Overview and Preliminary Conclusions
February 6, 1997
study sponsored by the U.S. Department of Energy, a team of Ukrainian
experts reviewed the risk of a serious accident at the operating Chornobyl
Unit 3 reactor resulting from the collapse of the damaged structures of
the adjacent Unit 4 reactor.
Preliminary conclusions of the
assessment are as follows:
- The risk of such an accident occurring
is very small.
- U.S. experts, who conducted a preliminary review of
the assessment, also agree that the risk of such an accident is small and
that this issue does not warrant special consideration beyond other safety
concerns at the Chornobyl plant.
- Because of the unlikely occurrence
of such an accident, U.S. participants believe that no special preventive
measures are needed at this time, and no further detailed evaluation is
The final report will be available for distribution
following a thorough technical review, which also will be used to confirm
the preliminary conclusions.
The assessment marks the first project
completed by the Chornobyl Center for Nuclear Safety, Radioactive Waste
and Radioecology in Slavutych, Ukraine. The United States supported
Ukraine in establishing the Center in 1996. The Center serves as an
international focal point for developing Ukrainian expertise in nuclear
safety and environmental remediation.
Background, Purpose, and
The Department commissioned this assessment a year
ago, after British press reports speculated on the potential consequences
if the shelter surrounding the destroyed Chornobyl reactor Unit 4 were to
collapse. The shelter, which was erected hurriedly in 1986 after the
catastrophic accident at that reactor, now is deteriorating. The concern
was that the reactor Unit 4 shelter or associated structures could become
unstable enough to collapse, creating a serious accident at adjacent
operating Unit 3.
The purposes of the study were to assess the
possibility of such an accident in Unit 3 and to identify potential
The Chornobyl Center for Nuclear Safety, Radioactive
Waste and Radioecology worked with the following organizations to prepare
and review this assessment:
- Scientific and Technical Center of
the Ministry of Environmental Protection and Nuclear Safety of Ukraine
- Interbranch Agency of the Ukrainian Scientific and Technical Center
- Chornobyl nuclear power plant
- Ukrainian Nuclear Regulatory
U.S. technical experts briefly reviewed the
assessment=s methods, application, and conclusions.
- The study evaluated potential serious accidents in Unit 3 that
could result from collapse of the adjacent Unit 4 structures. The area
requiring the most careful evaluation was potential damage to
safety-related equipment such as control rods or pressure tubes.
- The possibility that such accidents could occur in Unit 3 was
determined to be very small.
- U.S. experts, in evaluating the
assessment, concluded that the approach used was sound and adequately
supports the conclusions.
- Based on the assessment=s findings, the
U.S. participants believe that no special preventive measures are needed
at this time to protect Unit 3 from structural collapse of the Unit 4
shelter. In addition, no further detailed evaluation is necessary.
Benefits of the Assessment
In addition to the technical
results of the assessment, this work generated several additional
- Ukrainian scientific and regulatory organizations
gained experience in in-depth risk analysis.
- A broad spectrum of
organizations in Ukraine and the United States worked successfully
together to conduct the assessment. This cooperation lends credibility to
the effort and builds the foundation for future technical collaborations.
- The assessment marks the first project completed by the Chornobyl
Center for Nuclear Safety, Radioactive Waste and Radioecology in
Slavutych, Ukraine. The United States supported Ukraine in establishing
the Center in 1996. The Center serves as an international focal point for
developing Ukrainian expertise in nuclear safety and environmental
The draft report
documenting the assessment contains minor technical errors and
inconsistencies. In addition, additional explanation and justification
are needed for technical assumptions used in the assessment. U.S and
Ukrainian experts are working together on these improvements. However,
the assessment=s conclusions are not expected to change.
assessment is planned for completion in the next two months.
following individuals from the Scientific and Technical Center of the
Ministry of Environmental Protection and Nuclear Safety of Ukraine
participated in performing the assessment:
- Project leader,
Scientific Director: I.M. Simonov
- Head of Department No. 130,
Strength and Structures Reliability: V.B. Kritsky
- Head of Laboratory
for Seismic Stability and Nuclear Power Plant Probabilistic Safety
Assessment Based on Strength Reliability: A.B. Kritsky
- Head of
Laboratory: A.A. Maliushitsky
- Head of Laboratory: O.A. Mazurkov
- Senior Researcher: L.M. Nikolayeva
- Head of Department: S.N.
- Engineers: Yu.V. Vigovsky, A.A. Karnaukhov, D.I. Ryzhov,
O.V. Gorbenko, M.I. Ulanovsky, A.P. Shugailo
- Technician: V.A.
The following individuals reviewed the
Interbranch Agency of the Ukrainian Scientific and
of the Chornobyl Nuclear Power Plant
- A.V. Nossovsky
- A.L. Knyshevich
- E.L. Belousov
Administration of Ukraine