ML20052B008
| ML20052B008 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 03/26/1982 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20052B003 | List: |
| References | |
| NUDOCS 8204290552 | |
| Download: ML20052B008 (18) | |
Text
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UNITED STATES
- [ ~ )q ' j NUCLEAR REGULATORY COMMISSION g
9 E WASHINGTON, D. C. 20555 7
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 67 TO PROVISIONAL OPERATING LICENSE NO. DPR-19 AND AMENDMENT NO. 59 TO FACILITY OPERATING LICENSE NO. DPR-25
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COMMONWEALTH EDISON COMPANY DRESDEN NUCLEAR POWER STATION, UNITS 2 AND 3 DOCKET NOS. 50-237 AND Sd-249 Authors: J. Hegner, K. Eccleston I. Introduction Analysis and evaluation of events at several operating reactors involving the Scram Discharge Volume (SDV) system have convinced the staff that SDV systems in all BWRs should be modified to assure long-term reliability. This Safety Evaluation Report (SER) discusses and evaluates the actions taken by the Commonwealth Edison Company (CECO / licensee) in response to the staff's requests to improve SDV reliability at the Dresden Nuclear Power Station',
Units 2 and 3.
l II.
Discussion In response to two events at Hatch 1 and Brunswick 1 on June 13 and October 19,1979,respectively, involving common-cause failures of SDV limit switches and SDV drain valve operability, we issued IE Bulletin 80-14, Degr&dation of BWR Scram Discharge Volume Capability. As a result of another event at Browns Ferry 3 on June 28, 1980 involving the SDV, we issued IE Bulletin 80-17, Failure of Control Rods to Insert During Scram at BWR, followed by several supplements.
In addition, to strengthen l
the provisions of the initial Bulletin and to ensure that the scram system would continue to. work during reactor operation, we sent a letter dated July 7,1980 to all operating BWR licensees requesting that they propose Technical Specification changes to provide surveillance requirements for reactor protection system and control rod block SDV limit switches.
An analysis and evaluation of these events convinced us that SDV systems in all BWRs should be modified to assure long-term reliability. The l
evaluation identified the need for improvements in three major areas:
SDV-Instrument Volume (IV) hydraulic coupling, level instrumentation, and system isolation. To achieve these objectives, an NRC taskforce and a subgroup of the BWR Owners Group was convened to develop revised l
SDV system design and safety criteria for use in establishbg acceptable l
SDV system modifications. By letter dated October 1,1980 we requested all operating BWR licensees to reevaluate installed SDV systems and modify 820429oSSL
g them as necessary to comply with the developed criteria.
Those criteria, and the long-term program, were described in a Generic Safety Evaluation Report," BWR ' Scram Discharge Volume," dated December 1,1980.
We are reviewing the changes proposed by licensees in response tb our July 7 and October 1,1980 requests in two phases.
Phase 1 consists of a review of the proposed Technical Specification (TS) improvements 'in surveillance requirements for vent and drain valves and instrument volume level switches.
Phase 2 consists of a review of the long-term SDV
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modifications and TS improvements made to comply with the revised des ~ign and performance criteria.
As part of a technical assistance program, the Franklin Research Center (FRC) was contracted to evaluate the licensee's Phase 1 responses. The FRC Technical Evaluation Report describing.that effort for Dresden 2 and 3 is discussed below.
Regarding Phase 2, CECO informed us by letter dated January 15,1981 of its intent to modify the Dresden 3 SDV system to meet the revised design and performance criteria during the refueling outage for Cycle 8 operation. Our evaluation of its submittal regarding the Phase 2 modifications for Dresden 3 is also discussed below.
III. Evaluation i
1' Phase 1 The enclosed report (TER-C5506-59/62) was prepared for us by FRC as part of a technical assistance contract program.
FRC's report provides the technical evaluation of the compliance of the licensee's submittal with the NRC-provided criteria for Phase 1 modifications.
FRC has concluded that the licensee's proposed TS revisions, as modified during our subsequent discussions with the licensee to incorporate FRC comments, meet the criteria in our July 7,1980 letter.
FRC concluded that, although the proposed TS did not meet Paragraph 4.3.1.1 and Table 4.3.1.1-1 of the model TS for channel Functional Test / Calibration for SDV water level high instrumentation, the proposed surveillance requirements were acceptable since the licensee is installing a second Instrument Volume containing four additional level switches, for a total of eight limit switches for the reactor protective system. The model TS were developed for plants which only have one instrument volume -
(four limit switches); therefore, the installation of a second instrument volume by the licensee significantly improves the design and reliability of the SDV. Taking this into account, we conclude that the objectives of the TS have been met and that the proposed TS represents. an acceptable alternative method of implementing the surveillance requirements.
i l
Regarding the same paragraph, FRC also noted that the licensee failed to propose a suitable caiibration frequency in accordance with the model TS.
In subsequent discussion with the licensee, it was determined that the
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" calibration" definition used by FRC was technically consistent with the
" functional test" definition used by-the licensee for testing the float-type level switches. We therefore conclude that periodic functional testing by the licensee meets the calibration objectives of the model TS for float-type level switches and is therefore acceptable.
Calibration of the differential pressure switches is acceptably addressed by the licensee in their proposed TS for Phase 2 modifications.
Phase 2 In the NRC Generic Safety Evaluation Report (SER) on the BWR_ Scram Discharge Volume dated December 1,1980, the format provides for each criterion:
a statement of the criterion; its technical bases;. additional staff criteria in excess of that developed by the BWR Owners Subgroup, where applicable; and a means acceptable to the staff for compliance with the criterion.
In response to our request dated October 1,1980 and in consideration of the Generic SER, the licensee informed us on January 15, 1981 that long-term
. design modifications in accordance with the criteria set forth in the Generic SER would be implemented for the Scram Discharge Volume for Dresden 3 during the refueling outage for Cycle 8 operation.
By letter dated March 18, 1982 the licensee proposed Technical Specification changes to support the long-term SDV modifications for Dresden Unit 3.
The proposed changes incorporate setpoint and format changes to reflect the impact of the long-term SDV modifications on the Limiting Conditions for Operation and surveillance requirement added in Phase 1.
We have reviewed the licensee's subnittals to determine compliance with the design, safety and functional criteria in the. Generic SER by evaluating them against the stated acceptance criteria provided in the Generic SER.
A detailed evaluation of each item is provided below.
For reference, tne numbering system used parallels that used in the Generic SER.
4.2.1.1 Functional Criterion 1 l
The scram discharge volume shall have sufficient capacity to receive and contain water exhausted by a full reactor scram without adversely affecting control rod drive scram performance.
Licensee Response The scram discharge volume at Dresden 3 has the capability of receiving a' maximum scram discharge of approximately 800 gallons of water or 4.5 gallons per drive. This volume includes all 4, 6 and 8-inch header piping as well as the 20-inch instrument volume piping.
Each scram discharge volume header is hydraulically coupled to a 20-inch instrument volume with 6-inch pipe. The calculated free volume does not include any 1-inch vent line piping or 2-inch instrument volume drain line piping.
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3 4
The scram dis' charge volume sizing requirement-pf 3.34 gallons per control rod drive.(stated in GE letter OER 54 dated March 14, 1972) is based on the following:
1.
control rod drive stroke 2.
ten (10) seconds of scram leakage flow of 10 GPM
(= 10 GPM x 10 sec./60 sec/m=1.667 gal / drive) 3.
added volume in the SDV to limit the pressure rise to 50 psig during a scram.
The Dresden TS limit for the slowest allowable control rod insertion time is 7 seconds. Therefore, control rod drive seal leakage during.a scram at Dresden Station would only lest for 7 seconds rather than 10 seconds as calculated above (10 GPM x 7 sec./60 sec/m=1.167 gal / drive).
Using this criterion, the maximum expected scram discharge during normal operation would be 2.84 gallons per drive. The current scram discharge' volume. size of 4.5 gallons per drive far. exceeds the 3.34 gallons per drive GE design criteria and 2.84 gallons.per drive operating criterion.
Staff Evaluation An acceptable means of meeting this criterion is to provide a minimum scram discharge volume of 3.34 gallons per drive in accordance with GE letter
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OER 54 dated March 14, 1972.
We have evaluated the licensee's design against the acceptance criterion and have determined that the design modification,resulting in an available volume of 4.5 gallons per drive that exceeds the11 zing criterion of 3_.34 gallons per drive in the referenced GE letter, meets the criterion and is.therefore acceptable.
'The limit switches for the RPS function are located in the IV and will scram the reactor when there are about 107 gallons of water in the IV.
The worst case scram /inleakage analysis results in 591 gallons of water discharged into the SDV/IV system for a total water volume of 698 gallons.
The total SDV/IV volume is about 800 gallons. Therefore, we conclude that the RPS function limit switch setpoint has been conservative'iy selected and provides sufficient margin under worst case conditions.
4.2.2.1 Safety Criterion 1 No single active failure of a com'ponent or service function shall prevent a reactor scram, under the most degraded conditions that are' operationally acceptable.
i Licensee Response The scram discharge system at Dresden 3 has been designed in such a manner that no single active failure of a component or service function shall prevent a reactor scram under the most degraded conditions that are operationally acceptable.
All vent and drain line valves are air operated and will fail closed on loss of air. All water level instrumentation will fail into the scram condition.
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5 Staff Evaluation An acceptable means of complying with'this criterion is to design the system such that partial losses of service functions as well as. full losses do not adversely affect system functions.
The licensee stated in response to Safety Criterion 4 that the instrumentation on each instrument volume has been designed and installed in such a manner that the maximum rapid water inleakage (5 gpm per drive simultaneously) into '
the SDV will be detected and an automatic scram initiated while sufficient volume still exists in the SDV. Thus in the case of a partial loss of service function, the system fur.ction would not be adversely affected (i.e., reactor scram would o'ccur).
We have evaluated the licensee's modifications against this criterion and Safety Criterion 4.and have determined that the system has been designed in accordance with the criteria and is therefore acceptable.
4.2.2.2 Safety Criterion 2 No single active failure shall prevent uncontrolled loss of reactor coolant.
Licensee Response Two air-operated isolation valves have been installed in series on each scram discharge volume vent line and instrument volume drain line at Dresden 3.
Each valve will fail closed on loss of control air.
Staff Evaluation An acceptable way of meeting this criterion is to provide two isolation valves in series in all SDV vent and IV drain lines which are sufficiently independent to avoid failure due to solenoid failures. This resolution j
will also correct the potential for excessive hydrodynamic force generation.
We have evaluated the licensee's modifications against this criterion and have concluded that the licensee has designed the system in accordance with the criterion and'is therefore acceptable.
4.2.2.3.
Safety Criterion 3 The scram discharge system instrumentation shall be designed to provide i
redundancy, to operate reliably under all conditions, and shall not be l
adversely affected by hydrodynamic forces or flow characteristics.
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Licensee Response The scram discharge system at Dresden 3 incorporates a diverse and redundant instrumentation design utilizing safety related Magnetrol float type water level switches and ITT Barton differential pressure water level transmitters used in conjunction with Rochester Instrument Zystems current / voltage alarms.
The modified scram dischnrge system has two scram discharge volume piping j
headers, each header having its own instrument volume.
Each instrument l
6 volume has six water level sensing instruments". One float type instrument notifies' the reactor operator that water is present in the instrument volume; one float type instrument prevents further. withdrawal of the control rods as the instrument volume water level rises; and two safety related float type water level switches and two safety related differential pressure water level transmitters automatically scram the reactor while sufficient volume still exists in the scram discharge volume to ensure safe shutdown.
The new instrumentation design incorporates a 1-out-of-2-twice logic scheme with each instrument volume having the ability to independently scram the reactor.
See Figure 1 for the scram signal initiation ~ logic.
Single failure of any one instrument on each instrument volume will not im-pair the ability to safely shutdown the reactor. The new system has been designed in such a manner as to ensure that all instruments will operate reliably under all conditions and shall not be adversely affected by hydrodynamic forces or flow characteristics.
It should be noted that ITT Barton transmitters and Rochester Instrument Systems current / voltage alarms are currently undergoing environmental and seismic qualification testing.
Due to equipment availability, it was impossible to obtain environmentally and seismically qualified equipment in the required time frame.
Pending test results, any installed equipment failing the required testing will be replaced with qualified equipment.
Staff Evaluation An acceptable means of complying with this criterion and addressing the additional staff concerns on common cause failure of instrumentation is as follows:
With respect to a single failure (random), provide sufficient redundancy in the autor>atic scram level instrumentation to meet the single failure criterion on each instrumented portion of the SDY.
With respect to common-cause failures:
(a) provide additional (or substitute) level-sensing instrumentation for the automatic scram function to include diversity as well as redundancy.
The diversity should, as a minimum, be achieved by level sensors that employ different operating principles for measuring the water level; and (b) for the instrumentation selected, demonstrate how common cause failure, such as those identified by operating history ~and those identified in the Foreword to IEEE 379-1977 will be considered.
We have evaluated the licensee's response to this safety criterion and find that sufficient redundancy has been provided to meet the single failure criterion. We also find that sufficient diversity has been achieved through the use of diverse level sensors employing different operating principles for measuring the water level.
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E-M I,-M 302-302-Y 100D 100B Chanel B Note:
- 1) Instruments 302 - 820, 82D, B-M, and E-m are all located 'on the east bank instrument volume.
- 2) -Instruments 302 - 82J, 82K, L-M, and H-M are all locatsd on the west bank instrument '
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volume.
3)~ One relay from each'chanel must de-energize to scram the reactor l
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8 In order to obtain protection from possible common mode failures resulting from external environmental effects, the Forewcrd to IEEE 379-1971 suggests that system components be designed, qualified, and installed to be immune to such anticipated challenges.
The licensee has stated that fully environmentally qualified equipment was not available for installation, but that qualification testing regarding the components in question is currently underway.
In the event the equipment does not pass the qualification testing, licensee shall replace it with qualifie.1 equipment.
The licensee has provided the following justification for permitting interim operation until all instrumentation is fully qualified:
the unqualified portion of the system only pertains to the components u::ed in the differential pressure instrumentation. The Magnetrol float-type level switches, which perform the same function, and have been installed to meet the diversity and redundancy criteria, are fully qualified. As such, they provide a comparable, environmentally qualified systen not susceptible to a single active failure and would perfonn their intended safety function in the event of a harsh environment.
During our review of licensee responses to our Safety Evaluations pertaining to Equipment Environmental Qualification, four categories under which licensees could justify interim operation with unqualified
. equipment were identified. These categories were (1) redundant equipment is available to substitute for unqualified equipment; (2) another systen, is capable of equipment; (3)providing the required function of the system with unqualified the unqualified equipment will have performed its safety function prior to failure; and, (4) the plant can be safely shutdown in the absence of the unqualified equipment.
We have reviewed the licensee's justification against the acceptance criteria developed during our review of licensee responses to our EEQ safety evaluations.
We find the licensee's justification meets the acceptance criteria for redundancy and backup equipment and is therefore acceptable.
l The Foreword to IEEE 379-1977 also suggests that in order to protect from l
common-mode failures resulting from design and manufaturing errors, the system components should be subjected to design and manufacturing quality l
assurance programs. The licensee has installed safety-related equipment in this modification. Appendix B of 10 CFR Part 50, Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants requires, in part, that licensees assure that manufacturers who provide equifunent for use in safety-related applications have design and manufacturing quality assurance programs consistent with Appendix B requirements. Therefore, the use of safety-related equipment in the SDV modification meets the intent of the IEEE Foreword and is therefore acceptable.
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4.4.4.4 Safety Criterion 4 System operating conditions which are required for scram shall be continuously monitored.
Licensee Response Diverse and redundant instrumentation installed on each instrument volume will continuously monitor system operating conditions required for scram.
The instrumentation on each instrument volume has been designed and installed in such a manner that rapid water leakage (5 gpm per drive simultaneously) into the scram discharge volume will be detected and an automatic scram initiated while sufficient volume st.11 exists in the scram discharge volume.
Staff Evaluation An acceptable means of complying with this criterion is provided,under Safety Criterion 3.
The licensee's response to that criterion was found to be acceptable.
Consequently, we find this item is also acceptable.
- 4.2.2.5 Safety Criterion 5 Repair, replacement, adjustment, or surveillance of any system component shall not require the scram function to be bypassed.
Licensee Response
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The scram discharge syst'em instrumentation has been designed in such a manner that a half-scram (1 out of 2) will be implemented in accordance with existing technical specifications during repair, replacement, adjustment, or surveill'ance of any system instrument.
Staff Evaluation An acceptable method to comply with this criterion would be to implement a half-scram (1 out of 2) in accordance with existing techni. cal specifications for instrument (or instrument channel) repair or replacem'ent.
We have evaluated the licensee's modifications against this criterion and l
the Dresden 3 Technical Specifications and have detemined that the system j
has been designed in accordance with the criterion and is therefore acceptable.
10 4.2.4.1 Design Criterion 1 The scram discharge headers shall be sized in a~ccordance with GE OER-54 and shall be hydraulically coupled to the instrumented volumes in a manner to permit operability of the scram level instrumentation prior to loss of system function.
Each system shall be analyzed based on a plant-specific maximum inleakage to ensure that the system-function is not lost prior to initiation of automatic scram. Maximum inleakage is the maximum flow rate through the scram discharge line without control rod motion summed over all control rods. The analysis should show no need for vents or drains.
Licensee Response The scram disc.harge headers have been sized to receive approximately 4.5 gallons per drive which is in excess of the GE 0ER-54 criteria.
Each instrument volume is hydraulically coupled to the low point of the SDV piping.
See Figure 2.
Each 20 inch diameter instrument volume is attached to the 4 inch. SDV. header piping with 6 inch schedule 80 pipe. The system has been designed to automatically scram without the need for vents or drains while a maximum inleakage of 5 gpm per drive occurs from each control rod simultaneously.
The system will automatically scram before sufficient volume is lost in the SDV and IV piping. An analysis verifying this performance has been made.
Staff Evaluation One method acceptable to the staff to meet this criterion is to provide an IV for each SDV which.is an integral part of the SDV (i.e., connecting directly to the SDV with piping of a diameter equal to or greater than the diameter of the SDV headers).
GE's recommendation for the use of independent IVs that are attached directly to the low point of the SDV piping and are essentially a vertical extension of the SDV satisfies this criterion.
In discussions with GE we have concluded that a maximum flow rate past the scram outlet valve without rod motion is 5 gpm per rod and this value should be used in the analysis to assure system function, or justification should be provided for using a different value. Any value that is used must be verified to be conservative by assured CRD seal maintenance requirements based on stall flow tests.
The only driving force for the fluid in this analysis should be that provided by the gravity drainage that has been verified from as-built drawings.
Further, the analysis must be performed according to the criteria, with no reliance on header venting. 'Given these assumptions are used by the licensee, we would find the analysis to be acceptable.
We have evaluated the licensee's modifications and drawings and have determined that the licensee has provided an IV which is an integral part of the SDV for each of the two SDVs. The licensee has also designed the system in accordance with the GE recommendations and has performed the supporting analyses. We find, therefore, the licensee's modifications meet the design criterion and are acceptable.
4.2.4.2 Design Criterion 2 Level instrumentation shall be provided for automatic scram initiation while sufficient volume exists in the scram discharge volume.
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12 Licensee Response As stated in the response to Design Criterion 1., level instrumentation shall be provided for automatic scram initiation while sufficient volume exists in'the scram discharge volume.
Staff Evaluation Acceptable compliance with Design Criterion 1 will result in acceptable compliance with this design criterion as well. As stated previously, we find the licensee's response to Design Criterion 1 to be acceptable; consequently, this item is also acceptable.
4.2.4.3 Design Criterion 3 Instrumentation taps shall be provided on the vertical instrument volme and not on the connected piping.
Licensee Response All instruments installed on each instrument volume are attached to, 2-inch instrument line piping rather than the body of the instrument volume itself. The 2-inch instrument lines are connected to the IV body and are independent of the instrument volume drain and fill lines (see Figure 13).
This type of installation protects the instruments from water hammer forces produced during the scram discharge and venturi effects that might be caused by the IV drain and fill lines.
Because of the new instrumentation ~
design, functional testing of water level instrumentation will not be made after every scram.
Staff Evaluation This criterion must be satisfied in order for the modifications to be acceptable.
Functional tests of the level switches using water after each scram must be continued since there remains concern for residual i
common-cause failures. An acceptable alternative specified in the model TS surveillance guidelines calls for functional testing of the instrumentation on a monthly basis when the design modification is in accordance with the Generic SER.
Based on the licensee's installed modification, they have elected to perform functional testing of the float-type level switches on a monthly basis rather than after each scram.
We have examined the licensee's design specifications and drawings fpr this modification against the crit rion and have determined th.at the instrumentation taps have been provided on the vertical IV in accordance with the Generic SER criteria and not on the connected piping.
We therefore l
conclude that the licensee's modifications meet the criteria and that the modifications are acceptable.
Based on having installed the design modification i
in accordance with the Generic SER criteria, we find the licensee's I
proposed surveillance frequency to be in accordance with our guidelines and is acceptable.
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13 6" fill line.
20" instrument volume 2" instrument piping 2" instrument piping safety related scram safety related scram instraments instrumerits Y
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Note: This sketch is a simplification of the actual instrument l
volume instr,umentation piping.
Instrument isolation valves and calibration taps are not shown.
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14 4_._2. 4. 4 Design Criterion 4 The scram instrumentation shall be capable of detecting water accumulation in the instrumented volumes assuming a~~ single active failure in the instrumentation system or the plugging of an instrument line.
Licensee Response
'Each instrument volume has two instrument lines (see Figure 3) with sufficient instrumentation on each line to automatically scram the reactor.
Single failure of any safety-related instrument or the plugging of an instrument line will not prevent detection of water accumulation and an resulting scram when necessary.
Staff Ev ;uation An acceptable means of meeting this criterion is to satisfy the requirements under Safety Criterion 3 and to install the instrumentation in such a manner.that no credible active or passive failure can significantly impact the ability of the instrumentation to monitor the SDV for the presence of or accumulation of water.
The licensee has provided an acceptable response to Safety Criterion 3.
In addition, we have reviewed ' the Design Specification for the Control Rod.
Drive Scram Discharge System Modification and have detennined that the instrumentation has been adequately designed and installed such that no credible active or passive failure can significantly impact the ability of the instrumentation to monitor the SDV for the presence of or accumulation of water. We, therefore, conclude that the licensee meets the requirements of this criterion.
4.2.4.5 Design Criterion 5 Structural and component design shall consider loads and conditions including those due to fluid dynamics, thermal expansion, internal pressure, seismic considerations, and adverse environments.
Licensee Response All safety-related piping components on the modified SDV system have been designed to consider seismic, fluid dynamic (water hammer), thermal expansion, l
and internal pressure effects.
Environmental qualification has been required for the scram level instrumentation, the vent and drain valve position indication, and solenoid valves whi~ h actuate the vent and drain valves.
c Environmental conditions, process conditions, loading combinations, material
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and fabrication requirements, and examination and testing requirements for the modified system are all listed.in specification 0590-008-S-0, Design Specification for the Control Rod Drive Scram Discharge System Modification.
Staff Evaluation We have reviewed the licensee's design and the supporting documentation.
We find that the licensee's design meets the technical bases specified on page 48 of the Generic Safety Evaluation Report for this Design Criterion and is, therefore, acceptable.
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4.2.4.6 Design Criterion 6 The power-operated vent and drain vanes shall close under loss of air and/or electric power.
Valve position indication shall be provided in the control room.
Licensee Response All vent and drain valves are air operated and will fail closed on loss of air or electric power. Each valve has control and position indication in the control room located on the 903-5 panel.
Staff Evaluation We have evaluated the licensee's design against the criterion and have determined that the. system has been designed in accordance with the criterion
~ and is, therefore, acceptable.
4.2.4.7 Design Criterion 7 Any reductions in the system piping flow path shall be analyzed to assure system reliability and operability under all modes of operation.
Licensee Response There is no reduction in the available flow area of pipe diameter in the SDV and SDV to IV piping.
Staff Evaluation The technical bases for this Design Criterion on page 49 o.f the Generic SER requires the analysis of piping systems when a reduction in the available flow area is caused through a reduction in piping diameter in the SDV and.
SDV to IV piping for lines less than 2 inches in diameter. The licensee has stated that there is no reduction in the available flow area of p.ipe diameter in the SDV and SDV to IV piping.
We have reviewed the licensee's design specifications and drawings and have determined that there is no reduction in system piping flow path.
We, therefore, find this criterion to be. not applicable.
4.2.4.8.
Design Criterion 8 l
System piping geometry (i.e., pitch, line size, orientation) shall be such that the system drains continuously during normal plant operation.
1 Licensee Response The scram discharge volume header piping is pitched in such a manner as to continuously drain water by gravity to the instrument volume. All vent and drain lines have been installed free of any loop seals to ensure venting and drainage.
In addition, as required by Design Criterion 1, the SDV system piping has been designed so that SDV to IV drainage will occur without ventilation.
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. Staff Evaluation This cri+erion addresses the need to provide a flow path which permits the continuous draining of coolant that results from normal rod leakage past individual scram outlet valves.
It requires a positive downward slope of the SDV and associated drain piping as well as piping that is free of loop seals and adequate in size to prevent buildup of water in the SDV.
We have reviewed the licensee's response and find that the system has been designed such that the system drains continuously during normal plant operation. We also find that, having satisfied this criterion, the assumptions of the analysis for system function under Design Criterion 1 are also satisfied.
We, therefore, find the licensee's response to this criterion to be acceptable.
4.2.4.9 Design Criterion 9 Instrumentation shall be provided to aid the operator in the detection of water accumulation in the instrumented volume prior to scram initiation.
Licensee Response Each hydraulically coupled instrument volume has two nonsafety related Magnetrol water level switches installed to detect water prior to scram initiation. One instrument notifies the reactor operator when water is present in the instrument volume.
The second instrument prevents further withdrawal of the control rods and warns the reactor operator as the instrument volume water level rises.
Staff Evaluation The present alarm and rod block instrumentation meets this criterion given adequate hydraulic coupling with the SDV headers.
We have evaluated the licensee's design and find that it provides adequate hydraulic coupling with the SDV headers.
Dresden 3 possesses adequate alarm and rod block instrumentation to allow the operator to recognize an SDV overfilling event that will eventually result in scram of the plant if the buildup continues uncorrected. The licensee has submitted proposed Technical Specification changes to include this alarm and rod block instrumentation.
As part of our Phase 1 evaluation, we concluded that the licensee's actions l
in this regard were acceptable. We, therefore, find chat the requirements 'of l
Design Criterion 9 have been met.
4.2.4.10 ' Design Criterion 10 Vent and drain line valves shall be provided to contain the scram discharge water with a single active failure and to minimize operational exposure.
Licensee Response As stated in the response to Safety Criterion 2, two air operated isolation valves have been installed in series on each scram discharge volume vent line and instrument volume drain line. Any single active valve failure will not impair the ability of the system to contain the scram discharge water.
l l
17 c
Staff Evaluation An acceptable way of meeting this criterion is to provide two isolation valves in series for all SDV vent and IV drain lines. As noted by the licensee, the basis for this criterion is given under Safety Criterion 2.
The licensee has provided an acceptable response to Safety Criterion 2; therefore, we find the.esponse to this criterion to also be acceptable.
Proposed Technical Specification Changes to Support Phase 2 Modifications at Dresden 3 We have reviewed the licensee's proposed TS changes transmitted by letter dated March 18,1982,in support of the long-term SDV modifications for Dresden 3.
The changes incorporate setpoint and format changes to reflect the impact of the long-term SDV modifications on the Limiting Conditions for Operation and surveillance requirements added under Phase 1.
The proposed TS changes support the design modifications discussed in the paragraphs above and are consistent with the changes necessary to reflect the diversity and redundancy of the system in order to meet the acceptance criteria of the Generic SER.
We, therefora, conclude that the proposed changes are appropriate to the modifications implemented in accordance with the Generic SER and are acceptable.
IV.
Summary Phase 1 Based upon our review of the contractor's report, we conclude that the~
licensee's proposed TS satisfy the guidelines of the July 7,1980 letter for surveillance of SDV vent and drain valves and for LCOs and surveillance require-ments for SDV limit switches.
Consequently, we find the licensee's proposed TS acceptable.
Phase 2 Based upon our review and evaluation of the licensee's submittals in support of the long-term SDV modifications, we find that the design objectives of the Generic SER dated December 1,1980 have been met. We find that the SDV system has been modified with (1) improved communication between the SDV headers and the IVs, (2) diverse and redundant water level instrumentation, and (3) improved vent and drain line functions.
Consequently, we conclude that the licensee's modifications meet the acceptance criteria for long-term SDV modifications set forth in our December 1,1980 Generic SER.
Based upon our acceptance above of the licensee's long-term SDV modifications, we also conclude that the proposed TS changes in support of the modifications are' appropriate and consistent with the changes necessary to reflect the I
diversity and redundancy of the modified system. We, therefore, conclude that the proposed TS changes submitted March 18,1982, are acceptable.
V.
Environmental Consideration We have determined that the amendments do not authorize a change in effluent types or total amounts nor an increase in power level.and will not result in any significant environmental impact. Having made this determination, I
18 we have further conc 1'uded that the amendments involve an action which is insignificant from the standpoint of e.nvironmental impact and pursuant to 10 CFR 551,5(d)(4) that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of the amendments.
VI.
Conclusion We have concluded, based on the considerations discussed above, that:
(1) because the amendments do not involve a significant increase in the
-probability or consequences of accidents previously considered and do not involve a significant decrease in a safety margin, the amendments do not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Date:
March 26,1982
Attachment:
Technical Evaluation Report (TER) 9 6
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