WASHINGTON — In 2011, Air Force Lt. Gen. Frank Klotz retired after a distinguished career that culminated with him running Air Force Global Strike Command, the service’s arm in charge of nuclear weapons. Three years later he was called back into service, this time as the head of the National Nuclear Security Administration, a semiautonomous branch of the Department of Energy that oversees the safety and development of America’s nuclear warheads.

After four years of service at NNSA, during which he drew praise from both the pro-nuclear and nonproliferation communities, Klotz retired on Jan. 19. Before he stepped down, he joined Defense News for an exclusive interview to discuss the state of America’s nuclear arsenal and what challenges await his successor.

Let’s start with an infrastructure question. You’ve been warning for years about having a backlog of more than $3 billion in deferred maintenance. Where is that now?

We have not, as a nation, made the investments that we have needed to make since the end of the Cold War to make sure that we can do the work that needs to be done in maintaining a safe, secure and effective stockpile. We still have a lot of facilities where we’re still conducting work that date back to the early days of the Cold War and some even back to the old Manhattan Project. We’ve been able to keep [deferred maintenance] at steady state for the last couple of years, largely because we’ve had very strong support from Congress, particularly from the House Armed Services Committee, Strategic Forces Subcommittee.

But at the end of the day, it’s a question of budget and what are the budget levels and how timely do we get our allocation. So what decision-makers would do is they would say: “Well, we absolutely must pay for the mission essential things. We’ll accept risks and defer repair and recapitalization and modernization of the infrastructure another year.” Well, one year becomes two years becomes 10 years, and you eventually get to a tipping point where you just absolutely have to do something. Shortly after I got here, we had a piece of ceiling fall at one of our facilities at Y12 in Oak Ridge, Tennessee. Fortunately, no one was hurt. Fortunately, no equipment was damaged. But it could have been a lot worse. That’s kind of the state of some of our infrastructure. A large portion of our infrastructure is that way.

The U.S. has not conducted a live nuclear test since 1992, instead relying on the Stockpile Stewardship program, which simulates those tests. There seems to be some renewed debate about whether testing may be needed again. Where do you come down on that?

We conducted 1,054 tests as a nation before we voluntarily entered into a moratorium in 1992. We’re archived a lot of that data. Now, what we decided to do in the ’90s was to develop a Stockpile Stewardship program that would allow us to use scientifically based tools to understand how weapons operate and how weapons age; and if you have to replace components in those weapons as a result of aging, how best to design them; and if you use them, how they will affect the safety, security and effectiveness of the weapon. In that time, we have developed some very, very sophisticated diagnostic tools and diagnostic experiments to test various components and various materials within the weapons in order to understand the things I just talked about. It has been said publicly by some laboratory directors that we probably know more about the science and engineering of a nuclear weapon now as a result of 20-plus years of Stockpile Stewardship than we did when we were testing.

We continue to invest in diagnostic and experimental capabilities. It’s important that we continue to invest in that because there are still things we would like to know better. I won’t describe those, but there are some things we would like to know better. So every year, by congressional statute, the three laboratory directors and the commander of U.S. Strategic Command are required to certify to the president through the secretary of energy and the secretary of defense that the stockpile is safe, secure, reliable and effective — and that there is no need to return to testing at this time. And every year for the past 20-some odd years that this statute has been there, they have so attested. So that’s where we are.

You sound confident.

I sound confident now, yeah.

What would change that?

I suspect the thing that would probably change that is if there was some technical issue that quite simply could not be resolved as a result of this suite of tools, experiments and high-performance [computing] codes that we have. And we’re not there. We’re not there.

NNSA is preparing to spend, according to one estimate, more than $350 billion in the next 30 years to modernize nuclear warheads and infrastructure. The Government Accountability Office, however, thinks it could be more, as do some analysts in the nuclear community. What do you say to those concerns?

Well, the only thing we can control are the variables we can control, and cost estimations, by the way, are an art, not a science. And by that I mean [there are] different methodological approaches as to how you estimate costs.

We can control requirements. We can control the quality of people we assign to these tasks. We can control how we lay out the schedule. We can’t control the timing of the funding. Yeah, the GAO has a point. And it’s one we absolutely subscribe to if you delay [funding].

The Congressional Budget Office released a report estimating the total cost to modernize the U.S. nuclear arsenal to rise to more than $1 trillion over the next 30 years.

But when we provide a cost estimate, we’re providing a cost estimate to what we think, given the funding profile. I will say what I’m most proud about is right now all four of our life-extension programs are on schedule and on budget. Right now they’re all on schedule, and we’ve delivered the vast majority, upward of 95 percent, of our multibillion-dollar construction portfolio since 2011 below cost, which to me is pretty, pretty significant.

You’re managing four major warhead modernization programs right now. Is there any one that you’re particularly worried about being able to get done on time, on cost?

No. But let me caveat that. I’m very confident in the skill and experience of the program managers we have and in the schedule that they have laid out and the work that is being done in the labs and our production facilities to do that work. Now, having said that, again it’s a function of funding. And there’s always risk involved.

The most substantial risk that we face is as we do these life-extension programs, we replace a lot of components. And many times the technology that was used, mostly non-nuclear components, the technology that was used to produce that component like a vacuum tube that no longer exists, nor would you want to use it if it did exist. In many cases we have to go out. And even though we have the design, which we may tweak a bit, we have to come up with a whole new way of fabricating that part. And if we try something new in a non-nuclear component, which we think will be more effective, more efficient in terms of the post-production maintenance associated with it, we’ll also have to design, qualify, certify that.

That is very challenging, technical work. And from time to time, there are challenges in producing these things to the level of quality that we expect them to be produced. That’s probably the greatest risk. The other great risk in the life-extension programs is we’ve never done more than one life-extension program at a time, since the end of the Cold War. We’re now doing essentially four. The point is we are working pretty much at full capacity.

There has been talk about trying to find commonality between, among other programs, the Air Force’s ICBM replacement and the recapitalized Navy Trident missile. Where do you come down on that debate?

I still think there is merit. Whatever we do, there is merit in looking for areas in which we can achieve some commonality between Air Force and Navy systems, whether it’s the warhead, or whether it’s the missile or it’s the missile guidance systems or fire control system. Whatever it may be. It only makes sense. Now, you always have to deal with the issue of single-point failure, but I will tell you — I was in Air Force Space Command when we decided that we would basically have two boosters, the Delta IV and the Atlas V, and that there would be some commonality in parts.

And there are ways that good systems engineers can and good aerospace technicians can deal with the issues of the potential for single-point failure in that. But it only makes sense to me that we do that. As we think about what we’re eventually going to do for [the new ICBM] and anything the Navy does in the future, we ought to look at ways in which we can take advantage of developments in one service or the other for the benefit of the one service or the other.

When it comes to developing new warhead designs or changing your current plans, how hard is it to do that at this point?

For every proposal that’s out there, there are essentially three things that have to be considered. First is technical feasibility of doing that. The second is the cost of doing that. None of these things are free. And then, as I said, the capacity of the enterprise as currently structured and configured to take on the additional work. It’s not like flipping a light switch. There are many things we think about that, from a technical point of view, are relatively straightforward. But when you get down into how you’re going to pay for it, how are you going to schedule it into the work, what’s the impact going to be on the other work that’s being done? Those are the things you have to think about.

We hear people saying that, today, the world is closer to nuclear war than it has ever been. Do you agree with that statement?

Here’s my take on it: The world has always been a very dangerous place. It’s always been a very complicated place. I think where we are right now is when the Cold War ended, it is as if we heaved a sigh of collective relief and said, “Thank goodness we don’t have to worry about that anymore,” and we didn’t. And part of where we are in terms of the state of the infrastructure in the nuclear enterprise and the responsiveness of the nuclear enterprise is a result of not having thought about it for 20-plus years.

We have a tendency as humans ― it’s a marvelous faculty ― to sort of romanticize the past. I can recall several years into the post-Cold War period people were saying how much simpler things were in the Cold War. “We knew who our adversary was, there was a consensus” and all that. I don’t remember it being simple. I remember it being extraordinarily complex. I remember heated debates within the Congress, within the American body politic about the wisdom of developing and deploying this type of system or that type of system, whether it was a conventional system or whether it was a nuclear system or whether it was a dual-capable system.

I am very concerned, personally, that while we have taken a pause in terms of recapitalizing our nuclear forces, the Russians are continuing to invest in their nuclear forces, both strategic and nonstrategic. And the Chinese have continued to steadily develop and diversify their nuclear capability. Other nations ― India, Pakistan ― continue to expand and diversify and increase the size of their nuclear forces.

Yes, it is a more challenging world, I think. But in this more challenging world, I go back to the first principles, and that is the basic foundation of our national security is nuclear deterrence. It is on that foundation which allows us to continue to project power around the world through conventional means. I think it’s extraordinarily important that we continue to devote the resources to this that are necessary to make up for the two-plus decades which we have not been paying as much attention to this as we should have been.

What do you expect the reaction will be to the Nuclear Posture Review, when it is released?

My hope is that when it is released, it will lead to that national debate, which brings out these issues, and hopefully it will result in a consensus that we need to continue to make the investments that we have made in the past.

By the way, NNSA has done very well in terms of having very broad support for the missions we’ve performed both within the executive branch and up on Capitol Hill. Both ends of Pennsylvania Avenue, both sides of Capitol Hill, both sides of the aisle. I expect that ― I hope that the dialogue that will come as a result of the NPR will reinforce that consensus as we go forward.

Updated 1/24/18 for clarity.