Despite KNOWING UK's Current SSN Reactors Leaked Radiation UK Chose to rely on Cheaper Computer Testing

I'd like to feature a comment of July 15, 2026, from a possibly new Anonymous:

"I'm not a nuclear engineer but I think the problems with the PWR2 reactor started with cost cutting back in the early 1990s. Previously (PWR1) the UK had built a prototype reactor at Dounreay to check performance and safety. 

For PWR2 this was replaced by using computer simulations instead. See https://www.bbc.com/news/uk-scotland-highlands-islands-51927359

This failed to detect problems with potential cracking on the coolant pipes, which could create a critical failure. This can be combatted with a lot of maintenance effort and full replacement of the pipes during full cycle maintenance. But that is a lot of work - years - each time.
https://www.rusi.org/explore-our-research/publications/commentary/uks-naval-nuclear-reactors-ageing-ungracefully
It seems to be taking all the RN's technical resources to do that for the Vanguard SSBNs. There is not enough left to do Astutes as well, since Vanguard SSBNs appear to have been prioritised.

In my view PWR2 has turned out to be a faulty reactor design."

Pete Comment

Supporting Anonymous' comment above - there was reliance on subsequent computer simulations even though Rolls Royce and the UK Ministry of Defence were aware of nuclear leaks from physical onshore testing.

[An onshore test version of PWR2, was] housed in the [Dounreay's] Shore Test Facility (STF), commissioned in 1987, and went critical with the PWR2's Core G the same year...In January 2012, radiation was detected in the reactor's coolant water, caused by a microscopic breach in fuel cladding. This discovery led to HMS Vanguard being scheduled to be refuelled and contingency measures being applied to other Vanguard and Astute-class submarines, at a cost of £270 million, before similar problems might arise on the submarines. This was not revealed to the public until 2014.^[2][7]

Even though physical testing at Dounreay had revealed serious radiation leaks the UK decided to end further onshore physical testing and instead decided to rely on cheaper computer simulations. 

The Australian Government has committed over A$5 billion in direct investments to expand the UK's Rolls-Royce industrial base and procure critical components for the PWR3 reactors that will power Australia’s future fleet of SSN-AUKUS submarines.

Australia should seriously consider whether it should spend additional $Billions paying for the UK's faulty submarine reactor "SAFETY" regime.

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For further related details see my:

"No UK Astutes Available Again! Safety Fears Demand Lengthy Repairs" of June 8, 2026 at https://gentleseas.blogspot.com/2026/06/no-uk-astutes-available-again-safety.html 

and my "AUKUS Failing TWO - UK cannot deliver on the SSN-AUKUS project" of June 23, 2026 at https://gentleseas.blogspot.com/2026/06/aukus-failing-two-uk-cannot-afford-ssn.html 

Also see a semi-paywalled 2011 UK Guardian article  at https://www.theguardian.com/world/2011/mar/10/royal-navy-nuclear-submarine-reactor-flaws and

a 2014 BBC article at https://www.bbc.com/news/uk-politics-26463923