lec24_2

Reactor Safety 22.091/22.903

Professor Andrew C. Kadak Professor of the Practice

Lecture 24

Current Regulatory Safety Issues

Topics to Be Covered

• Reactor Vessel Integrity – Embrittlement

• PWR Sump Performance

• Reactor Coolant System Weld Issues

• Davis Besse Head Degradation

• Fire Protection (Hemyc Insulation)

• Plant Security and Terrorism

• Ground water contamination – t ritium

• Safety Conscious Work Environment – S afety Culture – Human Factors

Reactor Vessel Integrity

• Driven in part by Yankee Rowe Vessel Issue

• Depending on weld and metal materials some vessels vulnerable to embrittlement

• Need to have in reactor specimens to gauge degree of embrittlement

• Reactor have chosen to manage fuel differently – l ow leakage cores

• Only major life limiting component in reactors

PWR Sump Performance

• During a LOCA debris from paint, insulation and other materials will clog sump screens

• Failing or cavitation recirculation spray

• Net Positive Suction Head insufficient

• Similar to BWR issue

Prof. Andrew C. Kadak, 2008 Page 4

De pa r t me nt of Nuc l ea r Sc ie nce & Engi nee r ing

Reactor Coolant System Weld Issues

• Primary Water Stress Corrosion Cracking

• Alloy 82/182/600 welds

• Temperature, residual stresses, Nickel based alloys

• Plants: Wolf Creek, V.C. Summer, South Texas Project, Crystal River 3, etc .

• Solution – i nspection and weld overlay

Prof. Andrew C. Kadak, 2008 Page 5

De pa r t me nt of Nuc l ea r Sc ie nce & Engi nee r ing

Fire Protection

• Objective to prevent fires and failures due to fires that affect safety of the plant

• Appendix R – governing regulation

• Required separation of trains

• Insulation – f ire doors – f ire watches

• Fire PRAs being developed

• Problems with tests of some insulation – H ymec failing to meet NRC fire retardant time issue.

Security and Terrorism

Aircraft Crash

Upgrade to physical security

Design Basis Threat – F orce on Force

Ground Water Contamination

• Water leaks containing tritium

• Big issue at Brookhaven National Lab – c hanged lab

• Leaks in water systems at Indian Point, Braidwood, Callaway, Dresden, Bryon, Palo Verde, Quad Cities

• Leaks frequently coming from spent fuel pool liners.

• Public outcry

• Reporting requirements refined

• Levels of tritium still low within limits.

Recent Enforcement Actions

Reactor Ac tions

Exelon G e neration Comp a n y, L L C (Byr on Station) E A -08 - 0 4 6

Sig n if ic a n c e De t e rmin a t io n F i n d in g . T h e N O V in vo lv e d vio l a t ion s o f 1 0 CF R P a rt 5 0 , Ap p e n d ix B Cri t eri o n XV I , “Corrective A c ti ons” , and 10 CFR Part 50, A p pe n d i x B, Criter i o n III, “Design Control”. Sp e c if ically , the l i c e nsee failed to take time ly corrective acti ons afte r the id e n t i f i c a t i o n of e xt e n s ive c o rr os io n on e s s e n t ia l s e r vic e wa te r r i s e r p i p e s a n d f a i l e d t o ve rif y th e adequ a cy of the methodol ogy and design in pu ts in c a lc u l a t io n s th a t s up p or t e d t h e d e cis i o n t o a c c e p t t h re e d e g r a d e d e s s e n t ia l s e r v ic e wate r r i se r pipe s fo r continued servi c e.

O n A p ril 1, 2008, a No ti ce of Vi ol ati on (NOV ) w a s i ssued fo r vi ol ati o ns a s soci ated w i th a Whi te

Appendix B violation – Q uality

Enforcement Action

Lumi nant Gen e r a ti on C o mpany , LLC (C oman ch e Pea k S t eam El ec tr i c St at i o n) E A - 08-0 2 8

Speci f icall y , Emergency Di esel Ge ne rator (EDG) 1 - 02 was made inoperable as a resul t of pai n t i n g a c ti vi t i es due to pai n t havi ng been de po si ted and rem a i n in g o n a t le a s t on e fu e l r a c k i n a locat i on that prevent e d moti on required to su pport th e oper ati on of the ED G. Thi s condi t ion caused E D G 1-0 2 to fail to start du ri ng a su rv eil l a nce te st on Nov e m b er 21, 20 07

O n F e bruar y 29, 2008, a No ti ce of Vi ol ati on w a s i s s u ed fo r a vi olati o n associ a ted w i t h a W h i t e Sig n ificance Determinatio n Find in g in v o lv ing a v i o l a t ion of the U n it 1 T e c h n i c a l Sp e c i f ic a t i o n (TS ) 3. 8.1, “A C S o urces - Oper ati n g, ” wh i c h requi r e s that while t h e p l ant is in Mod e s 1 , 2, 3 , o r 4, tw o di esel gener a to r s (D Gs) capa bl e o f su ppl y ing th e onsi te C l ass 1E pow e r di str i buti on subsy s t e m ( s) shal l be o p erabl e . Fr om Nov e m b er 1, 2007, t h ro ugh No vem b er 21, 2007, wh il e th e pl ant w a s i n Mode 1, one of the two DGs capabl e of suppl y i n g t h e on si te Class 1E po w e r di stri buti on su bsystem (s) w a s i n operabl e , and act i on was not take n t o ei th er r e s t o re t h e D G to a n o p e r a b l e s t a t u s w i t h i n 7 2 h o u r s o r b e i n M o d e 3 w i t h i n 6 h o u r s a n d M o d e 5 w i t h i n 3 6 h o u r s

Summary

• Even though nuclear plants are performing to high capacity levels for the last 5 years - i ssues remain.

• Safe operation requires constant vigilance, attention to detail and strong NRC oversight to assure that complacency does not set in.

• Role of industry NEI and EPRI are important to resolution of generic issues to assure balance.

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22.091 Nuclear Reactor Safety

Spring 200 8

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