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The IMS Cannot Detect Militarily Significant Nuclear

Testing

It is quite feasible to conduct militarily significant

testing with little or no risk of detection.  Nuclear

testing could be masked by other explosive activities.

Also, testing could be conducted in the ocean, where iden-

tifying the origin of the device may be impossible.

The most likely cheating scenario may be an under-

ground nuclear explosion in a cavity.  That would muffle

the energy, reducing the blast signal by as much as a fac-

tor of 70.12   Thus, a 1-kiloton explosion could be made to

look seismically like a 14-ton explosion; a 5-kiloton

explosion could look like a 70-ton explosion.13

The IMS of the CTBT is expected to provide the abili-

ty to detect, locate, and identify nonevasive nuclear

testing of yields of 1 kiloton or greater.  It will not be

able to detect, with any significant degree of confidence,

nuclear testing below 1 kiloton.  If the test is evasively

conducted, the system will not detect a test of several

kilotons.

CTBT proponents say that supplemental data from U.S.

national technical means will fill the gap.  This argument

is not entirely accurate.  The United States has stated

that its objective is to have the capability of identify-

ing and attributing with high confidence evasively conduct-

ed nuclear explosions of about a few kilotons yield in

broad areas of the globe.  At present, the capability does

not exist.  Furthermore, the U.S. intelligence community

has acknowledged that this is a complex task that will

require much effort, time, and resources to achieve.  For

the present, even with a fully functional IMS supplemented

with data from U.S. national technical means, it is possi-

ble that a militarily significant test could be evasively

conducted without detection.

CTBT proponents argue that, once the IMS is operat-

ing, the technology will continue to improve and may make

it possible someday to detect low-yield events with cer-

tainty.  Even if so, however, there would still be virtu-

ally insurmountable problems.  One is that, at very low

yields, the whole world becomes a potential test site.

For example, tests in the tons can be done in old mines or

underground cavities, and tests in the pounds can be done

almost anywhere.14   Russia is so large that we will never

know if it is conducting such low-level tests, even if the

verification regime entails full test-site transparency.