ML20118B749
| ML20118B749 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 09/28/1992 |
| From: | Zeringue O TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-92-04, GL-92-4, NUDOCS 9210070124 | |
| Download: ML20118B749 (7) | |
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,,,- v +, n m,w,. w~ w-w, o a w n mnovo A o l*rtmchmt (thfit f tarf y 0;w,' d@e4 SEP 2 81992 U.
S. Nuclear Regulatory Commission ATTH: Document Control Desk Washington, D.
C.
20555 10 CFR 50.54(f)
Gentlemon:
In the matter of
)
Docket Hos. 50-259.
Tennesseo Valley Authority
)
50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN) - RESPONSE TO GENERIC LETTER (GL) 92 RESOLUTION OF THE ISSUES RELATED TO REACTOR VESSEL WATER LEVEL INSTRUMENTATION IN BWRs PURSUANT TO 10 CFR 50.54(f)
This lotter providos the information requestod by.the NRC in GL 92-04 pursuant to 10 CPR 50.54 (f) for TVA's Browns Ferry Nuclear Plant.
The answers to the specific Roguested_Actionn are as fo)'.ows:
Regnested__ Action 1.
1.
In light of potential errors resulting from the offects-of noncondensible gas, each licenseo should determino:
a.
The impact of potential lovel indication errors on automatic safety system responso during all licensing basis transients and accidents; b.
The impact of potential lovel indication errors on operator's short and long term actions during and after all licensing 1 asis accidents and transients; o.
The impact of potential lovel-indication errora
{Qs()(( on operator actions prescribed in emergency operating procedures or other affected proceduros I ' not covered in -(b). 9210070124 920928 i PDR -ADOCK 05000259 P PDR. } lI
l 2 U.S. Nuclear Re'ulatory Commission SEP 2 av llefdlQRse 1232 On August 28, 1992, The BWR Owners' Group (BWROG) provided to the NRC and each of the member utilities report BWROG 92-074 BWR Reactor Vessel Water Level Instrumentation, Revision 1. BWROG 92-074 addresses the safety impact of potential water level indication errors on automatic system response during all licensing basis transients and accidents. The analytical basis is contained in Section 6.0 Safety Analysis. Plant responce is summarized in Section 2.2, Plant Besponses to Postulated Accident Epenarios. TVA recognizes that there are differences between the designs of BWR plants and systems; however our review of the report and Attachment 2 to the report, Eeneric AnoliGability of This Report's Safety Analysig by GE Nuclear Energy, reinforces TVA's general understanding that the basic plant response to the design basis transients and accidents is sufficiently similar to obviate the need for additional plant-specific analysis. The diverse initiating signal for low pressure Emergency Core Cooling System for Browns Perry (BFN) requires both a high drywell pressure and a low reactor vessel pressure rather than only a high drywell pressuro as in the Report. Since the two required signals are not dependent on reference leg inventory, the conclu-sions of the report are still valid. 1.b. BWROG 92-074 section 6.9 ODerator Responses, addresses the operator actions that could be anticipated in response to potential water level indication errors. In the short term the report discusses in section 6.0 that the automatic safety actions will be performed as necessary. Additional guidance has been provided to the plant operations personnel as indicated in Enclosure 1. The guidance has sensitized the operators to the possible concerns with accurate water level readings following a rapid depressurization while not necessitating a change to the existing long term guidance pr ovided in the Emergency Operating Instructions (EOls). n
-.-. - ~.. - _-, ? 4 3 U.S. Nuclear Regulatory Commission SEP 2 61992 1192 As stated in section 6.9 of BWROG 92-074 and 1.b. above, the operators have adequate information in the present EOIs as augmented by the additional training support in Enclosure 1. The BWROG Emergency Procedures Committee will evaluate the information from the BWROG program of analysis and testing to determine if there is a need for any additicnal guidance in the EOIs. Recuested Action 2. 2. Based upon the results of (1), above, each licensee should notify the NRC of short term actions taken, such as: a. Periodic monitoring of level instrumentation system leakage; and, b. Implementation of procedures and operator training to assure that potential level errors will not result in improper operator actions. Epsnonse 22 TVA has informed its operators of information relating to noncondensibles (NCs) in the reference leg issue per. The existing information about the configuration of the cold-leg water level instrumentation has been reviewed and provided to-the BWROG to be factored into the test confi~urations in the BWROG program (provided to the NRC in the August 12, 1992 letter from the BWROG). The significhnce of different configuration characteristics on reference legs will be better understood after the results of the BWROG test and analysis program are available. In accordance with Surve121ance Instruction SI-2,_ water level indications are checked and compared each shift (some indications are e compared daily). Unacceptable differences in indication ^ require a review by the Senior Reactor Operator'with assistance as required by the Technical and Maintenance staff. g t -r*,v e:-+--m,---=-~c-w y--c'- v-wm~_e-..---y-m w.--e.,, -w.- e n.- +,*.w,g. m +.--1 ,iv-, e m .w--we
~ 4-U.S. Nuclear Regulatory Commission 5 SEP 2 81332 Re_ quested nglion 3 3. Each licensee should-provide its plans and schedule for corrective actions, including any proposed hardware modifications necessary to ensure the level instrumentation design is of high functional reliability for long term operation. Since this instrumentation plays an important role in plant safety and is coquired for_both normal and accident conditions, the staff recommends that each utility implement its longer term actions to assure a level instrumentation system of high-functional reliability at the first opportunity but prior to_ starting up after the next refueling _ outage commencing 3 months after the date of-this letter. Resnonse 11 TVA ondorses the BWROG plans originally provided in BWPOG letter to the NRC on August 12, 1992. The BWROG testing and analytical development program should provide a more accurate estimate of the effects of NCs coming out of solution on reference legs under depressurization considering such factors as representative rather than instantaneous depressurization rates, gravity effects on diffusion gradients, friction effects, bubble separation, boundary layers, correct gas species, and so-on. TVA expects that the results of this investigation will show that Browns Ferry has a level instrumentation system of high functional reliability. Should the BWHOG investigation-program determine that modifications are required to ensure high functional reliability, Browns Ferry will be modified in consideration-of the results of the BWROG program. A sun. mary list of the commitments associated with this letter is provided in Enclosure 2.
5 U.S. 11uclear Regulatory Commission S U' P 6 1332 If you have any questions, please contact Greg Pierce at (205) 729-7566. Sincerely, ? /) (/ I O.! J. ' Z e r i n j u e Subscribed and sworn to before me on this yd c'ay of 19f_4 46-8 ' 11ssk pk !fotary Public 14 Commtskn g,e Enclosures cc (Enclosures): IJRC Resident Inspector Browns Ferry 11uclear Plant Route 12, Box 637 Athens, Alabama 35611 Mr. Thierry M. Ross, Project Manager U.S. fluclear Regulatory Commission One White Flint, 11 orth 11555 Rockville Pike Rockville, Maryland 20852 Mr. B. A. Wilson, Project Chief U.S. Iluclear Regulatory Commission Region II 101 Marietta Street, 11W, Suite 2900 Atlanta, Georgia 30323
c ENCLOSURE 1
SUMMARY
OF TRAINING PROGRAli FOR OPERATORS ON HOPCO!1DENSIBLES IN REFERENCE LEGS On July 30, 1992, Operators were notified of-the potential for level indication errors due to noncondensibles coming out of solution when the reactor is depressurized. This was accomplished via shift briefings. Urgent required reading information packages 92-0731 and 92-0902 sore issued on July 31, 1992 and September 9, 1992.respectively to provide operators with additional information and guidance regarding NCs in reference legs. Urgent required reading is required to be reviewed within 15 days to maintain shift qualifications. This training will be reinforced and amplified via trainira dispatches and lectures as appropriate. I h s t ~ -.o. r,.
l + ENCLOSURE 2
SUMMARY
LIST OF COMMITMENTS RELATED TO GL 92-04 1. TVA will continue to support the program of analysis, -testing and development of possible hardware changes wh '
- t is being conducted by the BWROG.
The results and l coat ions of the BWROG program will be evaluated for possaole applicability to Browns Ferry Nuclear Plant.- 2. TVA will review the results of the BWROG program for j potential training requirements f r operators. 4 9 - =- -}}