ML20078Q966
| ML20078Q966 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 02/15/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20078Q963 | List: |
| References | |
| NUDOCS 9502220150 | |
| Download: ML20078Q966 (5) | |
Text
.
g.aaroy J.
UNITED STATES
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SAFETY EVALUATION BY THE OFFICE OF NVCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0. 185 TO FACILITY OPtRATING LICENSE N0. DPR-65 NORTHEAST NUCLEAR ENERGY COMPANY THE CONNECTICVT LIGHT AND POWER COMPANY THE WESTERN MASSACHUSETTS ELECTRIC COMPANY MILLSTONE NUCLEAR POWER STATION. UNIT NO. 2 DOCKET NO. 50-336
1.0 INTRODUCTION
By letter dated April 25, 1994, as supplemented September 21, 1994, the Northeast Nuclear Energy Company (NNECO or the licensee) submitted a request for changes to the Millstone Nuclear Power Station, Unit No. 2 Technical Specifications (TS). These proposed changes are in response to Generic Letter (GL) 90-06 " Resolution of Generic Issue 70, ' Power-Operated Relief Valve and Block Valve Reliability,' and Generic Issue 94, ' Additional Low-Temperature Overpressure Protection for Light-Water Reactors,' Pursuant to 10 CFR 50.54(f)."
GL 90-06 represents the staff's technical position on the two generic issues; (GI) GI-70 which involves the evaluation of the reliability of pressurizer power operated relief valves (PORV) and block valves, and GI-94, which addresses the concerns of overpressure protection and the need to restrict the allowed outage time for a low-temperature overpressure protection (LTOP) channel in operating Modes 4, 5, and 6.
The specific proposed TS changes related to GI-70 are TSs 3.4.2.1 and 3/4.4.3 and the specific proposed TS changes related GI-94 are TSs 3.4.1.4, 3.4.9.1, and 3/4.4.9.3.
Also included in the submittal, are proposed TS char.ges to correct a deficiency identified in Licensee Event Report (!.[R) 93-016-00, dated August 27, 1993. The licensee identified that the assu'nptions in the boron dilution event analysis and the related plant operating procedures conflicted with the requirements, on the shutdown cooling (SDC) system operation.
The specific proposed TS :hanges related to boron dilution are TSs 3/4.1.1.3, 3.1.2.2, 3/4.1.2.4, 3.1.2.8 and 4.9.8.
To enhance plant safety, the licensee also proposed TS changes to improve shutdown risk management.
The specific proposed TS changes are TSs 3.1.2.1 and 3/4.5.3.
9502220150 950215 DR ADOCK 05000336 PDR
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' finally, the licensee proposed modifications to TS 3/4.1.2.3, Charging Pumps -
Shutdown, so that the TS will remain consistent with the previously discussed proposed TS changes.
The September 21, 1994, letter provided clarifying information that did not change the initial proposed no significant hazards consideration determination or expand the scope of the original Federal Reaister Notice.
2.0 EVALUATION The licensee's submittal encompasses four related issues; PORV and block valve reliability, LTOP, boron dilution and shutdown risk management. The staff review of the proposed changes is discussed below.
2.1 Changes Due to GI-70, PORV and Block Valve Reliability The staff determined that over a period of time the role of PORVs has changed to perform more safety-related functions. Therefore, a need has arisen for increased reliability of both the PORVs and the associated block valves.
Based on the findings of GI-70, the staff concluded, in GL 90-06, that the following actions should be taken to improve the reliability of PORVs and block valves.
1.
Include PORVs and block valves within the scope of an operational quality assurance program that is in compliance with 10 CFR Part 50, Appendix B.
This program should include the following elements:
a.
The addition of PORVs and block valves to the plant operational Quality Assurance List.
b.
Implementation of a maintenance / refurbishment program for PORVs and block valves that is based on the manufacturer's recommendations or guidelines and is implemented by trained plant maintenance personnel.
c.
When replacement parts and spares, as well as completed components are required for existing non-safety-grade PORVs and block valves (and associated control systems), it is the intent of this generic letter that these items may be procured in accordance with the original construction codes and standards.
2.
PORVs, PORV control air systems and block valves should be covered by subsection IWV of Section XI of the ASME Code.
PORV testing should be performed in Modes 3 or 4.
PORVs and block valves should be included in motor-operated valve (MOV) test program discussed in GL 89-10.
3.
Modify the limiting conditions for operations for Modes 1, 2, and 3 as specified in Attachments A-1 through A-3 of GL 90-06.
. To address PORY reliability, the licensee has proposed changes to TSs 3.4.3, 3.4.2.1 and surveillance 4.4.3.1.c.
NNEC0 proposes to modify TS 3.4.3 to allow the manual cycling of the valve in the case where the valve has been declared inoperable but can still be closed and therefore continue to perform the intended safety function.
The modification would not change the PORV and block valve actuation circuitry or the valves' power supply configuration.
The proposed modification to TS 3.4.2.1 eliminates the applicability of the reactor coolant system (RCS) safety valves during Mode 5 operation. The safety valves are not used for LTOP mitigation, therefore the reference to Mode 5 does not apply. This change is consistent with the guidance of GL 90-06.
The licensee proposes to bench test their PORVs in lieu of in-situ testing.
By [[letter::B14245, Submits Info to Resolve NRC 921106 Comments on Util 901221 & 910321 Responses to GL 90-06, Resolution of GI 70, PORV & Block Valve Reliability & GI 94, Addl Low Tempr Overpressure Protection for Light-Water Reactors|letter dated January 11, 1993]], the licensee indicated that they will follow the staff position of having the PORVs bench tested by qualified laboratory at conditions representative of Modes 3 or 4.
The licensee further agreed to ensure that the proper reinstallation of the PORVs and controls is performed and verified for continued operability. This alternative is in agreement with the position outlined in a letter from the staff to the licensee dated November 6,1992, and is, therefore, acceptable.
NNECO has proposed changes to the TS that will increase the reliability of the PORVs and associated block valves through increased surveillance testing and increase the availability of the PORVs by allowing manual actuation. These changes are within the guidance of GL 90-06 and, therefore, the staff finds these proposed changes acceptable.
2.2 Low Temperature Overpressure Protection (GI-94)
GI-94 was developed after the implementation of Multi-Plant Action Item B-04 because a number of LTOP events were still occurring.
It was noted in the l
staff review of these events that at least one LTOP channel was out of service and in a few cases both LTOP channels were inoperable.
This led to the staff's conclusion that a substantial improvement in LTOP system availability was necessary when the potential for an overpressure event is the highest, especially during water-solid operations. Therefore, based on the findings in GI-94 the staff has concluded, in GL 90-06, that the current Technical Specification for Overpressure Protection should be modified to reduce the allowed outage time (A0T) for a single channel from 7 days to 24 i
hours when the plant is operating in Modes 5 or 6.
This guidance is applicable to plants that rely on both PORVs and residual heat removal (RHR) safety relief valves (SRVs) or that rely on RHR SRVs only. The licensee proposed the following TS changes to meet the requirements of GL 90-06 while enhancing the availability of equipment to reduce shutdown risk.
The current TS requires either one high pressure safety injection (HPSI) or one charging pump be operable during Modes 5 and 6.
The proposed changes for TSs 3.1.2.1 and 3.1.2.3 are to ensure that one HPSI and one charging pump are operable during Mode 5 or 6 and if an additional HPSI pump or charging pump is
e
. a o)erable the RCS must be vented by a vent 2 2.8 in. As stated by the NNECO, tie control of the number of boron injection flowpaths during shutdown, will (1) ensure that an LTOP condition is not created by the operation of too many pumps, (2) maximize the capability of mitigating shutdown risk scenarios by requiring an additional injection source, and (3) ensure that the LTOP and boron dilution analysis remain bounding.
The proposed modifications to TS 3/4.4.9.3 indicate that both PORVs are to be operable during Mode 4 when the RCS temperature $; 275 'F and Modes 5 and 6 whgnthereactorvesselheadisonandtheRCSisnotventedbyavent22 in. TS and surveillance 3/4.4.9.3 are modified to increase operational flexibility by using the PORV or RCS vent for venting purposes.
The A0T for the LTOP system was also reduced from 7 days to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> during Modes 5 and 6.
The changes to these TSs are consistent with the guidance of GL 90-06.
The proposed modification to TS 3.4.1.4 limits the number of reactor coolant pumps allowed to be operable during Mode 5.
TS 3.4.9.1 proposes to add a restriction, of 5 'F per hour on the cooldown rate when the RCS is less than 120 *F.
These modifications are in response to NRC Information Notice 93-58, "Non-Conservatism in Low Temperature Overpressure Protection for Pressurizer Water Reactors", and compensate for the non-conservatisms found in the LTOP analysis, ensuring that unanticipated pressure rises do not occur.
Based on the intent of GL 90-06 to reduce the occurrence of LTOP events and the licensee's compliance with the guidance and information of GL 90-06 and IN 93-58, the staff finds the proposed modifications acceptable.
2.3 Boron Dilution The previous boron dilution event analysis (October 1988) required a minimum shutdown cooling flow of 2450 gallons per minute (gpm) in Modes 4 and 5.
Plant operating procedures required the shutdown cooling (SDC) flow rate to be less than 1500 gpa to prevent vortexing at the SDC suction line in Mode 5 and when the RCS is drained to the centerline of the reactor vessel hotleg.
The changes to TSs 3.1.1.3, 3.1.2.2, 3.1.2.3, 3.1.2.4, 3.1.2.8, 4.1.1.3, 4.1.2.3, and 4.1.2.4 are to alleviate the conflict and to provide added assurance that the boron dilution analysis remains bounding when the SDC flow rates are reduced to prevent vortexing.
The changes to TS 3/4.1.2.3 were discussed in the previous section.
TS 3/4.1.1.3 proposes to reduce the minimum RCS flow rate from 3000 gpm to 1000 gps.
The lower flow limit allows operation at lower flow rates during mid-loop - when vortexing is of great concern. This lower flow rate was included in the revised boron dilution analysis.
The licensee indicated that although the flow reduction reduces the potential mixing during a boron dilution event, the required operator action times are still satisfied.
O s
o TS 3.1.2.2 and 3.1.2.8 increase the shutdown margin from the current 1% to 3.6% oK/K. The licensee proposes to change these TSs to make them consistent with the Core Operating Limits Report and provide additional margin in a boron dilution event. The 3.6% oK/K was included in the boron dilution reanalysis.
These changes satisfy the conflicting requirements of the previous boron dilution analysis and the operating procedures.
Since this change imposes a greater restriction on the licensee than the current TS and the boron dilution analysis remains bounding, the TS changes are acceptable.
2.4 Shutdown Risk Included with these TS changes are proposed TS changes based on the recommendations of NUMARC 91-06, " Guidelines for Industry Actions to Assess Shutdown Management," and Millstone's self-assessment of unit practices with respect to minimizing shutdown risks.
TS changes 3/4.1.1.3, 3/4.1.2.1, and 3/4.1.2.3, which were discussed in previous sections, fall in this category.
TS 3.5.3 and 4.3.5.2 propose to modify Hillstone's method of securing an inoperable HPSI pump. The current method of isolating an inoperable HPSI is enhanced by an added step of key locking a discharge valve downstream of the HPSI pump and tagging the valve in the closed position. As indicated by the licensee, the improved method will ensure that (1) flow can readily be restored from the control room and (2) inadvertent actuation is lessened by requiring the operator to obtain the key from the shift supervisur.
TS 4.8.9.1 proposes to impose a minimum RCS flow rate of ;t 1000 gpm when a reduction in boron concentration is made. This will lessen the chance of vortexing occurring in the intake line, and therefore, lessen the occurrence of a loss of shutdown cooling event.
The licensee has included a number of TS changes that modify both operation and surveillance requirements.
The licensee proposed to adopt the recommendations of GL 90-06 with regard to LTOP and improved reliability of PORVs and their associated block valves.
The licensee also included the TS and surveillance modifications that would correct a conflict in the current operating requirements of the shutdown cooling system and the boron dilution analysis.
Finally, the licensee incorporated the recommendations of NUMARC 91-06 with regards to minimizing shutdown risk.
The staff finds the licensee's proposed TS changes acceptable because (1) the changes proposed by the licensee impose greater operating restrictions on the plant operation, (2) the licensee is proposing to implement the guidance of GL 90-06 and IN 93-50, which will improve LTOP reliability, and (3) the reanalyzed boron dilution event remains bounding.
4 e
3.0 STATE CONSULTATION
In accordance with the Comission's regulations, the Connecticut State official was notified of the proposed issuance of the amendment. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The 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 and changes surveillance requirements. The NRC 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 Comission 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 27060). 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
[QNCLUSION The Commission 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 complitnce with the Comission's regulations, and (3) the issuance of the amendment will not be inimical to the comon defense and security or to the health and safety of the public.
Principal Contributor:
S. Brewer Date: February 15, 1995
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