TNAG-1503-FCO40-2061-Guangdong-nuclear-power-station-project-at-Daya-Bay-safety-c-1986 — Page 57

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FOLLOWING FR.

AVADY

CH LEVEL

CONFIDENTAL

SITTES WITH SOF

WELL PREPARED

PRESENTATIONS BY THE SOVIET EXPERTS ON THE CANCE . . : THE CHIPA BYL DISASTER, EMERGENCY MEASURES AND RADIOLOGICAL CONSEQUENCES, OVER 400 INTERNATIONAL EXPORTY

MEASURE OF AGREEMENT WAS PEACHED ON THE MAIN

ON THE NEED FOR FURTHER EXPERT EXCHANGE IN DETAIL

•

ATTENDED. AN IMPORTANT

INITIATING EVENTS AND

VORIETY OF ARE 46.

2. THE USSR FIELOLD & TEM OF TOP EXPERTS LED BY ACADEMICIAN

LEGASOV, DEPUTY DIFECTOP OF THE KURCHATOY INSTITUTE. PRIOR TO THE

MEETING THEY HAD TABLED A DETAILED ACCOUNT C THE ACCIDENT WHICH IN

EFFECT ACKNOWLEDGED THAT OPERATOR IRROR WAS COMPOUNDED BY WEAKNESSES

IN THE DESIGN WHICH HAD ALLOWED OPERATORS TO OVERRIDE SAFETY

INSTRUCTIONS IN 4 SEPIES OF UNAUTHORISED ACTIONS. THE DOCUMENT

CONCLUDED THAT QUOTE THE ACCIDENT ASSUMED CATASTROPHIC PROPORTIONS

BECAUSE THE REACTOR WAS TAKEN BY THE STAFF INTO & NON-REGULATION

STATE IN WHICH THE POSITIVE VOID COFFFICIENT CF REACTIVITY WAS ABLE

SUPSTANTIALLY TO ENHANCE THE POWER EXCURSION UNQUOTE. THIS WAS AN INFORTANT ADMISSION. WE HAD EARLIER FEARED THAT THE EMPHASIS WOULD

SE PLACED ENTIRELY ON OPERATOP ERPOR WITH THE IMPLICATION THAT ALL

REACTOR DESIGNS (INCLUDING THOSE IN WESTERN COUNTRIES) WERE EQUALLY

VULNERABLE TO OPEPATOF ERROR. 45 IT IS, THE RUSSIANS ITEMISED DESIGN WEAKNESSES WHICH WERE IDENTIFIED BY UK EXPERTS IN 1977. LEGASOV

EXPLAINED THAT WHEN REMK REACTORS WERE FIRST PLANNED MOPE THAN 20

YEARS AGO THEY REALISED THAT THE CONCEPT HAD SEVERAL SHORTCOMINGS,

BUT IT HAD THE MERIT OF BEING PUILDABLE PY PUSSIAN INDUSTRY AT THAT

TINE. THE DECISION WAS TAKEN TO GO AHEAD AND USE ENGINEERING TO

OVERCOME THESE SHORTCOMINGS. HE ACCEPTED THAT THE DESIGNERS MADE A

FUNDAMENTAL MISTAKE IN RELYING UPON WRITTEN INSTRUCTIONS TO THE OPERATORS, NOT TECHNICAL MEANG, TO RETAIN A SUFFICIENT SAFETY MARGIN. THE RUSSIANS NOW REALISED THAT THIS PLACED TOO MUCH

RESPONSIBILITY ON THE OPERATORS.

3. THERE WAS GENERAL AGREEMENT AT THE MEETING THAT, AT THE BEGINNING

OF THE ACCIDENT, THE REACTOR UNDERWENT WHAT IS KNOWN AS QUOTE PROMET

CRITICAL EXCURSION UNQUOTE. IN THIS THE NUCLEAR CHAIN REACTION

SPEEDS UP. THE EXCURSION CAUSED AN EXPLOSION IN THE FUEL AND

TRIGGERED AN ENORMOUS STEAM EXPLOSION WHICH FLEW THE TOP OFF THE

REACTOR. THE ACCIDENT HAPPENED IN THE COURSE OF A TEST TO ME 4SURE

CONFIDENTIAL