ML20205F195
| ML20205F195 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 08/08/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20205F168 | List: |
| References | |
| NUDOCS 8608190113 | |
| Download: ML20205F195 (6) | |
Text
,
)
=
~
.# "c%
p
- c, UNITED STATES NUCLEAR REGULATORY COMMISSION
. ?,,
<S WASHINGTON, D. C. 20586 4
%,*...*/
i SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 94' TO FACILITY OPERATING LICENSE NO. DPR-28 VERMONT YANKEE NUCLEAR POWER CORPORATION VERMONT YANKEE NUCLEAR POWER STATION DOCKET NO. 50-271 t
1.0 INTRODUCTION
c.
By letter from W. Murphy, Vermont Yankee Nuclear Power. Corporation, to H g
Denton, Nuclear Regulatory Consnission (Reference 1), Technical 4
Specification (TS) changes were proposed for Vermont Yankee Nuclear Power Station (VY) to permit extended operation with only one recirculation puinp in operation and to address thermal-hydraulic stability monitoring (during this Single Loop Operation (SLO) as well as in Two Loop Operation TLO).
Following discussions with the staff, there was a second submittal by VY (Reference 2) revising some details of the TS relating to SLO limits and Thernal-Hydraulic Stability (THS). Also submitted was a letter (Reference
- 3) enclosing a report (Reference 4) by General Electric (GE) providing an analysis of SLO for VY.
l l
VY current TS permit SLO only for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and there are no provisions for potential alteration of safety and operating limits because of SLO conditions, and no provisions for THS monitoring, if needed, either for SLO or TLO. The proposed changes would permit SLO for unlimited time frames and without specific additional power limits, and provide for needed changes to operating limits and require THS monitoring. A primary resistance to proposals by VY and others to extend SLO has been NRC concerns relating to THS analyses and monitoring. These concerns have l
been largely resolved in the past year, and a number of plants have proposed TS changes to permit SLO and these have been reviewed and t
accepted by the staff. Principle examples of these changes and acceptances may be found in References 5 and 6, the Safety Evaluation Reports for Duane Arnold, a lead plant for the changes, and for Susquehanna, the most recent example of evolving TS.
The staff approved resolution of the THS problem is based primarily on the approval of the GE surveillance mode of " detect and suppress" expressed in the GE Service Information Letter (SIL) 380 (Reference 7). This mode of 8608190113 860808 DR ADOCK 05000271 PDR j
l l
2 4
operation may be used for both TLO (instead of providing approved THS analysis-for each reload cycle) and for SLO. This mode of operation is now required by the staff for SLO without specific regard to THS analysis.
The NRC has recently p'ublished two generic letters (References & and 9) relating to THS and SLO. These generic letters present staff positions in this area including acceptance of surveillance modes recommended in SIL-380 and provide a basis for review of TS changes.
The VY proposal is similar to the previously approved requests for SLO and TLO " detect and suppress" TS changes and is in accord with staff positions in the generic letters. VY will use surveillance for TLO as well as SLO and will not provide THS analyses for each cycle.
2.0 EVALUATION There are two principal areas related to SLO which require TS changes.
They are (1) changes to some safety and operating limits and instrument I
setpoints resulting from altered reactor conditions and reanalysis of relevant transient and accident events, and (2) operating limits related
~
1h _ '
to the power-flow map location and monitoring of THS and the suppression of possible oscillations. The VY original submittal (Reference 1) presented TS changes and supporting information in both areas. The supporting information for changes to limits and setpoints included the report by GE (Reference 4) of the analyses of relevant transients and accidents for SLO for VY and the derivation of appropriate limits and operating conditions. The changes to provide monitorinc and suppression of oscillations were based on SIL-380 and generally patterned after the Duane Arnold TS. After the initial submittal there were several discussions with the staff, largely related to required time frames for limit resetting actions and monitoring related activities and these resulted in a supplemental submittal (Reference 2) altering some of the time related values as well as some flow restrictions and baseline requirements.
The GE analyses of SLO (Reference 4) provide the following changes to l
Safety Limit (SL) and Operating Limit (0L) Minimum Critical Power Ratio (MCPR) and Maximum Average Planar Linear Heat Generation Rate (MAPLHGR) limits, and to Average Power Range Monitor (APRM) and Rod Block Monitor (RBM)setpoints. These analyses and changes are similar in content and magnitude to those approved in previous reviews.
(1) SL MCPR and OL MCPR: The SL MCPR is increased by 0.01 to account for increased uncertainties in core flow and power distribution measurements.
The OL MCPR is increased for VY by the same amount. Limiting transients were reexamined to assure that this is a sufficient increase throughout I
the achievable power-flow range. No additional increase in OL MCPR is necessary since transient events initiated from TLO remain limiting.
These changes are acceptable.
4
.v-
,. m
-8
~
(2) APRM screm and rod block and RBM flow biased limit functions: These equations have an added term to account for the difference between single and two loop drive flow for the same core flow. This adjustment accounts for the difference between actual and indicated flow and preserves the original relation between limits and effective drive flow. These changes are acceptable.
(3) MAPLHGR: GE has performed a series of LOCA analyses for VY to provide a MAPLHGR multiplier for this' event. The principle change in the analysis is the assumption of an earlier occurring boiling transition. The multiplier for YY for all GE fuel was determined to be 0.83. This is y
T acceptable.
s I
Other relevant transients and accidents were examined and evaluated and found to require no additional changes to the TS. This included an
+
analysis of the SLO recirculation pump seizure accident for which it was found that the minimum MCPR remained greater than the St MCPR by 0.14 g_,
(Reference 10). This analysis is acceptable.
5 In addition to these analyses GE recommends that the flow control should
{
be in manual. This condition is in the TS.
To handle possible problenis of THS in TLO or SLO VY has provided new TS providing operating restrictions and/or monitoring of APRM and selected Local Power Range Monitor (LPRM) noise levels when in certain regions of the power-flow map. These requirements are in accord with the k
recommendation of SIL-380 and, as worked out in discussions with the staff, a
are similar in content to THS restrictions and monitoring approved in the past year (e.g., Reference 5 and 6).
Aprinciplefeatureoftherestrictionsistheregioninthepower-[ low map above the 80 percent power-flow line and between 34 and 45 percent flow in which APRM and LPRM monitoring is required (34 percent flow corresponds to two pump minimum flow for VY). Below 34 percent flow (and above the 80 percent line) SLO is not permitted. Baseline noise levels are required and in the monitoring region action must be taken to suppress oscillations if the noise levels are greater than 3 times the baseline levels. Appropriate time intervals 4are set up in which to carry out these operations. These action and surveillance TS for THS are acceptable.
Since VY will monitor THS in TLO as well as SLO they are not required to submit a stability analysis for this or future reloads.
a The initial submittal had a core flow (maximum) limit of 45 percent for SLO to address flow-induced core plate delta p noise.
In response to staff digcussions this was altered to require only an administrative limit, i.
requitting procedures such th'at SLO above 50 percent core flow would involve monitoring core plate delta p noise. This is an acceptable alternative.
h s
~.
4 Although the subject is not discussed in the VY submittal, it may be noted that some general questions have arisen about the adequacy of SLO surveillance methods which have been used in some plants to mon.itor jet pump operability in accordance with NUREG/CR-3052 to close out problems presented in IE Bulletin 80-07, "BWR Jet Pump Assembly Failure." Since VY has replaced all 20 of the hold down beams in question with an acceptable improved design, the question regarding SLO jet pump surveillance adequacy is not applicable.
3.0 TECHNICAL SPECIFICATION CHANGES To accomplish the required changes for SLO limits and THS monitoring the following TS have been changed.
(Therearealsominoradministrative changes). Most of the specifications were altered in the second submittal (Reference 2) to change action and surveillance times and other THS factors previously discussed.
(1) 1.1 and Basis 1.1: The SL MCPR has been increased by 0.01 to 1.08 g
for SLO because of an increased noise uncertainty contribution. This' is acceptable.
(2) 2.1.A. 2.1.B. Figure 2.1-1 and Basis 2.1: The equation for'the APRM Flux Scram setting and APRM Rod Block trip setting have an added delta W term to account for the difference between TLO and SLO drive flow at the same core flow. This has been previously discussed and is acceptable. There are also some administrative page changes to accommodate the technical changes.
(3) Tables 3.1.1 and 3.2.5 and accompanying footnotes and Basis 3.2:
These changes address the setpoint changes required because of flow changes for SLO discussed for TS 2.1 above. These tables provide the settings for the Reactor Protection System and Rod Block instrumentation. The changes add the same delta W tenn as in TS 2.1.
They are acceptable.
(4) 3/4.6.G. H and J Figure 3.6.4 and Bases 3/4.6.G, H and J: These changes and additions provide for and describe the TLO and SLO 1
surveillance regions in the power-flow map, the nature of the APRM-LPRM surveillance, baseline and operation information required, and the levels and time frames for action in providing this surveillance and acting on it. Manual flow control is required for SLO. As previously discussed these requirements provide a satisfactory representation of the recommendation of SIL-380 and the staff generic position and previous approvals, and are acceptable.
There are also some administrative page changes and a change relating to previously aproved Amendment 92.
(5) 3.11.A and C, Bases 3.11.A and C and Tables 3.11-1B through IE, IG and 2: These changes provide for the decrease in the MAPLHGR limit
8 tm 5
)
i by the factor 0.83 for SLO, and also for an increase in OL MqfR by
}
0.01. The changes.are acceptable.
We have reviewed the reports submitted by VY proposing TS changes relating to SLO and THS. Based on this review we conclude that appropriate documentation was submitted and that the proposed changes satisfy staff positions and requirements in these areas. SLO operation and THS monitoring in the manner thus described is acceptable.
4.0 ENVIRONMENTAL CONSIDERATION
S This amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The staff has deterr.ined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Comission has previously issued a proposed finding that 5
- g. -
-this amcadment involves no significant hazards consideration and there has been no public coment on such finding. Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.
5.0 CONCLUSION
We have concluded, based on the considerations discussed above, that:
will not be endangered by operation in the proposed manner, and (2) public (1) there is reasonable assurance that the health and safety of the such I
activities will be conducted in compliance with the Comission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
H. Richings Dated: August 8, 1986 l
~
l l
l
t, 6
REFERENCES Letter from W. Murphy, Vermont Yankee Nuclear Power Corporation (VYNPC),
1.
to H. Denton, NRC, dated March 12,1986, " Proposed Technical Specification Change for Single Loop Operation...."
2.
Letter from R. Capstick, VYNPC, to V. Rooney, NRC, dated May 9,1986
" Single Loop Operation and Thermal-Hydraulic Stability" 3.
Letter from R. Capstick, VYNPC, to V. Rooney, NRC, dated March 27, 1986,
...-Supporting Document" p
5 is.
g 4.
General Electric Report NED0-30060, " Vermont Yankee Single Loop
~
Operation," dated February 1983.
Letter from M. Thadani, NRC, to L. Liu, Iowa Electric Light and Power 5.
Company, dated May 28, 1985, Docket No. 50-331.
Letter from E. Adensam, NRC, to H. Keiser, Pennsylvania Power and Light 6.
Company, dated April 11, 1986, " Amendment Nos. 56 and 26..... Susquehanna Units 1 and 2."
General Electric Service Information Letter No.380, Revision 1. February 7.
10, 1984.
1 Generic Letter No. 86-02, " Technical Resolution of Generic Issue 8.
B-19-Thermal Hydraulic Stability," January 23, 1986.
9.
Generic Letter No. 86-09, Technical Resolution of Generic Issue No.
B-59-(N-1) Loop Operation in BWRs and PWRs," March 31, 1986.
LetterhromR.Capstick,VYNPC, tov.Rooney,NRC,datedJune9,1986, 10.
l.
".... Response to Request for Information."
.-