ML19264C528
| ML19264C528 | |
| Person / Time | |
|---|---|
| Site: | Fermi, Susquehanna, Limerick, 05000000, 05000378, Zimmer, Shoreham, Allens Creek, Black Fox, Yellow Creek |
| Issue date: | 02/08/1982 |
| From: | Tedesco R Office of Nuclear Reactor Regulation |
| To: | Atomic Safety and Licensing Board Panel |
| Shared Package | |
| ML19264C529 | List: |
| References | |
| TASK-AS, TASK-BN-82-08, TASK-BN-82-8 BN--82-08, BN-82-8, NUDOCS 8203010287 | |
| Download: ML19264C528 (28) | |
Text
.
.e Y
Docket Nos. 50-322 s
50-341 D
50-358 cf,_ ^.,
50-387/388 c
50-466 y
50-556/557 met 10RANDUM FOR: The Atomic Safety & Licensing Boards for:
s Shoreham Nuclear Power Station, Unit 1 Enrico Fermi Atomic Power Plant, Unit 2 William H. Zimmer Nuclear Power Station, Unit 1 Susquehanna Steam Electric Station, Units 1 and 2 Allens Creek fluclear Generating Station, Unit 1 Black Fox Station, Units 1 and 2 FROM:
Robert L. Tedesco Assistant Director for Licensing Division of Licensing
SUBJECT:
BOARD NOTIFPCATION - ERRORS IN BWR VESSEL WATER LEVEL INDICATION (Board i;otification 82-08)
- n accordance with present NRC procedures regarding Board notifications, the enclosed information is being provided for your information as constituting new information relevant and material to safety issues This information is generic and has applicability to all dockets with boiling water reactors.
Original signed by Robert L Tedem Robert L. Tedesco Assistant Director for Licensing Division of Licensing
Attachment:
DSI/NRR memo dated 1/15/82 cc: See next page 8203010287 820208 CF ADOCK 05000322 CF U
DL:LB#2/PM DL :L8'#2/BC DL
/L c,,,g sunu m >
.My.c h ;.p.t..
ASchwencer.
RTedescg D ATF ).2/ /.O b..
.b[..*,.[.0 2..
.2 [..
.b..
OFF1ClAL RECORD COPY utom mi-mwa NRCFORM 316 00-8M NRCM ma
pa " coq fi k
UNITED STATES NUCLEAR REGULATORY COMMISSION y
y ' ' p, g
I WASHINGTON, D. C. 20555 g%...../
e Docket Nos. 50-322 FEB 9 1982 50-341 50-358 50-387/388 50-466 50-556/557 MEMORANDUM FOR:
The Atomic Safety & Licensing Boards for:
Shoreham Nuclear Power Station, Unit 1 Enrico Fermi Atomic Power Plant, Unit 2 William H. Zimmer Nuclear Power Station, Unit 1 Susquehanna Steam Electric Station, Units 1 and 2 Allens Creek Nuclear Generating Station, Unit 1 Black Fox Station, Units 1 and 2 FROM:
Robert L. Tedesco Assistant Director for Licensing Division of Licensing
SUBJECT:
BOARD NOTIFICATION - ERRORS IN BWR VESSEL WATER LEVEL INDICATION (Board Notification 82-08)
In accordance with present NRC procedures regarding Board notifications, the enclosed information is being provided for your information as constituting new information relevant and material to safety issues.
This information is generic and has applicability to all dockets with boiling water reactors.
< c sc~
Robert L. Tedesco Assistant Director for Licensing Division of Licensing
Attachment:
DSI/NRR memo dated 1/15/82 cc: See next page
FEB 9 1982 DISTRIBUTION OF BOARD NOTIFICATION Allens Creek, Docket No. 50-466 ACRS Members Texas Public Interest Research Dr. Robert C. Axtmann Group, Inc.
Mr. Myer Bender Hon. Ron Waters Dr. Max W. Carbon Region IV Mr. Jesse C.'Ebersole Bryan L. Baker Mr. Harold Etherington Margaret Bishop Dr. William Kerr Dr. John H. Buck Dr. Harold W. Lewis Dr. E. Leonard Cheatum Dr. J. Ca rson Mark Carolina Conn Mr. William M. Mathis J. Gregory Copeland, Esq.
Dr. Dade W. Moeller Stephen A. Doggett, Esq.
Dr. David Okrent Mr. John F. Doherty Dr. Milton S. Plesset Robin Griffith Mr. Jeremiah J. Ray Carro Hinderstein Dr. Paul G. Shewmon Leotis Johnston Dr. Chester P. Siess Christine N. Kohl, Esq.
Mr. David A. Ward Rosemary N. Lemmer Mr. Gustave A. Linenberger Enrico Fermi, Docket No. 50-341 D. harrack Brenda A. McCorkle Mr. David E. Howell Hon. John R. Mideska Peter A. Marquardt, Esq.
Jack P.. Newman, Esq.
Gary L. Milhollin, Esq.
Mr. William Perrenod Dr. David R. Schink Susan Plettman, Esq.
Mr. Frederick J. Shon Mr. Wayne Rentfro Eugene B. Thomas, Jr., Esq.
Alan S. Rosenthal, Esq.
Mr. William J. Schuessler Susquehanna, Docket Nos. 50-387, 50-388 Hon. Jerry Sliva Sheldon J. Wol fe, Esq.
Gerald R. Schultz, Esq.
Robert W. Adler, Esq.
Shoreham, Docket No. 50-322 Mr. Glenn 0. Bright Dr. John H. Buck MHB Technical Associates Robert M. Gallo Edwa rd M. Ba rrett, Esq.
Mr. Thomas M. Gerusky Ezra I. Bialik, Esq.
James P. Gleason Howard L. Blau, Esq.
Mr. Thomas J. Halli gan Joel Blau, Esq.
Dr. Judith H. Johnsrud Lawrence Brenner, Esq.
Ms. Colleen Marsh Dr. James L. Carpenter Mr. Thoras S. Moore Hon. Peter Cohalan Dr. Paul W. Purdom Jeffrey C. Cohen, Esq.
Jay Silberg, Esq.
David H. Gilmartin, Esq.
Mr. DeWitt C. Smi th Marc W. Goldsmith Bryan A. Snapp, Esq.
Stephen B. Latham, Esq.
Dr. Emmeth A. Luebke Mr. Brian McCaffrey W. Taylor Reveley, III, Esq.
Ralph Shapiro, Esq.
Mr. Jeff Smith
Distribution of Board Notification - p. 2 Zimmer, Docket No. 50-358, Black Fox, Docket Nos. 50-556, 50-557 Dale D. Brodkey Mr. Lawrence Burrell Troy B. Conner, Jr., Esq.
Mrs. Carrie Dickerson Andrew B. Dennison, Esq.
Mr. Gerald F. Diddle Michael C. Farrar, Esq.,
Joseph R. Farris, Esq.
James H. Feldman, Jr., Esq.
Joseph Gallo, Esq.
Lawrence R. Fisse, Esq.
Martha E. Gibbs, Esq.
Mr. John H. Frye, III Richard B. Hubbard W. Peter Heile, Esq.
Mr. Maynard Human Timothy S. Hogan, Jr.
Dr. W. Reed Johnson Dr. Frank F. Hooper Michael I. Miller, Esq.
M. Stanley Livingston Dr. Paul W. Purdom David K. Martin, Esq.
Dr. M. J. Robinson William J. Moran, Esq.
Mr. Richard S. Salzman George E. Pattison, Esq.
Mr. Frederick J. Shon Mr. Samuel H. Porter Dr. John B. West Dr. Lawrence R. Quarles Mr. Clyde Wisner Richard S. Salzman, Esq.
Sheldon J. Wol fe, Esq.
Mrs. Deborah Webb, Esq.
Mrs. Ilene H. Younghein John D. Woliver, Esq.
Dr. John C. Zink Atomic Safety and Licensing Board Panel Atomic Safety and Licensing Appeal Board Panel Docketing and Service Section
Mr. M. S. Pollock Vice President - Nuclear Long Island Lighting Company 175 East Old Country Road Hicksville, New York 11801 cc:
Howard L. Blau, Esquire MHB Technical Associates 1
Ham on Avenue, M e K 7 Ne r
Road San Jose, California 95125 Hicksville, New York 11801 Stephen Latham, Esquire Jeff rey Cohen, Esquire Twomey, Latham & Schmitt Deputy Commissioner and Counsel Post Office Box 398 New York State Energy Office 33 West Second Street Riverhead, New York 11901 re Stat aa Albany, New York 12223 Joel Blau, Esquire New York Public Service Commission Energy Research Group, Inc.
The Gov. Nelson A. Rockefeller Bldg.
400-1 Totten Pond Road Empire State Plaza Waltham, Massachusetts 02154 Albany, New York 12223 Jeff Smith Ezra I. Bialik, Esquire Shoreham Nuclear Power Station Assistant Attorney General Post Office Box 618 Environmental Protection Bureau Wading River, New York 11792 New York State Department of Law 2 World Trade Center W. Taylor Reveley, III, Esquire New York, New York 10047 Hunton & Williams Post Office Box 1535 Resident Inspector Richmond, Virginia 23212 Shoreham NPS, U.S.N.R.C.
Post Office Box B Ralph Shapiro, Esquire Rocky Poin't, New York 11778 Cammer & Shapiro 9 East 40th Street New York, New York 10016 Mr. Brian McCaffrey Long Island Lighting Company 250 Old Country Road Mineola, New York 11501 Honorable Peter Cohalan Suffolk County Executive County Executive / Legislative Building Veteran's Memorial Highway Hauppauge, New York 11788 David Gilmartin, Esquire Suffolk County Attorney County Executive / Legislative building Veteran's Memorial Highway Hauppauge, New York 11788
Mr. Norman W. Curtis Vice President Engineering and Construction Pennsylvania Power & Light Canpany Allentown, Pennsylvania 18101 ccs: Jay Silberg, Esquire Ms. Colleen Marsh Shaw, Pittnan, Potts & Trowbridge P. O. Box 538A, RD #4 1800 M Street, N. W.
Mountain Top, Pennsylvania 18707 Washington, D. C. 20036 Mr. Thomas J. Halligan Edward M. Nagel, Esquire Correspondent General Counsel and Secretary The Citizens Against Nuclear Dar 'ars Pennsylvania Power & Light Campany P. O. Box 5 2 North Ninth Street Scranton, Pennsylvania 18501 Allentoum, Pennsylvania 18101 Mr. J. W. Millard Mr. Willian E. Barberich Project Manager Nuclear Licensing Group Supervisor Mail Code 395 Pennsylvania Power & Light Campany General Electric Company 2 North Ninth Street 175 Curtner Avenue Allentown, Pennsylvania 18101 San Jose, California 95125 Mr. G. Rhodes Robert W. Adler, Esquire Resident inspector Office of Attorney General P. O. Box 52 505 Executive House Shickshinny, Pennsylvania 18655 P. O. Box 2357 Harrisburg, Pennsylvania 17120 Gerald R. Schultz, Esquire Susquehanna Environmental Advocates P. O. Box 1560 Wil kes-Barre, Pennsylvania 18703 Mr. E. B. Poser Project Engineer Bechtel Power Corporation P. O. Box 3965 San Francisco, California 94119 Dr. Judith H. Johnsrud Co-Director Environmental Coalition on Nuclear Power 433 Orlando Avenue State College, Pennsylvania 16801 Mr. Thomas M. Gerusky, Director Bureau of Radiation Protection Resources Commonwealth of Pennsylvania P. O. Box 2063 Harrisburg, Pennsylvanja 17120
Mr. Harry Tauber Vice President Engineering & Construction Detroit Edison Company 2000 Second Avenue Detroit, Michigan 48226 t
cc:
Mr. Harry H. Voigt, Esq.
LeBoeuf, Lamb, Leiby & MacRae 1333 New Hampshire Avenue, N. W.
Washington, D. C.
20036 Peter A. Marquardt, Esq.
Co-Counsel The Detroit Edison Company 2000 Second Avenue Detroit, Michigan 48226 Mr. William J. Farner Project Manager - Fermi 2 The Detroit Edison Company 2000 Second Avenue Detroit, Michigan 48226 Mr. Larry E. Schuerman Detroit Edison Company.
3331 West Big Beaver Road Troy, Michigan 48084 David E. Howell, Esq.
3229 Woodward Avenue Berkley, Michigan 48072 Mr. Bruce Little U. 5. Nuclear Regulatory Commission Resident Inspector's Office 6450 W. Dixie Highway Newport, Michigan 48166 Dr. Wayne Jens Detroit Edison Company 2000 Second Avenue Detroit, Michigan 48226 Mr. James G. Keppler Nuclear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn, Illinois 60137
Mr. Earl A. Borgmann Senior Vice President Cincinnati Gas & Electric Company Post Office Box 960 Cincinnati, Ohio 45201 Deborah Faber Webb Troy B. Conner, Jr., Esq.
7967 Alexandria Pike cc:
Conner, Moore & Corber Alexandria, Kentucky 41001 1747 Pennsylvania Avenue, N.W.
Washington, D. C.
20006 Andrew B. Dennison, Esq.
200' Main Street Mr. William J. Moran Batavia, Ohio 45103 General Counsel Cincinnati Gas & Electric Company George E. Pattison, Esq.
Post Office Box 960 Clermont County Prosecuting Attorney Cincinnati, Ohio 45201 462 Main Street Batavia, Ohio 45103 Mr. Samuel H. Porter Porter, Wright, Morris & Arthur Mr. Waldman Christianson 37 West Broad Street Resident Inspector /Zimmer Columbus, Ohio 43215 RFD 1, Post Office Box 2021 U. S. Route 52 Mr. James D. Flynn, Manager Moscow, Ohio 45153 Licensing Environmental Affairs Cincinnati Gas & Electric Company Mr. John Youkilis Post Office Box 960 Office of the Honorable William Cincinnati, Ohio 45201 Gradison United States House of Representatives David Martin, Esq.
Washington, D. C.
20515 Office of the Attorney General 209 St. Clair Street Timothy S. Hogan, Jr., Chairman First Floor Board of Commissioners Frankfort, Kentucky 40601 50 Market Street, Clermont County Batavia, Ohio 45103 James H. Feldman, Jr., Esq.
216 East 9th Street Lawrence R. Fisse, Esq.
Cincinnati, Ohio 47c'0 Assistant Prosecuting Attorney 462 Main Street W. Peter Heile, Esq.
Batavia, Ohio 45103 Assistant City Solicitor Room 214, City Hall Mr. Jame's G. Keepler Cincinnati, Ohio 45220 U. S. NRC, Region Ill 799 Roosevelt Road John D. Woliver, Esq.
Glen Ellyn, Illinois 60137 Legal Aid Security Post Office Box #47 550 Kilgore Street Batavia, Ohio 45103
~
BLACK FOX Mr. G. W. Muench, Manager Black Fox Station Nuclear Project Public Service Coapany of Oklahoma P.O. Box 201 Tulsa, Oklahoma 74102 cc:
Mr. Vaughn L. Conrad Ms. Ilene H. Younghein Public Service Co. of Oklahona 3900 Cashion Place P.O. Box 201 Oklahone City, Oklahoaa 43112 Tulsa, Oklahoma 74102 Andrew T. Dalton, Jr., Esq.
Mr. John C. Zink 1437 South Main Street Manager, Nuclear Licensing Tulsa, Oklahoma 74119 Public Service Co. of Oklahoca P.O. Box 201 Joseph R. Farris, Esq.
Tulsa, Oklahona 74102 Greem, Feldman, Hall & Woodard 816 Enterprise Building Mr. Michael I. Miller Tulsa, Oklahoma 74103 Isham, Lincoln & Beale One 1st National Plaza Sheldon J. Wolfe, Esq.
Suite 4200 Atomic Safety & Licensing Board Chicago, Illinois 60606 U.S. Nuclear Regulatory Commission Washington, D. C.
20555 Isham, Lincoln & Beale Mr. Joseph Gallo Esq.
Mr. Paul W. Purdom, Director Room 325 Environmental Studies Group 1120 Connecticut Avenue, N.W.
Drexel University Washington, D. C.
20036 32nd and Chestnut Streets Philadelphia, Pennsylvania 19104 Dr. M. H. Robinson Black & Veach Mr. Frederick J. Shon P.O. Box 8405 Atomic Safety & Licensing Board Kansas City, Missouri 64114 U.S., Nuclear Regulatory Commission Washington, D. C.
20555 Mr. Maynard Human General Manager Jan Eric Cartwright, Esq.
Western Farners Electric Cooperative Attorney General P.O. Box 429 State of Oklahoma Anadarko, Oklahoma 73005 112 State Capitol Building Oklahona City, Oklahona 73105 Mr. Gerald F. Diddle General Manager John T. Collins, Regional Administrator Citizens Action for Safe Energy, Inc.
U.S. Nuclear Regulatory Commission, P.O. Box 754 Region IV Springfield, Missouri 65801 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011 Ms. Carrie Dickerson Citizens Action for Safe Energy, Inc.
P.O. Box 924 Claremore, Oklahoma 74107
ALLENS CREEK Mr. J. H. Goldberg Vice President Nuclear Engineering and Construction Houston Lighting & Power Company P.O. Box 1700 Houston, Texas 77001 cc:
R. Gordon Gooch, Esq.
D. Marrack Baker & Boots 420 Mulberry Lane 1701 Pennsylvania Avenue, N.W.
Bellaire, Texas 77401 Washington, D. C.
20006 Mr. Wayne Rentf ro J. Gregory Copeland, Esquire P.O. Box 1335 Lowenstein, Newman, Reis & Axelrad Rosenberg, Texas 77471 1025 Connecticut Avenue, N.W.
Washington, D. C.
20036 Rosemary N. Lemmcr 11423 Dak Spring Mr. P. A. Horn Houston, Texas 77043 Project Manager, ACNGS Houston Lighting & Power Company Leotis Johnston P.O. Box 1700 1407 Scenic Ridge Houston, Texas 77001 Houston, Texas 77403 Mr. Ray Matzelle Mr. William J. Schuessler Project Manager, ACNGS 5810 Darnell Ebasco Services, Inc.
Houston, Texas 77043 19 Rector Street New York, New York 10005 Margaret & J. Morgan Bishop 11418 Oak Spring Mr. Ray Lebre Houston, Texas 77043 Project Manager, ACNGS General Electric Stephen A. Doggett, Esq.
175 Kurtner Avenue Pollan, Nicholson & Doggett San Jose, California 95125 P.O. Box 592 Rosenberg, Texas 77471 Susan Plettman, Esquire David Preister, Esquire Bryan L. Baker Texas Attorney General's Office 1923 Hawthorne P.O. Box 12548 Houston, Texas 77098 Capitol Station Auston, Texas 78711 Robin Griffith 1034 Sally Ann Mr. and Mrs. Robert S. Framson Rosenberg, Texas 77471 4822 Waynesboro Drive Houston, Texas 77035 Mr. William Perrenod 4070 Merrick Mr. F. H. Potthoff, III Houston, Texas 77025 1814 Pine Village Houston, lexas 77080
e%
p 9
UNITED sT ATEs f.'
y
,.;( ',g NUCLEAR REGULATORY COMMISSION E
WASHINGTON, D. C. 20555 s \\'[
s
.o JAN 15 1982 MEMORANDtli FOR:
Roger J. Mattson, Director Division of Systems Integration Themis P. Speis, Assistant Director for Reactor Safety FROM:
Division of Systems Integration ERRORS IN BWR VESSEL WATER LEVEL INDICATION
SUBJECT:
Attachment A provides a summary of the results of work done to date in the RSB and ICSB under Task Interface Agreement 81-21 " Pilgrim 1, Water Level Instrumentation Oscillation."
It is emphasized that review of this issue is not complete, even though we have proposed some short and long-term recommendations.
By copy of this memo, I am requesting that comments or other relevant feedback on the contents of this memo, and especially the proposed recommendations, be provided to C. Graves by 1/27/82.
W
.L Y Themis P. Speis, Assistant Director for Reaptor Safety Division of Systems Integration
Enclosure:
As stated cc:
H. Denton W. Hodges J. Rosenthal G. Lainas C. Graves T. Ippolito B. Sheron S. Rubin G. Mazetis L. Rubenstein C. Berlinger H. Thompson V. Thomas L. Phillips D. Ziemann W. Mills T. Dente (BWR Owners Group)
D. Eisenhut T. Novak F. Rosa S. Hanauer E. Rossi CONTACT:
C. Graves (x29404)
J. Rosenthal (x29459)
ATTACHMENT A BWR WATER LEVEL INDICATION ERRORS I.
INTRODUCTION On September 26, 1931, during a routine reactor shutdown and cooling operation at Pilgrim 1, there were several large oscillations of Yarway level detection indication (reference 1).
The first oscillation caused high level isolation followed by low level scram.
The oscillations were attributed to high con ~
tainment temperatures, which caused flashing in the heated reference legs of the Yarway instruments.
At the time, the reactor coolant temperature was about 220 F while the temperature in the upper part of the drywell was 240 F.
In a Task Interface Agreement of October 1981 (reference 2), NRR was assigned the following action plan items:
1.
Review event to establish the generic licensing implications; (DSI/RSB & ICSB) 2.
Review adequacy of Pilgrim Tech Spec on high containment temperature; (OSI/RSB) 3.
Determine acceptability of oscillations in safety related instruments; (DSI/RSB & ICSB)
This memorandum summarizes the results of work in RSB and ICSB to date, provides preliminary responses to the Task Interface Agreement action items and lists some possible short and long-term solutions.
It is emphasized that the in-formation in this memorandum is preliminary since the review is not completg. A report dealing with the problem which was prepared for the BWR Owners was ob-i tained from General Electric on 1 2/31/ 81 and has been given only a cursory review thus far.
Detailed discussions with General Electric personnel w*ill be held after staff review of the GE report.
. 11. BACKGROUND As the result of the TMI-2 accident in March 1979, both the staff and industry have reviewed the adequacy of level detection instrumentation under accident conditions.
In April,1979, IE Bulletin 79-08 (reference 3) requested information from each licensee. on vessel level indication.
IE Bulletin 79-21, "Temperaturo Ef fects on Level Measurenent" (reference 4) was issued in August,1979.
This bulletin addressed errors in steam generator water level resulting from high energy line breaks, including LOCA, inside containment and consequential high containment temperature which caused temperature increases and possible flashing of water in the reference leg of the level indicator.
The problem was identified in a Westinghouse letter of June 1979.
Although the bulletin sent as information to all BWR required actions from PWR operators, it was also A staff letter (reference 5) addressing this problem was sent to operators.
all BWR licensees in July 1979.
In July,1979, General Electric notified its customers of false level indication caused by high temperatures and possible flashing of water in the reference legs of Yarway level instruments under post-LOCA conditions (reference 6).
In September,1980, General Electric again notified its customers of the importance of compensating for these false level indications in Yarway instruments and described false level indications in cold reference leo instruments caused by flashing in the sensing lines (reference 6).
A staff review and evaluation of level instrumentation errors for BWRs, based on a review of GE information provided in Auoust 1979 in NED0-24708 (refe,rence
- 7) is presented in NUREG-0626 (reference 8).
Additional information on the safety significance of errors in or total loss of level indication was provided during 1980 in f1EDO-24708A (reference 9) and fiE D0-25224 (reference 10).
Some current information is available in the proposed emergency procedure guidelines for BWRs which are presently under staff review (see reference 11 and recent revisions) and in the Shoreham docket (referei.ce 12).
e
_4 111..
WATER LEVEL INSTRUMENTATION All level measurement systems in BWRs employ differential pressure transmitters, a reference leg connected to a condensing pot and in turn to the reactor vessel steam space, and a variable leg connected to the vessel at a lower elevation.
Several differential pressure cells share common impulse legs.
Temperature compensated and uncompensated reference legs are employed.
Those level r.easure-ment systems which use a temperature compensated reference leg are called Yarways. Those level measurement systems which use an uncompensated reference Teq are called cold leg instruments or, often, GEMAC.
BWR 1, 2, 3 and some 4's use two redundant Yarways to generate engineered safety feature actuation signals and cold reference leg instruments for indication and control.
The remaining BWR 4's and all 5 and 6's use redundant cold reference leg systems exclusively.
A.
Yarway (Heated Reference Leg) Instrument A schematic of a Yarway level detector is presented in figure 1.
Steam condensed
'in the condensing chamber maintains the reference leg water level by overflow to the variable leg.
The condensate heats the variable leg which, in turn, heats the reference leg.
A thermal shield is provided to reduce heat loss to containment and to maintain relatively high reference leg temperatures.
For short column Yarways,
metal clanos have also been used to imorove heat transfer between the legs.
Information in reference 9 indicates that the reference leg temperature is roughly equal to local containment temperature plus 40 percent of the difference between reactor steam temperature and local containment temperature.
For example, a local containment temperature of 135 F and steam temperature of 546 (Tsat at 1000 psia) would result in a reference leg temperature of 300 F.
The sensing lines leading from the Varway to the differential pressure cell outside of the drywell are 1" schedule 80 stainless steel pipino.
Flow in these lines is blocked by the differential pressure cell.
During normal operation, the stagnant water in these lines should be approximately at local containment temperature.
If the lines are installed close to each other in containment, they should have about the same elevation change and local temperature, Hence, the effects of water density variations along the lines should be cancelled and have a minor effect on level measurement.
The Yarway level detector, which measures the collapsed water level in the outer annulus region of the reactor vessel, is subject to a number of uncertainites.
Those resulting from differences between actual and assumed values of average coolant density in the annulus (affected by system pressure, subcooling and carryunder) were shown to be small in reference 9.
However.in 1979 the General Electric Company identified rather large uncertainties associated with high reference leg temperatures that could occur under some accident conditions (steam line breaks) for which local containment temperatures up to 340 F are predicted
The high reference leg temperatures would result in false high water level sionals.
In addition, a constant indicated lower water level could be reached even though the actual water level has dropped well below the low level tap at the reactor vessel.
Hence, GE recomended that its customers review calibration of the Yantay instruments, increase certain trip points and take other corrective actions to com a
pensate for this effect.
High containment temperature combined with reactor depressurization can also lad to false water level readinos because of flashing or boiling in the reference leg or the sensing lines within containment leading to the differential pressure sensor.
Flashing in the lines might occur during depressurization if the local containment temperature exceeds the saturation temperature corresponding to vessel pressure.
Flashing in the reference leg might be expected ear lier in the transient because of GL higher initial temperatures in the reference leg. The GE conmunication of 1979 wcs concerned only with the ef fects of flashing in the reference leg of Yarway instruments.
Apparently, flashing in cold reference leg instruments was considered to be of minor importance at the time.
In a later communication (September 1980), flashing in the sensing lines of cold reference leg instruments was also considered.
Flashing in the reference leg or lines could occur during normal system depressuriza-tion in preparing for initiation of RHR cooling or under accident conditions.
During the cooldown event at Pilgrim on 9/26/81 (see reference 1), flashing of the reference legs in the Yarway instruments was indicated by several oscillations in the level readings.
At the time, the reactor coolant temperature was 220 F and peak local containment temperatures were about 240 F. ' Under accident conditions such as a steamline break, local containment temperatures can reach 340 F.
Hence, when vessel pressure drops below about 112 psig (p at 340 F) flashing could occur in the sat lines.
If it is assumed that the reference leg temperature rapidly increases to the steady state value for a containment temperature of 340 F and RCS temperature of 546 F, flashing in the reference leg might occur when vessel pressure drops below about 300 psig (Psat at 422" F).
1
\\
s Another scenario involviry flashing '.n the eve [a tsce leg could occur for larger breaks and times such that the vessel pres"/se is apout equal to containment pres-In this case, as discussed in reference 13, 'he rapid reductinn in containment sure.
pressure following initiation cf the containment spray, conbined with the deby in Tests reduction of metal temperatures, could cause flashing in the reference leg.
T%
were conducted to confirm that large erro-s 'n level indication could occur.
solution to this flashing problem involved inst $10aticn of a cooling ab:ket arr ond the reference leg which was supplied with water bc4 the conta l/Tient spray ?. me.
Even without a break, loss of the non-safet} grade contaim.Ont cfoiers wou'M cause s
m the centainment to heat up and could cause flashb 5 upors dN%&;zativ..
~
~
\\
With respact to the flashing prchlem it shoulds be noted that thers would hc. a tim delay involv'd in the heating of the referec^.eg and lincs under accideni con 6
\\
A delay h heat transfer yould be expected' because of the relatively large
" ions amcant of metal in the walls of the reference. leg and lines and the relatively low heat transfer coefficients expected for surfaces in (ont?ct with the containment atnos-phere.
In reference 9, the thermal time conMant for the Yar.tay detector was estimated This value may have bacn calculated assuming only high to be about 20 minutes.
For steam-air mixtures, the,'ancensa tion on cold surfaces results temperature air.
in appreciably larcer heat transfer coefficients than those for air at the same temp-It should also be noted that water expelled by flashing in the heated erature.
reference leg and corresponding line to the differential pressure sensor may.not be replaced quickly.
At the high containment temperatures and lower vessel pressure expected under accident conditions, the condensing chamber could cease to function.
Hence, refill would be delayed until sometime after the vessel water level increases Even under these cir-to a point above the tap leading to the condensing chamber.
cumstances, boiling could occur for a while in the reference leg and lines as the re-sult of continued high local containment temperatures.
In the case of degraded core
cooling when water level remains well below the tap to the condensing chamber and noncondensible gases end rheated steam could be present, there could be extended time periods with lar9e false indications of vessel water level.
In fact, purging of the lines could be required to remove non-condensibles.
B.
Cold Reference Leg Instruments A schematic of a cold reference 109 instrunent is presented in Figure 2.
In this case, the reference leg upper level is maintained by overflow of condensate in the condensing chamber back through the tap to the vessel.
Water density effects and flashing in tJe lines within containment which lead to the di'ferential pressure sensor could be of concern.
Changes of elevation in the lines inside of containment range from 1 to 40 feet in operating plants.
Hence, flashing in the lines under accident conditions could cause false water level indications and delay in refill problems such as those discussed in Se tion A.
Flashing in cold reference leg level instru-ment lir.9s was recognized in the guidelines developed by GE (reference 11).
This situation (loss of reliable level indication for both heated and cold reference leg detectors) was treated by operator instructions to initiate ADS and ECCS actuation to fill the vessel and overflow to the suppression pool via the S/R valves.
-9 I V.
RESP 0t!SE TO SPECIFIC ACTIO!1 ITEtS:
1.
Review event to establish the generic licensing implications.
All BWR vessel level instrumentation, to some degree, is susceptible to reference leg flashing and consequential loss of level indication following rapid vessel depressurization such as observed at Pilgrim The generic BWR emergency procedure guidelines
- include caution and action statements related to loss of level indication.
The suscepta-bility of the level indication system to substantive non-conservative errors during event sequences which include depressurization, and the adequacy of emergency procedures is discussed below.
2.
Review adequacy of Pilgrim Technical Specification on high containnent temperature.
The Pilgrim Technical Specifications do not include drywell temperature as a limiting condition for operation.
We believe such a specification would be credent to prevent undue equipment aging.
However, a LCO on the pre-accident drywell temperature will not preclude post accident loss of vessel level indication.
3.
Determine acceptability of oscillation in safety relateo instruments.
Engineered safety feature actuation signals are generated using the following process variables:
High pressure core spray (HPCS) - vessel level or drywell pressure Low pressure core spray (LPCS)
- vessel level or drywell pressure
- These guidelines are presently under review by the staff and are not, to date, employed at Operating Reactors.
Low pressure coolant injection (LPCI) - vessel level or drywell pressure Automatic depressurization system (ADS) - vessel level and drywell pressure Containment Spray (CS) - vessel level and drywell pressure Reactor Core Isolation Cooling (RCIC) - vessel level only.
Delays in initiation of engineered safety features due to reference leg heatup and boiloff have been considered in response to IE Bulletins 79-08 The staff concluded in NLREG-0626 that for all break sizes, the and 79-21.
reactor either depressurizes fast enough to allow timely initiation of the low pressure system on high drywell pressure, or the breaks are small enough that (at worst) ECC functions occurred before the potential boiling of the reference leg fluid.
Furthermore, ESFAS systems employ latching circuitry except on the ADS level permissive to ensure that safety actions, once initiated, 90 to completion (IEEE 279).
Hence, concerns related to initiation accuracy for automatic safety systems due to reference leg heatup and/or flashing and concerns related to potential reference leg fluid occillation have been previously and adequately addressed for design basis events; however, there are event sequences involving multiple equipment failure which will require manual initiation of engineered safety features.
For some accident scenarios involving a break inside containmerit, adequate indication of actual vessel water level could be lost for all pertinent level instruments as the result of flashing and boiling in the reference legs.
The emergency guidelines (reference 11 and revisions) consider the case
11 -
where the operator has recognized that vessel level cannot be determined.
For this case, the guidelines involve actions to depressurize the reactor and to refill the system until it overflows to the suppression pool via However, if the operator fails to recognize that he has the S/R valves.
lost level indication and has a false high reading of water level, he m,ht take action to throttle or stop ECCS systems in order to avoid filling steam In this case, the flash-lines or to reduce load on emergency pcwer systems.
ing or boiling in the reference legs could lead to operator actions prejudicial to plant safety.
- li ~
V.
RECOMMENDA110NS Once we have received feedback from people on the distribu-These are preliminary.
tion list and met with the BWR Owners Group, they will be finalized.
A.
Short-Term Recommendations (1) Operators should be warned that all level indication is susceptible to We are concerned that operators may have been trained large inaccuracies.
to unduly depend upon cold leg instrumentation should they recognize errors in Yarway reference leg instrumentation.
A cursory examination of plant procedures at Pilgrim 1 and Browns Ferry show that concerns related to cold leg instrumentation inaccuracies have not been incorporated in their procedures.
The operators may have been warned of these concerns by other mechanisms such as training sessions.
We believe that utilities are aware of potential water level inaccuracies in Yarway and cold leg instrumentation based on staff review of GE docu-Early ments prepared for the staff and documents prepared for GE owners.
Later docu-documents recommended reliance on cold leg instrumentation.
ments warned that these instruments, depending on the plant specific in-We do stallation, might also exhibit substantive indicated level errors.
not know whether'or not these concerns and corresponding warnings and actions have been communicated to the control room operators.
Plant specific emergency procedures should be confirmed and/or modified to:
(2)
Clearly identify which level indicators in the control room employ (a)
Yarway reference legs and which employ cold reference legs, and direct the operator to the appropriate indicators.
(b)
Include procedures to help the operator decide when level instru-mentation is to be mistrusted.
Relate specific drywell temperature indication, readily and reliably available to the operator in the control room, to reference leg temperature.
(c)
Include procedures to help the operator recognize those plant conditions and observed instrument responses which indicate successful refilling of reference legs following flashing.
(3) Operability limits of the temperature sensors used in (2)(b) above should be included in the plant Technical Specifications.
B.
Long-Term Recommendations We believe that it is prudent to provide the operator with continuous reliable l evel information.
Event sequences have been identified during which reliable indication will be temporarily lost.
This potential is addressed in the Hardware modi-emergency procedure guidelines now under review by the staff.
fications should be sought to address this problem.
We believe that operator recognition of loss' of accurate level information as The addressed in the emergency procedure guidelines is cumbersome at best.
operator is to relate indicated water level and drywell temperature using a Indicated table contained in a caution statement of the emergency procedures.
water level values beyond the ranges shown in the table are to be mistrusted.
Automation of these actions and decisions seems in order.
Should the operator decide that the water level indicators are to be mistrusted, the operator is to fill the vessel.
Supposedly reference legs would ultimately refill.
At some point in the event sequence, the operator should be previded with positive means to confirm that reliable water level indication has been restored.
This problem may not be adequately addressed in the emergency guide-i line procedures which are presently under staff review.
. Several potential plant modifications are being considered by the staff.
It is not our intent to dictate hardware fixes.
Rather, we give the below recommendations as illustrations that reference leg flashing is a tractable pro bl em.
(1 )
Perform plant specific analysis of susceptibility of cold leg level in-strumentation to reference leg flashing and/or local heatup and corres-ponding water expulsion.
Those plants which are designed with small vertical drops of reference legs inside the drywell should be satisfactory as designed.
(2)
Consider rerouting of reference legs to meet condition (1) above.
(3)
Install temperature measurement of the reference leg.
Such measurements could be used to confirm operability following a drywell temperature excursion and subsequent cooldown.
The measurement w ald be of little use should high drywell temperatures be sustained.
(4)
Develop means to cool the reference leg by establishing flow within the leg.
Two techniques have been suggested:
(1) the temporary opening of equalization valves and/or drain valves, and (2) pumping water with a positive displacement pump from outside the drywell, up reference lines and into the vessel.
Equalization and drain valves are local manual valves.
They are hypothetically accessible following an accident.
The drain lines are routed to the waste treatment system.
Following vessel depressurization, reference leg flashing and subsequent vessel filling in accordance with emergency procedures, temporary opening of the valves could be used to ensure reference leg filling.
No hardware modifications would be required.
Should a sufficiently large LOCA occur, or should an event sequence involving multiple equipmer.t failure occur, such that the
4,
vessel cannot be filled above the reference leg taps, this technique would be of little use.
Pumping water up reference legs would ob-viously require hardware modifications.
The flowrate need only be high enough to overcome the heat load on the reference legs inside the drywell under accident conditions. This technique would permit refer-ence leg filling even if high drywell temperatures existed and the vessel could not be filled to the reference leg tap.
(5)
Develop means to cool the reference leg by using a coolant jacket and diverted ESF flow.
~
REFERENCES 1.'
Licensee Event Report 81-055/OlT-0, "High Drywell Temperatures" Pilgrim Nuclear Power Station, 10/15/81.
2.
Task Interface Agreement, Task No. 81-21, " Pilgrim 1, Water Level Instrumen-tation Oscillation", October,1981.
3.
IE Bulletin 79-08, " Events Relevant to Boiling Water Power Reactors Identi-fied During Three Mile Island Incident", April 14, 1979.
4.
IE Bulletin 79-21, " Temperature Effects on Level Measurements", August 9,1979.
5.
Letter from T. Ippolito, NRC to C. Reed, Commonwealth Edison Company, "Addi-tional Information Required for NRC Staff Generic Report on Boiling Water Re-actors", July 13, 1979.
6.
Telephone conversation with General Electric Company personnel, December,1981.
7.
NEDO 24708, " Additional Information Required for NRC Staff Generic Report on Boiling Water Reactors", August,1979.
8.
NUREG-0626, " Generic Evaluation of Feedwater Transients and Small Break Loss-of-Coolarit Accidents in GE-Designed Operating Plants and Near-Term Operating License Applications", January,1980.
9.
NEDO 24708A, Revision 1, " Additional Information Required for NRC Staff Generic Report on Boilirlg Water Reactor.;", December,1980, 10.
NEDO 25224, "GESSAR Assessment Report, Review of BWR/6 Protection In-Depth for Transient and Accident Events", June,1980.
11.
NEDO 24934, " Emergency Procedures Guidelines - BWRl-6", January,1981.
12.
Attachment to letter from B. McCaffery of Shoreha'm Nuclear Power Station to H. Denton, NRC, August 18, 1981.
13.
Memorandum to Carl Berlinger, CPB, NRR, and Faust Rosa, ICSB/NRR, from N.
Kondic, ICB, DF0, "Two Phase Fluid Water Level in Nuclear Vessels (Reactor SG, PZR),
November 23, 1981.
ORYWELL ACCU'AU'#
nL AC10R pnyWELL IN Wall yttL L CONOf NS'"b C H ^ ta S E R Y
,j
-~
_ nttAOTE VfLSIL g n otC Al TON inCON1HOL t t VE L n O Oth n
[
y s'
/
~
',i v3ni Ari t t
/
/ //
/,
ll k /
/
/
,-HEAT
/
/
j
/
/
+
TH AN5f EN
/'
/,
C LA TAPS IS HO H T CO L UtA N ON L d
~
/
/
f
/
/j
[
~
f-CONI BOL taOO
/
~~
/
/,
-n i
/)
WAl L R rLOW q
}
,,j
/'t ONE H
,etvtt
/
TAP f
/
Figure 1.
Yarway (Heated Reference Leg) Level Detection Instrucment (From NEDO-24708A)
Dry w-N Cone /en nnf Wa //
%.5.se /
CAe e b e p f
Re fu u u w, y, s,. Lcy aev L L ower,
Top e) P Cc//
N d
lN i
?
M- ~.'s 4 4)
~
Figure 2.
Cold Reference Leg Level Detection Instrument