Effects of Nuclear Earth-Penetrator and Other Weapons (2005)

The Department of Defense (DOD) estimates that there are 10,000 known or suspected hard and deeply buried targets (HDBTs) worldwide as identified by the Defense Intelligence Agency. Of that number, about 20 percent have a major strategic function, and of those, about half are in or near urban areas. HDBTs are used for the protection of senior leaders, command and control functions, and storage of weapons of mass destruction (WMD), among other purposes. Some of them are buried in rock at depths greater than 300 meters, and some are hardened to withstand overpressures of about 1 kilobar.

A U.S. military requirement exists for capabilities to hold these HDBTs at risk. Past U.S. capabilities to satisfy this requirement for the deepest known HDBTs relied on a nonpenetrating, air-delivered, nuclear bomb of the largest yield in the inventory, the B53, now retired. Another existing nuclear weapon, the B61-7, was modified to become the B61-11, so as to have limited penetration capabilities.

Current DOD plans are to develop capabilities that can provide several options to hold HDBTs at risk. These include strike operations involving nuclear and non-nuclear weapons, Special Forces operations, and nonkinetic approaches (e.g., information operations). For all targets, the lowest yield would be used to achieve necessary destruction while at the same time minimizing collateral damage. To further reduce reliance on nuclear weapons, the 2002 Nuclear Posture Review¹ called for the development of high-precision conventional weapons to replace nuclear systems wherever possible.

The Department of Energy’s (DOE’s) National Nuclear Security Administration (NNSA) and the Air Force are conducting a 3-year study (now in its second year), including early research and development (R&D), toward a robust nuclear earth penetrator (RNEP) weapon, which is to be based on one of two existing nuclear designs, the B61-7 and B83, each to be studied at one of the two nuclear weapons laboratories. At present, only the B83 part of the study is funded. At the study’s conclusion, NNSA will state which (if either) of the two competing approaches it would recommend for further R&D. At present, no plans exist for conducting nuclear tests related to RNEP or other nuclear weapons.

Previous congressional actions related to the RNEP have included limiting the obligation of funds for the RNEP study pending a report from the DOD and DOE “that sets forth: (1) the military require-

ments for the RNEP; (2) the nuclear weapons employment policy for the RNEP; (3) the detailed categories or types of targets that the RNEP is designed to hold at risk; and (4) an assessment of the ability of conventional weapons to address the same types of targets that the RNEP is designed to hold at risk.”² This congressional directive does not mention collateral effects, but the responding reports from the DOD and DOE discuss (without details) the general expectation that collateral effects would occur if the RNEP were to be used, and that such effects would be much larger if a nonpenetrating weapon were employed to destroy the same HDBTs.

The Defense Threat Reduction Agency (DTRA) and the Air Force have conducted and are continuing to conduct studies, modeling and simulations, and non-nuclear tests to achieve a better understanding of the complex phenomena involved if nuclear or non-nuclear weapons are exploded in or near the location of hardened WMD storage or production facilities. The Thermobaric Weapon Demonstration is an ongoing program to provide an air-to-ground weapon capability to functionally defeat hard and deeply buried tunnel targets—with an emphasis on those for protecting leadership and command and control facilities. Additionally, DTRA has a conventional Counterforce Agent Defeat program that is working specifically on developing weapons and weapon payloads effective against facilities containing chemical and biological agents. One of its products was the BLU-119/B agent defeat weapon, which uses a 2,000 lb blast/fragmentation warhead (modified MK-84) developed and fielded as the Quick Reaction program for Operation Iraqi Freedom to damage fixed biological and chemical targets without contaminating the area. In the early 1990s, there were studies and some R&D on a low-yield (less than 5 kiloton) precision nuclear weapon for the destruction of chemical and biological agents in hardened facilities. In 1994, under the Defense Authorization Act,³ Congress prohibited R&D that could lead to the production by the United States of a new low-yield nuclear weapon, including a precision low-yield warhead, which as of the date of the law’s enactment had not yet entered into production. This restriction was repealed in 2004 for R&D up to but not including the engineering development phase.

Section 1033 of the Bob Stump National Defense Authorization Act for Fiscal Year 2003 (Public Law 107-314) directed the Secretary of Defense to request that the National Academy of Sciences study the anticipated health and environmental effects of nuclear earth-penetrator and other weapons.

As requested, the study examined the following:

1. The anticipated short-term and long-term effects of the use by the United States of a nuclear earth-penetrator weapon on the target area, including the effects on civilian populations in proximity to the target area at the time of or after such use and the effects on the United States military personnel who after such use carry out operations or battle damage assessments in the target area.

2. The anticipated short-term and long-term effects on civilian populations in proximity to a target area:

   1. if a nonpenetrating nuclear weapon is used to attack a hard and deeply buried target; and

   2. if a conventional high-explosive weapon is used to attack an adversary’s facilities for storage or production of weapons of mass destruction and, as a result of such attack, radioactive, nuclear, biological, or chemical weapons materials, agents, or other contaminants are released or spread into populated areas.

The National Research Council, the operating arm of the National Academies, convened the Committee on the Effects of Nuclear Earth-Penetrator and Other Weapons under the auspices of the Division

on Engineering and Physical Sciences to conduct the study. The committee received briefings from the DOD, DOE, congressional staff, nongovernmental organizations, and individuals, in both classified and open sessions. To assist in its considerations of Congress’s questions, the committee asked the DTRA and Lawrence Livermore National Laboratory to estimate the number of civilian casualties for a range of nuclear weapons yields and depths of burst for possible target areas.

The issues raised in the statement of task are stated briefly and refer to specific combinations of factors. Here, the committee makes clear its understanding of the terms and factors involved. It assumes that the health and environmental effects of nuclear earth-penetrator and other weapons would be produced by an attack expected to be militarily effective. “Hard and deeply buried target” is taken to indicate primarily hard targets, which may be buried at various depths. “Deeply buried” refers to depths beyond those of craters formed by the largest nuclear weapon that might be used to destroy such targets.

The statement of task refers explicitly to WMD only in the case of a conventional weapon being used to attack facilities containing WMD and does not mention WMD in connection with the effects of a nuclear attack on HDBTs. The committee thinks that a fully effective attack on an HDBT, whether a nuclear or non-nuclear attack, should involve the destruction or complete sealing off of contained WMD.

In general, in this report, discussion of WMD often lumps chemical and biological agents together. Chemical and biological agents, however, have distinct properties that lead to differences in the effects of their release and in the difficulty of their destruction.

In a comparison of the effects of nuclear explosions, consideration must be given to other effects besides radioactivity. Local blast and thermal effects of near-surface nuclear explosives can be more lethal than the radioactivity.

To understand the statement of task’s asymmetry between nuclear and conventional weapons, the committee heard from congressional staff involved in developing the task statement and from the DOD sponsors. It was clear that tasks 1 and 2a were the key issues and would require extensive analysis, including substantial original calculations. Task 2b, regarding conventional weapons, was of much lower importance and was to be examined if time and resources permitted. Unfortunately, the efforts on tasks 1 and 2a were more demanding than estimated, particularly because of the need to develop and analyze the material presented in Chapter 6. Consequently, less time and fewer resources were available to work on task 2b.

With the understandings and assumptions specified above, the committee organized its response to the statement of task as follows.

Chapter 2 defines HDBTs and discusses their types, locations, functions, size, overall numbers, different depths in different geologies, and trends in types of HDBTs. It gives examples of some HDBTs with details and emphasizes the need for accurate target intelligence.

Chapter 3 defines earth-penetrator weapons (EPWs) and discusses the history of EPW technology, key penetrator characteristics, geologies in which experiments have been done, empirical equations for predicting EPW penetration, maximum credible penetration depths, the B61-11 EPW, the current Robust Nuclear Earth Penetrator program, and some characteristics of nuclear weapons for surface burst.

Chapter 4 addresses the calculated effects of nuclear weapons against hard and deeply buried

targets, with particular attention to target destruction, tools to calculate damage, and the uncertainties involved.

Chapter 5 discusses collateral effects of the fallout from air, surface, and underground bursts, as well as two computer programs that are in wide use to model the effects of release of hazardous chemical, biological, radiological, and nuclear materials into the atmosphere and their effects on civilian and military populations. The computer programs discussed are the Hazard Prediction and Assessment Capability code (HPAC) developed by DTRA and its predecessor agencies and those used by the Lawrence Livermore National Laboratory—the NUKE code from Sandia National Laboratories to model the prompt effects of a nuclear explosion and the K-Division Defense Nuclear Agency Fallout Code (KDFOC) to analyze the spread of radioactivity. Also discussed are the uncertainties involved in the use of computer modeling and simulation.

Chapter 6 addresses the health and environmental effects of nuclear explosions. Computer modeling and simulation calculations are presented for notional representative targets attacked with weapons over a range of yields. In addition, health effects of attacks on chemical and biological weapons facilities are addressed.

Chapter 7 discusses conventional high-explosive weapons, both current and under development for direct or indirect attack, to support the emerging Global Strike Mission.

Chapter 8 discusses sources of uncertainty—factors to which the results of calculations such as those discussed in Chapter 6 are most sensitive—and compares the variations in effects due to uncertainty with the variations expected from substituting an EPW for a surface burst. It addresses effects of uncertainty regarding target location, geology, accuracy of delivery, ability of a weapon to function, and model inputs, as well as effects of uncertainty in the models themselves and in analytical tools.

Chapter 9 presents the committee’s conclusions.

The four appendixes provide supplemental and study-process-related information.