The Reactors at Juaragua
|Juragua 1 and 2 are VVER-440 reactors, a type still in use in eastern
Europe, Finland, and the former Soviet Union (table) Further information
on the VVER-440
reactors can be found on the International Nuclear Safety Center Web Site.
"VVER" is the Soviet designation for a pressurized light water moderated reactors, which is designated PWR in western designs. This type of unit is generally regarded as less vulnerable to fire than the RBMK graphite-moderated reactors (LGR) employed at Chernobyl. The number that follows VVER, in this case 440, represents the gross capacity. In the United States, all operable reactors are either of the PWR type or Boiling Water Reactors (BWR). In addition to the PWR type and LGR type in use in Russia and the Ukraine, Russia has one Fast Breeder Reactor.
Juragua units 1 and 2 belong to the “second generation” of the VVER family. Reactors in this generation reflect the “first uniform safety requirements” incorporated by Soviet designers.(1) The “second generation” includes Model V318, a version not generally regarded as meeting western standards but clearly superior to the V230 and to the RBMK type. The VVER-440 Model V318 reactors at Juragua are based on V213. Model V318 added a number of safety features, including a steel-lined concrete dome-shaped structure to inhibit the release of radioactive particles.(2) Excellent diagrams of both the RBMK type reactor and the Model V230 reactor can be viewed in the Nuclear Energy Institute Sourcebook.
In 1989, the U.S. Nuclear Regulatory Commission completed a limited special study that compared the Cuban VVER 440/318s and a somewhat similar U.S. pressurized light water reactor. NRC concluded that both reactors are designed to accommodate similar types of accidents, but it is difficult to determine the relative capability of the different designs to deal with more severe accidents. “An assessment of the actual relative risk of the Cuban plants may well be different, depending on specifics that have not been evaluated and on information we do not have.”
Unlike Chernobyl 4, the VVER-440 incorporates a containment structure to inhibit the release of radioactive materials during a nuclear accident. Lacking such a structure, Chernobyl 4 spewed contaminants into the atmosphere, soil, and groundwater. Juragua’s containment structure is divided into two zones, and this leads to one of the criticisms of the design. If there is a nuclear accident, the top of the structure is weaker than the bottom. “The result of the two-zone system is that while the lower zone is designed to accommodate a maximum over pressure of 1.5 atmospheres, the upper zone can only accommodate a maximum over pressure of 0.5 atmospheres.”(3) By comparison, the VVER-1000, (a newer) Soviet model comparable to western designs, can accommodate 4 atmospheres over pressure throughout.
The Helms Burton Act lists a number of concerns about the Juragua reactors’ design. In Section 111, entitled, “Withholding of Foreign Assistance from Countries Supporting Juragua Nuclear Plant in Cuba,” the Act states:
To ensure accuracy and impartiality, the following testimony on the Nuclear Regulatory Commission's 1989 study of the Juragua design is quoted in its entirety without comment:
In his testimony before the House, Keith O. Futz, Assistant Comptroller
General, U.S. General Accounting Office, summarized the concerns cited
in a 1989 study by the U.S. Nuclear Regulatory Commission. According to
On June 16, 1997, the Cuban Mission responded by a circular letter to the International Atomic Energy Agency to allegations in the Helms Burton Act and subsequent U.S. efforts to discourage third party investment in the Juragua project. The Mission noted that the Section 111 (F) of the Act entitled, “Withholding of foreign assistance from countries supporting Juragua nuclear plant in Cuba” is based on unsubstantiated suppositions and speculations.(5) The letter also insists on Cuba’s right to pursue nuclear power for peaceful purposes. Because the letter does not contain specific technical details, it is not clear which data (if any) are regarded as inaccurate.
The potential problems are not limited to the design. From 1984 to 1991, Pelayo Calante Garcia, a nuclear scientist and engineer, participated in the project. He later left Cuba. According to his subsequent testimony before the U.S. House Western Hemisphere Subcommittee, Mr. Garcia was responsible for inspecting the containment structure. He cautioned that the system to reduce pressure in the structure had never been tested. Also, he cited “defective welds in seals in the containment building and in support structures.”
Whatever the weaknesses of the Juragua reactors, proponents insist that the design is superior to that of some Soviet-built reactors still in service. The design is less vulnerable to fire than the RBMK reactors that continue to operate in Russia and Ukraine. Critics warn that the weaknesses of the Juragua design, whether or not they can be regarded as critical, have been magnified by poor construction, inferior materials, and insufficient oversight. The efforts of the International Atomic Energy Agency to train Cuban workers and to improve oversight may help reduce problems in the future.
On June 14 through 18, 1999, the International Conference on Strengthening Nuclear Safety in Eastern Europe discussed the VVER-440 and other Soviet reactors.(6) The Conference was conducted by the International Atomic Energy Agency (IAEA) at its headquarters in Vienna, Austria. IAEA noted several design concerns, including "confinement integrity" (leak tightness) and some of the steps being taken to address the problem.
The results of the Conference are available to be viewed on the IAEA home page.
1. Nuclear Energy Information Center, Source Book on Soviet-Designed Nuclear Power Plants 1996.
2. The Natural Resources Defense Council, "Backgrounders: The Juragua Nuclear Plant."
4. "Nuclear Safety: Concerns with the Nuclear Power Reactors in Cuba," Statement of Keith O. Fultz, Assistant Comptroller General, Resources, Community, and Economic Development Division, United States General Accounting Office, to the U.S. House of Representatives, Committee on International Relations, Subcommittee on the Western Hemisphere, August 1, 1995, p. 3.
5. International Atomic Energy Agency Information Circular, INFCIRC/537, July 30, 1997.
6. International Atomic Energy Agency, "International Conference on Strengthening Nuclear Safety in Eastern Europe."