ML20195H440
| ML20195H440 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 06/21/1988 |
| From: | Bird R BOSTON EDISON CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 88-097, 88-97, NUDOCS 8806280290 | |
| Download: ML20195H440 (7) | |
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Pilgrim Nuclear Pcmer station Rocky Hill Road Plymouth, Massachusetts 02360 Ralph G. 81rd June 21, 1988 senior vice President - Nuclear BECo Ltr. #88-097 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Hashington, D.C. 20555 Docket No. 50-293 License No. DPR-35
Subject:
NRC Inspection Report 50-293/88-11
Dear Sir:
Attached is Boston Edison Company's response to the unresolved items described in the subject inspection report.
An excerpt from the appropriate section(s) of the inspection report is first stated, followed by the Boston Edison Company response.
The corrective action for each of the item; has been satisfactorily completed to support plant operation.
Please do not hesitate to contact me directly if there are any questions.
hd R.G. Bird CS/bl :
Response to Unresolved Items :
Evaluation of Combustible Gas Control Discrepancy cc: Mr. William Russell Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Rd.
King of Prilssia, PA 19406 Sr. Resident Inspector - Pilgrim Station g806200290090621
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R ADOCK 05000293 0
ta ATTACHMENT 1 Resoonse to Unresolved Items (Inspection Report 88-11)
NRC Unresolved Item 88-11-01 Excerot from Insoection Reoort. Section 4 Comparison of Plant Specific Technical Guidelines, BWR Owners Group Emergency Guidelines and Emeraency Ooeratino Procedures (EOP's) -
Plant Specific Technical Guidelines (P-STG)/EOP Review "All E0Ps and those portions of satellite procedures which contained steps based on the P-STGs were compared to the P-STG.
The following differences were noted.
"EOP-3:
Primary Containment Control" "PSTG steps PC/H-2.1 (suppression chamber spray), 2.2 (torus or drywell vent), 2.3 (purge), and 2.4 (drywell spray) were reordered in the E0P in the order of:
2.2, 2.3, 2.1, 2,4.
The licensee had not previously identified this potential safety-significant deviation.
Either analysis of the acceptability of E0P sequence or procedure revision to match the PSTGs is required.
This is an unresolved item (50-293/88-11-01)."
BECo Resoonse to Unresolved Item 8&-11-01 This condition has been evaluated and determined to not be a safety significant deviation.
The detailed evaluation is provided as Attachment 2.
This item is a technical inaccuracy and will be corrected as part of the next major revision to the E0Ps.
This discrepancy is formally captured as verification discrepancy number D-7-2 for E0P-3.
MRC Unresolved Item 88-11-02 Excerot from Insoection Reoort. Section 8 "Halkthrouah of Emergency Ooeratina Procedures and Satellite Procedures" "A number of the ECP-related items identified by the inspectors h,ad also been identified by the facility review process and actions were being taken to address the observed problems. However, the facility review of the satellite procedures was still in progress even though the procedures were approved and issued, i.e., they had not yet finished their own walkthrough of the satellite procedures.
Furthermore, the operction management agreed to assure that the plant labeling was consistent with the E0Ps and satellite procedures.
Therefore, pending further NRC review following completion of the facility walkthrough of the satellite procedures and the licensee actions.
to correct the identified deficiencies, this item will remain unr'esolved (50-293/88-11-02)."
Page 1 of 3
ATTACHMENT 1 (cont'd)
BECo Resoonse to Unresolved Item 88-11-02 Review of E0P satellite procedures has been completed.
The discrepancies identified by the NRC, including those identified in Attachment C of the Inspection Report, and by walkdowns performed by PNPS licensed operators have been corrected.
NRC Unresolved Item 88-11-03 Excerot from Insoection Reoort. Section 4 "P-STG/EOP Review" "EOP-3:
Primary Containment Control" "Primary containment venting was allowed by procedure after torus pressure exceeds 11 psig but before reaching the Primary Containment Pressure Limit (PCPL; 48 psig) irrespective of resultant reactivity release rate.
Procedure 5.4.6 stated that venting, irrespective of resultant reactivity release rate, was appropriate only when the primary containment pressure is above the PCPL (or when drywell or torus hydrogen concentration was above 6'/.).
The licensee stated that they will revise the procedures to remove the incorsistency and instruct operators to vent before reaching the PCPL."
"Satellite Procedures Reviewd "5.4.6:
Post Accident Containment Control (Ventina)"
"The procedure directed using both a small vent path (1 or 2 inch valves) and a large path (through 8 inch valves) for containment venting.
In some scenarios it may not be necessary to open both sets of valves if after opening only the 2 inch or the 1 inch valves the containment pressure is controlled appropriately. The licensee agreed to revise the procedure or justify not revising it."
"A caution containad the words "If at all possible,... shall...".
This statement did not provide clear direction to the SRO.
The licensee agreed to revise the procedure or justify not revising it."
"Step 2 of Attachment A of this procedure stated that the E0P is applicable when primary containment pressure reaches 2.5 psig, as opposed to above 2.5 psig. The licensee agreed to revise this statement."
"The caution statement about rupture of the ductwork with ven' ?ng did not include notification of Health Physics.
The licensee agreed.o revise the procedure or justify not revising it."
"Step 2 of Attachment A of this procedure was missing a statement regarding opening the appropriate valves as necessary to perform the step.
The licensee agreed to consider revising this statement."
"Step 3 of Attachment A of th;s procedure did not provide clear direction to the operator on the value o' primary containment pressure to terminate torus venting.
The licensee agreed to revise the procedure or justify not revising it."
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ATTACHMENT 1 (cont'd)
"The items concerning containment venting will be collectively included as part of unresolved items 50-293/88-11-03. See Section 8 for additional containment venting items."
"Excerot from Insoection Reoort. Section 8" "One item identified during the walkthrough of the E0Ps was an apparent need for additional training on when to initiate and when to terminate venting of the containment in accordance with the intent of the EPGs and the procedures.
Items concerning containment venting will be considered an unresolved item (50-293/88-11-03.)"
BECo Resoonse to Unresolved Item 88-11-03 PHPS Procedure 5.4.6, "Primary Containment Venting and Purging Under Emergency Conditions" - Attachment A, has been revised (Revision 18) to correct all the identified discrepancies.
Operator training on when to initiate and when to terminate venting, in accordance with the intent of the PSTGs, is given as part of training module 87-0-RQ-05A-01-07.
The intent of venting is stressed to each operating crew.
NRC Unresolved Item 88-11-04 Excerot for Inspection Reoort. Section 11 "EOP Ouality Assurance Measures" "A review was conducted to determine if Quality Assurance Measures are adequate to ensure that high quality E0Ps are developed, implemented and maintained."
"The QA measures associated with the development of the E0Ps were found to be acceptable, based on discussions with the Quality Engineering Division Hanager and Senior Quality Engineer.
However, it was concluded that a programmatic approach to ensure the continued quality of the E0Ps through audits of the maintenance of the E0Ps did not exist in the area of auditing l
of the E0P program."
"In subsequent discussions with the Vice President, Nuclear Engineering Division and Quality Assurance management, BECo con.mitted to revise the 1988 Internal Audit Schedule to include an annual audit of the E0P program.
This audit will be performed as a Safety System Audit in the fourth quarter of l
1988.
The proceduralization of continued quality assurance measures is an Unresolved Item (50-293/88-11-04)."
l BECo Resoonse to Unresolved Item 88-1'-04 l
As indicated in the inspection report excerpt, the 1988 Quality Assurance Audit Schedule was revised to include an annual audit of the E0P program beginning in the fourth quarter of 1988.
The Audit Schedule revision was formally approved March 17, 1988.
In addition Quality Assurance Department Procedure No. 18.01. "Preparation, Performance, Reporting and follow-up of Quality Assurance Department Internal Audits" was revised on April 25, 1988 to reflect, an annual audit frequency for the E0P program.
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AT7MHMENT 2 EVALUATION OF THE E0P-PSTG DISCREPANCY RELATIVE TO COMBUSTIBLE GAS CONTROL When primary containment hydrogen and oxygen concentrations reach the deflagration limits (6% and 5%, respectively), the PSTGs require wetwell spraying, venting, and purging in that order (PSTG Steps PC/H-2.1, 2.2, and 2.3).
Procedure 5.4.6 (Rev.17) specifies that venting precede purging.
However, E0P-3 (Rev. 0) does not specify that wetwell spraying should precede the vent and purge evolution.
The effect of this discrepancy between the PSTGs and the E0Ps may be evaluated by examining all events to which E0P-3 may apply.
All such events may be segregated into two classes:
those for which the containment remains inerted (i.e., oxygen concentratiot remains below 5%) throughout the event and those for which it does not.
Events within the former class are not affected by the E0P discrepancy because the ionditions required for execution of the discrepant step, hydrogen and oxygen cc.ncentrations reaching their deflagration limits, are not met.
Thus the discrepancy can affect only those events within the latter class.
This smaller set of potentially affected events, those for which the containment does not remain inerted, may be further segregated into two additional classes:
those for which the containment is deinerted when the event initiates (e.g.,
events initiated within one of the 24-hour periods when power operation is permitted without containment inertion) and those for which the containment becomes deinerted during the event. The Boston Edison Company has removed all air sources from within the Pilgrim primary containment.
Therefore, with the exception of deliberate deinertion, which is not called for in the E0Ps, the primary containment will become deinerted during an event only if its pressure is reduced to the point ut which the reactor-building-to-torus vacuum breakers open, drawing air from the reactor building into the wetwell airspace.
This will happen only if containment temperatures are reduced to well below those which existed when the event initiated, and the only viable mechanism for effecting such temperature reductions is the prolonged operation of containment sprays.
However, the E0Ps preclude the use of containment sprays when containment pressure is below 2.5 psig.
Thus the Pilgrim systems configuration together with l
the E0Ps preclude the containment from becoming deinerted during an event, so that there are no events within the latter class and the E0P discrepancy can affect only those events within the former.
This smaller set of potentially affected events, those which initiate during a period when the containment has been deinerted, may be further segregated into two classes:
those which initiate before the reactor has developed a significant power history (i.e., startup events) and those which initiate afterwards. With no significant power history, the reactor core cannot develop decay heat sufficient to generate enough hydrogen to approach the hydrogen deflagration limit.
Events within the former class are therefore not affected by the E0P discrepancy because the conditions required for execution of the discrepant step, hydrogen and oxygen concentrations reaching their deflagration limite, are not met.
Thus the discrepancy can affect only the events within the latter class.
Page 1 of 3
ATTACHHENT 2 (cont'd)
This smaller set of potentially affected events, those which initiate during a period when the containment has been deinerted but only after the reactor has developed a significant power history, may be further segregated into two additional classes:
loss of coolant accidents (LOCAs) and non-LOCAs, During a LOCA the steam released into the drywell will quickly increase containment pressure to the Suppression Chamber Spray Initiation Pressure (refer to the definition of the SCSIP in Appendix A of the BHORG EPGs), and this will occur before any appreciable hydrogen can be generated.
E0P-3 requires initiation of wetwell sprays before containment pressure reaches SCSIP, so that the operator will have been directed to operate wetwell sprays before the conditions required for execution of the discrepant step, hydrogen and oxygen concentrations reaching their deflagration limits, are met.
Thus the E0Ps will require wetwell spraying before the vent and purge evolution for any event within the former class, so that the E0P discrepancy can affect only those events within the latter.
This smaller set of potentially affected events, non-LOCAs which initiate during a period when the containment has been deinerted but only after the rcactor has developed a significant power history, may be further segregated into two additional classes: those for which adequate core cooling is maintained and those for which it is not.
If adequate core cooling is maintained then no sigr.ificant hydrogen generation occurs and the conditions required for execution of the discrepant step, hydrogen and oxygen concentrations reaching their deflagration limits, are not met.
Thus the discrepancy can affect only those events within the latter class.
This smaller set of potentially affected events, non-LOCAs, with loss of adequate core cooling which initiate during a period when the containment has been deinerted but only after the reactor has developed a significant power history, may be further segregated into two additional classes:
those which generate sufficient hydrogen to reach the deflagration limit and those which do not.
Clearly events within the latter class are not affected by the E0P discrepancy because the conditions required for execution of the discrepant step, hydrogen, and oxygen concentrations reaching their deflagration limits, are not met.
Thus the discrepancy can affect only those events within the former class.
This smaller set of potentially affected events, non-LOCAs with loss of adequate core cooling, which generate sufficient hydrogen to reach the deflagration limit, and which initiate during a period when the containment has been deinerted but only after the reactor has developed a significant power history, must be further reduced to actually define the set of events which can be affected by the E0P i
discrepancy. As a minimum, the following subsets of events must be excised:
1.
Events in which the RPV is blown down to the suppression pool after the pool has been substantially heated.
Ae E0Ps require that the RPV be rapidly depressurized prior to loss of PJequate core cooling and, therefore, prior to any significant hydrogen genera: ion.
If the RPV is depressurized by blowing i
down to the suppression pool, tnen the thermal energy transferred to the pool will raise the wetwell water temperature, which in turn raises the partial pressure of the water vapor in the wetwell airspace and the temperature and partial pressure of the dry gas in the airspace.
If the wetwell water temperature is relatively high when the* blowdown is initiated, this will be sufficient to raise containment pressure to the Suppression Chamber Spray Initiation Pressure.
E0P-3 requires initiation of wetwell spr;ys before containment pressure reaches the SCSIP, so that the operator will have been directed to operate wetwell sprays before the conditions required for execution of the discrepant step, hydrogen and oxygen concentrations reaching their deflagration limits, are met.
Thus the E0Ps will require wetwell i
spraying before the vent and purge evolution for these events.
Page 2 of 3
ATTACHMENT 2 (cont'd) 2.
Events in which safety valves open for any appreciable amount of time before significant hydrogen generation occurs.
Because the Pilgrim safety valves are unpiped, any continued steam discharge through these valves will raise containment pressure to the Suppression Chamber Spray Initiation Pressure.
E0P-3 requires initiation of wetwe!1 sprays before containment pressure reaches the SCSIP, so that the operator will have been directed to operate wetwell sprays before the conditions required for execution of the discrepant step, hydrogen and oxygen concentrations reaching their deflagration limits, are met.
Thus the E0Ps will require wetwell spraying before the vent and purge evolution for these events.
3.
Events in which the main condenser is utilized to control RPV pressure (e.g.,
the SRVs are inoperable).
For these events, any hydrogen generated will be discharged through the offgas system and will therefore not accumulate in the primary containment.
Thus the conditions required for execution of the discrepant step, hydrogen and oxygen concentrations reaching their deflagration limits, are not met for these events.
4.
Events in which reactor core decay haat cannot be effectively removed from the primary containment for a prolonged period before significant hydrogen generation occurs. Under these conditions, the thermal energy transferred to the pool will raise the wetwell water temperature, which in turn raises the partial pressure of the water vapor in the wetwell airspace and the temperature and partial pressure of the dry gas in the airspace.
If this occurs over a prolonged period, this will raise containment pre:sure to the Suppressien Chamber Spray Initiation Pressure.
E0P-3 requires initiation of wetwell sprays before containment pressure reaches the SCSIP, so that the operator will have been directed to operate wetwell sprays before the conditions required for execution of the discrepant step, hydrogen and oxygen concentrations reaching their deflagration limits, are met.
Thus the E0Ps will require wetwell spraying before the vent !ad purge evolution for these events.
Thus the set of events which may be affected by the E0P discrepancy is bounded by the preceding logic.
The probability of occurrence of any event from within the set is vanishingly small and clearly does not warrant correction of this discrepancy in the near term (i.e., before the E0Ps undergo their next revision).
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