ML20034G491
| ML20034G491 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 03/03/1993 |
| From: | Dan Dorman Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| GL-88-01, GL-88-1, GL-92-04, GL-92-4, NUDOCS 9303090591 | |
| Download: ML20034G491 (25) | |
Text
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E NUCLEAR REGULATORY COMMISSION
~f WASHINGTON, D.C. 20556-0001
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Marcn 3. 1993 Docket No. 50-271 LICENSEE: Vermont Yankee Nuclear Power Corporation I
FACILITY: Vermont Yankee Nuclear Power Station
SUBJECT:
SUMMARY
OF FEBRUARY 23, 1993, MEETING WITH REPRESENTATIVES OF VERMONT YANKEE NUCLEAR POWER CORPORATION On February 23, 1993, pursuant to notice, the NRC staff met with representatives of Vermont Yankee Nuclear Power Corporation at Rockville, Maryland, to discuss licensing issues related to the Vermont Yankee Nuclear Power Station (VY). A list of attendees is provided as Enclosure 1.
Mr. Ashok Thadani, Director of the Division of Systems Safety and Analysis, NRR, opened with remarks on the staff's general view of the generic issue regarding boiling water reactor (BWR) water level indication system errors.
He noted that the effects of non-condensible gas may prevent the system from satisfying various regulatory requirements which were identified by the staff in Generic Letter (GL) 92-04. He stated that the staff's expeditious issuance of GL 92-04 following identification of the issue demonstrates that the staff feels that the issue is significant and that action should be taken promptly following completion of the BWR Owners' Group (BWROG) testing program.
Finally, he emphasized the staff's expectation that modifications to the systems will be needed to demonstrate compliance with the regulatory j
requirements cited in GL 92-04.
Mr. James Pelletier, Vice President, Engineering, of VY, provided opening remarks for the licensee. He stated that VY is different from most BWRs in that the licensee has pursued improvements to the water level indication system since about 1984. He stated that the licensee supports the efforts of the BWROG, will review the BWROG results carefully and "do the right thing" for VY. He noted that the licensee is not convinced that changes to its level indication system will be needed, and needs to understand the basis for the statement that modifications must be made.
Mr. George Hengerle, of Yankee Atomic Electric Company (YAEC), provided a presentation on VY's level indication system, highlighting changes that were made to the system during refueling outages in 1987 and 1989 (handout attached as Enclosure 2). The licensee contended that system geometry, new larger condensing chambers with relatively high condensing rates, and one-inch Schedule 80S welded pipe from the condensing chamber to the instrument cabinet made VY's instruments less susceptible to instrument errors than the i
instruments at other BWRs.
The licensee also stated that it had completed walkdowns of the instrument sensing lines and had observed no leakage.
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. _. March 3, 1993-The staff stated that other licensees have experienced instrument errors where no i
leakage had been detected during walkdowns.
The staff further noted that, although VY's system may be more robust than others, it could still develop leakage over time. The staff, indicating a need for confidence in this area, stated that it will take a very strong case to convince the staff that modifications will not-be needed. The staff and licensee agreed that the licensee will review the results of the BWROG testing program and determine appropriate action for the level indication system at VY.
If the licensee's determination is that no further action is needed, the licensee will inform the staff at the earliest opportunity.
Regarding Proposed Change No.166 to the plant Technical Specifications (TS), the j
staff noted that it had received comments from the New England Coalition on Nuclear Pollution (NECNP) in opposition to the proposed no significant hazards considerations determination, and a request for public hearing. The staff noted that the NECNP comments would be added to the scope of the review.
The licensee stated that it had reviewed the staff's letter of January 21, 1993, regarding incorporation of leakage detection requirements into the TS. The licensee stated its intention to propose a TS change for leakage rate detection related to intergranular stress corrosion cracking in BWR piping, following the guidance of GL 88-01.
The staff stated that it was preparing a response to the licensee's relief request regarding extension of the second ten-year in-service inspection and in-service testing intervals, and that the response should be issued within a few weeks.
Daniel H. Dorman/s/, Project Manager Project Directorate I-3 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation
Enclosures:
1.
List of Attendees 2.
Licensee's Handout cc w/ enclosures:
See next page
. DISTRIBUTION:
Docket File.50-271 W. Butler R. Perch NRC & Local' PDRs D. Dorman A. Cubbage PDI-3 Reading File R. Eaton J. Clifford T. Murley/F. Miraglia T. Clark OGC J. Partlow A. Thadani E. Jordan S. Varga G. Holahan ACRS (10)
J. Calvo R. Jones V. McCree, EDO C. Hehl, RI J. Linville, RI OFFICE LA:PDI-3 PM:PDI-3 D:PDI-3 T')
NAME TC1arJMO' DDorman:mwk WButier DATE J/3/93 5/ 3 /93 j d /93 0FFICIAL RECORD COPY Document Name: VYMTGSUM.223
I
. March 3, 1993 i
The staff stated that other licensees have experienced instrument errors where no leakage had been detected during walkdowns. The staff further noted that, although VY's system may be more robust than others, it could still develop l
leakage over time.
The staff, indicating a need for confidence in this area, stated that it will take a very strong case to convince the staff that modifications will not be needed. The staff and licensee agreed that the i
licensee will review the results of the BWROG testing program and determine appropriate action for the level indication system at VY.
If the licensee's determinat1on is that no further action is needed, the licensee will inform the staff at the earliest opportunity.
Regarding Proposed Change No.166 to the plant Technical Specifications (TS),
the staff noted that it had received comments from the New England Coalition on Nuclear Pollution (NECNP) in opposition to the proposed no significant hazards considerations determination, and a request for public hearing. The i
staff noted that the NECNP comments would be added to the scope of the review.
l The licensee stated that it had reviewed the staff's letter of January 21, 1993, regarding incorporation of leaktge detection requirements into the TS.
The licensee stated its intention to propose a TS change for leakage rate detection related to intergranular stress corrosion cracking in BWR piping, l
following the guidance of GL 88-01.
l The staff stated that it was preparing a response to the licensee's stief request regarding extension of the second ten-year in-service inspection and in-service testing intervals, and that the response should be issued within a few weeks.
.I u&
Daniel H. Dorman, Project Manager Project Directorate I-3 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation
Enclosures:
1.
List of Attendees 2.
Licensee's Handout cc w/ enclosures:
See next page
~
Vermont Yankee Nuclear Power Station CC:
l Mr. Jay Thayer, Vice President G. Dana Bisbee, Esq.
Yankee Atomic Electric Company Office of the Attorney General 580 Main Street Environmental Protection Bureau Bolton, Massachusetts 01740-1398 State House Annex 25 Capitol Street Regional Administrator, Region I Concord, New Hampshire 03301-6937 U. S. Nuclear Regulatory Commission 475 Allendale Road Resident Inspector King of Prussia, Pennsylvania 19406 Vermont Yankee Nuclear Power Station U.S. Nuclear Regulatory Commission R. K. Gad, III P. O. Box 176 Ropes & Gray Vernon, Vermont 05354 One International Place Boston, Massachusetts 02110-2624 Chief, Safety Unit Office of the Attorney General Mr. Richard P. Sedano, Commissioner One Ashburton Place,19th Floor Vermont Department of Public Service Boston, Massachusetts 02108 i
120 State Street, 3rd Floor I
Montpelier, Vermont 05602 Mr. David Rodham, Director Massachusetts Civil Defense Agency Publ.'c Service Board 400 Worcester Rd.
State of Vermont P.O. Box 1496 120 State Street Framingham, Massachusetts 01701-0317 Montpelier, Vermont 05602 ATTN: James Muckerheide Chairman, Board of Selectmen Mr. Raymond N. McCandless Town of Vernon Vermont Division of Occupational Post Office Box 116 and Radiological Health Vernon, Vermont 05354-0116 Administration Building Montpelier, Vermont 05602 Mr. J. P. Pelletier, Vice President Vermont Yankee Nuclear Power Mr. L. A. Tremblay Corporation Senior Licensing Engineer 580 Main Street Vermont Yankee Nuclear Power Bolton, Massachusetts 01740-1398 Corporation 580 Main Street Bolton, Massachusetts 01740-1398
~.
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l LIST OF ATTENDEES LICENSING ISSUES MEETING REGARDING VERMONT YANKEE NUCLEAR POWER STATION ROCKVILLE. MARYLAND FEBRUARY 23. 1993
!LeiE AFFILIATION TITLE Dan Dorg.ar.
NRC/NRR/PDI-3 Project Manager Len Tremblay Yankee Atomic Electric Company Sr. Licensing Engineer VY Project Stan Miller Yankee Atomic Electric Company Manager - VY Project Dean Porter Vermont Yankee Nuclear Power Corp. Engineering Project Sup.
Jim Pelletier Vermont Yankee Nuclear Power Corp. VP, Engineering George Hengerle Yankee Atomic Electric Company Sr. I&C Engineer Robert Perch NRC/NRR/DSSA/SRXB Section Chief Ashok Thadani NRC/NRR/DSSA Director i
Gary M. Holahan NRC/NRR/DSSA Deputy Director
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Ron Eaton NRC/NRR/PDI-3 Sr. Project Manager Amy Cubbage NRC/NRR/DSSA/SRXB Reactor Systems Engineer Robert Jones NRC/NRR/DSSA/SRXB Chief Walt Butler NRC/NRR/PDI-3 Director i
Jim Clifford NRC/NRR/PDV Sr. Project Manager Jose Calvo NRC/NRR/DRPE Assistant Director for Region I Reactors t
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NRC Meeting with Vermont Yankee Nuclear Power Corporation I
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Vermont Yankee believes that Reactor Water Level is the single most important indication to the Operator in assuring the core is adequately cooled.
i Because of this belief...
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Responded to Generic Letter 84-23 in a detailed and conservative manner.
i Initial evaluation considered over 24 references and publications,
'l YAEC-1536, Report on Design Chanoe Alternatives to the Vermont Yankee Reactor Vessel Water Level Measurement System to Address Generic Letter 84-23, i
evaluated numerous design options to select the most appropriate design for Vermont Yankee's needs; Operator awareness heightened through the training
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process; EDCR 85-403, Reactor Vessel Water Level Reference Leo Upgrad_q, was generated to replace the Yarway Columns with a cold reference leg design and utilizing a dual condensate pot configuration (Refer to Figures),
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YAEC-1605, Summary Report of VYC-628 - Reactor Vessel Water Level Error Analysis, identified level errors l
associated with all modes of plant operation at various actual v.s. Indicated levels.
Evaluation (LOCA 87-165), " Fuel Zone Variable Leg Tap Rearrangement", was conducted to determine the-i advantages / disadvantages of utilizing a different vessel
,l tap for use with the 200 inch level measurement j
system.
Calculation VYC408, Vermont Yankee Reactor Water Level Measurement System LOCA Analysis, detailed the anticipated level indication responses over a full range of LOCA scenarios.
Evaluation, Vermont Yankee Reactor Water Level Instrumentation Response Under Accident Conditions, provided additional details of the anticipated water level j
response and how the indications available to the j
Operators could be used.
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EDCR 85403 (1987 refueling outage) addressed the following i
issues-I Size and type of condensate pot to utilize; j
i Condensation rate with dual condensate pot; i
Elevation of condensate pot above vessel tap, including vessel growth; Size and slope of steam supply line; Slope of reference leg impulse lines from the condensate pot down to the drywell penetrations; i
Slope of the variable leg impulse lines from the upper vessel taps down to the drywell penetrations; i
Noncondensible gases; and Calibration & error criteria.
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EDCR 87-403 (1989 refueling outage) provided temperature monitoring capability to inform the Operator when reference leg fluid approached saturation conditions.
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4 4.
Subsequent to Generic Letter 92-04:
VermontYankee has performed a detailed evaluation of the reference leg installation; Strip chart recordings and computer output were evaluated; l
Operations input pertaining to the response of the reactor water level system was obtained;
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A walkdown procedure was initiated to locate and l
identify any leakage (Refer to Figure);
Followed the industry program and has had a i
representative at each of the appropriate committee meetings; Operator awareness has been heightened (read & sign, training, etc) to consider the noncondensible gas phenomena; and Based on conservative but reasonable assumptions founded on the information available at the time, i
postulated errors were identified.
The plant computer (ERFIS) has been programmed to automatically trend and save data associated with the reactor water level system anytime reactor pressure drops below 500 psig for more than 10 seconds.
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The conclusions of the detailed evaluation are as follows:
Potential level errors due to' noncondensable gases will have no affect on automatic safety system response j
during alllicensing basis transients and accidents. Errors associated with post-accident monitoring are enveloped by j
an estimate of 10 inches for the 77 inches to 177 inches range and 20 inches for the + 200 inches to -200 inches l
ranged instruments.
Operators have been trained to recognize the effects of noncondensable gases in reference legs. There are no short or long term impacts as a result of this issue.
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Errors postulated to exist due to these gases are enveloped by existing training and procedures.
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Why Vermont Yankee believes noncondensable gases are not a problem at Vermont Yankee:
Historically, there has been no indication of noncondensable gases coming out of solution; There have been no level mismatches, which indicates no gross leakage and that the condensate pots are working efficiently; Our installation has a calculated condensation rate higher e
than the rate normally associated with condensing chambers (due to the larger size of the Vermont Yankee condensate pot);
There has been negligible leakage at fittings, valves, and the primary mechanism by which components noncondensable gases are brought down into the reference legs; All reference leg piping is properly sloped at greater than 0.5 inches per foot and is oversized at one (1) inch, allowing additional volume, from the condensate pots to the instrument racks; Operators have been trained on this phenomenon; and Plants experiencing noncondensable gas issues have installations which are inconsistent with GE SIL-470; Vermont Yankee agrees that the phenomenon may exist at some piants. However, base on the above, there is no reason to believe this phenomenon will cause the Operators to perform incorrect actions following a rapid depressurization4or long f
term post-LOCA level control.
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experienced these problems.
7.
Based on our design and our experience, Vermont Yankee concludes:
The existing reactor water level installation has proven to be highly reliable and functionally acceptable; Hardware modifications are not appropriate nor planned at this time; 4
Due to the importance associated with this issue, i
Vermont Yankee will continue to follow the industry's efforts; Vermont Yankee will evaluate the results of the Owners Group's efforts to determine if further actions are necessary.
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