NRC Generic Letter 1981-20

NRC Generic Letter 1981-020: Safety Concerns Associated with Pipe Breaks in the BWR Scram System

ML031210330
Person / Time
Issue date:	04/10/1981
From:	Eisenhut D G Office of Nuclear Reactor Regulation
To:
References
GL-81-020, NUDOCS 8112170367
Download: ML031210330 (4)

v , UNITED STATESNUCLEAR REGULATORY COMMISSIONIWASHINGTON, 0. C 20555**** APR 1 c nTO ALL BWR LICENSEESSUBJECT: SAFETY CONCERNS ASSOCIATED WITH PIPE BREAKS IN THEBWR SCRAM SYSTEM (GENERIC LETTER 81-20)Yesterday, we discussed with your representatives the NRC's Office ofAnalysis and Evaluation of Operational Data report entitled, "SafetyConcerns Associated with Pipe Break in the BWR Scram System." TheReport describes a potential sequence of events which could result froma break in the BWR scram discharge piping during a scram conditionconcurrent with an inability to reclose the scram outlet valves.Concerns identified include the quality of the scram discharge volumepiping, the ability to detect and isolate such a break, and potentialwater and steam degradation of available ECCS equipment as a resultof the break. A number of recommendations were made in the report toremedy the potential concerns.We are presently studying these issues and recommendations to determinewhether BWR design basis accidents should be modified and as a consequencewhether appropriate actions should be taken for operating BWR plants.The purpose of this letter is to provide to you the AEOD report sothat you can evaluate its applicability to your plant and determineappropriate remedial measures, and to request information from youconcerning your evaluation in order to assist in determining anappropriate course of action for the NRC.Therefore, pursuant to 10 CFR 50.54(f) please provide us in writing,under oath or affirmation, within 45 days of your receipt of this letter,the following information:1. A generic evaluation of the applicability of theindicated sequences of events in the report to theBWR plant design, your estimate of the probabilityof occurrence of such sequences, and the bases-forthese conclusions,2. A generic evaluation of the applicability of theindicated safety concerns and findings in thereport relative to BWR plant construction, design,and operation and the bases for these conclusions,and! 1121703367 81044o )-D t1~ .PDR

EWR Licensees -2 -3. A generic evaluation of the recommendations listedin the report discussing the degree to which therecommendations are being or have been implementedwith bases why the recommendations should or shouldnot be completely Implemented on BWRs.In addition, pursuant to 50.54(f) provide the following information inwriting within 120 days of your receipt of this letter:1. Provide an evaluation of the applicability of the-. 45 day generic evaluation to your plant. Thisevaluation should contain plant specificconsiderations related to system design, instru-mentation, construction, operation, operatortraining, and emergency procedures for yourplant.2. In light of the AEOD report and the 45 day genericevaluation, provide a plant specific evaluation ofyour facility's Scram Discharge Volume Systemconformance to GDC 14, GDC 35, GDC 55, §50.2(v),50.55a (including footnote 2), and 150.46 of theCommission's regulations. This evaluation shouldaddress which portions of the Scram DischargeVolume System are considered to be part of thereactor coolant pressure boundary, the qualitygroup and safety class of the Scram DischargeVolume System, the codes and standards used forthe design, fabrication.and inservice inspectionof this system, and your bases for the aboveclassifications or groupings.3. Provide by analysis or reference a demonstrationthat a break located anywhere in the Scram DischargeVolume System could meet the requirements of 550.46of the Commission's regulations, taking into accountthe environmental and flooding aspects of such abreak.T -

• -\.-v'1iBWR Licensees -3 -This request for information was approved by GAO under a blanket clearancenuuber R0072 which expires November 30, 1983. Comments on burden andduplication may be directed to the U.S. General Accounting Office,Regulatory Reports Review, Room 5106, 441 G Street, N.W., Washington,D.C. 20548.ncerely,Darrell G. sen uDivision ofL icensingOffice of Nuclear Reactor RegulationEnclosure:As statedcc: Service List with Enclosure

4 T'I ' .,.'....I IBWR Licensees-3 -This request for information was approved by GAO under a blanket clearancenumber R0072 which expires November 30, 1983. Comments on burden andduplication may be directed to the U.S. General Accounting Office,Regulatory Reports Review, Room 5106, 441 G Street, N.W., Washington,D.C. 20548.Division ofyLicensingOffice of Nuclear Reactor RegulationEnclosure:As statedcc: Service List with Enclosure