This 2006 report about the UK’s historical production of defense HEU describes issues concerning HEU production records:

This review has been conducted from an audit of annual accounts and the
delivery/receipt records at sites. A major problem encountered in examining the records was that a considerable number had been destroyed for the early years of the programme. There is only a legal requirement for the companies to keep such records for 30 years. In some cases older records were destroyed when they reached this age. There is a greater awareness now of the need to keep these records and this past practice has now been stopped, but too late for the purposes of this review. The task of locating early records was intensive and great efforts were made by all concerned to locate corroborating older records, but the search cannot claim to be comprehensive.

–Even where records have survived other problems have been encountered, including:

–not all records differentiated between civil and military production, so assessments had to be made of the ultimate destination. This was complicated by the fact that HEU produced at Capenhurst subsequently went to Windscale for processing before onward movement to the final customer, making distinction between new make and recycled HEU difficult

–some early records make no specific mention of waste and effluent disposals

–some records lacked the precision now required; no units of mass identified, or were
difficult to decipher, against the quantities, and consequently assessments had to be made to establish units. Other records did not identify quantities to decimal places and may have been rounded. As individual figures this may be acceptable but when accumulated into total quantities it can produce inaccuracies in final figures

–in some cases no indication of enrichment value was available. Average figures were used, or knowledge of the process used to assure that the material was indeed HEU

–changes in the structure of the contractors have presented difficulties in tracing
documentation It also has to be borne in mind that instrumentation and measurement techniques were not as accurate in the early years as they have become over the past 20 years or so

The 1956 U.S. heavy-water supplyagreement may be found here.

Here is a 1992 UN report titled South Africa’s Nuclear-Tipped Ballistic Missile Capability.

From IFP. See IR-8 centrifuges.

I love history, and I always like primary sources. In 2008, CSIS published these audio files of interviews with key players in US-UK nuclear cooperation.

This just never gets old. From Protect and Survive:

After a nuclear attack, there will be a short period before fall-out starts to descend. Use this time to do essential tasks.

Nor groundbreaking, but I think it’s worth highlighting this Chinese statement to the CD:

Emphasizing his delegation’s support for the total elimination of nuclear weapons, he said China is committed to not being the first to use them, threaten their use, or use them against non‑nuclear‑weapon States. However, the disarmament process must be gradual and enjoy consensus among all stakeholders, he stressed…. China supports the drafting of a fissile material cut‑off treaty in the Conference on Disarmament, he said.

Here are selected matters of which the UNSC is seized:

Small arms (24 September 1999; 5 February 2020).

Non-proliferation of weapons of mass destruction (22 April 2004; 27 September 2021).

Non-proliferation (29 March 2006; 30 June 2021)

Threats to international peace and security caused by terrorist acts (12 September 2001; 19 August 2021).

Non-proliferation/Democratic People’s Republic of Korea (14 October 2006; 11 December 2019).

The India-Pakistan question (6 January 1948; 5 November 1965)

The situation between Iran and Iraq (26 September 1980; 31 January 1991).

The situation in the India/Pakistan subcontinent (4 December 1971; 27 December 1971).

In January, Muhammad Omar, Pakistan’s First Secretary to the UN in Geneva, gave the most recent iteration of Islamabad’s explanation concerning the Khan network debacle:

The so-called Network comprised of several people from over two dozen countries spanning four continents. A.Q. Khan‟s involvement in this international network was an individual act, not sanctioned by the State of Pakistan. 

Pakistan thoroughly investigated his involvement and shared its findings with the IAEA and other concerned countries. It helped in exposing the international associates of this clandestine supply network and he was placed under strict restrictions which remain in place to this day. Other countries‟ nationals involved with the network did not meet the same fate and in most cases escaped punishment altogether. The AQ Khan issue is a closed chapter. Since this incident, Pakistan has taken a series of effective measures to preclude any possibility of such an occurrence in the future. 

This document submitted by Pakistan to the IAEA in 1978 has some Information about the country’s nuclear power program.