India Nuclear News and Discussion 4 July 2011

[williams]

Just for fun - Can you answer this - without looking it up ..

Q.Which was the first princely state to declare its intention to remain independent in 1946 due to its strategic location and monopoly over monazite (a mineral rich in thorium)?
(a) Hyderabad
(b) Junagadh
(c) Kashmir
(d) Travancore

It definitely has to be in south India - so no Kahsmir or Junagadh. I am leaning towards Hyderabad or Travancore. Although I am not sure Hyderabad had any coastal territory.

[ernest]

Construction-ready, but full-scale deployment has been conservative due to regulatory and geopolitical caution.

construction ready, really? We really need to become energy independent. Do not understand why we are waiting, when China is blowing its trumpet on Thorium

Just for fun - Can you answer this - without looking it up ..

Q.Which was the first princely state to declare its intention to remain independent in 1946 due to its strategic location and monopoly over monazite (a mineral rich in thorium)?
(a) Hyderabad
(b) Junagadh
(c) Kashmir
(d) Travancore

Did Travancore really declare an intention to remain independent?

[Amber G.]

^^^A classic question in Indian modern history from UPSC ..

In 1946, Travancore was the first to declare its intention to remain independent rather than join India or Pakistan.

The strategic reason - Travancore had a monopoly over monazite, a mineral rich in thorium, which was seen as a valuable nuclear resource even back then.

The Dewan of Travancore, Sir C.P. Ramaswami Iyer, made the announcement, citing Travancore’s strategic importance and resource wealth.

This decision led to political tension with the Indian government, and after an assassination attempt on the Dewan in 1947, Travancore acceded to India.

(Monazite: A rare earth phosphate mineral containing thorium-232, which can be used to breed uranium-233)

.

[Amber G.]

A new legal architecture for nuclear power sector

The article argues for comprehensive legal reforms in India’s nuclear energy sector to boost investment, promote private and foreign participation, and facilitate the development SMRs .

The authors propose amendments to the Atomic Energy Act and CLNDA to align with international norms, clearly define liability limits, and open the sector to regulated private and foreign involvement. They stress that while the government must retain control over the nuclear fuel cycle, private entities should be allowed to build and operate reactors under strict oversight.

[Amber G.]

NuScale SMR gets approval:

NuScale Power’s Small Modular Reactor (SMR) Achieves Standard Design Approval from U.S. Nuclear Regulatory Commission for 77 MWe

NuScale remains the only SMR technology company to have received approval from the NRC for its SMR technology design; today’s announcement marks NuScale’s second design approved by the United States’ nuclear regulator


CORVALLIS, Ore., May 29, 2025--(BUSINESS WIRE)--NuScale Power Corporation (NYSE: SMR), the industry-leading provider of proprietary and innovative advanced small modular reactor nuclear technology, today announced that it has received design approval from the U.S. Nuclear Regulatory Commission (NRC) for its uprated 250 MWt (77 MWe) NuScale Power Modules™.

The U.S. NRC’s uprate approval of the NuScale SMR technology now strengthens ENTRA1 Energy to produce and deliver energy as the most near-term American SMR power solution via ENTRA1 Energy Plants™ with NuScale SMR technology inside. ENTRA1 Energy is NuScale’s partner and independent power plant development platform, which holds the global exclusive rights to the commercialization, distribution, and deployment of NuScale’s SMRs.


The uprate approval by the U.S. regulatory authority increases the power output per module from NuScale’s previously-approved 50 MWe design, enabling ENTRA1 Energy Plants to provide a wider range of off-takers and consumers with reliable, carbon-free energy. NuScale remains the only SMR technology company with design approval from the NRC, and the company remains on track for deployment by 2030.

"We are thrilled that the NRC has approved our second SDA application, this time for our 77 MWe design. This marks a historic moment not only for NuScale, but the entire industry, as NuScale and ENTRA1 move closer to meeting the demands of clean energy users," said John Hopkins, NuScale President and Chief Executive Officer. "For more than a decade, our team has proudly worked alongside the NRC to achieve the successful approval of our designs. The NRC is domestically and internationally recognized and respected for its rigorous safety standards, and this approval is a crucial step toward meeting our goal of providing clean, reliable, and, most importantly, safe energy to off-takers and consumers."


NuScale’s first Design Certification Application (DCA) for its 160 MWt (50 MWe) SMR design was accepted by the NRC in March 2017. Subsequently, the NRC affirmed its approval of NuScale’s 50 MWe SMR design, marking the first design to receive its approval.

NuScale’s uprated design features the same fundamental safety case and passive safety features previously approved by the NRC with a power uprate and select design changes to support growing capacity needs. Originally slated for approval later this summer, today’s announcement marks the early completion of the NRC review process.

---
NuScale’s SMR tech, just approved again by the U.S. NRC, is clearly aimed at the American market—but there are definitely takeaways here for India. From a technical standpoint, a modular 77 MWe design like this makes a lot of sense for India. It fits well with India's ambitions to bring clean energy to remote areas and reduce emissions in hard-to-abate sectors like industry and transport.

That said, (FWIW - My take) India has some real hurdles to adopting something like NuScale’s design outright. Our current laws only allow government-owned entities to run nuclear plants, and the supplier liability rules are still a sticking point for foreign tech providers. But if those issues can be worked through—maybe via a joint pilot project or study under the U.S.-India nuclear agreements—I think there’s real potential. Even if India ultimately builds its own SMRs, learning from NuScale’s experience could help us get there faster and more cost-effectively.

[drnayar]

^^^A classic question in Indian modern history from UPSC ..

In 1946, Travancore was the first to declare its intention to remain independent rather than join India or Pakistan.

The strategic reason - Travancore had a monopoly over monazite, a mineral rich in thorium, which was seen as a valuable nuclear resource even back then.

The Dewan of Travancore, Sir C.P. Ramaswami Iyer, made the announcement, citing Travancore’s strategic importance and resource wealth.

This decision led to political tension with the Indian government, and after an assassination attempt on the Dewan in 1947, Travancore acceded to India.

(Monazite: A rare earth phosphate mineral containing thorium-232, which can be used to breed uranium-233)

.

I am from that erstwhile state ., its not just monazite., the Travancore Titanium Products was established in 1946 .. my uncle was a chief engineer in that enterprise

TTP has also been producing certain strategic rare earths materials used in nuclear and aerospace industries [ esp cerium, lanthanum, and yttrium ] for several decades now.

[ https://indianexpress.com/article/resea ... s-7767241/
The narrative as presented by the makers of Rocket Boys does shed light on the lesser-known story of Travancore’s Thorium reserves and its bid for independence. It is also true that Nehru along with Shanti Swaroop Bhatnagar and Homi Bhabha did have to negotiate and convince the Travancore state to hand over access to its monazite reserves. ]

[Amber G.]

^^^A classic question in Indian modern history from UPSC ..

In 1946, Travancore was the first to declare its intention to remain independent rather than join India or Pakistan.
<snip>
The strategic reason - Travancore had a monopoly over monazite, a mineral rich in thorium, which was seen as a valuable nuclear resource even back then.

I am from that erstwhile state ., its not just monazite., the Travancore Titanium Products was established in 1946 .. my uncle was a chief engineer in that enterprise

TTP has also been producing certain strategic rare earths materials used in nuclear and aerospace industries [ esp cerium, lanthanum, and yttrium ] for several decades now.

[ https://indianexpress.com/article/resea ... s-7767241/
The narrative as presented by the makers of Rocket Boys does shed light on the lesser-known story of Travancore’s Thorium reserves and its bid for independence. It is also true that Nehru along with Shanti Swaroop Bhatnagar and Homi Bhabha did have to negotiate and convince the Travancore state to hand over access to its monazite reserves. ]

Thank you so much for adding that valuable context! It's fascinating to hear from someone with a personal connection Most people don't realized the extent to which TTP contributed to processing other rare earth elements like cerium, lanthanum, and yttrium, which are indeed critical in modern strategic technologies.

You're absolutely right — while monazite and thorium get much of the spotlight, the broader industrial and scientific infrastructure in Travancore played a key role in why the region was so strategically significant. The fact that Nehru, Bhabha, and Bhatnagar had to negotiate access underscores how crucial those resources and capabilities were to India's early scientific ambitions.

Thanks again for sharing this.

---

FWIW Let me add
Travancore’s coastal sands, especially around regions like Chavara and Manavalakurichi, are rich in heavy mineral deposits that include several rare earth elements (REEs) and strategic materials. Beyond thorium (from monazite), here are some of the other key rare earths and minerals.

- Ilmenite (source of titanium)
and Zircon (Crucial in nuclear reactors for cladding fuel rods)

Kerala and Tamil Nadu coastal sands are significant sources.

Cerium,
Lanthanum( used in hybrid car batteries -like those in the Toyota Prius
Yttrium (Used in LEDs, superconductors, lasers etc).
Neodymium
etc..
---
From what I think - Today India manages its rare earths with strategic focus and national security. While it hasn’t yet scaled to match China, India is laying the groundwork for a more secure, indigenous supply chain — especially vital as global demand for REE's.and Heavy rare earths (HREEs).(Our goal is to compete with China's dominance in rare earth processing) .. I posted about this earlier in BRF (There are many details - worth reading for anyone interested)

Links:
- <Brf post 1>

and few posts later:
<Brf post 2
viewtopic.php?p=2635210#p2635210

[KL Dubey]

Travancore-Cochin (the lands of my great ancestors) have come a long way, with many cutting edge technologies being practiced due to Bharat sarkar - ranging from aircraft carriers to space exploration to supersonic missiles. Additionally the provision of nukular fuels. Remove the commie-jihadi mentality from these lands, and it will truly be gods own kandry again.

[A_Gupta]

Just for fun - Can you answer this - without looking it up ..

Q.Which was the first princely state to declare its intention to remain independent in 1946 due to its strategic location and monopoly over monazite (a mineral rich in thorium)?
(a) Hyderabad
(b) Junagadh
(c) Kashmir
(d) Travancore

And at which Jawaharlal Nehru lost his temper and advocated military action?

[A_Gupta]

Answer:
https://arunsmusings.blogspot.com/2006/ ... e.html?m=1

[Amber G.]

^^^ Interesting learnings from last question..thanks..
FWIW: Again

Just for fun — Can you answer this without looking it up?:

Q1 Which Indian physicist, played a key role in applying nuclear physics to national planning, and was instrumental in the early conceptualization of India's atomic energy program — before Homi Bhabha formalized it?

(a) D.M. Bose
(b) K.S. Krishnan
(c) D.D. Kosambi
(d) M.N. Saha


Q2. In the early days of Indian nuclear development, thorium was considered a long-term strategic asset. Which reactor design was explicitly developed to utilize thorium in a closed fuel cycle?

(a) PHWR (Pressurized Heavy Water Reactor)
(b) AHWR (Advanced Heavy Water Reactor)
(c) FBTR (Fast Breeder Test Reactor)
(d) CANDU

Q3 - A coastal region in India is famous for its black sand beaches rich in monazite, leading to naturally high background radiation. In fact, in some houses there, the annual radiation measured exceeds 50 millisieverts.

Using Amber G.’s favorite unit BED -“Banana Equivalent Dose”- (Popularized in BRF, and quite often used in other places now) approximately how many bananas per year would give you the same dose as living in one of those homes?

(a) 5,000
(b) 50,000
(c) 500,000
(d) 5,000,000,

(Bonus question: “How many bananas would it take to trigger an airport radiation detector?” (A real anecdote once shared on BRF!)

And the last one;

Q4 - A Brfoldie of Bharat Rakshak once posed a puzzle: A uranium sample with 3% U-235 is enriched for reactor fuel. Which of the following enrichment levels is closest to the minimum required for light water reactors?
(a) 0.7%
(b) 3-5%
(c) 20%
(d) 90%

(Comments welcomed .. )

[Tanaji]

Without looking :

Q1: either a or b. Saha was an astrophysicist and Kosambi was a mathematician I think

Q2: FBTR as the ahwr came later. CANDU was the first design from Canada and PHWR is a generic term. Fast breeders are required to build up the seed stock of Pu so that it can be used in the later stages?


Q3 - 5000

Q4 - b 3% i think

[Amber G.]

Tanaji Thanks I will post my comments some time later..

Meanwhile reliance-adani-railways-greenko-vedanta-hmel-jsw-group-hindalco-npcil-small-nuclear-reactor-project-
Summary:
- Reliance Industries, Adani Group, Rail Vikas Nigam Limited (RVNL), Greenko, Vedanta, JSW Group, Hindalco, and NPCIL are among the companies exploring opportunities in India's rail and nuclear energy sectors.
- key points:
RVNL is working on railway projects, while companies like Greenko and JSW Group are focusing on green energy.
NPCIL plans to set up small nuclear reactors.
Reliance Industries and Adani Group are also investing in various projects, including energy and infrastructure.

[Amber G.]

Without looking :
Q1: either a or b. Saha was an astrophysicist and Kosambi was a mathematician I think

Thanks. (After seeing your answer, I realized my question might have been a little imprecise )..

Q was:

Q1 Which Indian physicist, played a key role in applying nuclear physics to national planning, and was instrumental in the early conceptualization of India's atomic energy program — before Homi Bhabha formalized it?

(a) D.M. Bose
(b) K.S. Krishnan
(c) D.D. Kosambi
(d) M.N. Saha

Correct Answer: (d) Meghnad Saha — but K.S. Krishnan also deserves partial credit for his later institutional role.


Short Answer & Perspective (from a physics-savvy lens):
Let’s be honest — both Saha and Krishnan made major contributions, but in different phases. So depending on what you mean by “key role” and “early conceptualization,” Saha takes the crown — but Krishnan wasn’t far behind when it came to building the actual system.

Why Saha Wins (for this question):

Meghnad Saha was talking about atomic energy in the 1930s–40s, before most people in India even knew what a nucleus was.

He saw science — including nuclear power — as essential to national development.

He pushed hard for state-led planning, wrote extensively on using science for public good, and even served in Parliament doing exactly that.

So while he wasn’t running labs, he was laying the intellectual groundwork and urging political investment.

Krishnan’s Timeline — and Real Contribution:

K.S. Krishnan came into the atomic energy picture more after Independence, late 1940s and 1950s.

He was co-discoverer of the Raman effect, had a strong background in experimental physics (solid-state, magnetism).

He joined the Atomic Energy Commission (AEC) and helped build its institutional base.

Nehru briefly considered him to head the atomic effort, but chose Bhabha instead.

So yes — Krishnan helped implement, but Saha was already conceptualizing.

D.M. Bose - Early nuclear research (cosmic rays), mentor to Bibha Big contribution in science and Mentoring but - limited role in planning and (politics, so less well known)
D.D. Kosambi - Very famous Mathematician (and Marxist historian); strong in planning, theory, but not involved in nuclear..

How Bhabha Overshadowed Saha and others :

Bhabha had charisma, Tata family connections, and Nehru’s trust.

He wrote the famous 1944 letter to the Tata Trust asking for support — and got it.

That led to TIFR, which became the nucleus (pun intended) of India’s atomic energy program.

While Saha stayed outside the Bhabha-Nehru institutional circuit, Bhabha got full control of the program by the late 1940s.

Atomic Energy Leadership Timeline (Simplified) (For interested people here):

- 1930s–40s Saha Advocated atomic energy in national development
- 1944 Bhabha Proposed atomic program to Tata Trust (via letter)
- 1945 TIFR founded Bhabha becomes de facto leader
- 1948 AEC created Bhabha leads; Krishnan joins commission
- 1950s Bhabha + Krishnan Build institutions and research programs
- 1960's-70's - Many young people (like me and institutes (including IIT's) - became interested in Nuclear Physics and Bhabha's vision )

If the question is about who first brought nuclear physics into the national planning conversation, (d) Meghnad Saha is the clear answer.

But if you're grading generously, K.S. Krishnan deserves a solid partial credit for helping turn the vision into a system — post-Bhabha, but still critical.

Comment on this (and other Q's welcome - I will post my thoughts also)

[Amber G.]

Q2: FBTR as the ahwr came later. CANDU was the first design from Canada and PHWR is a generic term. Fast breeders are required to build up the seed stock of Pu so that it can be used in the later stages?

My comments:

Q2. In the early days of Indian nuclear development, thorium was considered a long-term strategic asset. Which reactor design was explicitly developed to utilize thorium in a closed fuel cycle?

(a) PHWR (Pressurized Heavy Water Reactor)
(b) AHWR (Advanced Heavy Water Reactor)
(c) FBTR (Fast Breeder Test Reactor)
(d) CANDU
Answer: (b) AHWR (Advanced Heavy Water Reactor)

Explanation:
India's Advanced Heavy Water Reactor (AHWR) is designed specifically to use thorium-232 as a fertile material, which is converted into fissile U-233. This is the third stage of India’s nuclear roadmap. While PHWRs and CANDUs use natural uranium, AHWR is part of India’s thorium strategy.

---
-Context & Reactor Comparison:

(a) PHWR Stage-1: Uses natural uranium (No use of Thorium directly) Produces plutonium for Stage-2
(b) AHWR Stage-3: Thorium-based (Uses Thorium) Designed for thorium-uranium-233 cycle
(c) FBTR Stage-2: Plutonium breeder (Use indirect Th) Breeds U-233 precursor fuels; not optimized for thorium
(d) CANDU Canadian design, basis for Indian PHWRs (No use of Th) India adapted it but not thorium-specific

India’s 3-Stage Nuclear Plan (in brief):
Stage 1: PHWRs use natural uranium → produce plutonium-239.

Stage 2: Fast Breeder Reactors use plutonium to breed U-233 or more plutonium.

Stage 3: AHWR-type reactors use thorium-232, which absorbs a neutron and becomes U-233, a fissile fuel — enabling a closed thorium cycle.


So while PHWRs and FBTRs are stepping stones, only (b) AHWR was explicitly designed for direct thorium utilization in a closed cycle. It’s the culmination of Homi Bhabha’s long-term vision for India’s energy independence.
(I did this summary many years/decades ago too - Hope this helps and useful)

[Tanaji]

No fair AmberG , I deserve at least partial credit for Q2. FBTRs are an explicitly required step for thorium cycle as we never had enough Pu stock required for step 3. I guess I misunderstood the question, now that you explained it.

[drnayar]

Q2. In the early days of Indian nuclear development, thorium was considered a long-term strategic asset. Which reactor design was explicitly developed to utilize thorium in a closed fuel cycle?

(a) PHWR (Pressurized Heavy Water Reactor)
(b) AHWR (Advanced Heavy Water Reactor)
(c) FBTR (Fast Breeder Test Reactor)
(d) CANDU
Answer: (b) AHWR (Advanced Heavy Water Reactor)

Explanation:
Stage 3: AHWR-type reactors use thorium-232, which absorbs a neutron and becomes U-233, a fissile fuel — enabling a closed thorium cycle.


So while PHWRs and FBTRs are stepping stones, only (b) AHWR was explicitly designed for direct thorium utilization in a closed cycle. It’s the culmination of Homi Bhabha’s long-term vision for India’s energy independence.
(I did this summary many years/decades ago too - Hope this helps and useful)

are there any operational thorium based reactors in india ?

[Amber G.]

^^^ No thorium-based commercial reactor is yet producing power in India.
- KAMINI uses U-233 from thorium, but is only for research.
- The AHWR, a key to Stage 3, remains under development.

For Kamini - Fuel - U-233, bred from thorium (NOT thorium itself as the fuel). It is a 30kW research reactor used for research, isotope production, and validation of thorium fuel cycle. AFAIK it is the only reactor in the world running on U-233, bred from thorium.

For AHWR is planned / under Development, designed by BARC.
-Fuel: (U-233/Th) + some LEU or Pu as driver fuel
- Construction has not yet begun on a full-scale AHWR but BARC has completed the design and experimental validation.

[drnayar]

Thank you Amberji. Google was just saying no !

[Amber G.]

No fair AmberG , ... FBTRs are an explicitly required step for thorium cycle as we never had enough Pu stock required for step 3....

Tanaji (and others) Thanks. Such comments are welcome!

So some comments..

India’s thorium approach is unique in its scale, ambition, and systematic design — it also faces delays and challenges.

Compared to others India is the most committed nation to building a thorium-based nuclear economy, but others (like China) are catching up with different approaches.

India’s Core Philosophy:
Based on Homi Bhabha’s 3-stage nuclear power program (1950s), which strategically integrates:

Natural uranium → energy + plutonium

Plutonium in fast breeder reactors → energy + U-233 from thorium

U-233 + thorium reactors for sustained energy

(India has ~25% of the world’s thorium reserves (monazite-rich sands, esp. in Kerala and Tamil Nadu but limited uranium resources → energy security depends on eventually unlocking thorium)

Stage 1: PHWRs (like Tarapur, Kaiga, etc.) – done

Stage 2: PFBR at Kalpakkam – still delayed

Stage 3: AHWR (Advanced Heavy Water Reactor) – designed, but not built yet

Also: KAMINI is a small-scale U-233-based research reactor

Global Comparison:
China: (See some posts in BRF)
Built a 2 MWt thorium-based molten salt reactor (MSR) in Gansu in 2021

First nation to build and test a working thorium MSR

Plans to scale up to larger commercial MSRs

9Not following a Bhabha-style 3-stage plan, but more engineering-focused, experimental, and modular0

Norway:
Thor Energy tested thorium fuels in conventional LWRs
( fuel-cycle safety and behavior, not full thorium economy)

USA:
Some research in universities (e.g. ORNL historically)
Startups like Flibe Energy and ThorCon developing thorium-based MSR designs
= little government commitment/interest (has plenty of U and existing tech so no need), and no commercial thorium use.

Russia:
Researched thorium fuels in fast reactors and VVERs
Focus remains more on uranium-plutonium MOX and fast breeders

[A_Gupta]

@Amber G -- any comments on this MIT Tech Review article?
https://www.technologyreview.com/2025/0 ... echnology/

A long-abandoned US nuclear technology is making a comeback in China

A thorium-fueled reactor is the latest idea being revived after getting shelved in the mid-20th century.
By Casey Crownhartarchive page
May 1, 2025

[gakakkad]

^ we had pages and pages of discussion on this a decade ago. It is supposed to be a safer design .

[Amber G.]

@Amber G -- any comments on this MIT Tech Review article?
https://www.technologyreview.com/2025/0 ... echnology/

A long-abandoned US nuclear technology is making a comeback in China

A thorium-fueled reactor is the latest idea being revived after getting shelved in the mid-20th century.
By Casey Crownhartarchive page
May 1, 2025

Great article. Long reply. (Hoping to make BRF a resource - ignore if not interested in details).

This article MIT Tech Review: A long-abandoned US nuclear technology is making a comeback in China brings back some old memories and thoughts. I’ve long followed thorium research—including the early US work at Oak Ridge—and it’s interesting to see China now trying to resurrect molten salt reactors (MSRs) from those 1960s experiments.

(Summary of the article: China is reviving an old U.S. thorium reactor concept—particularly molten salt reactors (MSRs)—and is now pushing forward where the U.S. stepped back in the mid‑20th century. The article underscores why thorium and MSRs have both promise and challenges.)

I'm repeating many parts below as this topic has been discussed here previously. I've given my thoughts in detail in previous posts (see below), which may be useful.

India-watchers might find this particularly relevant. As many here know, thorium has always been central to India’s long-term nuclear vision. Our three-stage nuclear program was practically designed around this:

Stage 1 – PHWRs using natural uranium

Stage 2 – Fast Breeder Reactors (FBRs) producing plutonium

Stage 3 – Thorium reactors (like AHWRs), producing and burning U-233 from Th-232

BARC, IGCAR, and others have done solid groundwork here. The upcoming Prototype Fast Breeder Reactor (PFBR) at Kalpakkam is a key stepping stone toward making thorium reactors viable.

Some similar points especially detials of China strategy were also discussed in older BRF threads—see these links for those interested:
-
→ Molten Salt Reactor vs PHWR: Technical Tradeoffs (and few posts near)
→ BRF Thread: India’s Thorium Vision )Many threads dealing with India Thorium anfd MSR etc
Also viewtopic.php?p=2626178&hilit=Thorium#p2626178 and other posts around there..

From one such discussion:


“What are the benefits of their proposed MSR over traditional PHWR-like designs? I've heard from some online discussions that MSR is the favored design for the future, and we should pivot to it. Is it just online gossip, or is there some substance to it?”

My two paise.

MSR vs PHWR
Our current PHWRs (220 MWe / 700 MWe) are optimized around natural uranium, heavy water moderation, and batch fuel cycles. They’re robust, Indianized, and well understood.

MSRs, by contrast, offer intriguing possibilities:

Higher efficiency: They operate at higher temperatures and lower pressures—better thermodynamics, and potentially cheaper containment.

Fuel flexibility: They can (in theory) use U, Pu, or even thorium dissolved in molten salt.

Online reprocessing: Some designs allow fission product removal during operation—better fuel burn-up.

Safety: Passive safety due to low pressure and freeze-plug-based dump tanks.

That’s why some online communities hype MSRs as “the future.” And honestly—there is some substance behind the buzz. The U.S. (TerraPower, ORNL), China (as this article shows), and EU consortia are all investing real R&D money into MSRs. Even BARC has published work on molten salt concepts and thorium salt cycles.

BUT… let’s not forget: India’s strength today lies in mature PHWRs. The entire ecosystem—manufacturing, regulation, personnel—is tuned for PHWRs and FBRs. MSRs would require a ground-up build of fuel supply, materials science (think: corrosion in hot fluoride salts), reprocessing pipelines, and safety culture.

MSRs could be a long-term goal. But pivoting too fast would derail the hard-earned progress of our staged roadmap. So IMO, for the next couple decades, PHWR + FBR → AHWR remains the right sequence.

Reprocessing

“Is reprocessing in MSRs more complicated due to constant mixing of fuel and fission products?”

Exactly. In PHWRs, you unload sealed bundles after burnup, then reprocess them offline. In MSRs, everything is already in molten form. Fission products and actinides are mixed in the salt. So to keep the reactor running, you need online chemical separation of xenon, krypton, lanthanides, and actinides—all while the reactor is operating. It’s elegant on paper… brutal in engineering.

China may have the political capital to attempt this at scale—but let’s see how far they go beyond testbeds.

In India’s context to summarize:

India’s thorium roadmap is different from China’s “resurrect and leap” approach. We’re playing the long game: from uranium to plutonium to ^233U—then thorium. The PFBR is loading core now. The AHWR, though delayed, is meant to validate the closed thorium fuel cycle.

If China’s MSR gambit pays off—great! Maybe we’ll adapt those lessons later. But for now, India’s staged model is scientifically solid, regulatorily safe, and aligns with our resource realities.

India has the thorium, the tech base, and the vision. What it needs is time, sustained funding, and engineering execution.

(Amber G.)

[Tanaji]

Thanks AmberG. A noob question, you say:

Stage 3 – Thorium reactors (like AHWRs), producing and burning U-233 from Th-232

Doesnt the AHWR take a fuel bundle of Th-232 and UO2 MOX and PuO2 and Th-232 MOX? Why is Pu used in addition to U233 in the fuel bundle? Is it for breeder purpose i.e to get back U233 in the end? Does that affect efficiency of the reactor?

[Amber G.]

^^Tanaji --
Yes, Pu is used partly to breed more U-233 from Th-232—but also to provide startup reactivity and sustain the chain reaction efficiently, especially when there’s not yet enough U-233 available.

Detailed reasoning:
- U-233 supply is limited at startup
(India doesn't yet have large stockpiles of U-233—it’s still being bred in pilot-scale reactors (like KAMINI or eventually the PFBR).

So, to start the AHWR, we need an external fissile material, and Pu-239 from the fast breeder program is the most available candidate.
Pu-239 provides necessary neutron economy
(Pu-239 is a strong fissile material, with a high neutron yield.)
(These neutrons are used to sustain fission and convert Th-232 into U-233 via neutron capture)

BUT AHWR can be loaded with a mixture Multiple fuel types → (flexibility & sustainability)
Th-232 + Pu-239 MOX (for breeding U-233)
Th-232 + U-233 (for sustaining once U-233 is available)
Pu-based MOX (for using surplus Pu from FBRs and PHWR spent fuel)

- Eventually, the goal is to transition to U-233/Th-232 only


But until then, Pu serves as the "starter fuel" and helps bootstrap the system.


Neutron economy: Pu-239 has a good neutron yield, but U-233 is actually slightly better in thermal reactors. However, breeding and handling U-233 is more complicated.

So yes, using Pu affects reactor characteristics, but not necessarily negatively. It's a trade-off between practical feasibility and long-term optimization.

Summary
- AHWR uses Pu along with Th-232 and U-233 to:
-Start the chain reaction before U-233 is widely available
-Breed more U-233 from Th-232 in situ
-Make use of India’s existing Pu stockpile from PHWRs and FBRs

Once enough U-233 is available, future AHWRs can move toward pure Th-232 + U-233 fuel, reducing waste and improving sustainability.

This makes the AHWR a very flexible transition-stage reactor—bridging our current plutonium-rich fuel cycle with the future thorium-based vision.

[vera_k]

Would the AHWR be a SMR (small modular reactor) like what's described as a SMR here?
What are Small Modular Reactors (SMRs)

[Amber G.]

Would the AHWR be a SMR (small modular reactor) like what's described as a SMR here?
What are Small Modular Reactors (SMRs)

Good Q! As said before. My take:

Technically, AHWR is not an SMR in the way IAEA defines it (i.e., under 300 MWe and modular/factory-built). AHWR is designed for ~300 MWe, so it just touches the upper SMR boundary—but it’s not modular or designed for mass factory production like the newer Gen IV SMRs (NuScale, etc.).

That said, AHWR does share some SMR features: passive safety, small core size, high safety margins. But it's more of a “mid-size advanced reactor” tailored to India’s thorium roadmap—not the plug-and-play SMR the article talks about.

[vera_k]

Thanks.
Is the AHWR expected to scale to a higher capacity?
If it stays small, are there technical hurdles in terms of safety or proliferation resistance to designing it as a SMR instead?

[Amber G.]

Just posting it here: (I am following Iran's nuclear events here just for records and learnings0
Israeli intends to target Iran's Arak heavy water reactor, after issuing a warning for residents of the nearby cities of Arak and Khondab in central Iran to evacuate for their safety.

[Amber G.]

Thanks.
Is the AHWR expected to scale to a higher capacity?
If it stays small, are there technical hurdles in terms of safety or proliferation resistance to designing it as a SMR instead?

FWIW (My take - simple short answer) Yes, AHWR is designed at 300 MWe, scalable in principle, but not as small as typical SMRs.
If redesigned smaller, safety remains excellent, but thorium/U-233 raises unique proliferation challenges (among other technical challenges) — needing clever design (like denaturing) to stay secure.

[Tanaji]

The professor sahib is slacking off in other threads and not marking submitted homework ….

[VinodTK]

Seeing as to what is happening in Iran and the need for heavy conventional bombs; India needs to build, test, and deploy danced variants of Gaurav; The current variant of Gaurav Long‑Range Glide Bomb is India’s heaviest conventional bomb to date, manufactured indigenously by DRDO.

• Weighs: approximately 1 000 kg
  Length: stretches 4 m long
  Glides: up to 100 km toward targets
  Precision: High