ML20073A126
| ML20073A126 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 09/15/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20073A116 | List: |
| References | |
| NUDOCS 9409200138 | |
| Download: ML20073A126 (3) | |
Text
.
[
pm%4 n.-
4 a
S UNITED STATES 5
NUCLEAR REGULATORY COMMISSION l
k..../
WASHINGTON. D.C. 205SH001 SAFETY EVALVATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 92 TO FACILITY OPERATING LICENSE NO. DPR-22 NORTHERN STATES POWER COMPANY MONTICELLO NUCLEAR GENERATING PLANT
]
DOCKET N0. 50-263
1.0 INTRODUCTION
By letters dated January 3, 1994 and August 29, 1994, the Northern States Power Company (the licensee) requested an amendment to the Technical Specifications (TS) appended to Facility Operating License No. DPR-22 for the Monticello Nuclear Generating Plant. The August 29, 1994, letter only provided additional test data and did not affect the staff's initial no significant hazards determination contained in the original Federal Reaister a
notice.
The proposed amendment would change the surveillance requirement for safety relief valves (SRV) to be consistent with the Section XI Inservice Testing Requirements of the ASME Code. ASME Section XI, Subarticle IWV-3200, states that pressure relief devices shall be tested in accordance with'the requirements of ANSI /ASME OM-1-1981.
Paragraph 1.3.3.1.2 of ANSI /ASME OM '
1981 addresses the applicable test frequency of Class 1 pressure relief.
devices and requires that, "all valves of each type and manufacture shall be-tested within each subsequent 5' year period with a minimum of 20% of the valves tested within any 24 months.
This 20% shall be previously. untested' i
valves, if they exist."
Currently, Monticello TS require that a minimum of seven SRVs be bench tested or replaced with a bench tested valve every i
refueling outage.
2.0 EVALVATION The eight main steam SRVs'at Monticello are 3-stage Target Rock design which
.I consist of a 2-stage pilot valve section, remote air actuator section and the-i main valve section.
The SRVs are designed to ensure that the reactor coolant system pressure safety limit is...never reached.
The SRVs are set to open at a j
pressure no higher than 105% of the vessel design pressure'and-they-limit the j
reactor pressure to no more than 110% of the reactor pressure vessel design pressure..Three of the SRVs'are assigned to the automatic depressurization system (ADS).
The function of the ADS is to provide a backup to the high'
. pressure coolant injection (HPCI)' system for automatically depressurizing the l
reactor vessel so that the low pressure coolant injection (LPCI) and the core-spray system can operate to protect fuel cladding.-
The SRVs are sized for overprWJre protection during a main steam isolation valve (MSIV) closure at full reacBr power.
As the system isolates, pressure rises'in the vessel until the SRVs cpen to mitigate the accident.
The
)
l
.. 9409200138 940915 i
PDR ADOCK 05000263 l
P
.PDR m
.. ~
.c
.i 1 evaluation assumes that;only see of the eight SRVs are operable and that they open at 1% over their setpoint with'a 0.4 second time delay.
As discussed in Updated Safety Analysis Report Section 4.4.4, it is'not feasible to test the SRV setpoints while the valves are4 installed in the plant-or during normal plant operation. The valves are removed for maintenance or bench checks and reinstalled during normal plant shutdowns.
In the past,-
i normal practice has been for all eight pilot assemblies to be bench checked or replaced with spare bench checked pilot assemblies during each refueling _
i outage, even though TS 4.6.E.1.a only requires this to be done for seven of the eight valves.
This was done in order to avoid an administrative oversight in missing a valve required to be bench checked during an outage.
In-addition, the main seats of two SRVs are inspected during each refueling outage as required by TS 4.6.E.1.b.
The proposed change reduces the test frequency from seven of the valves being i
bench tested every refueling outage to 20% of the valves being tested within' any 24 months.
The decreased test frequency is permitted by ANSI /ASME OM -
1981, which has been reviewed and approved by the ASME Code Committee for industry-wide use and has been imorporated by reference.through the 1986 Edition of Section XI of the ASME Code in 10 CFR 50.55a, May 5,1988 (Federal Reaister, Vol. 53, page 16051). The current Inservice Test Program _for Monticello was developed to the 1986 Edition of Section XI. The proposed change is also consistent with Surveillance Requirement 3.4.3.1 of NUREG-1433,
" Standard Technical Specifications, General Electric Plant, BWR/4," which specifies the frequency of SRV testing to be in accordance with inservice i
testing requirements.
The licensee states in its evaluation that the change will have no adverse impact on the reliability of the SRVs. The licensee also' states that, although the change may result in any single valve being tested or changed out less frequently, the overall reliability of the valves may increase bec;pe the most common performance problems' associated with the valves can be A 9d by handling' or disassembly work. The proposed change'will minimize such a;r' on the ' valves.
The licensee also stated in its' January 3,1994,. submittal that as before, all eight SRVs will continue to be exercised each refueling-outage in accordance with ASME Section XI requirements during plant startup.
The licensee has not experienced problems with setpoint drift that plants with -
the different ' design, 2 stage Target Rock SRVs, have experienced as verified.
by the data submitted if the licensee in its letter dated August 29, 1994. The letter contains the as-found SRV Mft pressures for SRV testing performed ~.
d wing the past 5 years. The results of the data show that only three valves in the past 5 years lifted at pressures outside of the as-found acceptance 1
-criteria (1076-1131 psig). Howear, the. valves are only designet to maintain their setpoint tolerance over the operating cycle to +/- 3% (16 '; 1142' psig).
1 Therefore, the as-found acceptance' criteria is more stringent than what the' valves are designed to provide. All the lift pressures ~ for SRV tests-i
~
performed during the past 5 years were within the design tolerances of.the valves.
1 1
-l a
E i.
f The staff has determined that the proposed change in SRV testing frequency is acceptable.
This conclusion is based on:
(a) compliance with the 1986 Edition of Section XI of the ASME Code and ANSI /ASME OM-1-1981, (b) compliance with NUREG-1433, " Standard Technical Specifications, General Electric Plant, BWR/4," surveillance requirements, and (c) reliable as-found setpoint data for the past 5 years of bench testing.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Minnesota State official was notified of the proposed issuance of the amendment.
The State official had no comments.
4.0 LNVIRONMENTAL CONSIDERATION The amendment changes a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The staff has determined 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 i
Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding (59 FR 10011).
Accordingly, the 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 the amendment.
5.0 CONCLUS10B The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Pr'ncipal Contributor:
B. Wetzel Date:
September 15, 1994 l
.