ML20043C026
| ML20043C026 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 05/23/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20043C025 | List: |
| References | |
| NUDOCS 9006010210 | |
| Download: ML20043C026 (6) | |
Text
- - _ _ _ _ _ _ _ - _ - _ - _ _ -.
.#M UGg%
8'
?,;
UNITED STATES NUCLEAR REGULATORY COMMISSION
{
W A$HINGTO N, D. C. M%
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.124 TO FACILITY OPERATING LICENSE NO. DPR-29 AND AMENDMENT NO.121 TO FACILITY OPERATING LICENSE NO. DPR-30 COMMONWEALTH EDISON COMPANY AND 10WA-ILLIN01$ GAS AND ELECTRIC COMPANY QUAD CITIES NUCLEAR POWER STATION, UNITS 1 AND 2 DOCKET NOS. 50-254/265
1.0 BACKGROUND
On October 31, 1972, Quad Cities Unit 1 Jet Pump Number 7 instrument line failed. The failure of the instrument line prevented.the use of flow indication directly from Jet Pump 7.
A visual examination of the No. 7 jet pump within the reactor vessel was performed to assure that the lack of flow indication was not due to damage of the jet pump. No indications were noted as a result of this examination. The licensee Commonwealth Edison Company (Ceco), evaluated the feasibility of repair of the damaged instrument line.
In early 1975 Ceco and GE expended considerable effort to develop a method of.
repairing the failed instrument line. A full scale mock-up was constructed by GE to test numerous tooling designs that could repair the instrument line.
Based on this work, it was demonstrated that repair was not feasible due to the limited access to the area, and the close proximity to instrument. lines for Jet Pumps 8 9, and 10 could cause them to be damaged. The personnel radiation exposurerelatedtotherepairorreplacementofthejetpumpuppersection would be significant. The costs associated with the repair appeared to be greater than the benefits to be gained.
Based on the factors discussed above, Ceco decided not to repair or replace the jet. pump flow indication sensing line. CECO performed a_ technical evaluation to determine the effects of the failed instrument line on plant operation and safety. This evaluation examined the effect of the failed instrument line on the accuracy of the flow measurement. The effect and ability to detect a jet pump failure using surveillance as described in current Technical Specifications (TS) and the effect on the Emergency Core Cooling System Performance Analysis were evaluated.
The analysis showed that continued operation with a failed jet pump' instrument was acceptable, By letter dated October 11, 1989 Ceco requested an amendment to the Facility Operating Licenses DPR-29 and DPR-30 for Quad Cities Station, Units 1 and 2.
$fk$b
,[
P
,m
-__-____m_J
2 The current TS for Quad Cities 1 and 2 requires plant shutdown if two jet pump flow indicators fail.
The proposed TS will allow plant operation with a 1
failure of two jet pump flow indicators.
TS changes for Quad Cities 2 are also requested for uniformity.
In a letter dated March 12, 1990, Ceco confirmed that on Unit 2 all efforts will be made to fix the flow indication on all 20 jet pumps before starting from cold shutdown. The proposed TS will allow startup of Unit 2 with one jet pump flow indication inoperable.
2.0 EVALUATION On Quad Cities Station, Units 1 and 2, there are 20 jet pumps. All of the jet pumps are provided with a single-tap (ST) diffuser-to-plenum delta-P transmitter.
The total core flow passing through 20 jet pump diffusers is determined by the single tap delta-P transmitter of each jet pump. The square root of delta-P signal from each individual jet pump is used to obtain a signal proportional to flow which h indicated in the control room.
The individual signals are then summed witn other jet pump flows to obtain the jet pump loop flows and the total core flow.
In addition, four of the jet pumps (two in each loop) are provided with a double-tap (DT) diffuser to diffuser delta-P transmitters.
These four jet pumps are calibrated in the laboratory prior to installation, and are referred to as calibrated, or double-tap, jet pumps.
In support of its application, the licensee, with the assistance of General Electric (the NSSS vendor), evaluated the potential implications on plant safety without flow indication from three of the 20 jet pumps. The staff review of the licensee submittal follows.
2.1 Total Core Flow Measurement Indicated total core flow is determined by summing individual jet pump flows
~
from 20 jet pumps. To commaate for the error due to loss of Jet Pump 7 flow indication, the measured f b: from Jet Pump 8, which shares a common recircu-lation flow inlet riser with Jet Pump 7, is adjusted based on historical flow bias data between this jet pump pair and input to the flow summer to simulate the Jet Pump 7 flow indication.
Base data obtained prior to the sensing line failure demonstrates the ratio of Jet Pump 7 flow to Jet Pump 8 flow to be 1.0057. General Electric has calculated the uncertainty in total core flow measurement using this technique for the failure of three flow indicators.
LossofflowindicationfordetPumpNumber7andtwoadditionalDTpumps(one from each loop) were assumed as the worst condition.
For 2-loop operation, the effect on core flow measurement uncertainty is calculated as 2.34% and 5.64% fo'r single loop operation.
Core measurement uncertainty bounding values
4 3
of 2.5% for two loop operation and 6% for single loop operation are applied in the General Electric Thermal Analysis Basis (GETAB) used for Quad Cities reload analyses. The loss of flow indication from three jet pumps still meets this requirement.
Loss of two DT pumps in one loop was not specifically evaluated, but would result in a much higher flow measurement uncertainty than calculated for loss of Jet Pump No. 7 plus-one DT pump per loop.
Hence, the proposed TS would not allow plant operation if flow indication failure occurs for both DT pumps on the same loco. We find this acceptable.
Since the partner jet pump sharing the same riser is critical to the measurement of the problem jet pump, the proposed TS will not permit plant operation-if flow indication failure occurs for both jet pumps on the same i
jet pump riser. We find this acceptable.
2.2 Recirculation Flow Monitoring
[
TheLPCI(LowPressureCoolantInjection)loopselectionlogicmonitorsthe delta-P changes in the jet pump loops to determine which. if any, recirculation loop is broken in the event of a LOCA signal.
The proposed operation will not impact this logic since it is not dependent on individual jet pump flow instrumentation.
Recirculation puma flow signals are input'to the Rod Block Monitor and to the flow biased APRM Rod Block and scram circuits.
However, the recirculation pump flow measurement does not depend on individual jet pump flow instrumentation; therefore, this protection logic is not impacted by the proposed operation.
2.3 Loss of Jet Pump Operability A loss of jet pump integrity can result in exceeding the allowable Peak Clad Temperature (PCT)'forthedesignbasisLOCA. Maintenance of jet pump-integrity is required to demonstrate-that the core can be reflooded to two-I thirds core height following a LOCA. Hence, the TS incorporate surveillance requirements for daily monitoring of established flow relationships which can provide indication of jet pump failures.
The current TS require simultaneous occurrence of the following two conditions i
I to indicate loss of jet pump integrity:
'(a) the recirculation pump flow differs more than 10% from established speed flow characteristics,
l 4
. o.*'
(b) the indicated total core flow is more than 101 greater than the core flow value derived from established core plate DP-core flow relationships.
The following alternate methods are also used to verify jet pump integrity.
(a) Recirculation pump speed to recirculation loop flow.
4 (b) Core flow to core power and flow control line.
3 (c) Core flow to recirculation drive flow.
(d) Recirculation pump speed to jet pump loop flow.
In addition to the above, the licensee is proposing an additional surveillance requirement.
Individual jet pump flow will be monitored to verify that the 1
individual jet pump flow does not differ by more than 10% from established flow to average loop jet pump flow characteristics. The individual jet pump flow deviation pattern will indicate jet pump displacement. The current and the proposed TS require two surveillance conditions to occur simultaneously-i before the jet pumps can be declared as inoperable.
But the surveillance procedures require engineering evaluation and root cause analysis if any one of the conditions is not satisfied. The requirement to satisfy two conditions simultaneously will not allow a jet pump to be " inoperable" due to a failed jet pump instrument. We find the proposed TS changes acceptable to monitor jet pump operability, i
2.4 Effect on ECCS Analysis The jet pump diffuser upper pressure taps are located at approximately.the same elevation as the bottom of the active fuel.
To minimize the signal noise j
and to account for any differences in the velocity distribution at the diffuser entrance, there are three 0.125 inch diameter holes at the diffuser-i entrance to measure the static pressure in the diffuser. A manifold connects these taps and the instrument line is connected to this manifold inside the i
vessel.
If the jet pump instrument line should break.inside the vessel, it
[
would establish an additional leakage path through these taps to the downcomer annulus which would allow water intended for core cooling to leak into the downcomer and delay core reflooding.
During reflooding, the leak through the severed instrument line would start to i
occur when the water level rises to the jet pump suction elevation which is at approximately two-thirds of the core height. This additional leakage was calculated to be less than 3 gpm through the three 0.125 inch pressure taps in any one diffuser.
Even if three diffusers were leaking at this rate, the total flow loss would amount to much less than 1% of the total ECCS flow available, previous sensitivity studies have shown that a leakage increase of this magnitude has no significant effect on ECCS performance limits.
l
.j 5
)
3.0 TECHNICAL SPECIFICATIONS a.
Limiting. Condition for Operation (LCO) 3.6.G.?
Replace "each" with "19."
This will' allow plant startup with a loss of flow indication on one jet pump. This is acceptable, j
1 b.
LCO 3.6.G.3 1
Replace existing text with "The indicated core flow is the sum of the-flow indication from each jet pump with operable' flow: indication.
In addition, for any jet pump with inoperable flow indication, the flow-l indication from the companion jet pump on the same jet pump riser shall i
be sumed a second time to compensate for the flow through the jet pump.
with the inoperable flow indication.
If flow indication failure occurs for three or more jet pumps, imediate corrective action shall be taken.
If flow indication for all but two jet pumps cannot be obtai_ned within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, an orderly shutdown shall be initiated and the~ reactor shall be in cold shutdown condition within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />." This is acceptable as-a previously discussed.
t c.
LCO3.6.G.4-(new) l "If flow indication failure occurs for'both' jet pumps,on-the same jet pump riser, imediate corrective action shall-be taken.
If flow indication for at least one of the jet pumps cannot be obtained within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, an orderly shutdown shall be initiated and the. reactor shall be in
?
cold shutdown condition within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />." This is. acceptable as previously discussed.
d.
LC03.6.G.5(new)
"If flow indication failure occurs for both calibrated (double-tap) jet pumps on the same recirculation loop, imediate corrective action shall be taken.
If flow indication for at least one of'the jet pumps gannot be obtained within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, an orderly shutdown shall be initiated and the-reactor shallebe in a cold shutdown condition within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />." This is acceptable as previously discussed, e.
Surveillance Requirement 4.6.G.1 Add "two of" and delete "two."
l Add "c.
Individual jet pump flow for each jet pump does not differ by more than 10% from established flow to average loop jet pump flow characteristics." This is acceptable as previously discussed.
I
o 1
~
{
3*.
' g.
6 J,
9; I
There are changes to bases shown on pages 3.6/4.6-23,3.6/4.6-13 addressing j
the above TS changes.
They suitably reflect the TS changes and are acceptable.
4.0 ENVIRONMENTAL CONSIDERATION
These amendments involve changes to requirements with respect to the installation and use of a facility component located within the restricted area as defined in 10 CFR Part 20. The staff has determined that these amendments involve no significant increase in the amounts. and no significant.
t change in the types, of any effluents that may be released'offsite and that there is no.significnat increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that these amendments involve no significant hazards consideration and there has been no public comment on such finding. Accordingly, these amendments.
meet the eligibility criteria for categorical ~ exclusion. set forth in 10CFR51.22(c)(9). Pursuantto10CFR51.22(b)noenvironmentalimpact statement nor environmental assessment need be prepared in connection with the issuance of these amendments.
5.0 CONCLUSION
' I 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, and (2): such activities will be conducted in compliance with the Commission's regulations,.
aad (3) the issuance of these amendments will not be inimical to the common l
defense and security nor to the health and safety of the public.
Principal Contributor:
George Thomas, NRR/SRXB
~
i L
Dated:
May 23, 1990 9
i 4
F
.