ML20238C852
| ML20238C852 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 12/17/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20238C839 | List: |
| References | |
| NUDOCS 8712310279 | |
| Download: ML20238C852 (4) | |
Text
[gs,* AICg,o UNITED STATES l ' 3,.
NUCLEAR REGULATORY COMMISSION
~
g pg a
WASHINGTON, D. C. 20555 o
%...+ /
e l
l SAFETY EV,A,LU,A, TION EY THE OFF,1,CE,0,F, NU, CLEAR RE,A,C,10R, R,E,GULATI,0N SOFPORTIf.G AMENDMENT NO. 13 TO FACILITY OPERATING LICENSE NO. DPR-21 h0RTHEAST NUCLEAR EhERGY COV.PAhY MILLSTONE NUCLEAR PCSER STATION, UNIT NO. 1 DCCKET NO. 50-245 IN,T,RODUCTION By letter dated October 20,19P.7, the Northeast Nuclear Energy Corpar.y (fifiECO, the licensee) submitted a recuest for changes to the Vi11 stone Nuclear Power Station, Unit No. 1 Technical Specifications.
The apendment wculd revise the Technical Specifications to reflect the rereval cf 1cw reactor pressure permissive switches PS 263-54 A and B from the ererger;cy core ccoling system (ECCS: core spray ar.d 1cw pressure coolant injectict.) purp start lo5 c.
These switches were rencved during the 1cE7 refueling cutege. A i
Temporary Vaiver cf Compliar.ce was issued on October 21, 1987 until December 21, 1087, to allow continued plant operation cer. ding issuar.ce of this amendrert.
EVALUATION The licensee stated in its October 20, 1987 letter that the catalyst fcr reacval of the two low reacter pressure pertrissive switches, PS 263-54 f and B, from the ECCS purnp steri logic was ar, internal study performed by NNECO in 1983 on Reactor Protection System (RPS) setpoint drift. This study looked at all RPS instrurnentation relative te its effect on transier.1 and accider.t detection and mitigation.
In addition, LERs and Plant Incident Repcrts (PIRs) were reviewed to determined which sensors had susceptibility to drift.
The list of sensors most susceptible to drift was then compared by NNECO to the list of sensors that could adversely affect a transient or accider.t if it drifted. The following four groups of ser. sors were found to be susceptible to drift, and the drift could adversely affect the cours'e of a transicr.t or accident:
1) 120-second autonatic depressurization system (ADS) Timers.
2)
ECC millisecond and Scram Delay Relays on Load Rejection.
3)
PS 263-52 A-D, Low Pressure Permissive fcr low pressure ECCS valve opening.
4)
PS 263-54 A and B, low Pressure Perriissive for low pressure ECCS purnp start.
m22; pag pfp P
)
-?-
c.
As a result of this study, the following actions were taken by NNECO to decrease the sensitivity and/or susceptibility to drift:
1)
The 120-second ACS tin.ers have been replaced with newer timers which are less susceptible to drift.
2)
The value assumed in the Load Rejection Without Bypass for scren; delay has been increased to 2EC milliseconds whi k maintaining the actual setpoint at T60 milliseconds. Thus, more room for drift is built into the analysis.
3)
The plant I&C departnent has been n.ade aware of the problem of drift witt l
regard to PS 263-SE A-D and has tightered the acceptance band for recalibration of these switches froni 325 psig t25 psi to 375 psig 21P psi.
I This assures timely ECCS flow as the FSt.F assunes ECCS flow at 300 psic.
4)
PS 263-54 A and B have been removed from the ECCS pump start logic.
It should be noted that in order to have setpoint drift actually adversely affect plant response, simultaneous drift of multiple sensors would be required prior to an accident initiation.
NNECO's actual, in-plant data de not show drifting of nultiple sensors to be occurring. Thus, the actions taken above are conservative.
Prior tc the modifications completed during the 1987 refueling outage, the ECCS pump start logic required high dryvell pressure, or low-low water level and low reactor pressure. This logic was originally intended to prevent 1r. advertent ECCS pump starts following scram-induced level decreases.
Operational e>perience has shown that this problem does not exist at Villstene Unit No. 1 and there is no need for a low reactor pressure interlock on ECCS l
pump start. Additionally, the removal of the low reactor pressure permissive i
switches decreases the probability of a malfunction of equipnent important tc safety since there are two less components that could either fail or have a setpoint drift large enough to have a safety impact. Therefore, the removal l
of the low reactor pressure permissive switches from the ECCS pump start logic does not affect the safety of the plant and may even enhance plant safety.
Furthermore, the core spray and LPCI admission valves are still interlocked on reactor low pressure, so even though the pumps may start, they would not l
deliver ECCS water until a reactor low pressure signal opens the admission valves. Therefore, from a system start;oint the functional operation of the j
ECCS pumps has not changed because of tie removal of these permissive switches.
1 The ECCS has mini-flow recirculation to assure integrity of the pumps.
While performing a routine, biannual review of Administrative Control Procedure j
ACP-QA-9.02A, " Surveillance Master Test Control List," khich includes e list of all the periodic surveillance tests to be performed, frequency intervals, appropriate test procedures and Technical Specification references, NNECO recently discovered that the appropriate changes to f1111 stone Unit No l's Technical Specifications had inadvertently not been implemented. NNECO ime-dietely notified the NRC staff of this condition in a telephone conversatier. cn October 16, 1987, and informed the staff of our intent to request a licens's 1
_A
i
' aner.dr+nt pursuant to 10 CFR 50.91 f r. t letter dated October 19, 1987, if!ECO committed to subn.it the license arendnent request no later than October ?0, 1987. Ttt license anendrent request was subraitted on October 70, 1957, and the staff issued a Temporary Waiver cf Compliance on October fl. 1SE7 until December 21, 1987, to allow continued plant operation perdir.g issuance of the requested etendnint.
In the treantirie, l't?ECO has initiated a review of all plant design changes that were implemented during the 1907 refueling outage to ensure that all a gropriate changes to the Technical Specifications and plant procedures were implemented.
Technical Specification Table 3.2.?, " Instrumentation that Initiates and Controis the Energency Core Cooling Systems," currently indicates in the " Remarks column for the reactor low-low water level trip function that the core spray and LPCI purrps vill start upon indication of reactor 1cw-low water level "in conjunction with low reactor pressure." Since the low reactor pressure permisshe ssitchts were removed from the ECCS pump start logic during the 1987 refueling cutage, Teble 2.2.? was revised.
The second remark pertaining to the reactor low pressure pern.isshe trip function in Table 3.7.7 shculd be deleted in its entirety. The removal of PS 263-54 A and B from the ECCS pump start logic has eliminated this permissivt function.
It should be noted that the first remark for the reactor low pressure permissive trip function is still applicable. The core spray and LPCI admissior.
valves vill still open until a reacter low pressure signal is received.
Technical Specification Table 4.2.1, " Minimum Test and Calibration Frequency for Core Cooling Instrumentation Rod Blocks and Isolations," also needs to be
)
revised. The reactor low pressure pern.issive switches have been rer.oved frcr the ECCS pump start logic, and thus, their functional tests and calibrations arenolon!errequired. The reactor low pressure permisshe switches which 1
permit ECC admission valve opening are still required to be tested and calibrated in accordance with Table 4.2.1 As discussed above, increased awareness of the sensitivity of these valve opening permissive switches to setpcint drift has been established.
i The staff has previously reviewed this issue and presented its findings in the Integrated Safety Assessment Report for Millstone Unit No. 1, issued April 1987 (tlUREG-1184). The staff agreed with the rationale for removing the pressure switches and found no negative impact on safety and noted that the renoval of the pressure switches may enhance plant safety because possible two contributors to failure of the ECCS punps to start have been removed.
ENVIRONMENTAL CONSIDERATION This amendment involves a change to a requirerrent with respect to the instella-tion or use of facility components located within the restricted area as defined in 10 CFR Part 20 and/or changes to the surve111erce requirements. The staff has determined that the amendment involves no significant increase in the arrcunts, and nc 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 Cottrr.ission has previously issued a proposed finding that this anendirer,t involves no significant hazards consideration and there has been no public corment on such finding. Accord-ingly, this arrendnent treets the eligibility criteria for categorical exclusion
4 set forth in 10 CFR 51.72(c)(9). Pursuant to 10 CFR 51.ET(b) no environmental impct stateur.t or environn. ental asscssnent need be prepared ir. connectior, with the issuance of this amendment.
CONCLUSION The staff has concluded, based on the considerations discussed above, that:
will r.ct be endangered by operation in the proposed mant.er, and (?) public (1) tbtre is reascrable assurer.ce that the health and safety of the such activities vill be conducted in compliarice with the Contrission's regulations sod the issuance of this aundn.ent will r,ct be inimical to the cono.on defense and security or tc the health and safety of the public.
Cated:
December 17, 1987 Prircipal Centributcr:
M. Boyle 4
4