Text

Response to NRC Request for Additional Information Regarding License Amendment Request 15-03, Application of Alternative Source Term
	ML15295A470
Person / Time
Site:	Diablo Canyon
Issue date:	10/22/2015
From:	Allen B; Pacific Gas & Electric Co
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	DCL-15-125, LAR 15-03
	Download: ML15295A470 (13)
	v • d • e

Pacific Gas and Electric Company October 22, 2015 PG&E Letter DCL-15-125 U.S. Nuclear Regulatory Commission ATIN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 Diablo Canyon Units 1 and 2 Barry S. Allen Vice President, Nuclear Services Response to NRC Request for Additional Information Regarding License Amendment Request 15-03. "Application of Alternative Source Term" Diablo Canyon Power Plant Mail Code 104/6 P. 0. Box 56 Avila Beach, CA 93424 805.545.4888 Internal: 691.4888.

Fax: 805.545.6445

References:

1. PG&E Letter DCL-15-069, License Amendment Request 15-03, "Application of Alternative Source Term," dated June 17, 2015 (ADAMS Accession No. ML15176A539)

2. PG&E Letter DCL-15-105, "Supplement to License Amendment Request 15-03, 'Application of Alternative Source Term,"' dated August 31, 2015 (ADAMS Accession No. ML15243A363)

3. E-mail from NRC Project Manager Siva P. Lingam, "Diablo Canyon 1 and 2-Requests for Additional Information for License Amendment Request 15-03 to Adopt the Alternative Source Term per 10 CFR 50.67 (TAC Nos. MF6399 and MF6400)," dated September 22, 2015 (ADAMS Accession No. ML15265A600)

4. E-mail from NRC Project Manager Siva P. Lingam, "Diablo Canyon 1 and 2-Requests for Additional Information for License Amendment Request 15-03 to Adopt the Alternative Source Term per 10 CFR 50.67 (TAC Nos. MF6399 and MF6400)," dated September 23, 2015 (ADAMS Accession No. ML15266A532)

Dear Commissioners and Staff:

Pacific Gas and Electric (PG&E) Letter DCL-15-069, "License Amendment Request 15-03, 'Application of Alternative Source Term,"' (Reference 1), dated June 17, 2015, and supplemented by PG&E Letter DCL-15-105, "Supplement to License Amendment Request 15-03, 'Application of Alternative Source Term,"' (Reference

2), dated August 31, 2015, submitted License Amendment Request (LAR) 15-03, "Application of Alternative Source Term."

On September 22, 2015, the NRC Probabilistic Risk Assessment Operations and Human Factor~ Branch (APHB) requested additional information required to A

member of the STARS (Strategic Teaming and Resource Sharing)

Alliance Callaway

Diablo Canyon

Palo Verde*

Wolf Creek

Document Control Desk October 22, 2015 Page2 PG&E Letter DCL-15-xxx complete the review of LAR 15-03 (Reference 3). PG&E's responses to the APHB staff's questions are provided in Enclosure 1.

On September 23, 2015, the NRC Steam Generator Tube Integrity and Chemical Engineering Branch (ESGB) requested additional information required to complete the review of LAR 15-03 (Reference 4). PG&E's responses to the ESGB staff's questions are provided in Enclosure 2.

This information does not affect the results of the technical evaluation or the no significant hazards consideration determination previously transmitted in PG&E Letters DCL-15-069 and DCL-15-105.

PG&E makes no regulatory commitments (as defined by NEI 99-04) in this letter.

This letter includes no revisions to existing regulatory commitments.

If you have any questions, or require additional information, please contact Mr. Hossein Hamzehee at (805) 545-4720.

I state under penalty of perjury that the foregoing is true and correct.

Executed on October 22, 2015.

Sincerely, t3ry 5_ 4&---

Barry S. ~en Vice President, Nuclear Services mjrm/4557/503071 01 Enclosures cc:

Diablo Distribution cc/enc:

Marc L. Dapas, NRC Region IV Administrator Thomas R. Hipschman, NRC Senior Resident Inspector Siva P. Lingam, NRR Project Manager Gonzalo L. Perez, Branch Chief, California Dept of Public Health A

member of the STARS (Strategic Teaming and Resource Sharing)

Alliance Callaway

Diablo Canyon

Palo Verde*

Wolf Creek

APHB Response 1

PG&E Letter DCL-15-125 PG&E Letter DCL-15-125 PG&E Response to NRC Request for Additional Information Regarding License Amendment Request 15-03, "Application of Alternative Source Term" NRC APHB-RAI-1 Please identify any operator manual actions that will be added, deleted, or changed to support the proposed license amendment. If there are changes to operator actions please include the following information:

What cues are provided to personnel that manual action(s) is/are required?

What cues are provided to personnel that the proposed action(s) is/are no longer required?

What administrative controls exist to assure that, when the action(s) is/are no longer required, the plant configuration is put in the correct configuration for the plant status?

PG&E Response Diablo Canyon Power Plant (DCPP) Emergency Operating Procedure (EOP) E-1.3, "Transfer to Cold Leg Recirculation," (current revisions Unit 1: 30, Unit 2: 21) will be revised. EOP E-1.3 currently has steps to align containment spray from residual heat removal (RHR) system to the recirculation mode, provided both RHR trains are in service.

EOP E-1.3 will be revised to add a time critical operator action (TCOA) to align containment spray from RHR, even if only one RHR train has been successfully aligned for cold leg recirculation. The EOP E-1.3 revision will provide clear guidance on the conditions required to implement these actions, and as an approved plant procedure, provides appropriate plant status control. No additional cues are added, deleted, or changed as a result of this proposed license amendment (LA).

NRC APHB-RAI-2 Please describe any changes to operating procedures needed to support the proposed license amendment.

PG&E Response To implement the proposed LA, the TCOA to manually initiate containment spray in the recirculation mode will be added to EOP E-1.3, as described in the previous response (APHB-RAI-1 ).

2

NRC APHB-RAI-3 PG&E Letter DCL-15-125 If the Emergency Operating Procedures are affected, describe any changes that were required of the Control Room task analysis that was done as part of your Detailed Control Room Design Review. If no update to the task analysis was necessary, describe how task requirements were developed.

PG&E Response A demonstration of the requirements for Verification and Validation per DCPP Administrative Procedure AD1.DC12, "Writer's Guide for Emergency Operating Procedures and Abnormal Operating Procedures," (current revision 9), and Interdepartmental Administrative Procedure (IDAP) OP1.102, "Time Critical Operator Action," (current revision 8A), was performed by three operating crews for the proposed changes to EOP E-1.3. This has aided in demonstrating that the procedures are technically correct, usable, and function as intended.

No changes to the Control Room task analysis are required. The relevant task in this case is performance of procedure EOP E-1.3. The proposed revision to EOP E-1.3 does not introduce any unique training elements that would require revising the associated task.

NRC APHB-RAI-4 Please describe any changes to controls or displays (including annunciators and alarms) needed to support the proposed license amendment.

PG&E Response The setpoints for the redundant safety related gamma sensitive area'radiation monitors (1-RE 25/26, 2-RE 25/26) will be updated (lowered) as described in Section 2.4 and of the LAR.

NRC APHB-RAI-5 Please describe any changes to training and the simulator needed to support the proposed license amendment.

PG&E Response No hardware or software changes to the simulator are required to support the proposed LA. Training coordination is required for revised EOPs. This coordination will determine the training timeline, the appropriate audience (licensed operators), and the venue for the training (classroom/simulator).

3

NRC APHB-RAI-6 PG&E Letter DCL-15-125 Please describe any changes to staffing or qualification needed to supporl the proposed license amendment.

PG&E Response There are no required changes to staffing or qualifications to support the proposed LA.

NRC APHB-RAI-7 What has been or will be done to assure that any new or changed human actions can be done within the time limits of the relevant scenario(s)?

PG&E Response:

A demonstration of the requirements for Verification and Validation (in accordance with procedures AD1.DC12 and OP1.102) was performed by three operating crews for the proposed changes to EOP E-1.3. Successful implementation of the procedure was demonstrated well within the required performance time of 12 minutes. Refer to the response to APHB-RAI-11 for additional description of the Verification and Validation demonstration.

NRC APHB-RAI-8 Has an operating experience review been done, including plant-specific condition reporls, Licensee Event reporls, Institute of Nuclear Power Operations (IN PO) reporls, and other relevant sources?

PG&E Response A precedence review was performed to identify applicable industry experience associated with implementation of the alternative source term methodology at other nuclear power plants. This review identified the previous NRC approval of crediting recirculation sprays following the loss of coolant accident for long term containment iodine removal for Salem Units 1 and 2, which was discussed in Section 4.2 of the license amendment request (LAR).

As discussed in the response to APHB-RAI-1, the actions to align containment spray from RHR system after switching to the recirculation mode are existing actions in EOP E-1.3. The revision is to add a TCOA to align containment spray from RHR even if only one RHR train has been successfully aligned for cold leg recirculation.

Because the changes proposed in the LAR do. not change how existing human-system interface components are used, in accordance with NUREG-1764, Revision 1, Section 3.2, an Operating Experience Review was not performed.

4

NRC APHB-RAI-9 PG&E Letter DCL-15-125 Please describe any increase in operator work load that will occur with the proposed license amendment.

PG&E Response There is minimal increase in operator work load from this change. The proposed LA does not change the circumstances under which EOP E-1.3 is performed, only a sequence of actions within the procedure. The revision to EOP E-1.3 ensures that containment spray is aligned to RHR even when only a single train of RHR is able to be placed in the cold leg recirculation line-up. There are no additional field actions required by the procedure revision and no new system control methodologies required. A new TCOA will be required to implement the proposed LA. However, simulator demonstrations of the procedure revision have proven that the new TCOA would be easily achievable.

NRC APHB-RAI-10 Please provide engineering design procedures related to the human factors design of the proposed license amendment, or describe how human factors design is accomplished.

PG&E Response There are no human factors design elements that are relevant with implementation of this proposed LA. Procedure steps within EOP E-1.3 will be revised to achieve the desired post-accident containment spray alignment. None of the proposed revised procedural steps involve new or unfamiliar tasks or introduce human factors concerns for control room operators. Administrative Procedure AD1.DC12 requires consideration for human factors during the revision to any EOP.

NRC APHB-RAI-11 Describe the process used to verify and validate the ability of your operators to accomplish the tasks required for the proposed LAR. In lieu of a description, you may provide the relevant administrative procedure(s) for verification and validation. Did the Validation include a representative sample of operators, and was it done with Technical Specification (TS) minimum staffing and nominal staffing?

PG&E Response A demonstration of the requirements for Verification and Validation per Administrative Procedure AD1.DC12 and IDAP OP1.1D2 was performed by three operating crews for the proposed changes to EOP E-1.3. Crews did not have prior review of the event or training on the proposed new steps to be added to EOP E-1.3. This demonstration was 5

PG&E Letter DCL-15-125 pertormed with a single Unit Shift Foreman who provided procedural direction and a board operator who pertormed equipment manipulations. This lineup is representative of Technical Specification (TS) minimum staffing. No staffing changes would be required to implement the revised portions of this procedure in the control room.

NRC APHB-RAI-12 Describe the process used to monitor manual actions to ensure that they remain feasible and reliable over the long term, and are not degraded because of design changes, inadequate training, or other mechanisms.

PG&E Response DCPP IDAP CF3.1D9, "Design Change Development," (current revision 49A) governs the design change process. Per CF3.1D9, specific coordination is required with Operations and Learning Services for designs that impact TCOAs. If the design modification impacts how a system or component is operated or changes required operator actions, coordination is required with Operations. Watch stander specific qualification cards are required for Operations personnel and require evaluated demonstrations to ensure adequate training on manual actions. For TCOAs, re-validations are required by IDAP OP1.1D2, "Time Critical Operator Action," on specified frequencies.

6

ESGB Response 1

PG&E Letter DCL-15-125 PG&E Letter DCL-15-125 PG&E Response to NRC Request for Additional Information Regarding License Amendment Request 15-03, "Application of Alternative Source Term" NRC ESGB-RAI-1 Identify all time-dependent or bounding values of strong acid concentrations in the sump for a period of 30 days post loss-of-coolant accident (LOCA). In addition, please include the decrease of sump water pH [the indicator of acidity or alkanity] due to them.

PG&E Response The conservative analysis performed to confirm that the sump water pH following a LOCA at Diablo Canyon Power Plant (DCPP) remains greater than 7.0 utilized bounding values of strong acids and focused on the estimated pH at the end of the accident period; i.e., 30 days.

The bounding pH analysis was developed by choosing masses and concentrations from either unit at DCPP that would minimize the pH calculated for the sump water initially, and at the end of 30 days.

Thus, for boric acid solutions the highest volume and boron concentration from either unit was selected. For the sodium hydroxide solutions, the smallest volume and lowest concentration was chosen. The volumes of the fluids that make up the sump water and utilized in the analysis (see Table 1) reflect their respective temperature and pressure at the beginning of the accident. Sump volume/density is reflective of containment conditions at the end of the containment spray recirculation phase because it is deemed representative of a well-mixed sump volume after accident initiation.

Table 1: Initial Sump Composition Volume Sump Mass CsoRON Boric Acid Wt% NaOH NaOH ft,j lb ppm Gm-moles Gm-moles Fluid from RWST 61,266 3,824,474 2,500 401 '126.4 Fluid from RCS 11,455 548,730 1,900 43,740.3 Fluid from 4 Accumulators 3,544 221,676 2,500 23,250.3 Fluid from Spray Additive Tank 207 17,000 0

0 30 57,835.7 Total 4,611,880 468,117 57,835.7 Vsumo 76,456ft,j or 2,164,992.8 liters Initial Sump Water Conditions Prior To Long Term Acid Addition pH CsoRON CNaOH Gm-mole/L Gm-mole/L

-7.8 0.2162 0.0267 The estimate of the minimum initial sump water pH (i.e., without long term acid production due to 30 days of irradiation) ranged from -7.8 (per conservative graphical analysis performed by CB&I), to 8.0 (based on comparison with DCPP Unit 1 Cycle 19 2

PG&E Letter DCL-15-125 and Unit 2 Cycle 18 minimum sump pH estimates provided by Westinghouse). For purposes of dose consequences, the initial sump pH was assumed to be - 7.8.

Table 2 provides the estimated long term acid production in the DCPP containment following a LOCA due to cable degradation as a result of irradiation (HCI) and radiolysis of the sump water (HN03).

Table 2: Net Acid Addition at 30 days Acid CACID Gm-moles Gm-mole/L HCI 11,324.3 0.00523 HN03 1,997.4 0.00092 Total 13,321.7 0.00615 After acid addition, the net free caustic available for buffering the boric acid solution was estimated to be (57,835.7-13,321.7 = 44,514 gm-moles) or CNaOH free = 0.0206 gm-moles/L available.

Table 3: Sump Composition at 30 days Gm-mole/L CsoRoN 0.2162 CNaOH free 0.0206 Cc,-

0.00523 CN03-0.00092 pH

>7.5 Thus the minimum ultimate sump pH at T=30 days following a LOCA taking into consideration long-term acid production inside containment was determined to be greater than 7.5.

NRC ESGB-RAI-2 The submittal information provided a high level description of the calculation for post-LOCA pH. Please provide a more detailed description of the calculation methodology including any computer codes used to determine the sump pH post-LOCA. In addition, provide the following details in order for the staff to verify your calculations:

a. Volume and concentration of sodium hydroxide [NaOH] solution injected in bounding case.

b. Volume of Refueling Water Storage Tank and concentration of boric acid in bounding case.

c. Volume of reactor coolant system and concentration of boric acid in bounding case.

d. Mass of ethylene propylene rubber [EPR]/Hypalon cables assumed in calculation.

3

PG&E Response PG&E Letter DCL-15-125 Available experimental data with respect to boric acid and NaOH concentrations in a solution and resultant pH was used to conservatively determine the ultimate sump pH at DCPP. The data assembled from a literature search was placed on a graph of NaOH versus boric acid concentration, and pH iso curves were drawn through the data. With the sump boron concentration and the "free" NaOH concentration calculated initially and at 30 days placed on the graph, the pH was conservatively read for both initial and final sump conditions.

As noted in response to NRC ESGB RAI 1, the CB&I methodology is conservative and yields pH values that are slightly lower than that predicted by Westinghouse.

When DCPP was initially constructed with a caustic addition system, the need to address acid production due to high post-LOCA radiation levels inside containment was not identified as part of the design basis. Thus, and as noted in Section 7.2.3.2.5 of of the Alternative Source Term (AST) License Amendment Request, in support of the AST application, in lieu of obtaining the actual cable insulation mass inside the DCPP Units 1 and 2 containments, a simplified conservative approach was utilized to address long term acid production by taking into consideration a) cable insulation data provided in NUREG/CR-5950 and b) data available for various Stone &

Webster (now CB&I) constructed nuclear plants.

The amount of electrical cable was conservatively estimated by reviewing the amounts of EPR/Hypalon cable from PWRs listed in Table 2.2 of NUREG/CR-5950, "Iodine Evolution and pH Control," and by examining the mass/type of cable installed in Stone and Webster, International (CB&I) constructed pressurized water reactors (PWRs). A safety factor of 1.5 was applied to the largest mass of cable identified (was determined to be for a 4-loop PWR with a power level slightly greater than DCPP), 82,060 lbs to estimate an upper bound of electrical cable installed inside the DCPP containments.

Additionally, although the mass of electrical cable identified was applicable to both insulation and conductors, the cabling mass used was conservatively assumed to be solely insulation.

An airborne LOCA radiation dose of 200 Megarads was used for the cable degradation dose in the production of HCI. This value is commonly used for evaluating environmental qualification of electrical equipment in PWR containments, and was recommended post-TMI in IE Bulletin 79-01 Bas a representative I upper bound value for the beta dose inside containment for PWRs, while the gamma dose estimate was a decade lower.

In developing the source term for nitric acid generated in the DCPP containment sump, the sump volume and radiation exposure data from a large 4 loop PWR was used. The 4 loop PWR radiation exposure of 40 Megarads was corrected for differences in sump volume (inversely proportional) and power level (linearly proportional). A safety factor of 1.5 was also used in the generation of the quantity of nitric acid.

4 PG&E Letter DCL-15-125 The acid production factors due to radiation exposure found in NUREG/CR-5950 were used.

2a Volume and Concentration of NaOH solution injected in the bounding case See response to NRC ESGB RAI 1, Table 1, "Initial Sump Composition," for the minimum mass of 30 wt0/o NaOH solution injected into the sump from the Spray Additive Tank.

2b Volume of Refueling Water Storage Tank (RWST) and concentration of boric acid in bounding case See value in response to NRC ESGB RAI 1, Table 1, "Initial Sump Composition,"

for the maximum mass of 2500ppmB solution injected into the sump from the RWST.

2c Volume of reactor coolant system and concentration of boric acid in bounding case See value in response to NRC ESGB RAI 1, Table 1, "Initial Sump Composition,"

for the maximum mass of 1900ppmB solution that has emptied into the sump from the reactor coolant system.

2d Mass of EPR/Hypalon cables assumed in calculation A mass of 123,090 lb (82,060 lbs with a safety factor of 1.5) was assumed. Note that mass of the conductor in the cable was conservatively assumed to be insulation for the purposes of calculating the mass of HCI evolved from the cable due to radiation exposure.

5

Pacific Gas and Electric Company October 22, 2015 PG&E Letter DCL-15-125 U.S. Nuclear Regulatory Commission ATIN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 Diablo Canyon Units 1 and 2 Barry S. Allen Vice President, Nuclear Services Response to NRC Request for Additional Information Regarding License Amendment Request 15-03. "Application of Alternative Source Term" Diablo Canyon Power Plant Mail Code 104/6 P. 0. Box 56 Avila Beach, CA 93424 805.545.4888 Internal: 691.4888.

Fax: 805.545.6445

References:

1. PG&E Letter DCL-15-069, License Amendment Request 15-03, "Application of Alternative Source Term," dated June 17, 2015 (ADAMS Accession No. ML15176A539)

2. PG&E Letter DCL-15-105, "Supplement to License Amendment Request 15-03, 'Application of Alternative Source Term,"' dated August 31, 2015 (ADAMS Accession No. ML15243A363)

3. E-mail from NRC Project Manager Siva P. Lingam, "Diablo Canyon 1 and 2-Requests for Additional Information for License Amendment Request 15-03 to Adopt the Alternative Source Term per 10 CFR 50.67 (TAC Nos. MF6399 and MF6400)," dated September 22, 2015 (ADAMS Accession No. ML15265A600)

4. E-mail from NRC Project Manager Siva P. Lingam, "Diablo Canyon 1 and 2-Requests for Additional Information for License Amendment Request 15-03 to Adopt the Alternative Source Term per 10 CFR 50.67 (TAC Nos. MF6399 and MF6400)," dated September 23, 2015 (ADAMS Accession No. ML15266A532)

Dear Commissioners and Staff:

Pacific Gas and Electric (PG&E) Letter DCL-15-069, "License Amendment Request 15-03, 'Application of Alternative Source Term,"' (Reference 1), dated June 17, 2015, and supplemented by PG&E Letter DCL-15-105, "Supplement to License Amendment Request 15-03, 'Application of Alternative Source Term,"' (Reference

2), dated August 31, 2015, submitted License Amendment Request (LAR) 15-03, "Application of Alternative Source Term."

On September 22, 2015, the NRC Probabilistic Risk Assessment Operations and Human Factor~ Branch (APHB) requested additional information required to A

member of the STARS (Strategic Teaming and Resource Sharing)

Alliance Callaway

Diablo Canyon

Palo Verde*

Wolf Creek

Document Control Desk October 22, 2015 Page2 PG&E Letter DCL-15-xxx complete the review of LAR 15-03 (Reference 3). PG&E's responses to the APHB staff's questions are provided in Enclosure 1.

On September 23, 2015, the NRC Steam Generator Tube Integrity and Chemical Engineering Branch (ESGB) requested additional information required to complete the review of LAR 15-03 (Reference 4). PG&E's responses to the ESGB staff's questions are provided in Enclosure 2.

This information does not affect the results of the technical evaluation or the no significant hazards consideration determination previously transmitted in PG&E Letters DCL-15-069 and DCL-15-105.

PG&E makes no regulatory commitments (as defined by NEI 99-04) in this letter.

This letter includes no revisions to existing regulatory commitments.

If you have any questions, or require additional information, please contact Mr. Hossein Hamzehee at (805) 545-4720.

I state under penalty of perjury that the foregoing is true and correct.

Executed on October 22, 2015.

Sincerely, t3ry 5_ 4&---

Barry S. ~en Vice President, Nuclear Services mjrm/4557/503071 01 Enclosures cc:

Diablo Distribution cc/enc:

Marc L. Dapas, NRC Region IV Administrator Thomas R. Hipschman, NRC Senior Resident Inspector Siva P. Lingam, NRR Project Manager Gonzalo L. Perez, Branch Chief, California Dept of Public Health A

member of the STARS (Strategic Teaming and Resource Sharing)

Alliance Callaway

Diablo Canyon

Palo Verde*

Wolf Creek