The NCG’s overall strategy was framed to suit the RF approach by:
• Establishing the datum condition of the Kursk taking into account the effects of the explosions and the degradation over a year of submersion.
• Examining the stability and residual strength of the datum condition, including the degree of defense in depth that might remain available for the essential reactor safety functions.
• Framing limits and conditions for the M-S operations to ensure that the residual strength and stability criteria could not be exceeded, nor the defense in depth totally undermined, together with allowance for unwanted interactions.
• Ensuring that there was an adequate radiological safety management regime in place to protect the M-S employees and contractors.
In light of this, the NCG set out to work with teams of RF specialists to check how each system had been and could be affected by events and thus establish the limits and conditions that had to be maintained during the M-S recovery operations. The actual and potential interactions of the many systems involved warranted a strong probabilistic evaluation but this was not favored nor, indeed, practiced by the RF for its own assessment. Instead, the approach of RF analysts and engineers was, predominantly, underpinned by reliance upon passive safeguards (e.g. containment, dormancy, etc.) for which probabilistic treatment is anyway not usually necessary. However, this reliance required, first, an accurate and reliable assessment of each ‘safeguard’, particularly the extent to which it may have sustained damage as a result of the original explosions and, then, an account of the degradation that it may have suffered over the year or more that it was submerged in the Barents Sea. Of particular concern to the NCG was the possibility of the M-S operations triggering a further explosion (of a torpedo or missile), and the potential consequences to the reactor plant and safeguards.
On one hand, all that the RF could offer was its assertion and confidence that the M-S salvage of the Kursk could be undertaken within the RF’s sometimes rather qualitatively defined limits of each of the ‘safeguards’ but, on the other hand, its engineers and technicians were enthusiastically responsive to any demands placed upon them by the NCG, often responding in detail once trust had been established, and explaining their sometimes brilliantly simple solutions to problems, as they were identified.
In the light of this, the NCG had to conclude that it was not in a position to provide a traditional assessment or review but, instead, had to weigh these RF statements to assess whether, when put together, they provided a sufficiently coherent and persuasive safety demonstration. In doing this, the NCG had to rely largely on its own judgment and experience.