ML20045H827
| ML20045H827 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 07/15/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20045H825 | List: |
| References | |
| NUDOCS 9307210333 | |
| Download: ML20045H827 (5) | |
Text
/
'o UNITED STATES
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^,j NUCLEAR REGULATORY COMMISSION y
WASWNGTON, D. C. 20555 o,..
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 81 TO FACILITY OPERATING LICENSE NO. NPF-62 ILLINDIS POWER COMPANY S0VLAND POWER COOPERATIVE. INC.
CLINTON POWER STATION. UNIT NO. 1 DOCKET NO. 50-461
1.0 INTRODUCTION
By letter dated April 16, 1993, the Illinois Power Company (IP, the licensee),
requested an amendment to Facility Operating License No. NPF-62 for the Clinton Power Station (CPS).
The proposed amendment would change Clinton Power Station Technical Specifications (TS) 3/4.1.3.2, " Control Rod Maximum Scram Insertion Times," 3/4.4.2.1, " Safety / Relief Valves," and 3/4.5.1,
" Emergency Core Cooling Systems " The proposed changes would reduce, or mitigate, certain time restrictions associated with surveillance testing required during plant startup.
2.0 EVALUATION Control Rod Scram Time Testino Surveillance Requirement (SR) 4.1.3.2.b currently requires that the maximum scram insertion time of specifically affected individual control rods be demonstrated, through measurement, following maintenance on, or modification to, the control rod or control rod drive systen, which could affect the scram insertion time of those specified rods. SR 4.1.3.2.b further requires that these scram insertion time tests be conducted with reactor coolant pressure greater than or equal to 950 psig and that during single control rod scram time tests the control rod drive pumps be isolated from the accumulators.
SR 4.1.3.2.b also contains a footnote "*" stating, "The provisions of Specification 4.0.4 are not applicable for entry into OPERATIONAL CONDITION 2 provided this surveillance requirement is completed prior to entry into OPERATIONAL CONDITION 1."
In their submittal the licensee points out the drawbacks of performing scram time testing during this time frame. The testing can not be performed until reactor pressure reaches 950 psig which also is the criteria for starting the l
12-hour time clock for testing the Automatic Depressurization System (ADS)
Safety / Relief Valves (SRV) and performing SRV acoustic monitor calibrations.
Each scram time test takes approximately 30 minutes.
If there are a large number of affected control rods to be tested, the reactor operators are under 9307210333 930715 PDR ADOCK 05000461 P
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' considerable pressure to complete the scram time tests in time to establish the necessary plant conditions for performing the SRV testing and to subsequently complete the SRV testing within the time limits.
In addition, if a scram time test should fail, eight additional control rods may be required to be tested for each control rod that fails, creating additional time constraints.
In order to avoid the drawbacks discussed above, the licensee's proposal gives more flexibility to the control rod scram time testing requirements. The current exception to Specification 4.0.4 is an option the licensee chose to retain in the TS for cases which involve a small number of affected control rods to be tested.
For a larger number of affected control rods to be tested, however, the licensee added an option of performing the scram time tests outside the 12-hour time limit during plant startup.
Specifically, the licensee's proposal deletes the current SR 4.1.3.2.b, reletters the current SR 4.1.3.2.c to become SR 4.1.3.2.b and creates a new SR 4.1.3.3.
The new SR 4.1.3.3 incorporates the current requirements of SR 4.1.3.2.b and adds an alternative that "those specific control rods may be determined OPERABLE with reactor coolant pressure less than 950 psig by demonstrating an acceptable scram insertion time to notch position 13.
The scram time acceptance criteria for this alternate test shall be determined by linear interpolation between 0.95 seconds at a reactor coolant pressure of 0 psig and 1.40 seconds at 950 psig.
If this alternate test is utilized, the individual scram time shall also be measured with reactor coolant pressure greater than or equal to 950 psig prior to exceeding 40% of RATED THERMAL POWER."
(Based on the licensee's request, the staff inserted the words "or equal to" into the last sentence.)
The value of 0.95 seconds for the scram time test acceptance criteria at 0 psig for notch position 13 was derived from the startup test program as reflected in CPS Updated Safety Analysis Report (USAR) Section 14.2.12.2.5,
' Control Rod Drive System," Figure 14.2.8.
The value of 1.40 seconds for the scram time acceptance criteria at 950 psig for notch position 13 is the most conservative maximum scram insertion limit provided in the current TS 3.1.3.2 (i.e., the scram insertion time limits provided for " fast" control rods in j
ACTION a.).
Consequently, linear interpolation between these values provides 1
adequate assurance that the control rod scram time has not been adversely affected by performance of the subject maintenance or modification.
Performing the test while the reactor vessel is at 0 psig will provide i
assurance of satisfactory control rod scram insertion capability prior to restarting the plant.
This option of testing the affected control rods will allow the plant to enter Operational Conditions 1 and 2 with the affected control rods considered operable.
Under this condition, the affected control rods will also be required to be tested again prior to 40% power along with the remaining control rods per TS 4.1.3.2.a.
Although the proposed option will thus require the scram time test (s) to be performed twice for the affected control rod (s), this option will alleviate some of the pressure on
i j the reactor operators to perform the testing under such unnecessarily restrictive time limits.
The proposed revisions to SR 4.1.3.2 and the addition of SR 4.1.3.3 are consistent with changes that have been previously reviewed and approved by the.
staff. The requirements proposed by the licensee are similar to that.found acceptable to the staff in the Improved Standard Technical Specifications for.
BWR/6 facilities. Therefore, the staff finds the proposed changes acceptable.
Safety Relief Valve and Acoustic Monitor Testina Surveillance Requirement 4.4.2.1.1.b requires, "The acoustic monitor for each safety / relief valve shall be demonstrated OPERABLE by performance of a CHANNEL CALIBRATION at least once per 18 months." Surveillance Requirement 4.5.1.e requires in part, "At least once per 18 months, manually opening ~each: ADS valve when the reactor steam dome pressure is greater than or equal to 100 p s i g"... " The footnote for both of these SRs states, "The provisions of Specification 4.0.4 are not appli:able provided the surveillance is performed within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after reactor steam pressure is adequate to perform the test."
The reactor steam pressure "ader,uate to perform the test" is specifi~ed by the SRV manufacturer to be 950 psig. Thus, the allotted 12-hour time period for completing the required testing begins when reactor pressure reaches 950 psig.
In addition to reactor pressure, steam flow is an important parameter. for maintaining reactor pressure control during stroking of the SRVs. Because opening SRVs can result in a reactor pressure transient which initially i
introduces negative reactivity, and subsequent SRV closure can result in.the introduction of positive reactivity (through-steam void collapse), two conditions must first be met before a stroke test of the SRVs is performed:
(1) adequate reactor pressure must exist to protect the SRV from damage when
-i stroking, and (2) sufficient steam flow must exist to open at'least 1-1/2 main turbine steam bypass valves (which occurs at approximately 16% power)..The latter is required because when an SRV is opened with less'that 1-1/2 bypass valves open, a slow depressurization of the reactor vessel will occur lafter the bypass valves fully shut in an attempt to control pressure. This slow cooldown combined with the subsequent SRV closure can result-in a pressure and corresponding reactor power spike and reactor scram.
As noted previously, per the current TS, the 12-hour time clock for performing.
stroke testing of the SRVs starts once adequate. reactor pressure (950 psig);is
. reached. However, as explained above, the tests on-the SRVs can not be performed until the required steam flow conditions are also achieved. - A i
period of time is required after reactor pressure reaches 950 psig to i
establish adequate ' steam flow.
Part of the allotted 12-hour test period is,.
thus, expended to establish the appropriate test conditions before stroke testing can actually begin.
j
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. The SRVs must also be stroked to complete the channel calibrations for the associated acoustic monitors.
Specifically, acoustic monitor gain adjustments are performed under steam-flow conditions for each SRV.
Performance of the SRV acoustic monitor gain adjustment requires each of the SRVs to be lifted at least twice, once to verify actuation and initial response of the monitor associated with each SRV and at least once to check the effect of the gain adjustment and verify that monitors on adjacent SRVs do not actuate. This procedure consumes much of the test time allotted by the current Specification 4.0.4 exception.
To alleviate unnecessary stress and time pressures on the reactor operators during reactor startups, CPS plans to revise the existing exceptions to Specification 4.0.4 within TS 4.5.1 and TS 4.4.2.1.1.
The licensee proposed to revise the current wording from "within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after reactor steam pressure is adequate to perform the test" to "within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after reactor steam conditions are adequate to perform the test." However, after discussions with the the staff, the licensee agreed to modify the above wording to "within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after reactor steam pressure and flow are adequate to perform the test." This would better define the start of the surveillance interval. The licensee believes the proposed change is consistent with the original intent of the TSs to permit testing to be completed within a reasonable time once adequate test conditions are achieved after entering the applicable operating conditions.
Under the proposed change, the point in time during plant startup when SRV/ acoustic monitor testing can begin would remain unchanged.
That is, the current practice at CPS of ensuring that adequate steam pressure and flow both exist prior to commencing such testing would be maintained.
The testing itself would continue to be performed within the required 12-hour time period.
The intent of the proposed change is simply to change or clarify the point when the 12-hour clock must begin.
The staff concurs with the licensee in that the safety impact of the proposed change is negligible. As discussed above, the proposed change in the TS merely reflects current practice at the Clinton Power Station and does not change the time when testing is performed. The safety (spr.ing) mode of operation of the SRVs is not affected by the proposed change as this function is independent of the relief mode or ADS function. In addition, the relief-mode of the SRVs also would not be impacted as the SRV pressure relief-instrumentation and ADS instrumentation is fully tested prior to reactor startup. As a result, the ADS valves would be expected to remain operable for i
reactor pressure control. With respect to the impact of the proposed change on the operability and testing of the acoustic monitors, the acoustic monitors merely provide indication that an SRV is open and do not provide any actuation signals.
In addition, there would be other indications that an SRV is open such as reactor water level, reactor pressure, and main turbine bypass valve position.
p l;
s l The licensee has submitted these proposed changes in order to. remove-unnecessary time constraints during reactor startups and, thus, reduce. stress l
on control room operators. The proposed changes will still meet the.
q requirement to perform the SRV/ acoustic monitoring and ADS valve testing.
u within a 12-hour time span during plant startup. Therefore, based-on the staff's review, the proposed changes are found acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Illinois Stat'e official' was notified of the proposed issuance of the amendment.. The State official-2, had no comments.
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4.0 ENVIRONMENTAL CONSIDERATION
l
-This amendment changes surveillance requirements. The NRC staff has.
determined that the amendment involves no significant increase in the. amounts,:
l and no significant change in the types, of any effluents that may be released '
i offsite, and that there is no significant increase in individual or cumulative l
occupational radiation exposure.
The 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. (58 FR 30196). At.cordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR
'l 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection'with the issuance of the amendment.
5.0 ' CONCLUSION The staff has concluded, based on the considerations discussed above,;that:
(1) there is reasonable assurance that the-health and safety of the public j
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.
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Principal Contributor:
R. Laufer l
Date:
July 15,1993 i
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