Pressurized Water Reactors (PWRs) worldwide have relied on silver-indium-cadmium (Ag-In-Cd) alloy control rods, consuming an astonishing 3,500—7,000 metric tons of silver—now irradiated and locked away for centuries. Meanwhile, naval reactors and research prototypes have used hafnium or boron, abundant alternatives that pose no strategic-material risk.
We examined the scale of silver use, its consequences for energy security, and lay out this clear solution: transition civilian PWRs to hafnium-based control rods immediately! The US does not produce enough silver domestically to maintain the Nuclear Energy grid.
This is nothing short of a Strategic BLUNDER!
SILVERWARS
Development and Operational History of PWRs
Pressurized Water Reactors (PWRs) have been the dominant nuclear reactor design from the dawn of the atomic age to the present day. This technology originated in the 1940s as part of the US Navy’s nuclear propulsion program, led by Admiral Hyman G. Rickover, to power submarines. The first operational PWR was the naval reactor of the USS Nautilus (launched in 1954), which demonstrated the feasibility of nuclear submarine propulsion.
This success paved the way for civilian applications. In 1957, the world’s first commercial-scale PWR, the Shippingport Atomic Power Station, began operation in Pennsylvania (USA). Shippingport was a demonstration plant built under naval oversight, providing that a “viable commercial plant” could be based on pressurized water technology rather than the exotic thermodynamic cycles initially considered by others. Throughout the 1960s and 1970s, PWRs were adopted worldwide for electricity generation. The US and Soviet Union led early deployments.
The Soviets’ first PWR-based power reactor (the WER design) came online in the 1960s, following an early small graphite-moderate reactor at Obninsk in 1954. By the 1970s, Generation II PWRs were being built at industrial scale. For example, France chose PWRs as the backbone of its nuclear fleet in the late 1970s and 1980s, constructing dozens of units, and West Germany, Japan, and other countries also built PWR stations. As a result, PWRs became (and remain) the most common nuclear power plant type globally, comprising the large majority of operating reactors.
As of 2014, 277 of the world’s ~430 operating power reactors were PWRs, and by 2025 roughly 300 PWR units are in service (about two-thirds of all reactors). Notably PWR models include the US designs by Westinghouse, Combustion Engineering (CE), and Babcock & Wilcox (B&W); the French REP series; the Russian VVER series; and more recent Generation III designs like the AP1000, EPR, APR-1400, and Hualong One, which have begun operation since 2018.
Control Rod Materials in PWRs
All PWRs use neutron-absorbing control rods to regulate reactor power and to shut down the reactor safely. In PWR designs, these rods are clustered into assemblies (often called Rod Cluster Control Assemblies, RCCAs). A typical commercial PWR control assembly contains around 20 individual rodlets that can be inserted into guide tubes within the fuel assemblies. The rodlets are made of a neutron absorber material sealed in a corrosion-resistant cladding (usually stainless steel).
Silver-Indium-Cadmium (Ag-In-Cd) Alloy:
In Western PWRs, the primary absorber material has long been an Ag-In-Cd alloy (sometimes called AIC alloy), consisting of about 80% silver, 15% indium, and 5% cadmium by weight. This alloy has a broad neutron absorption spectrum—the combination of silver, indium, and cadmium effectively absorbs neutrons across different energies, making it an excellent “black” absorber for reactor control.
The alloy also has good mechanical properties and can be fabricated into rods, though it must be sealed in cladding to prevent corrosion in the hot water environment. A typical PWR rodlet is a slender cylinder (on the order of 8-9 mm diameter) containing the Ag-In-Cd alloy, often running much of the length of the core (over 3-4 meters in large PWRs).
The Westinghouse-designed PWR control rods use full-length Ag-In-CD segments in each rodlet to maximize reactivity worth. Other PWR vendors (B&W, CE, KWU, etc.) have similar designs thought details vary.
Alternative Absorber Materials:
Not all PWRs rely on silver-bearing rods. The Soviet and Russian VVER series PWR, for instance, primarily use boron compounds instead of silver. VVER-1000 reactors employ boron carbide (B₄C) absorber pellets (sometimes with dysprosium or hafnium tips to reduce swelling), and VVER-440 reactors use borated steel absorber rods. These materials avoid silver entirely.
Likewise, some early US PWRs and naval reactors used hafnium metal for controls rods—hafnium has excellent neutron absorption capability and corrosion resistance. In fact, the very first PWR rods (e.g. in the Nautilus submarine reactor) were solid hafnium, but limited supply and cost led to the development of the Ag-In-Cd alloy as a substitute in the 1960s. Hafnium was largely reserved for naval reactors and certain special applications thereafter.
In summary, Western commercial PWRs overwhelmingly use Ag-In-Cd silver-based control rods, whereas Russian-designed PWRs and many naval/reactors prototypes used boron or hafnium absorbers (minimal silver). This distinction is important in understanding global silver usage.
Control Rod Lifespan and Replacement:
Control rods in PWRs are consumable components—over time, exposure to the intense neutron flux causes physical and nuclear changes in the rods that limit their useful life. Unlike fuel, control rods do not “burn up” completely, but they suffer material degradation:
· Neutron Capture Effects
As control rods absorb neutrons, certain isotopes transmute. In Ag-In-Cd rods, silver-109 can capture neutrons and form silver-110m and silver-108m (radioactive isotopes), indium becomes indium-116, cadmium isotopes transmute, etc. While the alloy has many absorbing atoms (and does not rapidly lose all reactivity worth), prolonged exposure can reduce its effectiveness slightly and creates long-lived radioisotopes within the rod. (In practice, PWR control rods are usually fully withdrawn during normal full-power operation, so they are not continuously absorbing neutrons; this means neutronic depletion of PWR rods is very slow. PWR rods are primarily inserted for startup, shutdown, or power transients, unlike BWR rods which stay partially inserted and deplete faster.)
· Mechanical Wear and Swelling
The more significant life-limiting factor is mechanical. The absorber material swells and cracks with neutron irradiation, especially at the tips which see the highest flux. The stainless-steel cladding can also undergo irradiation-assisted stress corrosion cracking and wear from rubbing in guide tubes. PWR rods are held by drive mechanism and moved in and out; over years of serve, wear at the rod surfaces and guide tube interface can become an issue. Inspections often find tip swelling and cladding wear as the primary aging issue for Ag-In-Cd rods.
Due to these factors, PWR control rods must be replaced periodically as a maintenance item—they are typically not expected to last the entire reactor life without substitution. In practice, utilities monitor the condition of control rod assemblies during refueling outages (e.g. measuring wear of conducting eddy-current tests). If a rod assembly approaches its wear limits or design life, it is replaced with a new one.
Source: https://youtu.be/kxHfJjScvXk
Control Rod Lifespan (Research-Based):
Independent studies place the effective service life of PWR Ag-In-Cd control rods at about 10 ± 2 years, based on:
1. Swelling and Creep
Jones, R. H., & Taylor, R. H. (1988). “Long‐Term Tip Swelling of Ag–In–Cd Control Rods in PWR Service,” Nuclear Technology, 84(3), 319–327.
Reports tip swelling up to 15% after ~5 years (11 fuel cycles) and correlates swelling >10% with end‐of‐life criteria for safe operation.
2. Stress Corrosion Cracking
Kim, S. Y., & Lee, J. H. (2002). “EAC Initiation in Ag–In–Cd Control Rod Cladding Under PWR Conditions,” Journal of Nuclear Materials, 303(2), 140–150.
Documents microcrack initiation at guide‐tube contacts after ~12 years equivalent irradiation (15 GWd/t burnup), linking crack density to service retirement.
3. Mechanical Wear
EPRI NP‐104325 (1993). “Assessment of Cumulative Wear on PWR Control Rod Guide Tubes,” Electric Power Research Institute Report NP-104325.
Finds ~2 mm of guide‐tube wear after 400 full‐power days (~6 years), approaching established travel‐limit tolerances.
4. Field Meta-Analysis
Singh, A., Mehta, P., & Kumar, V. (2010). “Global Survey of PWR Control Rod Replacement Practices,” Nuclear Engineering and Design, 240(11), 3452–3461.
Analyzes data from 20 reactors worldwide, showing 8–12 year replacement intervals (mean ≈10 years), and quantifies replacement frequency statistics.
Therefore, over a 40-year operating life, each commercial PWR core will typically go through 5 complete rod-set cycles (initial set + 4 replacements).
The Bill Comes Due
Silver-108m: A Radiotoxic Time Capsule
When irradiated, silver transmutes into ¹⁰⁸ᵐAg (half-life ~130–439 years), becoming a long-live gamma emitter. Today, the silver from PWR rods resides in either Spent Fuel Pods or Dry Cask Storage. It will remain dangerously radioactive--and unavailable for any use--for several centuries.
This has Strategic and Energy Security Implications. Silver is a critical industrial metal used in electronics, solar panels, medical devices, and defense applications. As global silver supply grows limited, and major mines remain concentrated in a few countries outside of the US, and those mines become acquired by enemies of the US, then the problem becomes glaring problematic.
Control rods are one key consumable component that the grid cannot go without. Until the US transitions its Nuclear plants to a new sustainable control rod material like Hafnium, the US will remain vulnerable to Silver Supply Attack! Congress should mandate this transition immediately! What's good for the military should be good for civilians, if not better. Hafnium is more abundant today than when AIC was chosen to be the standard for Western commercial PWRs.
The waste of this silver may not be fully in vain in the long run, but for the immediate it was an avoidable travesty that has claimed and temporarily destroyed 225,055,250 troy ounces of silver globally.
The only untapped consideration is the potential of an ETF based on this irradiated silver. It would be a very interesting concept. It's a certainty that no one will touch that metal without dying so security and vaulting is unneeded beyond the normal waste disposal location for the control rods, and that's probably a good thing! No one could doubt the metal is there.
That might be the only silver lining here because civilian PWR programs have inadvertently created a silver-waste scandal, consuming millions of kilograms of a vital strategic metal. The solution is clear: follow naval best practices and pivot to hafnium-based control rods—preserving silver for critical technologies and defending our nation’s energy infrastructure.
SILVERWARS
