ML20236S179
| ML20236S179 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 11/16/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20236S169 | List: |
| References | |
| NUDOCS 8711240271 | |
| Download: ML20236S179 (13) | |
Text
-
og UNITED STATES
[
g NUCLEAR REGULATORY COMMISSION g
j WASHINGTON, D. C. 20555 kv,/
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NOS.
84 AND 56 TO FACILITY OPERATING r
LICENSE NOS. DPR-70 AND DPR-75' PUBLIC SERVICE ELECTRIC & GAS COMPANY PHILADELPHIA ELECTRIC COMPANY DELMARVA POWER AND LIGHT COMPANY ATLANTIC CITY ELECTRIC COMPANY SALEM NUCLEAR GENERATING STATION, UNIT NOS. 1 AND 2 DOCKET NOS. 50-272 AND 50-311 1
1
1.0 INTRODUCTION
By letter dated May 5, 1987,.and supplemented by letters dated September 2, 1987 and October 1, 1987, Public Service Electric & Gas Company i
(PSE&G), the licensee, requested an amendment to Facility Operating License Nos. DPR-70 and DPR-75 for the Salem Nuclear Generating Station, j
Unit Nos. I and 2.
The proposed amendments would change the T.echnical Specifications due to modification of the reactor trip system and engineered safety features response times to accommodate the removal of l
the RTD bypass system.
A new reactor coolant system'(RCS) temperature measurement system would be installed in place of the RTD bypass system.
l This system will use narrow range dual element mounted resistance temperature detectors (RTDs).
This design modification is to overcome-major drawbacks of the RTD bypass system which lacked reliability.
8711240271 871116 PDR ADOCK O 22 P
w
t 1
(leakage from valve packing or mechanical joints) and resulted in high radiation doses during the performance of maintenance around the RTD bypass system.
The licensee's supplementary.submittals of September 2 and October 1, 1987 were made as a result of an NRC staff request to correct and clarify the language of the original submittal, and do not contain substantive changes.
2.0 EVALUATION AND
SUMMARY
The new method proposed for measuring the hot and cold leg temperatures uses narrow-range, dual element, fast response RTDs manufactured by the Weed Company.
One of each of the RTD dual elements is used while the other is installed as a spare.
The RTDs are placed in thermowells to allow replacement without draindown.
The thermowells, however, increase the response time.
The three RTDs in each of the hol legs are placed within the three existing scoops.
Outlet ports are provided in the scoops to direct the sampled fluid past the sensing element of the RTDs.
This method of measuring the hot leg temperature by scoop mixing was conceived by Combustion Engineering (CE) and is a proprietary design.
Since there is no temperature streaming problem in the cold leg, only one dual element RTD is installed in a thermowell associated with the cold leg to provide the cold leg temperature reading.
Because of the variation in temperature in the cross-section of the hot legs due to hot leg streaming, the three RTD measurement locations in each hot leg are used to get an average:value of the variation.
An
.. s electronic system is used to perform the averaging.of the reactor coolant-hot leg signals from the three RTDs in each hot leg and then to transmit the signal for the average hot leg temperature to protection and control systems.
There is a rou' tine for performing a quality check of the three l
temperature signals for each hot leg.
A' failed RTD would be picked up by
'l the T,y, or delta T deviation alarm.
Also, each channel is checked every eight hours.
On failure of a RTD, the channel,would be tripped and the 1
Technical Specifications action statement would go into effect.
The 1
second element of each RTD is a spare and its leads can be switched from the failed RTD leads in the control room instrument panel.
The overall response time of the proposed thermowell RTD hot leg I
temperature system (6.0 seconds) has been designed to remain the same as l
in the former RTD bypass system (6.0 seconds).
The licensee has reported that the combined RTD/thermowell response time of 4.75 seconds for the proposed system is conservative as the RTD instrument specification requires that both elements be less than 4.0 seconds and typical,results for the same model Weed RTD in CE plant thermowells have demonstrated that response times less than 4.0 seconds are realistic.
The licensee t
has reported that the response times will be checked as part of the reactor trip system instrumentation (Technical Specification-Item 7, l
Table 3.3-2) and engineered safety features response time (Item 5. Table 3.3-5).
The surveillance requirements state that response time checks are required at each refueling.
RTD response times have been.known to degrade and Loop Current Step Response (LCSR) methodology is the recommended on-site method for checking RTD response times.
The licensee plans to use the LCSR method for checking the RTD response time at each refueling.
________m___---
1 Based on the above information the staff finds that t.he RTD response time has been addressed in an acceptable manner.
The new method of measuring each hot leg temperature with three thermowell RTDs, used in place of the RTD bypass system with three scoops, has been analyzed to be slightly more accurate than with the RTDs l
in the existing bypass system.
As previously mentioned, the scoops are used to obtain a sampling of the flow (five holes in each scoop) at three 120 degree sectors in each of the hot legs in order to obtain a more accurate hot leg average temperature that accounts for the non-uniform temperature streaming.
Previously, the RTD bypass system took the sampled flows from the. scoops and made an external RTD temperature measurement in a plenum section.
The new method with the RTD bypass' system I
removed will measure the sampled mixed coolant flow with a dual element i
Weed RTD mounted in a thermowell.
The Weed RTD is mounted in the existing scoop near new outlet ports in the scoop.
This proprietary l
design has been evaluated by the licensee.
A model test has been I
completed and calculations performed to ascertain that an accurate mixed 1
mean temperature will be measured.
The model test provided information l
for the selection of the proper location of the RTD sensor in the scoop for accurate measurement and the expected temperature bias.
The licensee has made a commitment to obtain confirmatory information on the mixed mean temperature accuracy.
This will be done by comparing j
pre-installation and post-installation calorimetric data on the RTD temperature measurements in the Salem plant for matching operating conditions.
The licensee will make these data available to the staff.
The dual element Weed RTD has improved accuracy over the existing RTDs.
l The total uncertainty is 1 0.7 F.
This value includes a drift (for 22.5 l
l
1 i
. i e
months) of + 0.4 F on top of the normal i 0.3 F accuracy (includes hysteresis and repeatability).
For the hot leg temperature measurement,.
there is a need to apply a small temperature bias.
This temperature bias is based on the model test information which identified 'a scoop RTD installation location effect for the hot leg temperature measurement.
1 i
Because three RTDs are used to measure each hot leg temperature instead' of the former single measurement, the error associated with the hot leg I
measurement is reduced to one over the square root of three compared-to
]
a single RTD. The impact et the additional electronics needed for the l
two additional hot leg RTD's per loop has been found by the licensee to be minimal.
l l
The three RTD signals are averaged to obtain the loop's T value.
The hot existing overall channel functional checkr 'nd calibration accuracy requirements are to be maintained.
The impact of the rack drift has been considered in the evaluation.
l There is no change to the cold leg's electronics.
Therefore, there is no impact to the cold leg accuracy other than the increase obtained from.
the more accurate RTD.
The licensee intends to replace 2 RTDs per refueling on the lead unit at each of the following two refueling outages.
They will review the-recalibration results from the RTDs removed, as well as other data anticipated to become available on the drift of the Weed RTDs, prior to making any subsequent long-range periodic RTD replacements.
Since the replacement RTD would have to be within the allowable deviation from the averaged reading, verification of no significant systematic drift will be obtained.
1 The net result of the proposed RTD bypass system modification is a slight improvement in the accuracy of the temperature related functions over the accuracy now achievable with the existing RTD's in the bypass system.
The licensee has reviewed the impact of the proposed modifications against the Salem setpoint study to verify that the accuracy of the temperature related functions are met.
Salem presently assumes a 3.5%
irror in primary flow determination.
This allowance continues to be conservative.
The failure of an RTD can be detected by the deviation alarm.
This alarm is set for a measurement deviation when T is calculated and ave also when delta T is calculated.
The impact of the RTD bypass elimination for the Salem plants on FSAR Chapter 15 non-LOCA accidents has been evaluated by the licensee.
Since the effect of the temperature response time and accuracy of the new system is not degraded, the former conclusions in the FSAR remain valid.
The elimination of the RTD bypass system has been found to not impact I
the uncertainties associated with RCS temperature and flow measurement.
It is concluded therefore that the elimination of the RTD bypass piping will not affect the LOCA analyses input and hence, the results of the analyses remain unaffected.
Therefore, the plant design changes due to the RTD bypass elimination are acceptable from a LOCA analysis standpoint without requiring any reanalysis.
5 The staff's review and evaluation is also based upon Sections 7.2 and 7.3 of the Standard Review Plan.
Those sections state that the objectives of the review are to confirm that the reactor trip and engineered safety features actuation system satisfy the requirements of
.o !
l t
the acceptance criteria and guidelines applicable to the protection i
system and will perform their safety function during all plant conditions for which they are required.
Since our re. view indicates that the modified system does not functionally change (except three hot leg RTD's are utilized instead of just one) the reactor trip and engineered safety features actuation systems, the staff's original conclusions for these l
l systems, as documented in Sections 7.2 and 7.3 of the SER dated I
October 11, 1974, for Salem Nuclear Generating Station remain valid.
Based on this and the licensee's statement that the new hardware for the RTD bypass elimination has been qualified to IEEE Std 323-1974, IEEE Std 344-1975 and 10 CFR 50.49, we find the plant modifications to eliminate the RTD bypass manifold and to install fast response RTD's directly in the reactor coolant system hot and cold legs to be acceptable.
1 As a result of the new instrumentation associated with the removal of 4
l the existing RTD bypass manifold and replacement by dual element RTD's, l
the following changes to the plants' Technical Specifications were proposed:
CHANGE 1 Change the entry under " ALLOWABLE VALUES" for Functional Unit 8, Overpower AT, in Table 2.2-1 from "See Note 3" to "See Note 4" for Salem Unit 1 and Unit 2.
CHANGE 2 On page 2-9 add a new note 4, "The channel's maximum trip point shall not exceed its computed trip point by more than 3.0 percent," for both units covering a new allowable value for overpower AT.
l I
i I
l 1
L i
, t CHANGE 3 Change the allowable value (for overtemperature AT) in q
Note 3 to Table 2.2-1 from "4.0 percent" to "3.1 percent"-
for both units.
I CHANGE 4 Change the entry under " RESPONSE TIME" for Functional Unit 7, Overtemperature AT, in Table 3.3-2 from "4.0" to "5.75" for both units.
CHANGE 5 Under " TABLE NOTATION" for Table 3.3-5, change identification of notes from symbols to numbers 1 thru 6 for Unit 1 only.
In Table 3.3-5 change all references to notes correspondingly.
CHANGE 6 Change the entry for the response time for Functional Units 2.f, 4.f, and 6.f, Auxiliary Feedwater Pumps, in Table 3.3-5 from "Not Applicable" to "60" for Unit 1 only.
Increase all the response time entries by 1.75 sec'onds CHANGE 7 for Functional Unit 5, Steam Flow in two Steam Lines -
High Coincident, in Table 3.3-5 for both units.
CHANGE 8 Change the entry for the response time for Functional l
Unit 5.f, Auxiliary Feedwater Pumps, in Table 3.3-5 from "Not Applicable" to "61.75" for Unit 1 only.
CHANGE 9 On the bottom of page 3/4 3-30 delete the note,:" Response time for Motor-Driven Auxiliary Feedwater Pumps on.all' SI signal starts $60."
l l
.g.
r CHANGE 10 -
Add a new Function Unit 14, Station Blackout, to Table 3.3-5 for Unit 2 only.
Include a new response time entry for " Motor-Driven Auxiliary Feed Pumps" of "560."
Changes 1, 2, and 3 are necessary: to reflect new allowable values based on revised instrumentation uncertainties resulting from the bypass manifold elimination.
These new values were calculated using-essentially the Westinghouse setpoint methodology as previously approved by the staff for generic use (see NUREG-0717, SER for_ Virgil C. Summer Nuclear Station) and are als'o more conservative.
The staff finds these changes acceptable.
Chinges 4 and 7 are new values based on revised individual component response times resulting from the bypass manifold removal.
Since the new individual response times produce total response times for the reactor trips and engineered safety features actuation which remain the l
same as those used in approved safety analyses for Salem Unit 1 and Unit 2, we find these changes acceptable.
Change 5 is an editorial change intended to add agreement between the Technical Specifications for Unit 1 and Unit 2.
On the basis that the-change in purely editorial, we find it acceptable.
Changes 6 and 8 are new entries for Unit I which add conservatism and consistency with Unit 2 Technical Specifications.
On this basis, we find them acceptable.
Change 8 also' reflects the revision resulting from Change 7 approved above.
. t Change 9 results from Changes 6 and 8 approved above.
On the basis that the note to be deleted is no longer necessary because of the additional entries provided by Changes 6 and 8, the staff finds this change acceptable.
Change 10 provides a new entry for Unit 2. Technical Specifications which adds conservatism and consistency with Unit 1 Technical Specifications.
On this basis, we find them acc'eptable.
The staff reviewed the licensee's intended inspections of field machined surfaces, welds, and weld materials to assure that all Code requirements will be met.
The staff has concluded that.all new' hot and cold leg connections and penetrations, and crossover piping capping meet i
appropriate Code inspection requirements.
In addition, b.oth the hot and cold leg, the nozzle, thermowell, and the entire thermowell/ nozzle astcmbly were analyzed to the ASME Code,Section III, Class I.
The analysis of the entire assembly considered the weight of the RTD, the RTD head assembly and an assumed length of cabling.
The effect of seismic and flow induced loads were considered.
Therefore, the staff concludes that the analyses of the RCS penetrations are acceptable.
Finally, the licensee has provided adequate assurance that all significant radiological conditions have been considered by:
1.
Identifying all major construction steps in the proposed RTD bypass system removal which could result in radiation exposure or generate radioactive wastes.
i 2.
Providing a dose estimation for the RTD bypass system modifications, performing manpower projections and work time estimates for these work areas, performing dose estimates for major RTD bypass system removal subtasks and the overall task (77.
person-rem per unit).
l l
3.
Projecting a net savings of 3,000 person-rem over plant life by RTD bypass system removal; assuming a 40 year operating license; and l
providing a comparison of dose incurred from task performance (77 person-rem per unit), and dose avoided through reduced maintenance and operational requirements (95 person-rem per unit).
In l
addition, one outage day may be saved on each unit due to the j
avoidance of leaks and equipment failures.
4.-
Identifying' specific ALARA measures to be employed for RTD bypass system removal, includ'ing preplanning of removal methods, use of temporary shielding, outage sequencing to minimize work area dose rates, work area familiarization; use of special tooling, and pre-job planning among job supervisors, health physics technicians, and ALARa staff.
5.
Identifying the sources, types, volumes, and relative level of radioactive wastes which should result from RTD bypass system I
removal.
l 1
6.
Evaluating the tasks for 'special radiological or operational considerations which could impact radiological conditions, or result in delays and additional exposures.
Additionally, the licensee's corporate and facility radiation protection and ALARA programs have previously been evaluated (i.e., in the Salem 1 and 2 SER, Chapter 12) and found to be adequate fo,r radiological protection of workers, the general public, and the environment.
__ _ = mm m- _ _ - -. _ _ _ -
e..
e
. i The staff has evaluated the radiological aspects of the RTD bypass.
I system removal using the criteria of Chapter 12 of the Standard Review-Plan (NUREG-0800), Regulatory Guide 8.8, "Information Relevant to Ensuring That Occupational Exposures At Nuclear Power Stations Will Be j
As Low As Is Reasonably Achievable," and licensee's commitments in the
]
Salem Updated Final Safety Analysis Report (UFSAR - Revision 7, July 22, j
1987), and concludes that the radiological aspects of the RTD bypass i
system removal have been fully considered and the radiation protection measures planned for the task are adequate to protect the worker,' the general public and the environment; and will result in doses that are as 1
low as is reasonably achievable (ALARA).
j 1
Based on the above the staff finds that the licen~see's radiological
]
protective peasures can be expected to be conducted in accordance with the requirements of 10 CFR Part 20 and within ALARA guidelines, and are adequate for ensuring that occupational radiation exposures will be ALARA.
We therefore find the radiation protection aspects of the RTD bypass system removal to support the Technical Specifications change j
i acceptable.
I
- 3. 0 ENVIRONMENTAL CONSIDERATION These amendments involve a change to 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 amendments involve 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 Commission has l
E f
>es.
-f u.
1 1 L
'l previously issued a' proposed finding.that the amendments-involve no l
significant hazards consideration and there has been no public coment on such finding.
Accordingly, the amendments meet the eligibility. criteria y
for categorical exclusion set forth in 10 CFR 51.22(c)(9). ' Pursuant ~to 10 CFR 51.22(b), no environmental impact's'tatement or' environmental assessment need be prepared in connection with the issuance of.the amendments.
4.0 CONCLUSION
The Comission made a proposed determination that the amendments involve no significant hazards consideration which was published in the Federal
. Register (52 FR 23106) on June 17, 1987 and consulted with the State of-New Jersey.
No public coments were receivsd and the State of New Jersey did not have any coments.
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 Comission's regulations and the issuance of'the amendments wil1 ~not be inimical to the comon defense and security nor to-the health and safety of the public.
L Principal Contributors:
F. Burrows,'. Balukjian, J. L. Minns H.
D. C. Fischer Dated: November 16, 1987
_ _ _ _