small events." Not surprisingly, Soviet desk officer Jack Matlock responded that the September 27 venting "had not been a small event."
More Soviet ventings occurred during the 1970s and the United States continued to lodge protests. In some instances, Washington had evidence suggesting that Moscow had taken precautions to "reduce the amount escaping Soviet territory," but that it should have known that there was a "virtual certainty of at least gaseous radioactive material escaping Soviet territory." In its protest notes, the State Department noted that the U.S. government has made "rigorous precautions" which "have proved especially effective." The implication was that Moscow needed to take "effective measures" to reduce or prevent leakages of radioactivity. Nevertheless, the Soviets stuck to their story and denied that any radioactive material had crossed their borders.
The U.S. developed better procedures to minimize the venting problems, but some incidents occurred, although nothing like the Soviet ventings -- the local environmental impact of which was often severe. The record of quiet complaints about venting continued into the mid-1980s, with both countries following the "gentlemen's agreement." It was not until May 1986, the time of the Chernobyl accident, that Assistant Secretary of Defense Richard Perle, in congressional testimony, acknowledged the secret record of U.S. protests. He did not, however, mention any non-disclosure understandings. Determined to continue underground testing, no doubt the Reagan administration wanted to avoid speculation that Washington had collaborated with Moscow to prevent their disagreements from being fully aired.