USER OFFICE REVIEWER: D. ROSS

PROPOSED

NEW DATA IS BEING CONSIDERED AS PARTIAL BASIS FOR MODIFICATION OF PRESENT ECCS RULE (10 CFR 50.46 AND APPENDIX K).
OPTIONS FOR RULE CHANGE INCLUDE ACCEPTABILITY OF NEW DECAY HEAT DATA IN ECCS LICENSING CALCULATIONS.
NEW DATA WILL BE INCORPORATED IN "BEST ESTIMATE" ANALYSIS CODES.
ASSESSMENT OF SAFETY MARGINS.
THESE CODES ARE INTENDED TO BE USED IN PROBABILISTIC

NEW DATA CONFIRMS MARGINS ALLOTTED IN PRESENT ECCS RULE ARE CONSERVATIVE.

(1.E., INCREASE PEAK KW/FT, ETC.). IF ACCEPTED FOR USE IN LOCA LICENSING CALCULATIONS, VENDORS COULD USE ADDITIONAL MARGIN IN DESIGN.

INITIATE RULEMAKING TO MODIFY APPENDIX K. THE COMMISSION APPROVED THE PROPOSED ACTION PLAN TO MODIFY APPENDIX K (SECY 78-26). NRR AND RES ARE PREPARING A REQUEST TO SD TO

APPENDIX K (ECCS EVALUATION MODELS). THESE STUDIES PROVIDE INFORMATION NECESSARY TO ASSESS THE DEGREE OF CONSERVATISM OF THE DECAY HEAT ASSUMPTIONS IN 10 CFR 50

RIL TITLE: SIMMER CODE FOR ANAL OF CORE DISRUPT ACCIDENTS IN LMFBR'S SPONSORING OFFICE(S): NRR

THE SIMMER CODE IS DESIGNED TO PREDICT THE MOTION OF FAST REACTOR CORES DURING POTENTIAL CORE DISRUPTIVE ACCIDENTS. A TRIAL
VERSION OF THIS CODE WAS MADE AVAILABLE TO NRC'S LICENSING STAFF AND HAS SUPPORTED NRC BRANCH POSITIONS ON THE ANALYSIS OF CORE
DISRUPTIVE ACCIDENTS FOR CLINCH RIVER BREEDER REACTOR LICENSING CONSIDERATIONS. SIMMER IS RECOGNIZED AS AN IMPORTANT FIRST STEP IN
THE DEVELOPMENT OF A MECHANISTIC CODE CAPABLE OF DESCRIBING PHENOMENA NEEDED TO ASSESS CORE DISRUPTIVE ACCIDENTS IN LIQUID METAL
FAST BREEDER REACTORS.

RIL IIILE CRITIQUE OF BOARD-HALL MOD FOR THERM DETON IN U02-NA SYS SPONSORING OFFICE(S): NRR

RES UNIT

RES TECHNICAL LEAD

A CRITIQUE OF THE BOARD-HALL MODEL FOR THERMAL DETONATIONS IN THE U02-NA SYSTEM

THIS CRITIQUE OF THE BOARD-HALL THEORY FOR THERMAL EXPLOSIONS IN A URANIUM OXIDE-SODIUM SYSTEM REINFORCED THE BELIEF THAT SUCH
DETONATIONS ARE OF LOW PROBABILITY. THE CRITIQUE HAS BEEN USED AS AN AID IN ANSWERING ACRS CONCERNS ABOUT THE POSSIBILITY OF
PRELIMINARY SAFETY ANALYSIS REPORT FOR THE CLINCH RIVER BREEDER REACTOR.
ENERGETIC FUEL-COOLANT INTERACTIONS IN ADVANCED REACTORS AND WAS EMPLOYED IN SUPPORTING NRR'S POSITION IN THE EVALUATION OF THE

OFFICE: NRR IMPACT STATEMENT

SCHED. RESP. DATE: 09/09/77

ACTUAL RESP. DATE: 09/09/77

ESTIMATES OF THERMAL DETONATION ENERGIES ARE DIRECTLY RELEVANT IN LICENSING DECISIONS RELATED TO CONTAINMENT REQUIREMENTS FOR
LMFBR, PARTICULARLY KINETIC ENERGY RELEASE, SYSTEM DAMAGE AND RADIOACTIVITY RELEASES. THE RIL TRANSMITTED A CRITIQUE OF THE BOARD
AND HALL (OKAEA) THEORY FOR THERMAL EXPLOSIONS IN THE U02-SODIUM SYSTEM. THIS INDEPENDENT THEORETICAL ASSESSMENT IS USEFUL IN
REINFORCING THE CURRENT NRR BELIEF THAT SUCH DETONATIONS ARE OF LOW PROBABILITY AND THAT FURTHER EXPERIMENTAL EFFORT IS REQUIRED.

*** NRR IMPACT OF RESULTS ***

ISSUES, SHOULD CONTINUE. IDENTIFIED PERCEPTIONS AND NEED FOR EXPERIMENTS. THE RESULTS OF THE CRITIQUE ARE MINIMAL IN THIS ON-GOING TECHNOLOGICAL EXPLORATION, EXCEPT AS NOTED ABOVE IN REINFORCING THE SUCH WORK, INDEPENDENT ASSESSMENTS OF IDENTIFIED AND POTENTIAL SIGNIFICANT SAFETY

*** NRR : COMMENTS AND REMARKS ***

THE INITIAL EFFORT OF AN EXPERIMENTAL AND ANALYTICAL EVALUATION OF THE BOARD AND HALL MODEL OF THERMAL EXPLOSIONS WAS UNDERTAKEN
BY DPM AT THE REQUEST OF THE ACRS (ACRS REQUEST DATED JULY 9, 1975 FOR BOARD AND HALL REVIEW). NOTE DPM RESPONSE TO THIS REQUEST
IN A LETTER FROM R. P. DENISE TO M. LIBARKIN, ACRS, DATED OCTOBER 24, 1975. THE PHENOMENON IS APPLICABLE IN THE ONGOING REVIEW
OTHER COUNTRIES.
OF THE FFTF REACTOR. NRR HAS BEEN IN CONTINUING CONTACT WITH RES STAFF ON THE RESEARCH PROGRAMS PERTAINING TO INVESTIGATIONS ON
THE BOARD AND HALL EFFECT, AND THE GENERAL SUBJECT OF THERMAL EXPLOSIONS, AND MAINTAINS COGNIZANCE OF SUCH WORK IN THE U. S. AND